Studies of Land Subsidence w GEOLOGICAL SURVEY PROFESSIONAL PAPER 437 This volume was published as separate chapters A—I DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director For sale by the Distribution Branch, Text Products Section, US. Geological Survey, 604 South Pickett St., Alexandria, VA 22304 lECS CONTENTS [letters designate the chapters] (A) Alluvial Fans and Near—Surface Subsidence in Western Fresno County, California, by William B. Bull. (B) Land Subsidence due to Ground—Water Withdrawal, Tulare-Wasco Area, California, by B. E. Lofgren and R. L. Klausing. (C) Prehistoric Near—Surface Subsidence Cracks in Western Fresno County, California, By William B. Bull. (D) Land Subsidence Due to Ground—Water Withdrawal, Arvin—Maricopa area, California, Ben E. Lofgren. (E) Land Subsidence Due to Ground—Water Withdrawal in the Los Banos—Kettleman City Area, California, Part 1. Changes in the Hydrologic Environment Conducive to Subsidence, by William B. Bull and Raymond E. Miller. (F) Land Subsidence Due to Ground-Water Withdrawal in the Los Banos—Kettleman City Area, California Part 2. Subsidence and Compaction of Deposits, By William B. Bull. (G) Land Subsidence Due to Ground—Water Withdrawal in the Los Banos—Kettleman City Area, California, Part 3. Interrelations of Water—Level Change, Change in Aquifer-System Thickness and Subsidence, by William B. Bull and Joseph F. Poland. (H) Land Subsidence in the San Joaquin Valley, California, as of 1972, by J. F. Poland, B. E. Lofgren, R. L. Ireland, and R. G. Pugh. (I) Land Subsidence in the San Joaquin Valley, California, as of 1980, by R. L. Ireland, J. F. Poland, and F. S. Riley. ' GPO 787-042/130 (DE—I’D" 77o 7DAY v,437vE Land Subsidence Due to Ground-Water Withdrawal in the Los Banos-Kettlernan City Area, California Part 1. Changes in The Hydrologic Environment Conducive to Subsidence GEOLOGICAL SURVEY PROFESSIONAL PAPER 437—E Prepared in cooperation with the California Department of Water Resources 15] . ”11‘ i H ".A.’.:=‘ 4‘23! " "’4’ E i 'i i a i Land Subsidence Due to Ground—Water Withdrawal in the Los Banos-Kettlernan City Area, California Part 1. Changes in the Hydrologic Environment Conducive to Subsidence By WILLIAM B. BULL and RAYMOND E. MILLER STUDIES OF LAND SUBSIDENCE GEOLOGICAL SURVEY PROFESSIONAL PAPER 437—E Prepared in cooperation with the California Department of Water Resources A description of the ground—water reservoir and the great stress imposed on the aquifer system by man’s mining of ground water UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON:1975 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress Cataloging in Publication Data Bull, William B. 1930— Land subsidence due to ground-water withdrawal in the Los Banos—Kettleman City area, California. (Studies of land subsidence) (Geological Survey Professional Paper 437—E—G) Pt. 2 by W. B. Bull; pt. 3 by W. B. Bull and J. F. Poland. Includes bibliographies and indexes. CONTENTS: pt. 1. Changes in the hydrologic environment conducive to subsidence—pt. 2. Subsidence and compaction of deposits. [etc] Supt. of Docs. No.: I 19.162437—E 1. Subsidences (Earth movements)—California—San Joaquin Valley. 2. Aquifers—Califomia—San Joaquin Valley. 3. Water, Underground—California—San Joaquin Valley. 1. Miller, Raymond E. II. Poland, Joseph Fairfield, 1908— 111. California. Dept. of Water Resources. IV. Title. V. Series. V1. Series: United States. Geological Survey. Professional Paper 437—E—G. QE75.P9 No. 437—E—G [GB485.C2] 557.3'08s[551.3'5] 7428239 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, DC. 20402 Stock Number 024—001—02608 CONTENTS Page Page Abstract __________________________________________________ E1 Description of the ground-water reservoir—Continued Introduction ______________________________________________ 1 Corcoran Clay Member of the Tulare Formation _________ E19 Inter-Agency Committee on Land Subsidence ____________ 2 Lower zone ____________________________________________ 19 Cooperative and Federal subsidence programs __________ 6 Physical and hydrologic character __________________ 23 Scope of field and laboratory work __________________ 6 Productivity ______________________________________ 25 Field program ________________________________ 6 Chemical character of water ________________________ 29 Laboratory program __________________________ 7 Saline water bOdy ———————————————————————————————————— 32 Natural flow system __________________________________ 32 Purposes 0f report """""""""""""""""" 7 Changes in the hydrologic environment caused by man ______ 34 Acknowledgments """""""""""""""""" History of ground-water development __________________ 34 Definitions "“j ““““““““““““““““““““““““““ 8 Trends in total ground-water pumpage ______________ 36 Geographlc setting _ ““““““““““““““““““““““ 8 Changes in ground-water levels ________________________ 39 Land subs1dence “““““““““““““““““““““ The water table __________________________________ 39 Compaction “"““‘”““i “““““““““““““ 9 The upper-zone semiconfined to confined aquifer Stresses tending to cause compactlon '. _____________________ 11 system ___________________________________________ 43 Description of the ground-water reserV01r __________________ 12 The lower-zone aquifer system ______________________ 45 General features """""""""""""""""""" 12 Changes in the potentiometric surface .......... 46 Upper zone ““““““““““““““““““““““““ 14 Seasonal fluctuation of the potentiometric level_- 59 Physical character ________________________________ 17 History of head decline ________________________ 61 Productivity ______________________________________ 17 Summary and conclusions __________________________________ 65 Chemical character of water ________________________ 17 References cited __________________________________________ 66 Index ____________________________________________________ 69 ILLUSTRATIONS Page FIGURE 1—4. Maps showing 1. Principal areas of land subsidence in California, due to ground-water withdrawal __________________________ E3 2. Topographic features __________________________________________________________________________________ 4 3. The boundaries, bench marks, observation wells, compaction recorders, core holes, and lines of sections referred to in this report _____________________________________________________________________________________ 5 4. Land subsidence, 1920—28 to 1966 ______________________________________________________________________ 10 5. Graph showing subsidence and artesian-head decline near bench mark GWM59 __________________________________ 11 6. Diagram of compaction-recorder installation ____________________________________________________________________ 11 7. Cross sections showing well-yield factors and depositional environments of the aquifer systems ____________________ 13 8. Longitudinal section showing general hydrologic units __________________________________________________________ 14 9. Cross sections showing general hydrologic units ________________________________________________________________ 15 10—13. Maps showing 10. General variation in the amount of water pumped from the lower zone or its stratigraphic equivalent __________ 16 11. Thickness and extent of the Sierra Sand overlying the Corcoran Clay Member of the Tulare Formation _________ 18 12. Depth to the base of the Corcoran Clay Member of the Tulare Formation __________________________________ 20 13. Structure of the Corcoran Clay Member of the Tulare Formation __________________________________________ 21 14. Graphs showing variation in the hydraulic continuity of the lower zone __________________________________________ 22 15—19. Maps showing 15. Areas in which part of ground water is pumped from pre-Tulare deposits of Pliocene age __________________ 24 16. Yield factors and types of lower-zone deposits ____________________________________________________________ 26 17. Thickness of the fresh-water-bearing deposits of the lower zone __________________________________________ 28 18. Maximum thickness of the perforated interval of the lower zone __________________________________________ 30 19. Variation in dissolved solids of the lower-zone water ____________________________________ _ _______________ 31 III IV FIGURE CONTENTS Page 20. Diagrams showing change in the natural-flow conditions in the central San Joaquin Valley ______________________ E33 21. Map showing areas of early ground-water development __________________________________________________________ 35 22. iMap showing increase in irrigated land ________________________________________________________________________ 37 23. graph showing estimated ground-water pumpage, 1935—66 ______________________________________________________ 38 24. Hydrographs of upper- and lower-zone piezometers at the Yearout site __________________________________________ 39 25. Map showing depth to shallow ground water, 1965 ______________________________________________________________ 41 26. Map showing change in depth to the water table, 1951—65 ______________________________________________________ 42 27—30. Hydrographs of 27. Wells perforated in the unconfined zone ________________________________________________________________ 43 28. Upper-zone piezometers at 15/ 14—15E __________________________________________________________________ 44 29. Wells perforated in the upper zone ______________________________________________________ 1 _______________ 44 30. Wells perforated in both the upper and lower zones ______________________________________________________ 45 31. Water—level contours for the lower zone or its stratigraphic equivalent, 1926 ______________________________________ 47 32. Water-level contours for the lower water-bearing zone, 1943 ____________________________________________________ 48 33. Minimum altitude of the potentiometric surface of the lower zone as of 1960 ______________________________________ 49 34. Map showing artesian head of the lower zone as of May 1960 ____________________________________________________ 51 35. Water-level contours for the lower-water-bearing zone, December 1962 __________________________________________ 52 36. Generalized water-level :contours for the lower zone, December 1965' ____________________________________________ 53 37—40. Graphs showing change in 37. Slope of the potentiometric surface of the lower zone southwest of Five Points, 1906—66 ____________________ 54 38. Slope of the potentiometric surface of the lower zone southwest of Firebaugh, 1906—66 ____________________ 54 39. Altitude of the lower-zone potentiometric surface, 1943—66, Tumey Hills to Mendota ______________________ 55 40. Altitude of the lower-zone potentiometric surface, 1943—66, Anticline Ridge to Fresno Slough ________________ 56 41—43. Maps showing 41. Decline in the altitude of the potentiometric surface of the lower zone, 1943—60 ____________________________ 57 42. Change in altitude of the lower-zone potentiometric surface between December 1962 and December 1965 ____________________________________________________________________________________ 58 43. Seasonal decline in the altitude of the potentiometric surface of the lower zone, December 1965 to August 1966 ____________________________________________________________________________________ 60 44. Graph showing variation in seasonal fluctuation of water levels in lower-zone wells in the central part of the Los Banos-Kettleman City area ______________________________________________________________ 61 45. Long-term hydrographs of lower-zone wells -1-1-1“________________________________,,,,1__1_____11_'_____ 62 46. Hydrograph of irrigation well tapping the Etchegoin and San Joaquin Formations _________________________ 63 47. Diagram showing trends of lower-zone pumping levels ___________________________________________________ 64 TABLES Page TABLE 1. Relation of yield factors to types of upper-zone deposits ____________________________________________________ E17 2. Relation of yield factors to types of lower-zone deposits ____________________________________________________ 25 3. Estimated ground-water pumpage, 1935—66, Los Banos—Kettleman City area ________________________________ 36 STUDIES OF LAND SUBSIDENCE LAND SUBSIDENCE DUE TO EEBEVD-WATER WITHDRAWAL IN THE LOS BANOS-KETTLEMAN CITY AREA, CALIFORNIA PART 1. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE By WILLIAM B. BULL and RAYMOND E. MILLER ABSTRACT About 500 to 2,000 feet of unconsolidated flood-plain, alluvial-fan, lacustrine, deltaic, and marine deposits are compacting at accelerated rates because of man’s changes in the hydrologic environment in the west-central San Joaquin Valley. Ground-water pumping has in- creased the stresses tending to compact the deposits by as much as 50 percent. Three basic hydrologic units comprise the ground-water reservoir between Los Banos and Kettleman City. An upper-zone aquifer sys- tem, 100—900 feet thick, extends from the land surface to the top of the second unit. It is a lacustrine confining clay. The upper zone consists mainly of poorly permeable alluvial-fan deposits derived from the Diablo Range that contain semiconfined water of poor quality. Little water is pumped from the fan deposits; however, water of good quality is pumped from an extensive wedge of arkosic, micaceous sands. These sands are flood-plain deposits derived from the Sierra Nevada that extend 4—10 miles west of the valley trough along the full reach of the area. The lacustrine aquiclude, the Corcoran Clay Member of the Tulare Formation, extends beneath the entire study area except for the southwestern part adjacent to the Diablo Range. The third hydrologic unit, the confined aquifer system of the lower zone, supplies about three-fourths of the ground water pumped and is the zone in which 50-95 percent of the compaction causing the subsi- dence occurs. The lower zone consists mainly of flood-plain deposits in the northern part, alluvial-fan deposits in the southern part, and diverse continental to marine deposits in the central part of the area. The thickness of the fresh-water bearing deposits and the perfo- rated interval of the deposits below the Corcoran rarely are the same. Some wells that have sufficient yields bottom 1,000 feet above the base of the fresh water. In other areas, 3,000-foot wells obtain a sufficient yield only by withdrawing part of their water from deep brackish-water-bearing marine deposits. The sodium-sulfate water of the lower zone indicates that the con- nate water has been flushed out of the marine and Sierra sands. Maximum concentrations of dissolved solids in the well water occur opposite the mouths of the two major streams and in the area of pumping from the marine sand. Initially the lower-zone potentiometric surface sloped gently from the bordering mountains to the valley trough where it was more than 20 feet above the land surface. Agricultural development has resulted in more than a million acre-feet of water being pumped from the ground-water reservoir each year since 1951; has lowered the potentiometric surface as much as 600 feet; has reversed an eastward gradient in the study area of 2—5 feet per mile to a westward gradient of 30 feet per mile; and has caused water levels to decline below the base of the Corcoran adjacent to the Diablo Range. The steep westward gradient of the lower-zone potentiometric sur- face has increased the recharge t0 the area. Pumpage stopped increas- ing in the early 1950’s when most of the land had been developed. By the early 1960’s, a rough balance between the amount of water being pumped from the lower zone and the amounts of water derived from compaction, recharge, and storage was obtained for most of the area. The potentiometric surface did not steepen further, and artesian-head decline ceased or decreased to rates of less than 5 feet per year in most of the area. Applied stresses on the lower zone have been greatly increased by the large historic decline of artesian head but have not been affected appreciably by water-table changes. Water-table rises of as much as 100 feet and declines of as much as 350 feet locally have caused large changes in applied stress on the upper-zone deposits. Water-table rise or decline causes little net change in applied stress on the lower zone because concurrent seepage stress changes more than offset the ef- fects of buoyancy change and the effects of change in the stress condi- tion of part of the contained water that occur when the degree of saturation is changed. Change to a water-table condition below the Corcoran decreases the future rate of increase in applied stress from 1.0—0.8 foot of water per additional foot of lower-zone water-level decline. INTRODUCTION By increasing the stress tending to compact the un- consolidated deposits by as much as 50 percent, man has created what is believed to be the world’s largest area of E1 E2 intense land subsidence in the west-central part of the San Joaquin Valley. Withdrawal of ground water for agriculture has caused more than 2,000 square miles to subside more than 1 foot. As of 1966, the area that had subsided more than 10 feet was 70 miles long and ex- tended 500 square miles. Maximum subsidence was 26‘ feet. Water-level changes in the aquifer systems have in- creased the applied stresses on the deposits and have caused compaction of the aquifer systems. Detailed knowledge of the interrelations of water-level change, change in thickness of the aquifer system, and the con- current changes in the altitude of the land surface is necessary for a more complete understanding of the mechanics of aquifer systems, compaction of sediments, and for the development of adequate criteria for the prediction of future land subsidence. The hydrologic environment and the changes man has made in it to cause land subsidence—which are the main topics of this paper—will be presented for one of four major areas of intense land subsidence caused by ground-water withdrawal in California. The general location of the Los Banos—Kettleman City subsidence area, and its geographic relation to the three other subsidence areas is shown in figure 1. The topographic and cultural features of the Los Banos—Kettleman City area and part of the area to the northeast of the study area of this paper are shown in figure 2. All the place names used in this paper also are shown in figure 2. The boundaries of the Los Banos—Kettleman City study area and the lines of sections and profiles referred to in this paper are shown in figure 3. The boundary of deformed rocks at the edge of the Diablo Range foothills is the southwestern boundary of the study area, al- though small parts of the area of deformed rocks sub- sided 1—2 feet during the 1943—66 period. The south- eastern boundary of the area is State Highway 41 on the northwest side of Tulare Lake bed between Kettleman City and Stratford. Small amounts of subsidence have occurred farther to the east between the Los Banos— Kettleman City and Tulare-Wasco subsidence areas (fig. 1). The northern boundary of the study area is State Highway 152 which passes through the town of Los Banos. The northeastern boundary, as originally defined (Inter—Agency Comm., 1958), for most aspects of this paper is the San Joaquin River, Fresno Slough, and the Kings River. However, as much as 8 feet of subsidence has occurred east of the trough of the valley. Therefore, in discussions STUDIES OF LAND SUBSIDENCE of the amount and extent of subsidence, the 1-foot sub- sidence line shown in figure 4 provides a better definition of the eastern boundary of the system being affected by appreciable compaction. Geologic and hy- drologic aspects east of the valley trough will be dis- cussed also. The effects of land subsidence have become increas- ingly costly in the study area, which is traversed by several canals of large capacity and low gradient. One canal, the San Luis Canal, is part of the California Aqueduct, which is the major canal for transporting water from areas of abundant water in northern California to areas needing water in the San Joaquin Valley and southern California. The amounts, rates, and distribution of subsidence pose serious problems in the construction and maintenance of the canals and their extensive distribution systems. Subsidence also poses problems for local water-distribution, sewage dis- posal, and drainage systems. A major drain just west of the present trough of the valley will be built to remove drainage water of poor quality and to assist in main- taining a salt balance. Another major expense resulting from subsidence is the damage that occurs to well cas- ings as the sediments adjacent to the wells compact to cause compressional casing failures. INTER-AGENCY COMMITTEE ON LAND SUBSIDENCE As a result of the problems posed by subsidence, the Inter-Agency Committee on Land Subsidence in the San Joaquin Valley was formed in 1954 with J. F. Po- land of the US. Geological Survey as its chairman. The purpose of the committee was to plan and coordinate a program that would provide information about the ex- tent, magnitude, rates, and causes of the various types of land subsidence in the San Joaquin Valley (Inter- Agency Committee, 1958, p. 21). Other objectives of the program were to estimate future subsidence under as- sumed conditions and to suggest ways of alleviating subsidence. Representatives from the Geological Sur- vey, US. Bureau of Reclamation, US. Coast and Geo- detic Survey, (now National Geodetic Survey of the National Ocean Survey), US. Army Corps of En- gineers. Soil Conservation Service, the California Department of Water Resources, California Division of Highways, University of California at Davis, and Stan- ford University composed this committee. A proposed program of investigation was prepared by the Inter-Agency Committee (1955), and in 1958 a prog- ress report on land-subsidence investigations in the San Joaquin Valley was published. 42° 40° 36° CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE 122° 120° 118° 116° l I E3 O \ \ V \ \ \ v x) K \ \ 1 , ‘\ o 100 MILES K \ \ o 100 KILOMETHES K \ s \\ San Francisco \ \ \ /7 O \ Santa Clara Valley \ L \ \ area \ \ (p \ \ \ \ \ Fresno ‘ O \ \ 4’ \ Los Banos— \ Kettleman City \ area f \ Tulare—Wasco \ area \ «e 4 \ V \ O \x «(x ,x Arvin—Maricopa area 0 O OLos Angeles 0 6‘ 7 4, .. — / — '— / FIGURE 1.———Principal areas of land subsidence in California due to ground-water withdrawal. Outline of Central Valley dashed; areas of major subsidence shaded black; areas of lesser subsidence hachured. E4 STUDIES OF LAND SUBSIDENCE 120°30’ 120°oo' 33 I Los Banos 15 Lo: / ° I , Dos 37 00 ' Palos / /\_Fr/e_:10_. -\,__ 120 33 31 09/, v: o 0 v (70 / 7* O '3; 7’ " Q 70‘ Ora Loma ’60 o 0‘ Q"? N?! Firebaugh <5“? ’0 2"" $8) fig? WAGON FRESNO /(€:;\00/ ego "\,—‘ «,\ v“ ,9!“ ’37 e190 Mendota ._L o 1, 180 \ / 00 ”3’0 so 76) 58‘ “‘5 erman N (O '3; are \Te%° 41 ( . o (0‘ me 7Q? \n o J Tranquillity°\ Panoch o ‘ 90 0 San Joaquin Creek 6:04, 000 \ (<55!— \~ 41 ‘y‘ O’Voq ‘ ~ 0 I _ 0/ 0 oCantua Creek ‘ 4 __ 36 30 «‘1 l°o \fi ’9 °¢ ‘6 ~ .‘ g ‘7¢ am ’33 620 came \ - Five Poin s i 099;: 3/“ % . a |_‘._ _ _ _ _ '_,'\_, 6’0 I \7 If 0 33 l K / EXPLANATION <08 :[ 4a Le oore . ly/(<8 2% 0 Boundary of deformed Tn “mks Skunk Hollow I . \\ \ ' JD ' +£— 0.9 W th n San Luis Canal—California 0"" / \ es 3"" o I Aqueduct Cr}; ' I X 5 J Strat— M SANT 00 find ‘ $0 IOO Cbalinga “f 8 65/65 0 5 1o 15 MILES \° g {9% n O 5 1O 15 KILOMETRES ‘Nofl‘fifi‘ é TULARE CONTOUR INTERVAL 40 FEET C' o DATUM IS MEAN SEA LEVEL LAKE 44'” K 1 / ett eman 36°00’ l I’ 33 <49 1 City BED Base from U.S. Geological Survey C Valley map, 1:250,000, 1958 entral FIGURE 2,—Topog‘raphic features of the Los Banos—Kettleman City area 37°00 36°30’ 36°00’ CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE E5 R IO E. II 12 13120°30’ 14 15 16 I7 120°00' 19 as I I " I I ,5 I Lq's BanOS I I I I I 15 ’ I | I I ‘7 I I I I s ____I____ I _ __I /__ _I _______ I _______ I _______ I__ I I I ‘D‘os 7" I I I | m I Palos lo I | . . resn ~._ I \I ' I I | . \__ ~I_/- m__I_\/_ I\_Rtver __ 33 I De] I I I w I I I ’4 ____I ____I ______ I_ 'ZL_____I _______ I _______ I _______ _ _ 9 | ro Lolnswasite | I | I I (' _ ‘” 1302 I ”9'2 “1 6I I I I I I /@ I 2 I I I I / I I O | . I I I I I I 32A2 9’29, Fuebaulgh I I I 0 I I I I —§AQ+7— $Q—Ti4yla— ——————— IL — — —+ ——————— T ———————————— ’ P $00 e0 | 3‘ ‘ I I I, I 17N2 VearoutIsIte U 9 o I I A0 4,3. 0/ 22N1 I 350115 J I | I l I_ O? ’9, I Cantua Creek | EXPLANATION 61 °o __II__ 2 __J ______ ,4____ _,._ o 6‘ 34m 5 I I (I, 6 ’27 ’( I 18E1 I ' “302 21N2 Boundary of deformed rocks $0 (‘I‘ I i Ie <0 $, I O V o o o I I o o o | I 0 Boundary of the Los Banos- _ 551 ___ “ _ ___.I ______ I —————— —II—§ - —— Kettleman City area 00 I 'E: I 17E1 I . \ .17P1 ’o I & 0‘5MII Core hole and well number <9< 33 I I 7N1\1701 I A (/6 Was-Qt! I Compaction recorder; if more than one, /~/,< --- ————— fire—1’0— number indicated inside symbol ‘5‘ I I3N1,2O I 16N1 23P2I I . O . El () | 22J1,2\ I Observation well and well number; If more I I 26N1 than one, number indicated inside symbol / _ ___... 3Tl____estha_vgn 35 05E1 // gt, I Hurono I Irrigation well from which water—level re- a, o (/4, I I 11013 3 cord has been obtained, and well number PL ASANT 6‘ . I I Xewmss I I I 33m I Bench mark and number Coaimai___ — ___—TL 69% A A' VAII.LEY . I I Q {I} : I Line of geologic section or hydrologic pro- ) file or section shown in succeeding illustra- Irs M2O tions 7‘» I ' "I ’ o 5 1o 15 MILES I «MI 0 5 1o 15 KILOMETRES ,I’ 33 I<(~S‘ Base from US. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 3,—The boundaries, bench marks, observation wells, compaction recorders, core holes, and lines of sections referred to in this report. E6 COOPERATIVE AND FEDERAL SUBSIDENCE PROGRAMS One result of the inter-agency cooperation was the initiation in 1956 of an intensive study of land sub- sidence in the San Joaquin Valley, by the Geological Survey, in financial cooperation with the California Department of Water Resources. The objectives of the cooperative subsidence program, of which this report is one result, were to define the rate, magnitude, and ex- tent of subsidence through a vertical-control measure— ment program; to determine the various causes of sub- sidence, and the depth intervals in which the compac- tion was occurring; to furnish criteria for the prediction of future subsidence; and to determine whether any part of the subsidence is reversible, and, if so, to what extent. In 1956, the Geological Survey also began a federally financed investigation of the mechanics of aquifer sys- tems: the fieldwork was concentrated chiefly in the San Joaquin and Santa Clara Valleys in California. It was recognized that those areas of active subsidence due to water-level change offered an unexcelled opportunity to study compaction of sediments in response to increase in effective stress. Objectives of the Federal program were to determine the principles controlling the change in aquifer-system thickness resulting from change in grain—to—grain load, and to appraise the meaning and utility of the storage coefficient in compactible aquifer systems. Within the Los Banos—Kettleman City area, both the change in stresses causing compaction of the saturated deposits and the change in thickness of the deposits can be measured at many sites. SCOPE OF FIELD AND LABORATORY WORK Many of the results of the cooperative and federally funded investigations are of mutual benefit, as is evi- dent from the following brief description of types of facts gathered to assess compaction of saturated deposits due to changes in water levels. FIELD PROGRAM A vital supporting program for the subsidence inves— tigations has been the periodic surveying of a network of bench marks by the Coast and Geodetic Survey to determine changes in altitude. Starting in 1955 and continuing until 1959, the network was surveyed every 2 years, and since 1959 the bench marks have been surveyed every 3 years. A method (see section on “Compaction”) was de- veloped for the measurement of compaction within specified depth intervals. Both unused irrigation wells and specially drilled wells were used for this purpose. The well-numbering system identifies wells accord- ing to their location in the township and range grid used for subdivision of public land. For example, well 14/ 13—1 1D6 designates the sixth well assigned a STUDIES OF LAND SUBSIDENCE number in the NW% of the NW% of section 11, Town- ship 14 South, Range 13 East. The letters that are used to indicate the 40-acre subdivision of the section are as follows. D C B A E F G H M L K J N P Q R Because all the wells within the study area are south and east of the Mount Diablo base and meridian, the foregoing abbreviation of the township and range is sufficient. A well canvass was made in the study area west of the San Joaquin River and Fresno Slough. The descriptions of the 3,600 wells that were canvassed have been tabu- lated by Ireland (1963). Periodic water-level measurements have been made at the times of the winter or spring recovery highs to determine the position of the potentiometric surface of the principal confined aquifer system in the study area. Water levels were measured each year during the 1950’s and bench-mark surveys during the winters in the 1960’s. A problem peculiar to land-subsidence areas is that the altitude of the reference point changes with time for all water-level, electric log, core hole, and other data. Errors in data, such as altitudes of geologic or hy- drologic horizons, could be partially corrected by estab- lishing for each data site a history of reference-point altitude change. However, this procedure is not practi- cal and would introduce additional problems. One prob- lem would be how to prorate the depth to geologic hori- zons at different depths in a system in which the unit compaction varies with depth. Subsidence corrections would also lead to misinterpretation of data. For exam- ple, if the depth to the water table at a subsiding site did not change over a long time period, a hydrograph of the altitude of the water table, if corrected for subsidence during the period of record, would show an apparent decline in the water table and could be interpreted er- roneously as a decrease in storage. One possible procedure is to make an altitude ad- justment for the measuring points of wells at the time of each releveling. However, this method results in dis- placement of the plot of water-level altitude at each time of adjustment. The approach of the Geological Survey has been to use the land-surface altitudes established on topographic maps made in the 1920’s as the reference altitudes for CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE all measuring points. This approach introduces a gradually increasing error in all maps, sections, and hydrographs dependent on altitude that is equal to the amount of subsidence since the 1920’s. The error is of little concern in areas of less than 10 feet of subsidence when one considers the general order of accuracy of altitude of a rapidly changing potentiometric surface or the altitude of the top of the confining clay. The problem can be circumvented; for example, indicate the change in the position of the water table by using change in depth instead of change in altitude. Observation wells are measured by the Geological Survey throughout the study area to obtain information about the changes in the water table and the poten- tiometric levels in the confined aquifer systems above and below the principal confining bed. Some of the ob- servation wells are unused irrigation wells, but many are wells that have been drilled by the Survey and other agencies to obtain a specific type of water—level informa- tion. At least one observation well is situated at each compaction-recorder site. The wells that are referred to in this paper are shown in figure 3. Another major source of water-level information has been the records of the Pacific Gas and Electric Co. These records have provided long-term histories of water-level declines based on both static and pumping measurements. Many of the hydrographs used in this paper are based on these records. Measurements usuo ally are made at least once a year. The time of meas- urement may be anywhere in the seasonal fluctuation range but most commonly is during the summer pump- ing season. The measurements selected for the hydro- graphs in this paper are those made at the times of low-water levels—the times of maximum applied stress on the aquifer system. Since 1964, the power-company measurements have been supplemented by measuring selected wells at the time of the summer low-water level in late August. Regional geologic studies also were made of the Los Banos—Kettleman City area and the adjacent foothill belt to provide an appropriate framework for the studies of compaction and land subsidence. The classification and correlation of the subsurface geologic and hy- drologic units tapped by wells and the mapping of the continental deposits exposed in the foothills adjacent to the study area are described in detail in a report by Miller, Green, and Davis (1971). In addition to estab- lishing the areal extent of the various components of the aquifer systems, the regional geologic studies provided valuable basic information about the lithology, source, and mode of deposition of the deposits. In order to provide additional information about the petrology, and mode and source of deposition of the sediments, four core holes were drilled along the axis of E7 the subsidence trough at the Oro Loma, Mendota, Can- tua, and Huron sites by the Inter—Agency Committee. These multiple-purpose holes were also used to obtain electric logs and caliper logs. LABORATORY PROGRAM A laboratory program that was part of the Federally financed investigation was conducted at the Geological Survey’s hydrologic laboratory on cored samples to pro- vide information about the physical, hydrologic, and engineering properties of the sediments that are com- pacting in this and the three other subsidence areas shown in figure 1. Some of the test results most applica- ble to the studies of land subsidence are particle-size analyses, specific gravity and unit weight, porosity and void ratio, consolidation and rebound, and permeabil- ity. The results are reported by Johnson, Moston, and Morris (1968). The core samples also provided abundant samples for laboratory petrographic examination. The general pe- trology of the deposits and the details of the clay mineralogy are discussed by Meade (1967). In a major contribution, Meade (1968) relates the variations in overburden load and petrologic factors to the variations in pore volume and fabric of the sediments of several subsidence areas in central California. PURPOSES OF REPORT This report is part 1 of a series of three reports con- cerned with land subsidence due to ground-water with- drawal in the Los Banos—Kettleman City area. It de- scribes the subsurface hydrologic environment in 2,000 square miles of the west-central San Joaquin Valley. Within this scope, the report has two specific purposes. The first is to describe the extent, thickness, and hy- draulic character of the deposits comprising the two principal aquifer systems and the confining clay that separates them. The second purpose is to assess the changes caused by man in the hydrologic environment that have been responsible for the increase in applied stress, the compaction of the ground-water reservoir, and the concurrent subsidence. The bulk of the information presented in this paper concerns events that occurred before April 1966 which was the time of completion of a complete leveling of the bench—mark network by the Coast and Geodetic Survey. Some 1966—68 data are presented and discussed, but only to present facts that cannot be demonstrated with the earlier data. The authorship of this report is as follows. Mr. Miller prepared most of the section, “Description of the Ground-Water Reservoir.” Mr. Bull is responsible for the rest of the paper. Mr. Miller’s detailed and careful study of the geologic and hydrologic framework of the study area (Miller and others, 1971) has been very E8 helpful in the preparation of all subsequent reports on the Los Banos—Kettleman City area. Two other papers on the Los Banos—Kettleman City area were prepared by W. B. Bull as companion reports to this paper. Part 2 (Bull, 1974) “Subsidence and Com- paction of Deposits”) describes the subsidence due to artesian-head decline, and compaction of the ground- water reservoir; the paper also discusses the geologic factors influencing compaction of the saturated de- posits. Part 3 (Bull and Poland, 1974, "Interrelations of Water-Level Change, Change in Aquifer-System Thickness, and Subsidence”) uses the data and in- terpretation' in Parts 1 and 2 as a basis for discussing some of the principles of mechanics of aquifer systems. ACKNOWLEDGMENTS The cooperation of numerous ranchers, landowners, and companies is acknowledged for supplying essential information to the subsidence project and for giving permission to install and maintain wells and equipment for obtaining water-level and compaction information. Particular assistance was given by the Pacific Gas and Electric Co., Westlands Water District, and Russell Gif- fen, Inc. The financial cooperation of the California Depart- ment of Water Resources made this study possible, and information provided by the US. Bureau of Reclama- tion from core holes and observation wells contributed significantly to the essential data. This work could not have been completed without the discussions, interest, and assistance of many people who have been associated with the land-subsidence studies of the Geological Survey since 1956. We ap- preciate the helpful discussions and review of the man- uscript by the Project Chief, J. F. Poland, and our col- leagues G. H. Davis, B. E. Lofgren, S. W. Lohman, and F. S. Riley. We enjoyed working together with R. L. Ireland and R. G. Pugh on a variety of jobs in the field and appreciate their extensive help in the collecting and assembling of field data. Particular credit is due Mr. Ireland for his meticulous care and thoughtful foresight in the installation and operation of the equipment for recording compaction and water—level changes during the entire period of record. DEFINITIONS The geologic and engineering literature contains a variety of terms that have been used to describe the processes and environmental conditions involved in the mechanics of stressed aquifer systems and of land sub- sidence due to withdrawal of subsurface fluids. The usage of certain of these terms in reports by the US. Geological Survey research staff investigating mechanics of aquifer systems and land subsidence is defined and explained in a glossary published sepa- rately (Poland and others, 1972). Several terms that STUDIES OF LAND SUBSIDENCE have developed as a result of the Survey’s investiga- tions are also defined in that glossary. The aquifer systems that have compacted sufficiently to produce significant subsidence in California and elsewhere are composed of unconsolidated to semicon- solidated clastic sediments. The definitions given in the published glossary are directed toward these types of sediments; they do not attempt to span the full range of rock types that contain and yield ground water. In defining the components of the compacting stresses, the contribution of membrane effects due to salinity or elec- trical gradients has been discounted as relatively insignificant in the areas studied. In this series of research reports, pressures or stresses causing compaction are usually expressed in equivalent "feet of water head” [1 foot of water =0.433 psi (pounds per square inch)]. ' A committee on redefinition of ground-water terms, composed of members of the Geological Survey, recently issued a report entitled “Definitions of Selected Ground-Water Terms” (Lohman and others, 1972). The reader is referred to that report for definitions of many ground-water terms. GEOGRAPHIC SETTING The area included in this paper includes about 2,000 square miles of the west side of the San Joaquin Valley adjacent to the Diablo Range in central California (figs. 2, 3). Most of the discussions will concern sites in the 1,500 square miles west of Fresno Slough, and the San Joaquin River between the towns of Los Banos and Kettleman City. However, the subsidence bowl extends far to the east of the trough of the valley (fig. 4). Between the trough of the valley and the Diablo Range to the southwest is a belt of coalescing alluvial fans 12—22 miles wide. The altitude at the base of this bajada ranges from 150 to 200 feet, from which the alluvial fans rise to altitudes of about 500-900 feet at their apexes. The slopes range from about 5 feet per mile near the base of the larger fans to about 150 feet per mile on the upper slopes of some of the small fans. Local relief gen- erally is less than 5 feet, except where stream channels are incised 10—40 feet. The Diablo Range to the southwest of the study area consists of several groups of foothills bordering the San Joaquin Valley and the main range, which rises to al- titudes of more than 5,000 feet about 10—15 miles from the valley. The core of the anticlinal part of the main range consists of deformed and slightly metamorphosed shale and graywacke of the Franciscan Formation of Jurassic to Late Cretaceous age and of ultrabasic rocks. The east flank of the range consists mainly of 20,000 feet of Cretaceous marine mudstone and sandstone. The foothill belt is underlain by anticlinally and monocli- CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE nally folded Cretaceous marine rocks, by easily eroded Tertiary marine rocks, and by Pliocene and Quaternary unconsolidated sediments. LAND SUBSIDENCE Changes in bench-mark altitudes in the Los Banos— Kettleman City area during the past five decades have been affected by tectonic movements, pumping of pe- troleum, and compaction due to wetting of moisture-deficient alluvial-fan deposits, but mainly have been caused by compaction of saturated deposits as a result of water-level change. The compaction due to wetting causes near-surface subsidence, which is superimposed on the compaction of the saturated deposits. About 130 square miles (fig. 4) have subsided; 3—10 feet of near-surface subsidence is common, and 10—15 feet of compaction due to wetting has occurred locally. Near-surface subsidence results chiefly from the compaction of deposits by an overbur- den load as the clay bond supporting the voids is weakened by water percolating through the deposits for the first time since burial. The amount of compaction due to wetting is dependent mainly on the overburden load, natural moisture conditions, and the type and amount of clay. Reports about near-surface subsidence within the study area include those by Lofgren (1960), and Bull (1964, 1972). Both the magnitude and extent of the subsidence due to artesian-head decline are larger than for the near-surface subsidence. Figure 4 shows the subsidence in the Los Banos—Kettleman City area between the time of the first topographic mapping in the early 1920’s, and the 1966 bench-mark leveling. The subsidence pattern is an elongate oval that is 90 miles long and 24 miles wide. As of 1966, more than 2,000 square miles had subsided more than 1 foot, and the area that had subsided more than 10 feet was 70 miles long and 7 miles wide. A maximum subsidence of about 26 feet had occurred 10 miles southwest of Men- dota. The histories of subsidence rates show that the rate of subsidence increased until about the mid-1950’s, but since then the rate of subsidence has decreased, but not so rapidly as the decrease in the rate of artesian-head decline. During the 1959—63 period, 480 square miles was subsiding more than 0.5 foot per year, and 63 square miles was subsiding more than 1.0 foot per year. An example of the change in land-surface altitude caused by artesian-head decline is shown in figure 5. Subsidence rates in the vicinity of bench mark GWM59 increased between 1940 and 1955 but since 1955 have undergone a continuing decrease in rate. The plot of artesian-head decline reveals a parallel history of ac- celerating and then decelerating rate of head decline. Since 1960 the summer low-water levels have shown E9 little decline, but subsidence has continued at a moder- ately rapid rate. Much of the subsidence since 1960 is interpreted as being the result of delayed compaction resulting from continued expulsion of water from fine-grained beds of low permeability years after pore- pressure decline had occurred in the aquifers adjacent to the aquicludes and aquitards (Bull and Poland, 1974). ' COMPACTION Special recorders operating in wells have been measuring most of the decrease in thickness of the aquifer system that has been responsible for the land subsidence. A diagrammatic sketch of one of the com- paction recorders is shown in figure 6. At well 19/16—23P2, the recorder is actually measuring casing shortening that results from the compaction of the adja- cent deposits. At other sites the anchor weight is set below the bottom of the casing, thereby allowing the compaction to be measured independently of the casing. For the recorder system shown in figure 6, a 300-pound anchor was set on the cement plug with a cable that was passed over sheaves at land surface, counterweighted, and linked to a recorder by a fine wire attached to the cable. The lAa-inch, 1 X 19 stranded, reverse—lay, un- coated stainless-steel cable resists corrosion, has low stretch and casing-cable friction characteristics, and has little tendency to untwist. Friction has been re— duced at the land surface by mounting ball-bearing sheaves in a teeter bar that can pivot about a fulcrum for short distances. The fine wire is passed over the drive sheave of a recorder, which records changes in the posi- tion of the cable clamp (fig. 6) relative to the concrete slab at a 1:1 scale. A 24:1 expanded-scale record is obtained by a second recorder (not shown in fig. 6) linked to the first by gears. A float-operated water-level recorder (not shown in fig. 6) is set on the table below the compaction recorders. The tension in the compaction cable is uniform only above the uppermost point of con— tact between the casing and the cable. In wells that have casing-cable friction, tension is less below the upper- most friction point than above it during compaction and is more during the periods of aquifer-system expansion. Thus, casing-cable contact not only introduces friction into the recorder system, but it also introduces a mechanical lag at those times when the direction of movement of the cable, relative to the casing, is re- versed. The mechanics of the compaction-recorder sys- tems and the locations of the compaction recorders and observation wells operated by the Geological Survey in the study area are described in Bull (1974). The proportion of the subsidence that is being mea- sured has decreased at some compaction—recorder sites. For example, at the Cantua site, the 2,000-foot compac- tion recorder measured 99 percent of the compaction E10 37°00’ 36°30’ 36°00’ STUDIES OF LAND SUBSIDENCE 120°30’ 120°00’ 33 Los Bano Dos Palos 33 0e, EXPLANATION Boundary of deformed rocks 6‘ Line of equal subsidence, in feet Dashed where approximately located. Com- piled chiefly as the sum of (1) a com- parison of topographic mapping by the U.S. Geological Survey done between 1920 and 28 and in 1955, and (2) level- ing of the U.S. Coast and Geodetic Sur- vey in 1955 and I 966. Controlled in part by leveling of] 943 and 1959 Boundary of near-surface subsidence areas as of 1961 a_)_ San Luis Canal section of the California Aqueduct 0 1O 15 MILES 0 5 10 15 KILOMETRES ~<\_€t=:".0/-..~\,__\/_.I\\_g.-m _ Madei'a '9 Fitebau gh 10 AQUIN endota\ 180 Wei-mane .. h) PL SANT Coalinga VALLEY TULARE LAKE 41 Kettleman BED City Base from U.S. Geological Survey Central Valley map, 11250.000, 1958 FIGURE 4.~Land subsidence, 1920—28 to 1966. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE 200 1 I Bench mark GWM59 — 0 Well 13/12-22N1 perforated 400- 400 — 1223 feet 300 Well 13/12-2201 perforated 602- 1090 feet SUBSIDENCE, IN FEET 500 - DEPTH TO PUMPING LEVEL BELOW LAND SURFACE, IN FEET 600 1940 1950 1960 FIGURE 5.—Subsidence and artesian-head decline near bench mark GWM59, causing subsidence between 1959 and 1963 and 88 per— cent between 1963 and 1966; it measured 79 percent of the subsidence that occurred between March 1966 and November 1967. The change in the percentage of sub- sidence measured suggests that pore-pressure decline and compaction are occurring at progressively greater depths below the anchor weight. The compaction rates are seasonal, they are most rapid during the late winter and the .summer when water levels are drawn down. The use of multiple compaction recorders at a site permits a determination of the unit compaction occur- ring at specific depth intervals. The annual unit com- paction has varied from zero for the 350—500 foot depth interval at the Oro Loma site to 0.00115 foot per foot per year in the 503—703 depth interval at the Cantua site. Casing-failure studies (W. E. Wilson, written com— mun., April 1968) indicate that little compaction is oc- curring in the upper 300 feet of deposits; that maximum unit compaction is occurring between 100 feet above the Corcoran and 400 feet below the Corcoran; and that only moderate amounts of unit compaction occur below a depth of 400 feet below the Corcoran. Many geologic factors influence the amounts and rates of compaction (see Part 2). The following geologic conditions promote large amounts of rapid compaction: a confined aquifer system that is undergoing large de- clines in head; a minimum overburden load that has compacted the deposits in the geologic past; many thin beds of montmorillonite clay with absorbed sodium in- terbedded with permeable, highly micaceous sands that have a large lateral extent. Meade (1968, p. 28) also points out that the presence of diatoms increases the compressibility of the deposits. STRESSES TENDING TO CAUSE COMPACTION The stress tending to cause compaction of all deposits is the grain-to-grain load that is transmitted to a given E11 /Hecorder Sheaves ,—C)—| mounted in teeter bar ‘ / V-’Compactuon tape . —\----I /Stee| table Counterweights /clamp Concrete slab Bench mark 5 A __ / Cable, 1/8»inch stainless/f". steel, 1 x 19 stranded " , reverse lav (IHH' (7...... . .-.. Well casing n. 4 to 13 inches '(1 Anchor weight, :':\-’: '.._ 200 to 300 pou ndskfl .- . FIGURE 6.#Diagram of compaction-recorder installation. bed as the result of the sum of all stress-producing factors in the overlying stratigraphic section. In the Los Banos—Kettleman City area and elsewhere, stress changes caused by man’s changes of the hydrologic en— vironment are superimposed on the natural stresses tending to compact the deposits. The ratio of manmade to natural applied stress varies considerably with geo- graphic area and depth, but it can be large. For exam— ple, the natural applied stress at the 600-foot depth at the Cantua recorder site was increased from about 330 to about 500 psi as the result of about 400 feet of artesian-head decline. About a 52 percent increase in applied stress has occurred as a result of man’s change in the hydrologic environment at the 600-foot depth level. However, at the 200-foot depth, no change in applied stress has occurred. The ZOO-foot depth is about 10 feet below the water table which has not changed position appreciably at the site during the past 60 years. Water-level changes in both the confined and unconfined parts of the aquifer systems have altered the E12 preexisting distribution of stresses. Changes in applied stress that result from changes in the hydrologic envi- ronment are concurrent with the water-level changes. Applied stresses become effective stresses only as rapidly as water can be expelled from a bed of a given lithology. A stress that does not tend to cause compaction is a neutral or hydrostatic stress. This stress, which is the weight of the interstitial water, is transmitted down- ward through the water between the grains. The hydro- static stress is considered neutral because, although it tends to compress each grain, it does not tend to change the grain—to-grain relationships significantly. The basic theory regarding the stresses produced by water-level change within an aquifer system has been discussed in detail by Lofgren (1968) and by Poland and Davis (1969). The computation of change in applied stress in the Los Banos—Kettleman City area studies is different with respect to item 4 in the following para- graph than the mode of computation used by Lofgren. For a complete discussion of the analysis of stress changes resulting from water-level change within the study area, the reader is referred to Part 3 (Bull and Poland, 1974). The following summary is included here in order to provide the reader with a brief background regarding the four components of change in applied stress and to demonstrate the need for detailed informa- tion about changes in water level in subsidence areas. Changes in water level resulting from pumping of ground water and irrigation have changed the applied stress tending to compress the deposits in several differ— ent ways. Change in total stress applied to a confined zone is the algebraic sum of the following stresses: 1. A seepage stress that is equal to the head differential caused by change in artesian head within the confined zone. 2. A seepage stress that is equal to the head differential caused by change in the position of the water table. 3. A stress caused by change in buoyancy of the de- posits within the depth interval that is being de- watered, or saturated, as a result of water-table change. 4. A stress caused by part of the pore water being changed from a condition of neutral stress to ap- plied stress, or vice versa, that occurs within the depth interval being affected by water-table change. The magnitudes of the various stress components on the confined zone, expressed in feet of water (1 foot of water = 0.43 psi), are as follows: an assumed porosity of 0.4, a specific gravity of 2.70, and an average moisture con- tent of the dewatered deposits of 0.2 the volume. Seep- age stresses resulting from either artesian-head change or change in water-table position cause 1 foot of change in applied stress per foot of change in head differential. STUDIES OF LAND SUBSIDENCE Buoyant changes cause 0.6 foot of change in applied stress per foot of water-table change. Change in the stress condition of part of the pore water causes 0.2 foot of change in applied stress per foot of water-table change. The effects of changes in buoyant support and in the stress condition of the pore water tend to cancel the effect of change in seepage stress caused by water- table change. The net effect of water-table change on the applied stress on the confined zone is an increase of 0.2 foot of water per foot of water-table rise and a de- crease of 0.2 foot of water per foot of water-table decline. DESCRIPTION OF THE GROUND-WATER RESERVOIR GENERAL FEATURES The 500 to more than 3,000 feet of poorly to moder- ately consolidated sediments that form the ground- water reservoir in the Los Banos—Kettleman City area was deposited in the San Joaquin Valley geosynclinal trough since late Pliocene time. As shown in figure 7, these sediments consist primarily of flood-plain, alluvial-fan, and lacustrine deposits. Some deeply buried deltaic sediments occur in the southern part of the area. Most of these deposits are part of the Tulare Formation, which is overlain by additional alluvium and underlain by Pliocene littoral and estuarine de- posits of the San Joaquin and Etchegoin Formations. The Pleistocene deposits accumulated rapidly as a re- sult of uplift and erosion in the Diablo Range and uplift and glacial scouring in the Sierra Nevada. The rapid rate of deposition is one reason for the poorly consoli- dated nature of most of the deposits. The subsurface geology of the fresh-water-bearing deposits is complex when the deposits are differentiated with respect to source, environment of deposition, and lithology. The subsurface geology is described by Miller, Green, and Davis (1971). Fortunately, the hydrologic units are not so complex as the geologic units. As pointed out by Davis and Po- land (1957, p. 421), a general threefold hydrologic sub- division of the continental fresh-water-bearing deposits can be made as follows: An upper unit, extending from the land surface to the top of the relatively impervious Corcoran Clay Member of the Tulare Formation at a depth ranging from less than 100 to 900 feet below the land surface; the Corcoran Clay Member ranging in thickness from a featheredge to 120 feet, which sepa- rates waters of substantially different pressures and chemical qualities; and a lower unit, 400 to more than 2,000 feet thick that extends down to the main saline water body. The two fresh-water-bearing units are re- ferred to as the upper zone and lower zones, and the lacustrine clay that separates the two zones is com- monly referred to as the Corcoran. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE E13 B B’ 1200' Tumey Hills — EXPLANAT‘ON 1 . la . — 35° 80° , (95) ‘00, _ Fresno Slough Well for which yield factor and water SEA Alluvial-fan deposits temperature is shown LEVEL Number above the line is the yield 400, _ factor which is the specific capacity (gallons per minute per foot of . drawdown) times 100 divided by 30° _ the thickness, in feet,of perforated interval; number below the line is 1200' - the water temperature in degrees . Celsius (0 F in parentheses) at the 1600' J 53""9 Win” bOdV point of discharge from the well. The position of perforated casing is 2000' ‘ “‘ ‘ by heavy line segment. Wells more than a mile from the profile are shown by dashed line: C C, E3 1200' — — Mouth of Cantua Creek Confining clay 800‘ — ' layer 400' — cant“ Creek Fresnol Slough — SEA l 1i; // r f 7.), iz—fié 1 125 E /— (u’.-° LEVEL (75 E Flood-plain deposits l(;?-,E(mic:geous:;andl =42}; I 5 == 4 ' — xizzzx - =====-— 00 / 12.7 :"1:6§:::: _.___6 o 800' — 1200' — Chiefly flood-plain 1600' -i deposits — 2000’ - Saline water body — 2400' 4 '— 2800' E E' 1200' — - Anticline Ridge 800' ~ — 40°. _ \ KingsI River — ( SEA I A xXLL; . ' L p======== LEVEL \ 2-3 " Alluvial-V:;/—l_._a<:l1\st‘_ine sand deposits / I 5:; Flood-plain deposits Ea: g 400'- 36° ~~1T===;;\ I {12:31:}:XXXXXXXXXX ==_ \ 97) 1.3 Tr, 3 3 ii / 5": 2 3.5 ‘ _ 800' .4 26° fan 31o ‘/ L31 \ (79) (32) 30° (88) / / 4 3 , (s7) , (86) / / 3 3 ‘ 1200 — deposits \ \ 31° 32° _ \ / (88) (39) Chieflv deltaie deposits 1600’ — Chiefly flood- _ plain i _ deposits 2000' - — 2400' ~ 2800' — .W— . . 5f. ‘ ' Saline water body 3200' \.—.__ __ . VERTICAL EXAGGERATION X 13 0 1 2 3 MILES D 1 2 3 KlLOMETRES For location of sections, see figure 3 FIGURE 7.——Cross sections showing well-yield factors and depositional environments of the aquifer systems, Lines of sections shown in figure 3. (From Miller and others, 1971, fig. 15.) The three hydrologic units are shown in figures 8 and report (Miller and others, 1971). 9, and the location of the sections is shown in figure 3. Most of the ground water pumped in the Los Banos The detailed geologic sections on which these sections —Kettleman City area is withdrawn from the lower are based have been presented by Miller in another zone. An accurate estimate of the proportion of water E14 800' Fresno—Merced County line K .— SEA LEVEL Fotentlometnc sur 855 ,flgt’egable fi—rF~_—* SEMICONFINED AOUIFER SYSTEM STUDIES OF LAND SUBSIDENCE Fresno—Kings County line Cantua Creek(town) (upper um.) M_ax 1960 _ \ SESXSXX‘IYW{SQ\Z\\XC\\:-\ - murmtfiktssr - \ \ - _ fl , _ :v XX: \\\\\:::::XXQ\.\Z\:\‘::: 33\\\\::Cm33::< Corcoran Clay Member Principal confining bed 800' r “ ." CONFINED (Lower zone) 1600' — AOUIFER MK _ NM 2400' I 4 0 4 8 MILES 4 O 4 8 KILOMETRES VERTICAL EXAGGERATION X 53 3200' — For location of section see figure 3 SYSTEM Saline water body FIGURE 8.—Longitudinal section showing general hydrologic units, (Modified from Miller and others, 1971, fig, 13,) pumped from the upper zone cannot be made with the data available because many wells tap both zones and because water moves between the zones through well casings and gravel envelopes around the casings. How- ever, study of the spacing and number of wells, perfo- rated intervals, and relative aquifer-system produc- tivities suggests that at least 75 percent and possibly 80 percent of the overall pumpage is from the lower zone. The general variation in the amount of water pumped from the lower zone or its stratigraphic equivalent is shown in figure 10. The proportion of lower-zone water pumped increases from east to west. The western mar- gin of the 50—75 percent area coincides with the western margin of the highly permeable, upper-zone sands de- rived from the Sierra Nevada (fig. 11). The amounts of upper-zone water pumped increase to the east of the western margin of these sands because the thickness of the Sierran micaceous sands increases towards the east. Southeast of Mendota, brackish water unfit for agricul- ture occurs in the upper zone (figs. 7, 9, 10, 11), and Virtually all the water pumped within this local area is from the lower zone. The areas of less than 50 percent pumpage from the lower zone are large, but much of the agricultural water supply for these areas is derived from imported surface waters. Surface-water imports reduce the amount of ground water pumped, thereby reducing the water- table or head decline when compared with areas totally dependent on ground water for agriculture. UPPER ZONE The upper zone has a water table, and locally the water is unconfined. In general, however, ground water in this zone is semiconfined to confined. Under condi- tions of pumping draft, head differentials of 100—400 feet have developed between the water table and the water levels in wells tapping the base of the upper zone immediately above the Corcoran. For example, see figure 28. Hence, confinement is known to be substan- tial in some parts of the area, but in places where the deposits are coarse grained and have a large vertical permeability, differences in head are not great. In the northern and central parts of the study area the upper zone consists of many semiconfined aquifers and aquitards. In the southeastern part of the area, most of the upper zone is as well confined as the lower zone because of extensive lake clays that occur at various depths. In the southwestern part of the area, lake clays (including the Corcoran) are absent, and where the de- posits are sufficiently coarse grained, unconfined condi- CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE E15 B B 1200' — Tumey Hills _ 800' — '~ — 400' — \\ — Mu" “we Fresnel Slough SEA LEVEL \ SEMICONFINED (r. \ \\\ Potentiometric surface (lower zone) Mex 1969; _ 4—- 4 — » ' ' —\ *\—— ——‘- —— — / Zone f brook .h 400' \ \ : Y _A:OUI FER SYSTEM (Upper 20mg _ :- 31: _,1 12&c__._\__§_. 411111: - \ ‘ — - — — — — ’ —c : —- -— _ W’t" table — _ l ‘ — 3 ’— 3' ~fl’VCorcoren CleyMember , Principal confining bed _ 30° — CONFINED. X ./ AOUIFER (Lower zone) 1200' ‘ SYiTEM — 1600‘ — — 2000' C C' 1200' — _ Mouth of 800' — Cantua Creek '— 400. _ W tame Camus Creek(town) Fresno Slough _ ate ~_ I SEA LEVEL \//L SEMICONFINED AOUlFER “:23;— E__— . > PotentiometerIW°nw Mix—13%,. f C ‘Zone of brackish water ' ~ _,_—— ===‘\\ :_ SYSTEM (gppgr zone) 40° _ -—::Y—:—3——'\Z:§:x:::::x Corcoran Clay Member 300' _ Principal confining herd”— CONFINED ‘ . . 1200. _ AQUIFER (Lower zone) 1600' — _ 2000' — _ 240°: _ Saline water body 2800' E El 1200' — _ Anticline Ridge 800' — ._ 400' — — \ \ m tabl __/_ Kingisiver - SEA LEVEL SEMICONFINEDTO CONFINED ‘ _ _\-§r \ \ \AEOLmtigmitric surface (lower ZQDgLMame. .——é :5? _ _ ‘ 'kx-C :f'=.=====x===_ 400. _ SEMICONFINED AOUIFEFI SYSTEM (Upper zone) _ __ °_" 'T"95'3V_bgdj:£;3: —==‘====‘\“ #—\=':*3:x:::x::::‘C‘ZCZS:ll_:_:_ll_k____=_ AQUIFEH ‘ 3 F 7 ' _ Corcoran Clay Member 800' _ SYSTEM ‘ Principal confining bed i- 1200' —‘ '_ CONFINED 1600. J AQUIFER (Lower zone) SYSTEM — 2000’ - 2400' — 2800' _ ase of Tulere Fgrmgtion 3200’ — Saline water body _ VERTICAL EXAGGEHATION X 13 O 1 2 3 MILES O 1 2 3 KILOMETRES For location of sections. see figure 3 FIGURE 9.—Cross sections showing general hydrologic units. Lines of sections shown in figure 3. (Modified from Miller and others, 1971, fig. 14.) E16 36°30’ 36 °OO’ AGE Q Los Banos Boundary of deformed rocks 62° 6‘ ESTIMATED AMOUNT OF IRRIGATION WATER WITHDRAWN FROM LOWER ZONE, IN PERCENT OF TOTAL PUMP- Western boundary of irrigated lands as of 1962 LAKE Q o 1 15 | O M LES A’Q Kettleman BED o 5 1o 15K|LOMETRES L (e ‘ City STUDIES OF LAND SUBSIDENCE 120°30' 120°00’ l Firebaugh Kermanc EXPLANATION 6v 6;, Q 75-100 50-75 25-50 0-25 "LJ-‘r‘ TULARE Base from U.S. Geological Survey Central Valley map, l:250,000, 1958 FIGURE lav—General variation in the amount of water pumped from the lower zone or its stratigraphic equivalent, CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE tions prevail for the upper deposits. Considered as a unit, the upper zone is termed a semiconfined aquifer system in this report. PHYSICAL CHARACTER The upper zone, which includes the upper part of the Tulare Formation and younger alluvium, ranges from about 100 to 900 feet in thickness. The primary upper- zone aquifer is a micaceous sand, which was deposited over 645 square miles of the Los Banos—Kettleman City area (fig. 11) as flood-plain deposits of streams draining the Sierra Nevada. The thickness of the micaceous sand ranges from a featheredge along its western margin to about 580 feet under the present valley trough. In the northern half of the area, volcanic glass and pumice fragments occur in the micaceous sand in the basal part of the aquifer. In the southern part of the area, many of the deep irrigation wells tapping the lower zone are also perforated opposite lacustrine sands associated with the \ Corcoran Clay Member. Most of these sands are in the upper zone and are from 100 to over 200 feet thick. The lacustrine sands have a low clay content, are well sorted, and are highly permeable. The alluvial-fan deposits in the upper zone are not productive aquifers except in a small area southwest of Los Banos, in the extreme northern part of the Los Banos—Kettleman City area. The sediments deposited by Los Banos Creek consist primarily of gravel; shallow wells, 100—250 feet deep, provide sufficient water for irrigation. South of the Fresno-Merced County line, the alluvial-fan deposits have a low permeability and con- sist of clayey sand layers with interbedded poorly sorted . silt and clay. The alluvial-fan deposits are derived from the Diablo Range and are easily recognized in well cuttings or in cores by their yellowish to brownish color. They are calcareous and gypsiferous and locally contain small calcareous concretions, serpentine, glaucophane schist, fragments of siliceous shale, chert, and jasper ——lithologies that are typical of Diablo Range source areas . PRODUCTIVITY The most permeable aquifers in the Los Banos —Kettleman City area are in the upper zone. These aquifers, however, are of limited extent. A comparison of yield factors1 (Poland, 1959, p. 32), which are approx- imate measures for the overall permeabilities of the water-bearing materials tapped by wells, indicates that the gravels forming the Los Banos Creek alluvial-fan Specific capacity (gallons per minute per foot of drawdown) X 100 1Yield factor = Thickness of deposits, in feet, tapped by perforated interval of well casing E17 TABLE l.—Relation of yield factors to types of upper-zone deposits Townships Mean Number represented yield of wells Area (Township/Range) factor represented Wells tapping only upper zone alluvial-fan deposits: Los Banos ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 108/10E 95 5 South of Fresno-Merced County line,_,, 168/1515; 188/17E 4 3 Wells tap ing only up er zone Sierra micaceous sands: West of gen Joaquin iver ____________ 10S/12E; 118/13E; 50 4 125/14E; 13S/15E West of Fresno Slough ________________ 15S/15E; 15S/16E; 21 13 IGS/IGE; 165/17E; 17S/16E; l7S/17E; l7S/18E; 17S/19E; 18S/18E East of Fresno Slough ................ 14S/17E; 15S/17E; 100 15 16S/18E; 16S/19E deposits are the most permeable. (See table 1.) These deposits are two to five times more permeable than the Sierra micaceous sands which form the primary upper- zone aquifer in the eastern part of the study area. The upper zone alluvial-fan deposits south of the Merced County line which are derived from the Diablo Range, have low permeabilities as indicated by the low produc- tivity of the few wells that tap only these deposits. A fivefold variation in mean yield factors of the upper zone Sierra micaceous sands occurs within the study area. A comparison of mean yield factors indicates that the Sierra micaceous sands are twice as permeable west of the San Joaquin River than west of Fresno Slough. Many shallow wells tapping these deposits west of the San Joaquin River yield about 1,400 gallons per min- ute. If the Sierra micaceous sands are present and are less than 200 feet thick, most irrigation wells tap both the upper and lower water-bearing zones. In the area west of the Fresno Slough, where sodium chloride water occurs in the upper zone (shown in fig. 11), wells are perforated only opposite the lower zone. Mean yield factors of wells 3—4 miles east of the Fresno Slough indicate that the micaceous sands are five times as permeable as the sands west of the slough. CHEMICAL CHARACTER OF WATER Ground waters of the upper zone generally contain high concentrations of calcium and magnesium sulfate. Pronounced changes in the chemical characteristics of these waters occur in adjacent areas along the eastern and western margins of the area, and gradational changes occur with increasing depth (Davis and Poland, 1957, p. 457—458). The calcium and magnesium sulfate ground waters occurring to a depth of 200—300 feet average about 3,000 mg/ I (milligrams per liter) of dissolved solids and have about 35 percent sodium. An abrupt change, however, occurs along the border of the area, where the water from the west side with high sulfate concentrations E18 STUDIES OF LAND SUBSIDENCE 120°30’ 120°OO’ \ 33 \ \ Los Banos 15 37° ' — / Dos 00 l Palos aired / 9"”0ta / \ e639 ’0 ‘v C/c? / @900 I Q / 377’ \ Mendota \ l \ LL 0/ 00 \ ,1 so '7 ‘S' / man 1‘ <9 «\ (O ’3; ‘ 41 ( (u, \\ \ \ , \ \ 9/0416 \ \ \\ (<6) \\ 44% \ 004 _ \ 0% \ We \ 36°30’ _ 1“ 9,0 \ oCantua Creek \f \ 9L 06‘ \ \ 3% \K 0 \ ’9 ’5} ’00 X \ 7¢ (( .300 \ O o \ ive Poin \\ \ 6‘ 9% a \0 mo — — —\ - EXPLANATION o, I [/1 ‘- 0 , - W, Q 33 K / Boundary of deformed rocks (IQ , V“ I 100 694‘ 2; Line of equal thickness of micaceous sand ‘9 l ‘3’?» derived from the Sierra Nevada; dashed < where approximately located; interval 100 -\ 19 feet J / / 7 Westh aveno T§ 1 7% Eastern boundary of Corcoran Clay Member / ’9, ’0 Hurono I \ \‘P. of the Tulare Formation a (’4’ \ \ Strat— « o \ ford PLEASANT O 0 I00 \ [ . é Coalmga $9 0‘5 Extent of water of high NaCl content in (376 ~ micaceous sand overlying the Corcoran VALLEY / \/__ Clay Member / LARE 4’63.) <6 LAKE 4, 41 o 5 1o 15 MILES 440’ , ’(< Kettleman BED 36°00, 0 5 10 15 KILOMETRES J 33 s City Base from US. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 1 LgThickness and extent of the Sierra sand overlying the Corcotan Clay Member of the Tulare Formation. (Modified from Miller and others, 1971, fig. 10.) CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE merges with the calcium and sodium-bicarbonate ground water of low dissolved solids from the east side of the San Joaquin Valley. The chemical character of the waters contained in the ‘ deposits from a depth of 300 feet to the top of the Corco- ran can be distinguished from the overlying waters by their decrease in total dissolved solids to about 1,500 mg/l and an increase in the percent sodium to about 55. West of the Fresno Slough the water in the micaceous sand immediately overlying the Corcoran Clay Member (with the exception of the brackish water area shown in fig. 11) has a mean total dissolved solids of around 850 mg/l, and the percent sodium is about 60. CORCORAN CLAY MEMBER OF THE TULARE FORMATION A widespread diatomaceous clay stratum in the upper part of the Tulare Formation was first described by Frink and Kues (1954, p. 2357—2370) and has been named the Corcoran Clay Member of the Tulare Forma— tion (Inter-Agency Committee, 1958, p. 120). This lacustrine clay extends beneath the entire Los Banos ~Kett1eman City area (fig. 12) except for a narrow zone adjacent to the hills in the southwestern part of the area where, as is shown in section E—E’ (fig. 7), it feathers out, presumably along a contour of the ancestral Los Gatos Creek fan. The Corcoran has two lithologies. The upper two- thirds of the Corcoran consists of thin-bedded clayey silt and silty clay. The lower third of the unit commonly is coarser grained, consisting of interbedded sand—silt- clay and clayey silt. The greenish-blue color indicates that the Corcoran is reduced, except in the extreme western part of the study area where it has been uplifted and partially oxidized to brown or red. 7 The Corcoran Clay Member of the Tulare Formation is the principal confining layer throughout much of the San Joaquin Valley. The vertical permeability of the Corcoran which, based on results of consolidation tests under a simulated natural overburden load, ranges from 4 x 10 ‘5 gpd (gallons per day) per square foot (0.002 feet per year) in the more sandy parts near the top and base to as 10w as 6 X 10 ’6 gpd per square foot (0.0003 feet per year) in the less permeable middle section (Johnson and others, 1968, table 9). By 1960, the difference in head in aquifers above and below the Corcoran was as much as 200 feet. The Corcoran was deposited in a fresh-water lake that was 10—40 miles wide and more than 200 miles long (Davis and others, 1959, p. 77 and pl. 14). Evidence presented by Janda (1965) indicates that the lake ex- isted in Pleistocene time about 600,000 years ago. The E19 longitudinal axis of the lake in which the clay was deposited was approximately 5—10 miles west of the present topographic axis of the valley. The exact west- ern areal extent of the Corcoran is difficult to deter- mine, because as it thins, it bifurcates and its sand and silt content gradually increases until it is not discerni- ble in electric logs from the littoral sands which occur along its west edge. The thickness of the clay varies considerably. The maximum known thickness of the Corcoran in the study area occurs 5 miles northeast of the mouth of Panoche Creek, where an electric log shows the Corcoran to be 120 feet thick (Miller and others, 1971, fig. 11). Adjacent to Monocline Ridge and Ciervo Hills, the Corcoran is less than 20 feet thick and is more than 900 feet below land surface. In most of the area the Corcoran is 30—60 feet thick. The map showing the structure of the Corcoran (fig. 13) indicates that there has been gentle postdeposi- tional folding and warping of this lacustrine clay bed. The shift in the structure contours in the Huron- Westhaven area occurs where contours are shown for the lower clay stratum in an area where the upper clay layer is absent. LOWER ZONE The lower zone is effectively confined by the Corcoran except in the southwestern part of the Los Banos —Kettleman City area where the Corcoran is absent and confinement is poor or lacking. The lower zone supplies about three-fourths of the ground water for irrigation in the Los Banos—Kettleman City area. , If an aquifer is defined as a permeable deposit that will yield water to wells, the entire lower zone can be considered an aquifer. Permeable sand units can also be considered as aquifers separated hydraulically to vary— ing degrees by the finer grained interbeds of silt and clay. Silt and clay, especially clay, are much more com- pressible than sand when compressive stresses are in- creased owing to artesian—head decline. Therefore, it is important in the study of compaction of deposits under increased effective stress to differentiate between a water-bearing unit that is composed entirely of perme- able material such as clean sand and one that contains many fine-grained beds of silt and clay. For purposes of differentiation in the studies of compaction and subsid- ence, a water-bearing unit that has hydraulic con- tinuity but that contains many fine-grained beds is termed an aquifer system. Under this definition, the lower water-bearing zone is a confined aquifer system. The beds of silt and clayey silt that impede ground- E20 37°00’ 36°30’ 36°00’ STUDIES OF LAND SUBSIDENCE 120”30’ 120°OO' 33 I Los Banos / \ 152 \ \ 7* \\ Dos \ _ \ P l a OS . Frey-h ~_ \__—_\/' —\‘\,~“ / \ \< 33 \ \Oelfe \ v; "100 / \ 7‘ A! \ 0° endow \ \ \ O o Okz Firebaufih\ \ \ \ \I RIVER évg Q ’o C?) / o 7 Q (3&60 “ 0° \ 1 °.> ° U 9 , $00 1, ° 3 go” I FRESNO Q / o ‘3 "\n 4; % ° Mendota \\l "L 0, $00 ,1 so \ ‘7(9 1. Kerman l“ ‘“ I (O 6% N 41 (m ' ‘ \ 500 \ \ \ ' a \ \ °\l gee \\ x \00 \\ < 6‘ (‘91- \\ \K \ \\\ 41° \ ‘- 004 \\ \' \ \ \ Ws \ we I _ “a $0 ‘ 3’6 \ — ‘9 Q .1 65 Lo’» 0/ 8 \l \ / \ “h (as . . ‘ \ 62¢ . Five Pomts \ \ ‘ 700 “‘ _ _ 0,0 V 7”“ “ ‘ EXPLANATION e d, I \ {/’ <°<- 00 r Boundary of deformed rocks ’ $31“ \m 600 \ )00 { Line of equal depth to base of Corcoran ‘< \ | 1, . Clay Member of the Tulare Formation; ” V \ dashed where approximately located; in— / / c‘ Westhaveno terval 100 feet / J / .4 . Hurono \ I ) St t ra — A O ford Boundary of Corcoran Clay Member of the A ASANT O Tulare Formation Coalinga ’ <2 hoe—990% O ' Q) 0 AVALLEY “€113 16° ULARE / / ‘K \ , 4's,» \ \r- 6’00 f (94"? (LAK\EO%\ 5 1 15 MI 4' o o LES / 8Q Kettlemgn \RED \ o 5 1o 15 KILOMETRES 1 , Q (s 1 City \ Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 12l—Depth to the base of the Corcoran Clay Member of the Tulare Formation CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE 120°OO’ \ ER I 120°30’ as \ \ . 5 Los Banos / \ \ \ o ,_ Dos 37 00 \ Palés / / e/ ”'3de (33”? Firebau h \\ , \g 99 \\ \ \ 450 — \ £3560 /0 \ \i‘ %‘ 490 \\ LO ‘90) "-3- C’/ \ 96 0 ‘3 go ‘° . Mendota 71, \ “’00 \ 0/ oo 76> s. \ . 6‘ 36b ( a \ \\\ O (( \ \ \ o v 00 all \ ; 4,24% \ (‘SJ' 440 Nocz [4,5 0 «9 36°30’ — a z '91. 00¢ ~LI o ,9 e» Va ’2» 62° EXPLANATION , 9’0 Boundary of deformed rocks < (I 400 Structure contour Shows altitude of top of Corcoran Clay Member of the Tulare Formation; dashed where approximately located. Contour interval 50 feet; above sea level, 100 feet. Datum is mean sea level // / 7 9/ Approximate boundary of Corcoran Clay ‘5 4, Member PLEASANT 6‘ , _ ----- — Coalinga Approxlmate boundary of upper clay stra- EY turn of Corcoran Clay Member where less VALL extensive than lower stratum. Corcoran is bifurcated on southwest edge 0 5 10 15 MILES 0 5 1O 15 KILOMETRES 36°OO’ Base from US. Geological Survey Central Valley map, l:250,000, 1958 FIGURE lit—Structure of the Corcoran Clay Member of the Tulare Formation. (From Miller and others, 1971, fig, 12.) E21 E22 100 140 180 STUDIES OF LAND SUBSIDENCE I | I I Oro Loma site 12/12716H5/ perforated 670-712 feet 12/12-16H6 perforated 770-909 feet 220 I I I I I- LLI Lu LL 2 i 340 I I I g Westhaven site 20/18-1102 < /perforated 755-805 feet LL I: 380 3 U) o z < 420 _l 5 \ \/ _, 450 _ 20/18-1103 \ / \ / _ it]; perforated 1885-1925 feet 20/18-1101 /\/ H‘— 0: perforated 650-710 feet Lu I- 500 ' l ' < a 540 I l I o |_ 15/13-1102 I perforated 900-960 feet\ '— a 580 — \\ / m 15/13-2N2 \ / a perforated 880-1959 feet/\ \ 620 I J I | 540 I \ I I I .\ \\\ 16/15-34N4 perforated 1052-111 16/15-33J1 /\\\\\\ 2 fem\/‘ 580 - perforated 1013-2792 feet \\ \J/ \ N/ \ 620 l I | | 1961 1962 1963 1964 FIGURE Dir—Variation in the hydraulic continuity of the lower zone. water movement may transmit appreciable water be- tween adjacent aquifers—they are called aquitards. Throughout most of the area the lower zone has good hydraulic continuity both laterally and vertically. The degree of hydraulic continuity is shown at four sites in figure 14. Lack of hydraulic continuity in the northern part of the area is shown by the marked separation in head and difference in water-level trends in wells 12/12—16H5 and 12/12—16H6 at the Oro Loma site. A second confining clay occurs about 300 feet below the Corcoran in this part of the area, and at the site of these wells it is 38 feet thick. Head differences of 60—7 5 feet occur between the two lower-zone aquifers, and the greater amount of seasonal fluctuation shown by the record of the deeper well suggests that most of the lower-zone wells in the vicinity are perforated mainly below the lower confining clay. The degree of hydraulic separation shown by the records of these two wells ex- tends about as far south as the southern part of town- ship 13 south. Hydrographs of two lower-zone wells at the West- haven site in the southern part of the area show a marked difference in the degree of hydraulic continuity when compared with those at the Oro Loma site. Well 20/ 18—11Q2 is perforated from 755 to 805 feet, and well 20/18—11Q3 is perforated from 1,885 to 1,925 feet; yet the records show similar water levels and amounts of seasonal fluctuation. The difference in artesian head between the two lower-zone wells has not exceeded 25 feet, although the seasonal fluctuation of head has been as much as 80 feet. The other two sets of hydrographs in figure 14 are CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE comparisons of water levels in observation wells perfo- rated in an aquifer a short distance below the base of the Corcoran and nonpumping water levels in nearby irri- gation wells. The irrigation wells are perforated to depths LOGO—1,700 feet deeper than the observation wells and are within a third of a mile of the observation wells. The small differences in head in each set of hy- drographs show that good hydraulic continuity exists throughout the lower zone for these sites in the central and southern part of the study area. The records also indicate that the shallow observation wells have water levels that are representative of nearby deep irrigation wells. PHYSICAL AND HYDROLOGIC CHARACTER In most of the study area, the fresh-water-bearing deposits below the Corcoran consist of poorly.consoli— dated alluvial fan, flood-plain, deltaic, and lacustrine deposits of the Tulare Formation. In the southern part of the area, the basal lacustrine deposits of the Tulare are moderately consolidated and contain brackish water. The productivity of the Tulare is generally inade- quate forirrigation purposes in a 3- to 7-mile wide belt along the margin of the valley between the towns of Huron and Cantua Creek. Northwest of the Five Points—Coalinga Road, deep wells extend into the mod- erately consolidated Pliocene marine littoral and es- tuarine sands and silty clays of the pre-Tulare San Joaquin and Etchegoin Formations. To the south, the deeper wells tap the upper part of the San Joaquin Formation. The wells tap those parts of the marine section that have been largely flushed of their connate water. From some wells brackish water of poor quality is pumped from the pre-Tulare Pliocene deposits, but when the poor quality water is mixed with better quality water being drawn through the perforations higher in the well, the quality is improved, and the net result is to increase the yield of the well to an amount that is adequate to irrigate the land in the vicinity. Pore- pressure decline and compaction occur regardless of the quality of the water being removed from unconsolidated or partly consolidated deposits. The areas where water is being pumped from pre- Tulare formations of Pliocene age are shown in figure 15. Although deposits that are considered to be Pliocene in age are tapped in a large area near the foothills of the Diablo Range, only the area adjacent to the Big Blue Hills and Anticline Ridge is largely dependent on ground-water supplies from the older deposits. In the northern area where Pliocene deposits are tap- ped, most of the ground water is pumped from flood-plain deposits in the first few hundred feet below E23 the Corcoran. A few wells are perforated in the upper part of the Kreyenhagen Formation of Eocene and Oligocene age, and many wells tap the deposits im- mediately above the Kreyenhagen—deposits that have been described by Miller, Green, and Davis (1971) as Pliocene continental deposits. The electric logs suggest considerable variation in lithology and water quality of the Pliocene continental deposits. Differences in the temperature of the well water being pumped are not apparent between wells that in part tap Pliocene conti- nental deposits and those that do not. Since 1960, the new wells have been tapping shallower zones. As much as 2,000 feet of pre-Tulare Pliocene deposits is tapped by water wells adjacent to the Big Blue Hills. In general, the water being pumped from the pre-Tulare Pliocene deposits in this area is distinctly hotter than the water being pumped by nearby wells that tap only the overlying Tulare Formation. Many of the wells tap- ping the San Joaquin and Etchegoin Formations have water temperatures of more than 38°C (100°F), and temperatures as high as 45°C (114°F) have been re- corded. Adjacent to the northern part of the Big Blue Hills, most of the water being pumped within 5 miles of the foothills probably is coming from the pre-Tulare Pliocene formations. The Tulare is so clayey that some wells are not perforated above a depth of 2,000 feet, and one well was perforated to a depth of 3,800 feet. Well yields generally are less than in areas where wells tap only the Tulare Formation. The area adjacent to the Big Blue Hills and Anticline Ridge has experienced as much as 500 feet of artesian- head decline, but the amounts of subsidence in those parts of the area where wells derive most of their water from the pre-Tulare Pliocene formations have been minor, presumably because of the partly consolidated nature of the deposits. Only 1 foot of subsidence has occurred in the area of 500 feet of head decline. The lower zone alluvial-fan deposits are derived from the Diablo Range and have low permeabilities. They are similar in lithology to the upper-zone fan deposits south of the Merced County line. In the southern part of the area, as shown on section E—E’ (fig. 7), most of the lower zone tapped by wells consists of alluvial-fan deposits, but 20 miles to the northwest (section C—C’, fig. 7) fan deposits form less than one-eighth of the lower-zone aquifer system. The moderately permeable flood-plain and deltaic de- posits which form the major part of the lower zone in sections C—C’ and E—E’ (fig. 7) were derived from the granitic rocks of the Sierra Nevada. Consequently, they are arkosic in composition and can be recognized in drill cuttings or core samples by their mica content. They are generally grayish green or blue green. The lower zone in the area of section B—B’ (fig. 7) is E24 37°00' 36°30’ 36°00’ STUDIES OF LAND SUBSIDENCE 120°30’ 120°00’ 33 I 15 Los Banos 152 / _. , Dos Palos / 33 Q” m I a / Y1 Firebaugh Mendota Kermanc EXPLANATION Boundary of deformed rocks Area of ground-water pumping from pre- Tulare Pliocene deposits based on electric logs or depth of well TULARE LAKE o 5 1o 15 MILES i—fi—‘—I—_l‘_—'—J / 40“ Kettleman BED o 5 10 15K|LOMETRES 1 , 9 o 1 City Base from US. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 15,—Areas in which part of ground water is pumped from pre-Tulare deposits of Pliocene age. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE E25 TABLE 2.—-Relation of yield factors to types of lower-zone deposits Townships Mean Number represented ield of wells Area (Township/Range) actor represented Wells tapping only flood-plain deposits derived from the Diablo Range: South of Los Banos Creek to vicinity of Fresno—Merced County line __________ 128/11E; 12S/ 12E 24 6 Vicinity of Fresno-Merced County line to Panoche Creek ____________________ 12S/11E; 128/ 12E; 9 26 13S/12E; 13S/13E; 14S/12E Wells tapping only flood-plain deposits derived from the Sierra Nevada: West of Fresno Slough ____________________________________________________ 14S/ 14E; 14S/ 15E; 11 9 15S/14E; 15S/15E; 17S/16E; 18S/17E Wells tapping only deltaic deposits derived from the Sierra Nevada: West of Kings River ______________________________________________________ 208/19E 9 2 Wells tapping intermixed flood-plain deposits derived from the Diablo Range and the Sierra Nevada: North of Monocline Ridge ________________________________________________ 138/ 13E; 13S/ 14E; 6 23 14S/13E; 14S/14E; 158/13E; 15S/14E Wells tapping only alluvial-fan deposits derived from the Diablo Range: Vicinity of Los Gatos Creek ______________________________________________ 198/16E; 19S/18E 3 2 Wells tapping intermixed alluvial-fan deposits derived from the Diablo Range and flood-plain and deltaic deposits derived from the Sierra Nevada: Tulare Lake bed to 12 miles northwest of Cantua Creek ___________ 16S/14E; 168/15E; 4 72 17S/15E; 17S/16E; 188/16E; ISS/I7E; 198/17E;198/18E; 20S/19E composed chiefly of flood-plain deposits derived from the Diablo Range. These deposits which form the bulk of the lower-zone deposits in the northern part of the Los Banos—Kettleman City area have low to moderately high permeabilities. They are greenish gray to greenish black and are characterized by andesitic and basaltic detritus, serpentine, chert, and other rock fragments derived from the Diablo Range. They are slightly to moderately micaceous, in contrast to the generally nonmicaceous character of the alluvial-fan deposits de- rived from the Diablo Range. This characteristic would suggest that the flood-plain deposits were derived from a different or larger source terrain than the overlying nonmicaceous alluvial-fan deposits. A variety of depositional environments are rep- resented by the deposits in the central part of the study area. Flood-plain and alluvial-fan deposits derived from the Diablo Range interfinger with flood-plain deposits derived from the Sierra Nevada and with lacustrine sands and clayey silts. PRODUCTIVITY The deposits forming the lower-zone aquifer system in the Los Banos —Kettleman City area locally are less permeable than the deposits forming the semiconfined aquifer system of the upper zone. However, because of the greater thickness of the lower-zone deposits and the general poorer quality of the water in the upper zone west of the Sierra sands (fig. 11), at least 75—80 percent of the irrigation water pumped in the Los Banos- Kettleman City area is from the lower zone. The yield factors of the lower water-bearing zone de- posits given in table 2 and the areal distribution shown in figure 16 indicate that where wells produce from only one type of lower—zone deposit, the flood-plain deposits derived from the Diablo Range are slightly less perme- able than the flood-plain deposits derived from the Sierra Nevada. However, yield factors indicate that where wells produce from lower-zone deposits which consist of Sierra flood-plain deposits interfingered with finer grained Diablo flood-plain deposits, the relative permeability is considerably lower. The general area where this interfingering occurs is in a north-south trending belt 8—9 miles wide which extends 18—25 miles north from Monocline Ridge. In the western part of the Los Banos—Kettleman City area, between the towns of Cantua Creek and West- haven, alluvial-fan deposits occur between the Corco- ran and the lower-zone Sierra flood-plain deposits. Wells in this area producing from the lower zone and with approximately 20—50 percent of their perforated intervals opposite alluvial-fan deposits have yield fac- tors ranging from less than 1 to a maximum of 9. The average yield factor of lower-zone wells in this area is 4. E26 37°oo' ' 36°30’ 36°00’ STUDIES OF LAND SUBSIDENCE 120 °30’ 120°OO’ )~ . (I ’y Q?“ EXPLANATION Boundary of deformed rocks Western boundary of Corcoran Clay Member of the Tulare Formation ,9 Boundary of genetic type Area of no significant pumping from lower water-bearing zone as of 1961 Sierra flood-plain and deltaic deposits S Diablo flood-plain deposits Q Diablo alluvial-fan deposits § Pumping from deep wells west of confining Corcoran Clay Member i 72 Upper number, mean yield factor for wells tapping only lower-zone deposits. Lower number, number of wells in sample 0 5 10 15 MILES O 5 1O 15 KILOMETRES 44° . ’l/Oc2 ,4, . 6‘ O '9 .7 $0 / ( %\ 6‘ v ' ’ ' Madera W JOAQUIN Coalinga VALLEY Kerman fl TULARE LAKE 41 Kettleman BE D City Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 16.—Yield factors and types of lower-zone deposits. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE Only two wells, both located in the Los Gatos Creek area north and east of Huron, are known to tap only lower— zone alluvial-fan deposits. The yield factors of both of these wells is between 2 and 3. A comparison of yield factors suggests that in general the lower-zone flood-plain and deltaic deposits are 3—5 times as perme— able as the lower-zone alluvial-fan deposits but only one-half to one-fifth as permeable as the upper-zone flood-plain deposits (Sierra micaceous sands of table 1). The yield of wells throughout the Los Banos —Kettleman City area does not vary much with the average permeability of the deposits tapped, because the yield needed for irrigation purposes is only from 1,000—2,000 gallons per minute, and yields within this range can be obtained in most of the area. Wells tapping the highly permeable upper-zone Sierra sand near Fresno Slough may be only 150—200 feet deep and yield 1,500 gallons per minute. In the western part of the area where the upper-zone deposits have low permeabilities and the majority of the lower-zone deposits consist of alluvial-fan deposits, wells must be 2,500—3,500 feet deep to obtain 900—1,200 gallons per minute. Thus, where average permeability is low, as indicated by the low yield factor, the discharge capacity needed for irri- gation can be obtained either by drilling wells to tap greater thicknesses of the deposits, or by installing pumps to operate with greater drawdowns from static level, or both. The thickness of the fresh-water-bearing deposits of the lower zone (fig. 17) has been compiled from two maps. One map shows the altitude of the base of the Corcoran (Croft, 1969, pl. 4). The other shows the al- titude of the base of fresh water determined from ex— amination of several hundred electric logs, using 3,000 micromhos specific conductance (approximately 2,000mg/1 dissolved solids) as the upper limit of fresh water (R. W. Page, 1971). Thus, the thickness map (fig. 17) represents the difference between the two altitudes. Comparison of figure 17 with the geologic sections showing the base of fresh water (Miller and others, 1971) indicates that the lower-zone thicknesses in figure 17 are, in general, several hundred feet less than in Miller’s geologic sections. Thus, the base of fresh water shown by Page in his appraisal of electric logs for water-chemistry purposes is several hundred feet above the base shown by Miller in his studies for geologic correlation purposes because Page used different criteria than Miller. The thickness of the fresh-water-bearing deposits of the lower zone (fig. 17) varies considerably in the north- ern, central, and southern parts of the study area. In the E27 northern part of the area, deposits that contain fresh water are 200—600 feet thick, and the maximum thick- ness occurs about halfway between the San Joaquin River and the Diablo Range. The thickness of fresh-water-bearing deposits in the central part of the area is highly variable. Near Fresno Slough the deposits are only 600 feet thick, but they thicken westward abruptly, and opposite the Big Blue Hills the thickness exceeds 1,600 feet in an extensive area, and locally is 2,200 feet. In general, the fresh-water-bearing deposits are the thickest in the southern part of the area, where thick- nesses range from 800 to more than 2,000 feet. The thickness increases progressively from Five Points to- ward Tulare Lake bed. V The thickness of the fresh—water-bearing deposits does not define the thickness of deposits being subjected to large amounts of pore-pressure decline and concur- rent compaction. In parts of the area, sufficient yields can be obtained by wells without having to drill to the base of the fresh-water-bearing deposits. In other parts of the area, sufficient yields can be obtained only by pumping part of the water from underlying deposits that contain water of poorer quality than 2,000 mg/l. The maximum thickness of the perforated interval of the lower zone, and locally of subjacent deposits con— taining saline water, provides useful information for subsidence-study purposes. Reduction of pore pressure may occur several hundred feet below the lowest per- forations in deposits that have hydraulic continuity. This factor is not taken into account in this study be— cause detailed information about hydraulic continuity is not known for the base of the lower zone. Further- more, the fine-grained lacustrine and deltaic deposits near the base of the lower zone are likely to cause poor hydraulic continuity in that part of the aquifer system in much of the study area. An alternative approach is to use the maximum depth of well perforations to approx— imate the depths to which pore-pressure. decline is oc- ‘ curring. Maximum pore-pressure decline may be occur- ring higher in the aquifer system where the greatest abundance of well perforations occurs. However the use of the maximum depth of the perforations partly takes into account pore-pressure decline that is occurring below the base of wells that bottom higher in the aquifer system. Maximum depths were not used if only a few deeply perforated wells were present in a township or if the depths appear to be anomalously deep. The max- imum thickness of the lower-zone perforated interval is based on the well tabulation compiled by Ireland (1963): this table lists the perforated-interval data for wells E28 37 °OO’ 36°30’ 36°00’ STUDIES OF LAND SUBSIDENCE 120°30' 120°00' 33 I 15 \ Los Banos 152 / , \ _ Dos Palos / \\ l,’ \Ffl/mJKK / 33 / 0% /’ ”4} \ \ 400 \ M / e“More \ o ’ 949 Firebaugh \ $690 10 9 eye é 9 o l 90 43' 0/ ’ 0 / 400 \ r; / Mendota ’L <27 on 0% *2 O ’( ~ - (0" \ A /\ } I, / o / 67(4’6‘ (‘9‘- '14 04,004 [4/5 _ 0/6 '9’0 oCantua Creek ‘1 51¢ ~g ° / \ 417 e? . EXPLANATION ”V0 ‘0 6\ A Boundary of deformed K g, rocks 9/0 ‘5 800 9% Q Generalized line of equal thickness of the 6‘ ) fresh-water-bearing deposits of the lower ‘0‘ zone (5‘ / \ Dashed where approximately located; in ter- \ val 200 feet. Compiledfrom map showing , altitude of base of Corcoran Clay Member I of Tulare Formation (Croft, 1969, p. 4) and map showing altitude of the base of Hmono fresh water (3,000 micromhos} (R. W. Page, I 1 9 71 ) SANT l . Coalinga {3 Boundary of Corcoran Clay Member of the r, VALLEY Tulare Formation , / 4— ' 67} I <64, 0 5 1O 15 MILES o 5 1o 15 KILOMETRES 1 ,’ Q Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 17.—‘Thickness of the fresh-water-bearing deposits of the lower zone‘ (Compiled by J r F Poland) CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE drilled before 1962. Since 1960 fewer wells have been tapping the brackish waters that occur below the base of the lower zone. The maximum thickness of the perforated interval of the lower zone is shown in figure 18. The thickness of lower-zone deposits being tapped ranges from less than 400 feet to more than 2,400 feet. The general pattern is one of overall increasing thickness of perforated inter- val toward the southwest. Thicknesses of more than 1,800 feet occur in the areas of pumping from the Etch- egoin Formation. Compari'son of figures 17 and 18 reveals some in- teresting differences for the various parts of the study area. In the northern part of the area, the perforated interval exceeds the thickness of the fresh-water- bearing deposits by 200—400 feet near the San Joaquin River. Toward the Diablo Range, however, wells tap progressively more of the underlying sediments con- taining brackish water; as is shown by the greater dis- parities between the thickness lines of the two maps. A maximum disparity of 1,000 feet locally is attained east of Panoche Hills. In the central part of the area, the overall patterns of lines in figures 17 and 18 bear little resemblance. The wells do not extend to the base of the fresh water in the eastern part of the subarea: they do extend as much as 200 feet below the base of the fresh water in the area that is dependent on water yielded from the Pliocene marine sands. In the southern part of the area, the productivity of the lower zone is sufficiently high that farmers do not need to drill wells to the base of the 'fresh-water-bearing deposits. South of Five Points, comparison of figures 17 and 18 shows that in nearly all the area the wells do not reach the base of fresh water. East of Westhaven, the thickness of the lower zone exceeds the thickness of perforated interval by as much as 1,000—1,400 feet. Pore-pressure decline is also occurring below the base of the well perforations in the vicinity of Fresno Slough and Kings River as a result of the large amounts of water being pumped from the deeper aquifers farther west. An example of this type of head decline is shown in figure 24 at the Yearout site (13/15—35D). CHEMICAL CHARACTER OF WATER Lower-zone ground waters are effectively separated by the Corcoran Clay Member from upper-zone water throughout most of the study area. The chemical character of the water has been discussed in some detail by Davis and Poland (1957, p. 459—460). Analyses of samples taken in August 1951 from wells with perfora- tions restricted to the lower zone and of samples from E29 older wells in that zone that were not gravel packed provide useful information about the chemistry of the lower-zone water. It is primarily a sodium sulfate water, with noticeably more bicarbonate than in the upper—zone waters. The chloride concentration of the water is generally 100 mg/l or less. The uniform salinity of the lower—zone water at a given site can be demonstrated by examination of spon— taneous potential electric logs. The mud used when drilling a well commonly is mixed with water from a nearby irrigation well, thereby causing a minimum of contrast between the resistivities of the formation fluids and the drilling mud. Under such conditions, the spon— taneous potential log will be virtually featureless un- less the salinity of the contained waters varies from bed to bed. The featureless spontaneous potential logs of the study area indicate that lower-zone salinities are very uniform or undergo change with depth in a gradual manner. The chemical character of the water in the lower zone has been influenced by variations in time and place of streamflow from the Coast Ranges, by the initial sources of the deposits and their contained waters, by the presence or absence of the Corcoran as a control for percolation to the lower zone, and by the activities of man. The variations in dissolved solids of lower—zone water shown in figure 19 probably have been little af- fected by man. The data for the map were taken from values of sums of determined constituents given by Davis and Poland (1957, tables 2 and 3). Some of the data were from wells that are perforated for short dis- tances immediately above the Corcoran, but sums of determined constituents for these wells do not differ appreciably from those for nearby wells perforated only below the Corcoran. The map showing the chemical character of the water in figure 19 is representative, in general, of the fresh- water-bearing section of the lower zone as shown in figure 17. The map is biased toward mean or minimum sums of determined constituents for two reasons. Anomalously high values could be the result of two causes: (1) The basal part of the perforations of some wells were known to extend below the base of the fresh water; and (2) the presence of poorer quality water in some wells was thought to have been the result of lack of prolonged pumping before sampling in wells that are perforated for a short distance above the Corcoran. In such wells, when the pump is idle, poorer quality upper-zone water may flow down the well and gravel pack and replace the lower-zone water immediately adjacent to the well. The concentration of dissolved solids in the lower- E30 STUDIES OF LAND SUBSIDENCE 120°3o' 120°00’ 33 I 15 Los Banos 152 o ,_ Dos 37 00 Palos / 09 I ’12 0° 0 . / \_,6 ”19/ Firebaugh 4 Mendota 7 16 iso \ l— 93;“ Kerm an o J" 6" ‘9‘]: \ Va 41 \ \ 6‘ 00 \ ly/ 476)— \ \ \ “'00 \‘\ fi‘ 2000 \\ \ ‘ \ \ k\ 36°30' — \ ‘ \ fl \ \ EXPLANATION Boundary of deformed rocks 800 Generalized line of equal maximum thick- ness of the perforated interval of the lower zone for wells drilled before 1962 In terval 200 feet. Short dashed where approx- imately located; long dashed for thick- ness below estimated stratigraphic equiva- lent of the Corcoran, where absent 'fi 1200 \ «a \ \ \t\ \ ' “am _/ r r ‘\ I <2 a Western boundary of the Corcoran Clay Member of the Tulare Formation / 16/ /)(/$ TULARE / LAKE v ‘5‘. 41 O 5 10 15 MILES ,7, K ttl t——r—‘—:——r—*———‘ ( e eman E 36000, 0 5 1o 15 KILOMETRES ’ 9 4s | City 3 D Base from US. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 18,—Maximum thickness of the perforated interval of the lower zone. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE E31 120°30’ 120°00’ 33 I 15 Los Banos 152 / / 37° ’ — Dos 00 Palos / / . . Fresno ___ /\ R' — \._.-\/' ___ .« \__Iver __ 33 w \/ v ‘ Madera 09, / m ta / d a ‘2 00 ‘° 0 Mendo‘tgg o 99 $0 / 5" o ’ 664'? Firebaugh R V 92 ’ RIVE € Q) C39 /0 £5,- 6% QUIN 43- 09 1, 50A FRESNO v” ,9 % "\n 00“ 2‘} 1200 00 Mendota l1 s 1, \— é’Q ('9‘. 0/ 00 2000 180 180 \ {5 0 765 ‘3‘,“ § 7“ Kerman J’ t A V (0 "? Q, \efio 41 ( X VJ‘ / , V\ \ Creek /\ \ 6 I 9°C“ % g 200 \ 9° 6704, S K < 6‘ (GP \\ Q \ 4104/0 ~90 \- ( . ’05 M9 36°30’ _ 0’6‘ 9,0 oCan ua Creek ‘\\ _/v E s\ <\ ‘— e pper zone / ‘—‘ H / 1916) ¥fl / er \ Corcoran Clay Member 6 has“ Wat g V ‘/ Eastern boundary of Corcoran 1000.4 Lower / 56 0t Clay Member of the Tulare \zone/y Ba Formation VERTICAL EXAGGERATION X 20 N 2000’ B Area of lower-zone confinement 20005‘ S B B, B" 3 ——l'——— 6' k . . I E g 3 Line Of section 3'3 , EEOIOEY 1000'. Potentiometric surface, g'fi, .2 i , - from Miller,Green, and Davis lower zone, 1966 E E § 3 (l971).B'-B”,geology from H.T. “‘93 W | Mitten (U.S.Geological Survey, SEA LEVEL written commun. May, 1968) —..’7 General direction of woo'< ground-water flow 0 5 10 MILES VERTICAL EXAGGERATION X 20 I———v—‘—v———4 2000’ 0 5 10 KILOMETRES C FIGURE Zoo—Change in the natural-flow conditions in the central San Joaquin Valley.A , Extent of lower~zone confinement B , Flow conditions in 1900. C, Flow conditions in 1966. E34 The largest recharge area for the deposits below the Corcoran is the 10- to 20-mile-wide belt of the San Joaquin Valley west of the Sierra Nevada. Major streams such as the San Joaquin River have supplied large amounts of water to the lower zone. Recharge directly from rainfall before the advent of irrigation probably was insignificant. Flow conditions in about 1900 are shown in figure 20B. Waters of markedly different chemical quality from the two source terrains moved under the Corcoran and migrated to the trough of the valley. General circu- lation and upward movement through the Corcoran occurred at very slow rates because of the exceedingly low permeability and large thickness of the lacustrine confining clay. As a result, the lower-zone potentiomet- ric surface was more than 20 feet above land surface in the valley trough area. The slope of the potentiometric surface toward the trough of the valley was only 3—4 feet per mile. The large-scale agricultural development of the west side of the valley resulted in the change in flow shown in figure 200 . The potentiometric surface, instead of being above the land surface, was below sea level in most of the area west of Fresno Slough in 1966. Near the Diablo Range, lower—zone water levels were below the Corco- ran, and water-table conditions existed. The slope of the potentiometric surface has been reversed to a major degree. Under the initial flow conditions, the poten— tiometric surface sloped to the east in all the area west of Fresno Slough. By 1966, a belt that was only a few miles wide adjacent to the Diablo Range was still an area of eastern gradient for lower-zone water move- ment. > Upper-zone conditions were not changed as much as the lower-zone conditions in the northern part of the study area because of the limited pumping of these waters. Recharge to the ground-water reservoir from the surface was occurring—in contrast to the times be— fore agricultural development—as a result of irrigation water percolating below the root zone. Upper-zone changes have been much greater in the central and southern parts of the area where the semiconfined and confined aquifer systems have been pumped heavily. CHANGES IN THE HYDROLOGIC ENVIRONMENT CAUSED BY MAN Man has greatly disrupted the natural flow system. Water-level changes have occurred in the different parts of the ground-water reservoir—the water table, the semiconfined aquifer system, and the confined STUDIES OF LAND SUBSIDENCE aquifer system. Significant hydrologic changes are re- sponsible for the increased applied stress that has caused land subsidence. HISTORY OF GROUND-WATER DEVELOPMENT The early settlers used the Los Banos—Kettleman City area for the grazing of cattle, sheep, and horses. The first canal diversions of surface water in the 1870’s, and the first artesian wells put down in the 1880’s were primarily for watering of livestock and for irrigation of land for pasture. The land was not irrigated and farmed on a large scale until the First World War. Although some wells were drilled for stock and domestic water supply as early as 1870 (Mendenhall and others, 1916, table 45), the first known artesian well in the Los Banos—Kettleman City area was drilled in 1886. At the time of the first Geological Survey well canvass in the San Joaquin Valley in 1905—6, 14 flowing artesian wells were reported in the area. In 1905, a well 2 miles west of Tranquillity was described as having a head sufficient to raise a column of water at least 22 feet above land surface. In 1914, artesian flows of more than 1,000 gallons per minute were measured from wells in the trough of the valley. In 1919, the water level in the San Joaquin City well was 19 feet above the land sur- face. These facts suggest that artesian—head decline was minor in the valley trough between 1905 and 1919. The use of ground water for irrigation expanded rapidly in the early 1920’s, initiating a rapid decline in artesian pressures. The last report of a flowing well in the Los Banos—Kettleman City area was in the winter of 1925—26. By this time 170 wells had tapped the confined aquifer system. In sec. 28, T. 19 S., R. 19 E., where there had been a flowing well in 1905, the static level was at a depth of 50 feet in 1926, indicating a mean head decline of about 3 feet per year. The first areas to use ground water for diversified agriculture were near Oro Loma, Mendota, Westhaven, and along Fresno Slough. The general areas of early ground-water development are shown in figure 21. In 1915, the area to the west of Oro Loma was subdivided into small tracts which were irrigated with water from 12 wells. In 1917, the Boston Land Co. began irrigation of 10,000 acres near Westhaven in the southern part of the area, and by 1924, 54 irrigation wells had been drilled on the property. Information about these wells is avail- able in an unpublished report made by H. L. Haehl and Hyde Forbes for the Boston Land Co. in 1926. In 1926, more than 170 wells had tapped the lower- CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE 120°30’ 120°00’ E35 37°00’ 36°30' 3 T Los Banos 152 \ , \ Dos Palos 33 \ \Loma \ EMendota mo *9, 4, < e (@1— EXPLANATION Boundary of deformed rocks Generalized areas of early ground-water development, from recorded distribution of irrigation wells from various sources _. o _. '9 N 4; 1924-31 1931-37 ’o< 41, « PL ASANT Coalinga VALLEY 1937-43 Western and eastern limits of flowing arte- sian wells in 1906, (from Mendenhall and others, 1916, pl. 1) 0 10 15 MILES 0 5 10 15 KILOMETRES | 5 36 °OO’ Kerm an Hurono €30 ‘\ Westh‘aven Kettleman City 41 LAKE BED Base from U.S. Geological Survey Central Valley map, 11250000, 1958 FIGURE 21.#Areas of early ground-water development. E36 STUDIES OF LAND SUBSIDENCE TABLE 3.—Estimated ground-water pumpage, 1935—66, Los Banos—Kettleman City area [Pumpage in thousands of acre-feet; for agricultural year beginning April 1 and ending March 31; data chiefly from Pacific Gas and Electric Co. Northern district is area from Fresno- Merced county line to north line of T. 16 8.; Southern district is area from north line of T. 16 S. to Kettleman City. East boundary is San Joaquin River, Fresno Slough, and Kings River} Northern Southern Northern Southern Year district district Total Year district district Total 1935—36 ____________ 20 135 1951—52 805 1,050 1936—37 ____________ 30 160 1952—53 ___ 935 1,275 1937—38 “1 75 215 1953—54 a- 840 1,190 1938—39 ____________ 110 260 1954—55 750 1,065 1939—40 ____________ 130 275 1955—56 725 1,130 1940—41 ____________ 130 270 1956—57 775 1,205 1941—42 ____________ 145 280 1957—58 ____________ 385 775 1,160 1942—43 ,,,,,,,,,,,, 170 320 1958—59 ____________ 405 700 1,105 1943—44 ____________ 175 340 1959—60 ____________ 375 765 1,140 1944—45 ____________ 175 350 1960—61 ____________ 370 720 1,090 1945—46 ____________ 190 370 1961—62 ____________ 345 685 1,030 1946—47 ____________ 255 455 1962—63 ____________ 375 730 1,105 1947—48 ____________ 355 595 1963—64 ____________ 360 685 1,045 1948—49 ____________ 410 645 1964—65 ____________ 330 780 1,110 1949—50 111111111111 590 845 1965—66 111111111111 310 675 985 1950—51 444444444444 695 1,000 zone waters in the Los Banos—Kettleman City area. By 1937, about 250 wells were pumping from the lower zone, and by 1942 the number had increased to at least 350. In 1960, there were about 1,100 activeirrigation wells, most of which were pumping from the lower zone. Irrigation with ground water expanded rapidly dur— ing the early 1920’s, but a low level of commodity prices in the late 1920’s and early 1930’s discouraged further agricultural expansion. After 1936, a renewed expan- sion occurred, and pumpage increased rapidly until World War II. The increase in the irrigated area since about 1940 is shown in figure 22. The growth of the ground-water service areas expanded most rapidly between about 1940 and 1950. Most of this expansion was associated with the high prices paid for crops after World War II. By 1955, most of the available land had been placed under cultivation. Since 1955, the irrigated area has edged closer to the foothills of the Diablo Range, par- ticularly in T. 14 S., R. 12 E., and T. 16 S., R. 14 E. TRENDS IN TOTAL GROUND-WATER PUMPAGE The total amount of ground water pumped in the study area increased until the early 1950’s. Early in the development of the area, the Boston Land Co. pumped an average of 12,500 acre-feet of water per year between 1917 and 1926 (Haehl and Forbes, 1926, unpub. rept.). In 1924, the total annual pumping draft from the area was about 35,000 acre-feet (Davis and Poland, 1957, p. 431). The ground-water pumpage in the Los Banos —Kettleman City area (excluding the small area north of the Merced County line) is shown in table 3 and figure 23 for the period 1935—65. Pumpage for a northern and southern district is shown, in addition to the total pumpage, in order to illustrate the rapid growth of pumpage in the southern district from 1945 to 1953. Pumpage in the area north of the Fresno-Merced County line was not included because the available figures for electric—power consumption included power used for many surface-water booster plants. The data for years 1935—36 through 1961—62 were compiled largely by E. J. Griffith, Pacific Gas and Elec- tric 00., Fresno, and were made available through the cooperation of the San Joaquin Power Division, Pacific Gas and Electric Co. The ground-water withdrawals were computed chiefly from the total power consump- tion per customer per year; and this amount was divided by an average figure for kilowatt hours per acre-foot for each customer as determined from pump efficiency tests for that customer. Pumpage from 1962—63 through 1965—66 has been compiled from a report by Ogilbee and Rose (1969). Before 1940, most of the ground water was pumped in the northern district, but the rapid expansion of ag- riculture in the southern district after 1945 caused the pumpage in that district to surpass pumpage in the northern district, and, since 1948, pumpage in the southern district has been about double that of the northern district (table 3). The total pumping rate increased until 1952—53 when 1,275,000 acre-feet of water was pumped. Since then the total pumpage has declined gradually to about 1,000,000 acre-feet in 1965—66. The end of the period of accelerated pumping coincided roughly with a sharply reduced rate of agricultural expansion. Although some CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE E37 37 °00’ 36°30’ 120°30’ 120°00’ 33 ‘ 15 Los Banos / / Dos Palos / o ,« ~ ' Fresn ~—— .”_\ Rive . \___~/ __> , \__ r _ ”V \/ Madera (ll 2 0° 0 99 go Q 0 9),! Firebaugh RIVER $1., Q3) 49 ‘3' Q-OO ’0 $9 0 9? (1‘1“q / @900 10A FRESNO é / n .o ‘-| 7 u 0/ 16 180 180 \ .7 Q; Kermanc <9 «\ (O 3% 41 (m )~ (‘9‘- 4”o 4/ 00‘, 4’s _ 9% _ EXPLANATION Lo ( 77/777777” “74/ a“ Boundary of deformed 62¢ rocks _ _ Areas receiving surface water as of 1940. ,/’ Irrigation supply wholly surface water or '7 supplemented by ground water ‘7‘ “3:. Areas irrigated with ground water as of 9 1940. Data chiefly from aerial photo- _.-,‘ graphs 1937, 1940, and 1942 7 ' § // ’9, ’0 uron §\\ a: 0 (4” Sftradt— or Growth of ground-water service area, 1940- PL SANT 6‘ 50, from aerial photographs 1950 . 7/ Coalmga % VALLEY Growth of ground-water service area, 1950- TULARE 55, from aerial photographs 1954-55 46,1144, 41 LAKE 5 1 15 MILES o 0 I I’/<< Kettleman BED o 5 1o 15 KILOMETRES / 33 s | City 36°OO’ Base from US. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 22,—Increase in irrigated land. E38 STUDIES OF LAND SUBSIDENCE 1400 ULos Banos '5 Northern - distirct , 0 1200 .1 ' Total pumpage . ~ .; . I! C1000 l- w Lu ‘+ a w i a g r * < Kettleman LOL Clty 800 in D Z 42 U) D O I Pumpage, southern l- district Z uI 600 0 E E D n. _l < D Z Z < ‘o’ ‘ { / \°‘~o\ /°\\o\ «\C/ Pumpage, northern \o/ \0\ district A / ‘” P-—0/ ,v 200 < ,o”°/ 0’ ( 0 1935-36 1945-46 1955-56 1965-66 AGRICULTURAL YEAR, APRIL 1 toMARCH 31 FIGURE 23.—Estimated ground-water pumpage, 1935—66 (area north of Merced County line excluded). new land has been irrigated for the first time since 1952, the amount of new land is small compared to the overall acreage being irrigated. The fluctuations in total pumpage since 1952 are largely the result of weather, crop practices, and changes in irrigation procedures. Long hot summers and larger proportions of acreage planted to crops such as alfalfa tend to increase the amounts of water pumped. The trend from furrow to sprinkler irrigation has reduced the amount of water needed to grow a given CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE crop and has required fewer wells because water can be readily transported several miles in pipelines. The tripling of the overall pumpage since 1945 has resulted in a large overdraft, declining water levels in the zones from which water is being withdrawn, and large amounts of subsidence as water is expelled from unconsolidated sediments to furnish about one-third of the water pumped. CHANGES IN GROUND-WATER LEVELS Pumping of ground water and irrigation has changed the water table as well as the water levels in the semiconfined aquifer system above the Corcoran Clay Member and in the confined lower zone. Water-level change varies greatly for the different depth zones of the ground-water reservoir and in the different parts of the area. The low permeability of the upper-zone deposits, and in some places the inferior quality of the upper-zone water, makes the upper zone generally undesirable as a source of irrigation water. However, in a belt parallel- ing the trough of the valley from Tranquillity to Strat- ford, permeable upper zone sands derived from the Sierra Nevada yield good quality water. Many of the wells in this belt are completed only in the upper zone, and they yield ample supplies of irrigation water. Else- where in the area many lower-zone wells are perforated opposite sands for a short distance above the Corcoran—a situation that is most common in the southern part of the area. Water-level trends in three Bureau of Reclamation piezometers east of Mendota at the Yearout site are shown in figure 24 to illustrate water-level trends in the main hydrologic units in the study area. The winter high and the summer low water levels are shown for the period 1951-66. Well 13/ 15—35D1 reflects the water level of the water table and the upper part of the semiconfined zone. Well 35D2 reflects the water levels in a confined zone above the Corcoran. Well 35D3 reflects lower-zone water-level changes. Most of the irrigation wells in the vicinity of the Yearout site are perforated only in the upper zone, but a few are perforated in both the upper and lower zones. The result is a 40-foot seasonal fluctuation in the pie- zometer tapping the upper-zone confined aquifer. The large seasonal fluctuation and the degree of separation between the water levels at well points 100 and 300 feet deep suggest that confinement is good. Water levels in. the confined part of the zone did not decline during the early part of the period of record but have declined 8 feet since 1958. The water level in well 35D1 remained about the same until 1960, but since then it has declined steadily with small seasonal fluctuations. The water-level trend E39 o l | l | l l I I l l l | I z 0 13/15-35D1, well point at 100 feet < _| /\/v E I— /\/\ /\ A W \—\ 3340 VA\V/\v \AAAA A LU LL m 2 V V V V VVV 5 L 13(15—35D2,wel| |_ U 80 pomtatSOOfeet . < < 3 LL 0 g \A l- A m 120 E 13/15-3503, well point at 590 feet \/\ fl (Iowerzone) o 16°olll|m|lllollllml L0 L0 LO 1.0 m °= e 2 FIGURE 24,—Hydrographs of upper- and lower-zone piezometets at the Yearout site. Data from the US. Bureau of Reclamation. may be representative, but the seasonal fluctuations in well 35D1 are much smaller than in irrigation well 34A1 (325 ft west of 35D1 and perforated at depths of 100—276 ft). Apparently, well 35D1 has limited hy- draulic continuity with the adjacent aquifer. The water levels in the lower-zone well, 35D3, have shown the steadiest and largest decline despite the fact that few wells in the area are perforated in the lower zone. The lack of nearby pumping from the lower zone accounts for the small amounts of seasonal fluctuation of water level. The high winter levels in 1956 and 1958 were coincident with two of the wettest winters since 1870. The 60-foot head decline in 14 years most likely is related to intensive lower-zone pumping farther west. This intensive pumping has produced a steep gradient on the east side of the Los Banos—Kettleman City area which has induced recharge from the east side of the San Joaquin Valley. Hydrographs of wells such as 35D3, from east of Mendota to Stratford, have histories of head decline resulting from the increase in gradient. In most of the project area, the seasonal fluctuation has been larger in the lower than in the upper zone, and water levels have declined more. THE WATER TABLE The surface of the unconfined water—the water table—in the Los Banos—Kettleman City area is difficult to define. Very few wells tap only the upper 10—50 feet of the saturated deposits. The lensing, heterogeneous character of the alluvium results in water levels that are not truly indicative of the water table in those wells that tap more than 50—100 feet of saturated alluvium. For example, a ZOO-foot well may have a gradually rising water level during a 10-year period suggestive of a rising water table that is receiv- ing irrigation water that percolates below the root zone. A nearby 100-foot well may have a more rapidly rising water level, thereby suggesting that it is more indica- tive of water-table conditions than the ZOO-foot well. E40 The minor differences in permeability of adjacent water-yielding beds are such that differences in head can exist between shallow wells during times of heavy pumping. Many of these shallow wells recover to the level of the water table during times of little pumping. Both semiconfined and perched conditions occur in various degrees. Apparent depths to the water table that are too deep are the result of semiconfinement of part of the beds penetrated by a well. Apparent depths that are too shallow result when the well is tapping a water body that is perched on a lense of fine-grained alluvium. Perched conditions occur where a fine-grained lense allows only part of the water to perco- late through it, has unsaturated deposits below it, and saturated deposits above it. In order to be able to analyze the change in effective stress that causes the subsidence, it is necessary to have knowledge of the changes in the position of the water table as well as the change in conditions in the semiconfined and confined aquifer systems. A rising or falling water table not only can cause expansion or compaction of the unconfined deposits, but also affects the effective stress on the deposits in the confined zone. The approximate position of the water table was de- termined by Davis, Green, Olmsted, and Brown (1959, p. 147, 148, pl. 16) on the basis of 1951 measurements and was supplemented by earlier measurements. The approximate position was determined partly by mea- surements in wells tapping unconfined and semiconfined zones and was supplemented by estimates of the top of the zone of saturation based on electric logs. The depth to water was less than 10 feet in a large area along the trough of the valley from Tranquillity to Los Banos. In general, the depth to water increased from east to west, and near the foothills of the Diablo Range the depth to water was more than 300 feet. These au- thors concluded that the position of the water table had remained approximately constant, declining slightly in some areas and rising some in others (p. 147).A compari- son of the altitude of the water table in 1951 (Davis and others, 1959, pl. 15) with the altitude of the water table in 1906 as plotted by Mendenhall (Mendenhall and others, 1916, pl. 1) suggests less than 20 feet of change in the position of the water table in the 46-year period. The water table declined as much as 20 feet in the southern part and rose as much as 20 feet in the north- ern part of the Los Banos—Kettleman City area. The Bureau of Reclamation has been obtaining more recent information regarding the water table, as part of projects to bring large amounts of surface water into the area in the Delta-Mendota Canal and the San Luis STUDIES OF LAND SUBSIDENCE Canal. The raising of the water table to near the land surface will require that drainage systems be built in order to continue growing crops. The Bureau of Recla- mation has drilled or augered more than 100 shallow wells to obtain information about water-levels in the unconfined zone. As a result of these studies, post-1961 water-table information is available for most of the area downslope from the San Luis Canal. The depth to shallow ground water in 1965 is shown in figure 25. Water levels in most of these wells approx- imate the water table, but for many wells it is not possible to determine the presence of perched or semiconfined conditions that might affect the water level to a minor degree. Most of the data northeast of the San Luis Canal were obtained from the Bureau of Rec— lamation. Electric logs of water wells drilled in the mid-1960’s were used to determine the depth to the water table in most of the area west of the canal. The general pattern of the depth to water is much the same as in 1951, with depths of more than 200 feet to water suggested by the map in the western part of the area. West of Huron, the depth to the water table ex— ceeded 500 feet in 1965. The area of depths to water greater than 400 feet at the mouth of Los Gatos Creek coincides with an area of permeable coarse-grained de- posits laid down on the ancestral alluvial fan of Los Gatos Creek. Little confinement is present in this area, and the great depth to the water table is the result of water-table declines caused by pumping of wells perfo- rated at depths of more than 1,000 feet. Davis and Po- land (1957, p. 429—430) note that the low water temper- atures and high sulfate content of the water suggests that recharge from Los Gatos Creek is able to reach the deposits tapped by wells. A similar situation probably exists at the mouth of Cantua Creek. Water levels were shallow in the eastern half of the area, the depth to water north of Five Points being less than 20 feet, and south of Five Points less than 50 feet. The area in which the depth to water was less than 10 feet was larger than in 1951. The change in the depth to shallow water between 1951 and 1965 can be obtained in a general way by comparing the 1951 and 1965 maps, as has been done in figure 26. Considerable variation in the trends of shal- low water levels are apparent in the different parts of the area. In the northern part of the area, water levels have risen from less than 25 feet to more than 100 feet. A large area in which the water table has risen more than 50 feet extends from the town of Cantua Creek to 15 miles west of Mendota. In 1951 the water table in this area was generally at a depth of about 100—150 feet. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE 120°30' 120°00, E41 37°00’ 36°30’ 33 l ' 15 Los Banos / Dos / Palos \F'ewm¢“R& / Mandate O ’ $29, Firebaugh <90 <90 $0 <9 0 1‘9 0114 § /Qé::9 90 J 0A0 Mendota O 1b 130 (763 93"“ 3“ Kermanc ‘ ’6: (O 2 We (as 5~ \ ‘\ ‘5 90 ‘ @\E \\ a J\ i ' “We _ , antua Creek {33 EXPLANATION ( ’27 \ 777W77777Z ’b . . Boundary of deformed Five Pomts \‘ rocks \ 100 I Generalized line of equal depth to shallow ground water (approximately the water table), in feet, 1965 2" Interval variable. From electric-log data, and an unpublished U.S. Bureau of Re- 50 clamation report entitled "Ground-Water conditions and potential pumping re- sources above the Corcoran Clay. An addendum to the ground-water geology and resources definite plan appendix 1963, 1965” | | \ Westh aven ‘ l Hu §\ 0 \ “on 00) N g O /00 \ / a“ e p. O 5 Western boundary of the Corcoran Clay Member of the Tulare Formation 6%.— San Luis Canal- California Aqueduct 36 °OO’ \ I \\ \ TULARE 4— 9r b > LAKE 93% o 5 1o 15 MILES 4’4, i—T—lfi—-fl—l—l / /( Kettleman BED o 5 1o 15 KILOMETRES , Q (s I City Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 25r—Depth to shallow ground water, 1965. E42 STUDIES OF LAND SUBSIDENCE 37°00'— 36°30' 120°30’ 120°00’ 33 I 15 Los Banos 152 / / Dos Palos / o ,1 Fresn ‘__ “W Rive \_ ___ , \__ f . / W \/ v’ ' Madera 33 0 ’ w 61,” / ‘71. 00 O / 419,40, 99 5V0 Q 0 o / 9%, Firebaugh “/53 g 459% R (3' 01“ JOAQ FRESNO r\r1 L‘ \ L. 80 3" Kerman T e e \ \\ \{p Cantua Creek <94 _ EXPLANATION K ¢ \ 77777777772 620 Fm Pom“ \ Boundary of deformed ‘*~ _ _ _ _ q rocks bx“ \» | - 450 .’ , Generalized line of equal change of depth 25 l ‘ 3/ to the water table, 1951-65 a I Q Interval 25 and 50 feet. 1951 depth to -25 32,- water from plate 16 (Davis and others, “-50 l '6’?» 1959). 1965 depth to water is from K electric log data and from an unpublished f U.S. Bureau of Reclamation report en- titled “Ground-water conditions and po- \Westhaveno tential pumping resources above the Corcoran Clay. An addendum to the :00 /\Hu\ron Strat— ground water geology and resources def- / ‘50) ° ford inite plan appendix 1963, 1965" 0 :/0/00 Western boundary of the Corcoran Clay ' Coallnga /&9:/) Member of the Tulare Formation VALLEY TULARE /4-$> \ ? ’26 LAKE 44 o 5 1o 15 MILES 44", ,__._,__-_,__,_n—a , ’< BED o 5 1o 15 KlLOMETRES 9 (s | 36 °OO’ Base from U.S. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 26e—Change in depth to the water table, 1951765. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE Outflow of water accumulating in the upper zone occurs as (1) movement of water toward Fresno Slough and the San Joaquin River, (2) westward movement toward V areas of lower ground-water table that are present be- cause of lesser amounts of water being received from irrigation or because the water table has been lowered by pumping; and (3) downward flow through the Corco- ran in gravel packs around well casings and through broken well casings. Water-level rises have been much less along the trough of the valley where many wells are perforated in the upper zone. The water table has risen less than 30 feet in most of this area. In the southern part of the area, the depth to shallow water has increased southwest of Westhaven and has decreased northeast of Westhaven. The areas in which the depth to water was less than 40 feet in 1951 had a shallower water table in 1965, but the rise has not been large because the water table was close to the land surface in 1951. Water-table decline occurred in the area west of the Corcoran. The effects of water-table decline west of the Corcoran have resulted in water-table declines for as much as 5 miles east of the western boundary of the aquiclude and may have influenced the rates of water- table rise for even greater distances to the east. The area of 250 to more than 350 feet of water-table decline at the mouth of Los Gatos Creek coincides with the area of maximum depth to water shown in figure 25. The overall pattern of water-table decline in the southern part of the area and of water-table rise in the northern part was the same as for the 1906—51 period. Three hydrographs of water-table wells are shown in figure 27. Each of these water levels is believed to be representative of water-table conditions although part of the perforations may be opposite beds in which the water is semiconfined. Wells 14/13—11D3 and 16/15—34N5 are at the Mendota and Cantua recorder sites. Well 12/13-32A2 shows the steady rising trend that is characteristic of the water table in most of the northern part of the area. Well 14/13—11D3 had a rising water level until 1964; since then the water table has declined. Well l6/15—34N5 has had a fairly constant or slightly rising water table—a situation that apparently has existed at the Cantua site since at least 1952 (fig. 27) and possibly since 1906 (Mendenhall and others, 1916, plate 1) when the depth to water in shallow wells in the vicinity was about 165 feet. THE UPPER-ZONE SEMICONFINED TO CONFINED AQUIFER SYSTEM Roughly 25 percent of the water pumped in the Los E43 0 I I I T I I I I I I I I l 12/13-32A2, 161 feetdeep __ /~ \/_—’ EB 40 _'L1J ”I'LL m2 I- uJuJ 8° 14/13—1103, :2 perforated E U- 180—240 feet 0‘1120 3 PU) E0 .12 3 3 16° 16/15-34N5, perforated 240~300feet 2°°o|||l gIFII gilll 3| 3 m 2 92 FIGURE 27.—Hydrographs of wells perforated in the unconfined zone. Banos—Kettleman City area is withdrawn from the upper zone. The areal distribution of water withdrawal is not uniform, as is shown by figure 10. In some areas, water is pumped entirely from below the Corcoran, and in other areas water is pumped entirely from above the Corcoran. In most of the area, and particularly south of Five Points, water is pumped from both the lower and upper zones. Most of the lower-zone wells that have perforations in the upper zone are perforated im- mediately above the Corcoran. In general, there is an improvement in water quality and an increase in per- meability of the deposits with depth in the upper zone, and in parts of the area the water obtained from im- mediately above the Corcoran is as usable for irrigation as the lower-zone waters. In most of the area, a large downward head differen- tial has developed across the Corcoran confining clay as a result of lower-zone pumping. Downward head differ- entials of 100—200 feet may be common in much of the northern part of the area. Water levels in wells tapping the lower zone and the base of the upper zone can be compared at two locations. Hydrographs for wells 15/ 14—15E3 (fig. 28), tapping the upper zone, and 15/ 14—14J 1 (fig. 44), tapping the lower zone, suggest a downward head differential of about 120 feet in 1965. Farther east at the Tranquillity site, in 1967 the water level in a well perforated a short distance below the Corcoran was 120 feet deeper than a well tapping the base of the upper zone. However, in the southern part of the area, head de- clines in the upper zone have been large where upper- zone water has been pumped intensively for irrigation. Observation wells tap both the upper and lower zones at the Westhaven site (figs. 3 and 14). The well tapping the sands (well 20/ 18—1 1Q1) immediately above the Corco- E44 ran has a deeper water level than the lower-zone wells (fig. 14). The record for well 11Q1 shows about the same seasonal fluctuation as for the lower-zone wells. This situation may represent pumping from a confined lense of sand of limited extent that is not connected with permeable beds leading to recharge areas. Upward gradients across the Corcoran may be fairly common in the southern part of the study area. At the Lemoore site, downward gradients of as much as 40 feet are present in the winter, but small upward gradients are present in the summer. The degree of confinement southwest of the edge of the Corcoran is highly variable. The head differential, as of 1943, between the water table and water levels in deep irrigation wells suggests only moderate lower- zone confinement in the area west of Huron (Bull, 1974). Head differentials in this subarea ranged from less than 50 feet to more than 100 feet. Hydrographs of three upper-zone Bureau of Reclama- tion piezometers are shown in figure 28. The three rec- ords are markedly different. The hydrographs illustrate the differences of confinement and separation of water bodies that occur in the upper zone as a result of heterogeneous lensing deposits derived from different sources. The summer low- and winter high-water levels have been used for the hydrographs. Well 15E1 shows little seasonal fluctuation and shows a steady rise in water level. Although this well taps both unconfined and semiconfined water, the rec- ord represents chiefly semiconfined conditions. The water table at the location has risen twice as much during the same period. Well 15E2 has a record of consistent seasonal fluctuations of 10—20 feet. The overall trend has been up, but the water-level rise has not been as much as in well 15E 1. Deposits Within the depth interval tapped by well 15E2 probably have a moderately good degree of confinement, but the amount of seasonal fluctuation is low because few nearby wells are perforated in this interval. Well 15E3 has a record of erratic seasonal fluctuations that exceed 80 feet in some years. The fluctuations indicate that water levels in this confined depth interval are influenced by irrigation wells in the vicinity that are pumping in part from the basal upper zone. An overall decline of water levels has occurred for this zone, which is immediately above the Corcoran. The hydrographs in figure 28 show why it is impossi- ble to make water-level maps, or water-level change maps, for most of the upper zone, in an area that is as large as the Los Banos—Kettleman City area. Even if abundant water—level data were available for the many different units within the upper zone, consistent results could not be obtained for more than a few miles because STUDIES OF LAND SUBSIDENCE 40 I I I I I I I I I I I I W/ 80 15/14-15E1, we” point at 230 feet 120 150 WWWWM A l /\ szlgzzzzza‘ m/V'VWV V MM m DEPTH TO WATER BELOW LAND SURFACE, IN FEET 15/14-15E3, V V V wellpointat 575feet 32°oll||m||1|ollllm LO LO (D (O m 2 9 9 FIGURE 28.—Hydrographs ofupper-zone piezometers at 15/141513. Data from the US. Bureau of Reclamation. of the many semiconfining beds of low permeability. Hydrographs of two unused irrigation wells perfor- ated in the upper zone are shown in figure 29. The rising trend in the water levels of well 13/ 14—17N2 is a result of recharge from irrigation water, which in this area is obtained largely from surface-water sources. The shal- low water level in 1959 appears to represent mainly water-table conditions. Later in the same year, how— ever, the water level rose rapidly to a depth of only 8 feet, probably as a result of a casing break that permit- ted unconfined water to dominate the water level. The abrupt rise in water-level indicates that the water tapped by this well was semiconfined although the well is only 196 feet deep. Well 15/16—20R1 was initially drilled to pump from both the upper and lower zones. Casing failures termi- OIIIIIIII / I l l | 4o / 13/14-17N2,196 feet deep / ~80 DEPTH T0 WATER BELOW LAND SURFACE lN FEET 4O MWMMAAA /\ 80 ' ' v15/16-'20R1 V v v V V . \ ”OgllllgllllgllTTgl 92 2 2. 2 FIGURE 29.—Hydrographs of wells perforated in the upper zone. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE E45 ’_ 160 I I I I I I I T I I I 17/1I7-21NI2, perIforate21403- 1397 feet ”$1 \ I\ /\ 240 l‘ E V \ N 8- 200 ‘ '/ ‘ / /\\/ \ l I \ \ l /l 3: \\/ \/\ 280 . V V V V V E _, 240 E 21/18-28M2, perforated 3 464-1221 feet Lu 320 m ,\ /\/\ 1960| | l l 1965 II E 280 V . A ‘ a \/\/ y. I l- 0. g 320 V/\\ 1945] l I 19501 | l | 1955l | | 1960| | l | l1965 FIGURE 30,—Hydrog-raphs of wells perforated in both the upper and lower zones. nated the use of this well for irrigation purposes and apparently sealed off the lower-zone waters. Another well, 1 mile away, that is representative of the lower zone has a water level more than 100 feet deeper than that of well 20R1. The winter high- and the summer low-water levels for well 20R1 have been obtained from a recorder that has been operating continuously since 1952. The consistent seasonal fluctuation of about 30 feet probably is rep- resentative of the upper zone, which is heavily pumped in the vicinity. The depth interval at which water moves in and out of the well casing is not known, but the large seasonal fluctuation indicates that the zone has good confinement. In 1956 and 1958, the summer low-water levels were abnormally high. These summers followed exceptionally wet winters. In these 2 years, a surplus of irrigation water from the Kings River was available for use in the vicinity, and apparently little ground water was pumped. The overall trend of the water level has been down—declining 10—13 feet in 12 years. Water levels in wells that tap both the upper and lower zones are shown in figure 30. The large seasonal fluctuation in well 17/17—21N2 is characteristic of ir- rigation wells southwest of Five Points. A declining trend of water levels is characteristic of the lower zone in this part of the area (fig. 45B), but the record obtained from well 21N2 is too short to show a well-defined water-level decline. The availability of the unused well probably was in part due to the fact that it was no longer usable for irrigation purposes. Casing breaks that shut off production from the deeper aquifers are common in the area; therefore, the record for well 21N 2 probably is representative of a much higher depth interval than indicated by the full perforated interval. As a result of the record obtained from this and other unused wells and the consistently high water levels noted in most unused irrigation wells during well rounds, it has been concluded that most unused wells are of dubious value for obtaining representative water-level records in a subsidence area. The record for well 21/18—28M2 was obtained from the California Department of Water Resources. This well is adjacent to Kettleman Hills and near the west edge of the Corcoran. Water levels in this area did not decline until the early 1950’s when agricultural de- velopment of the area near the Kettleman Hills ex- panded rapidly and numerous wells were drilled. A steady overall decline of about 6 feet per year has oc- curred between 1955 and 1963, and hydrographs of other wells in the vicinity (fig. 47) show that the decline was continued at about the same rate through 1965. In general, not many mixed-zone wells were moni- tored because of the difficulty of determining the rela- tive effects of the heads in the upper and lower zones. The differences in head and permeability of the various water-yielding beds make it difficult to use perforated interval in more than a general way to determine the effect of upper- or lower-zone head on the composite water levels or on the amounts of seasonal fluctuation. THE LOWER—ZONE AQUIFER SYSTEM The Corcoran Clay Member of the Tulare Formation provides excellent confinement for artesian pressures in nearly all of the Los Banos—Kettleman City area (see E46 fig. 12). The thick sequence of alluvial deposits below the Corcoran furnishes roughly three-quarters of the irrigation water pumped in the area. Overdraft has resulted in large declines in head in the lower zone, and it is here in the lower zone that three-fourths of the compaction that causes subsidence occurs. Fortunately, a large amount of water-level data is available for the lower zone, and a measurement of a single well is likely to be representative of the potentiometric head in the vicinity because the hydraulic continuity within the lower zone is good in most of the area (fig. 14). CHANGES IN THE POTENTIOMETRIC SURFACE The potentiometric surface was nearly flat prior to the pumping of ground water. On the basis of measure- ments made in 1906, Mendenhall, Dole, and Stabler (1916) estimated that the potentiometric surface sloped 2—5 feet per mile to the east and had a northward com— ponent of slope along the trough of the valley of about 11/2 feet per mile. By the time that Haehl and Forbes made their study for the Boston Land C0. in 1926, the potentiometric sUrface had been lowered, particularly in areas irri- gated with lower-zone water. Generalized contours of the potentiometric surface in the southern part of the area as of 1926 are shown in figure 31. The three major depressions of the potentiometric surface coincide with the areas of early agricultural development (fig. 21). Similar pumping depressions probably existed in the areas of early development west of Mendota: these are indicated by scattered measurements made in about 1929. Unfortunately, the density of the control points is insufficient to permit contouring of the potentiometric surface north of the area studied by Haehl and Forbes. With the expansion of agriculture, measurements were made available through the pump-efficiency tests made by the Pacific Gas and Electric Co. The static and 10-minute recovery levels made by‘ this company in 1943 are numerous enough to permit preparation of a map of the lower—zone potentiometric surface (fig. 32). The 1943 map shows that the trough of the poten- tiometric surface in the southern part of the area had moved west of the 1926 position and that a pronounced trough in the potentiometric surface extended from Tulare Lake bed to the Merced-Fresno County line. Part of the potentiometric surface southwest of Firebaugh had been depressed to below sea level. Pumping over- draft within the area had established a recharge gra- dient of 13—35 feet per mile along the east side of the area. STUDIES OF LAND SUBSIDENCE A widespread survey of the area was made by the U.S. Coast and Geodetic Survey in 1943. Thus, the 1943 vertical control and water-level control provide a base for comparison with more recent years. By 1960 the gradient had steepened to 18—44 feet per mile, and the trough of the pumping depression had moved even further west (fig. 33). The westward migra- tion of the trough of the pumping depression shown in figures 31—33, 35, and 36 is in the same direction as the increase in irrigated area shown in figure 22. By 1960 the potentiometric surface had been depressed below sea level in virtually all the area, and much of the area along the trough of deepest water levels was more than 250 feet below sea level. Northwest of Mendota the potentiometric surface was not at its historic low in 1960 because initiation of surface-water deliveries by the Delta-Mendota Canal in 1954 had decreased the amount of ground water pumped, thereby causing water levels to rise locally. The minimum altitude of the potentiometric surface in the area northwest of Mendota is based on historic low-water levels measured prior to 1960—mainly in the middle 1950’s. The time of year in which the water levels are meas- ured has a distinct influence on the altitude and configuration of the potentiometric surface. The lower- zone seasonal fluctuation within the study area ranges from less than 10 feet to more than 150 feet, therefore it is desirable to make water-level measurements in the area either at the winter high-recovery level or at the summer low-recovery level caused by intensive pump- ing. Numerous and well-spaced static measurements are much easier to obtain in December when most of the wells are shut down—a factor that contributes to an accurate map. Static measurements are not easy to ob- tain in August when most of the wells are pumping, but measurements made in August are more meaningful because they are made at the times of maximum applied stress and maximum compaction rates. Instead of summer static measurements, static levels (actually 10—minute recovery levels) made by the Pacific Gas and Electric Co. as part of pump-efficiency tests were used. By using selected measurements made in those months of the year in which there is intensive pumping (early spring and the summer), the minimum altitude of the potentiometric surface shown in figure 33 was obtained. The 1960 measurements were supplemented in part by measurements made in the summer of 1959, and in areas where no Pacific Gas and Electric Co. measure- ments were made, spring measurements made by the US. Geological Survey were used. Most of the spring CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDEN CE 1 20 ° 00’ E47 120°30’ 33 I 15 Los Banos 15 / / o , __ Dos 37 00 Palos / \Ffl/mu“Rv / / 33 09,,” u; re. 4, 0° / ”More o 2° / 940/ Firebaugh RIVER S' {9% Q 43' Q92 /0 $8) 09“: 1 OAQUIN FRE NO 0 ; J S / Q- 0/ r_\ r! ’0 Mendota |‘IL o \ / ‘76) 95‘,“ if). Kerman. .l’ (O 6% {>19 41 ( X m \‘ \ )\ \ (I \ 9,4, x < 6‘ <6“- \K MONOO ‘d\_ _ (”Vs 135/04 36°30’ ;_ 0/0 49,0 oCantua Creek \32 _ 9L 06‘ o ’9 '3; / \ ‘\ ”a 2,, 06‘ A \ . Five Poin\ts \ l EXPLANATION 6, \ \ \ 3 \ 1 , Xf’“ _ o \ I"; \ IN ' 77777777777 9 e \ \ a I ""° '/ Boundary of deformed (Os ) ’50 _/ \ \ rocks 6% \I) \ Key .1; 5 \ 125 {5‘ / \ \ / \L ’3’?» Generalized potentiometric contour \\ \ ( I ’35 Shows altitude of potentiomem‘c surface of , ‘\ ‘ \ \\ 19 \ lower water-bearing zone. Contourinterval ; \Wes a l "w\ 25 feet. Datum is mean sea level. Measure- » ° \ '2 ments from unpublished report by Haehl ‘3 \ and Forbes, 1926 \ Strat— OO \\ ford /_ \ l / ”’9; \, l 3 9‘» \‘LULARE § 1 \ LAKE 0 5 1O 15 MILES Kettleman BED 36°OO' O 5 10 15 KILOMETRES City Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE Bil—Water-level contours for the lower zone or its stratigraphic equivalent, 1926‘ E48 STUDIES OF LAND SUBSIDENCE 120°30’ 120°00’ 33 I 15 Los Banos 152 / / o ,_ Dos 37 00 Palos / ~‘.\_F_‘I:efla/.—._\.\’___\-/._"'\\_River _ / 33 e], / w a / y; Meadow Q o A v a / 9‘2?! Fuebaugh RIVER € 4;? Q9 a [5- / 0 961°C? ”‘6 <20”I ,QS’QO 1; 10A FRESNO Q / “n 1‘; Mendota ‘; L‘L 0/ $0 180 180 \ ‘76) 95‘,“ t9 Ker-man. J‘ ( 94a. o 2Q \o 41 m \ \‘ A ‘39 ‘ co , \ )‘ % \ (I ) \\ ’9/(1761— 751‘ \ 6‘ *9 \ 6‘0 ‘3 _ 4104/00 .3\ \ —\_ — Cf/l\/$ \ \ C k \ MQ o ,_ z '9 oCantua ree \f; _ 36 30 «61 IO \ \K A» °¢ \ t 44/ ’< ‘\ O v Five Points \ 6‘ \ \r EXPLANATION \ II V. , I . 77777777777! 2 ,// Boundary of deformed 7’ rocks I [five 75 \ 1%?” Generalized potentiometric contour / Shows altitude of potentiometrt'c surface of / l B lower water-bearing zone. Dashed where W ) approximately located. Contour interval \\ esthave '73. 25 feet. Datum is mean sea level. Chief ’ \\ k‘150 s: source of water-level measurements used ‘ Hurono \ 7 Strat— for control was the Pacific Gas and ‘\ O) 25 ‘~ ford Electric Co. 3/ O 900 [ __ 30% Western boundary of the Corcoran Clay €qu»; Member of the Tulare Formation ' \ ‘ 200/ \ TULARE (641 ’6‘0 41 LAKE 4 15 MI E 4’ 36°00, o 5 1o 15 KILOMETRES 1 s j City Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 32r—Water-1evel contours for the lower water-bearing zone, 1943, 37°00’ 36°30’ - 36°OO’ CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE E49 120°30’ 120°00’ 33 l 15 \ Los Banos 152 \ m0 , . ~.v\_F_":e\/——»-\.\’___\/_,“Mliwer __ w \ ‘3 \ o: \ 99 g 0 l 3 e F' b h R ire aug I RIVE % 3 Q UIN who i FRESNO r\ n endota I L-L 180 l 180 \ _ Kernian T '3‘). \\ Q»? |\ 41 \ \_\ ,\ \ \\\ \ \ \9 \ EXPLANATION 9/9176 \ \ \ X \ a \ , <<¢+ \ \ \\\\ \\ \ B d f d f0 rn d . oun all-’Oste r e 4104/00 \ v30 \ \\ \.\- 1 \ 450 (”Vs \ ‘ \\ X590 \ Generalized potentiometric contour 0/ ’9’ \ Cantua ree\ \ ~53? \ _ Shows altitude of potentiometric surface of the 6:9 0 \ \ \ \ lower zone. Dashed line indicates approximate 1— 06‘ \ \ \ \ \ position in areas of poor minimum water-level 0’9 \ \ \ \ \ ‘ control. Contour interval 25 feet. Datum is ’9 /( \ \ \ \ mean sea level. Chief sources and dates of ‘74, ( A \ \ water-level measurements used for control: 0 ‘5‘ \ ~ Five Points \ \ Pacific Gas and Electric Co., 1959-60, but (0 ‘9 990 \G \ mainly summer 1960 (recovery about 10 min- 6‘0 \ \ \ \ ~ ~ ‘ utes after pump off); and U .5. Geological S ur- \\ \ a [—K; —— — - vey, May 1960, and in part May 1959 *300 \ G \\\ \ \ ‘ >7\’_/ ~ \_ unuooonnuuuuo 0’0 \ >>\ {.3 I / — Areas in which contours are drawn on 33 / \\ 6‘ 1‘ / , minimum water levels that occurred between 0< / ~ 1; \ , l 1950 and 1958 °s (- 13 \\ , Water levels in this area rose for several years \ ‘9) ‘2) \l \ 7‘ prior to 1960 because water from the Delta- Q \ ‘5‘ ‘9 o‘ \ «1. Mendota Canal has in general replaced (6- \ ‘3» \ v :15“ ground water for irrigation T \\ \\ — \\ K Western and eastern boundaries of the Corco- \\\ i \T\ \ \ - \ ‘\\Xfl? I ran Clay Member of the Tulare Formation \ \\ \ \ Wes thaven \§ &, Water-level control points west of the Corcoran / / '7 a l \ \\ ‘ ' ‘ O \\ .2. \ are from measurements in wells that are perfo- / .9 , Huron \ \ 9‘ \ rated in the same stratigraphic unit as the ’00? \ \ . ‘ \ o \ \ S t lower-zone wells in areas of the Carcoran 412° \ . \ ~ ‘ or: - F—F' PL ASANT \\\\ :\ ) \ \ Line along which the slope of the potentiometric _ :3“ m surface was computed from maps represen- Coallnga \\ / tative of the period 1926-65. See figures 37 u \ / 3 and 38 VALLEY gem / / / l \ \ / / / ,TULARE 4— 6» \ / E/ f g6 \ / / LAK 4,, 41 “50/ o 5 1o 15 M I LES ”Iv/Y , 33 /(< Kettleman BED 0 5 1O 15 KILOMETRES , 6‘ City Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 33.—Minimum altitude of the potentiometric surface of the lower zone as of 1960. E50 measurements were not made at times of maximum pumping, and those parts of the map are dashed. The 1943 map is also based on measurements made by the Pacific Gas and Electric Co. The measurements were made at various times of the year, but mainly during times of maximum pumping. Thus, the 1943 map is more representative of the summer lows than of the winter highs. Although the decline had been large as of 1960, sufficient pressure remained in the lower zone to cause water levels in wells to rise above the base of the Corco— ran in most of the area. The artesian head of the lower zone as of May 1960—a time of seasonally high water levels——is shown in figure 34. Artesian head of 300—500 feet above the base of the Corcoran still existed in most of the study area. The amount of head present decreased to the southwest. In the southern part of the area, 200—400 feet of head was still present at the western boundary of the Corcoran. In the central part of the area, the lower-zone head was less than 100 feet near the mouth of Cantua Creek. The lower-zone water levels were more than 200 feet below the base of the Corcoran adjacent to the Diablo Range in the northern part of the area where the Corcoran has been strongly folded (fig. 13). Water-table conditions exist where the lower-zone water levels have declined below the base of the Corcoran if deeper confining beds are not present. The decline of lower-zone water levels below the base of the Corcoran does not greatly change the rate of increase of stress being applied to the lower zone, how- ever, the processes of stress increase are changed mark- edly. During water-level declines under confined condi- tions, increase in applied stress equal to 1 foot of water will occur for each foot of additional decline in artesian head. The process involved is one of increased seepage stress equal to the magnitude of the head differential. After the lower-zone water levels have declined below the Corcoran, further decline in head does not cause further increase in seepage stress. Instead the applied stresses are increased as a result of two other types of processes. Under the assumptions specified in the sec— tion "Stresses Tending to Cause Compaction,” removal of buoyant support of the grains in the aquifers during the course of dewatering will cause an increase in ap- plied stress equal to 0.6 foot of water for each foot of additional water-level decline. Added to this stress in- crease is 0.2 foot of water that results from part of the intergranular water changing from a neutral to an ap- plied stress condition—the amount being equal to the water of specific retention. The overall effect of lower-zone water levels dropping STUDIES OF LAND SUBSIDENCE below the Corcoran and then continuing to decline is a decrease in the rate of stress application of about 0.2 foot per foot of additional water-level decline. The amount of increase in applied stress under such conditions has decreased from 1.0—0.8 foot of water per additional foot of lower-zone water-level decline. The 1962 map (fig. 35) is representative of the winter high in the potentiometric surface, and all the mea- surements were made in about a week. In most of the area, the December 1962 potentiometric surface is higher than in the summer of 1960. The lowest part of the potentiometric surface was northeast of the Big Blue Hills where the surface was more than 325 feet below sea level. The gradient along the east side of the area was more uniform and had a more gentle slope than in the summers of 1943 and. 1960. In December 1962, the gradient ranged from 22 to 33 feet per mile. The trough of the potentiometric sur- face was farther west than in earlier years, and it was narrower than the troughs in the summers of 1943 and 1960. The water-level measurements of December 1962 and December 1965 were made 2—4 months before the bench-mark network was releveled by the Coast and Geodetic Survey. The potentiometric surface just before the 1966 releveling of the bench—mark network, is shown in figure 36. Comparison of the potentiometric surfaces at the time of the winter highs of 1962 and 1965 shows that the configuration and altitude of the poten- tiometric surface were virtually the same in 1965 as in 1962. All the maps for the previous years (most of which are not included in this paper) show a progressive de— cline of the potentiometric surface (figs. 39, 40), and a westward migration of the trough of maximum depth to the potentiometric surface. By 1965, winter water levels were slightly higher in part of the area than in 1962. The overall similarity of the 1962 and 1965 maps suggests that a rough balance had been established between total pumpage, the amount of water derived from compaction, and the amount of subsurface re- charge to the lower zone as a result of change in the gradient of the potentiometric surface along the north- east side of the study area. The hydraulic gradient along the east side of the study area has steepened as a result of increased pump- ing of ground water to the west. Changes in the slope of the potentiometric surface along two section lines have been derived from maps of the potentiometric surface and are shown in figures 37 and 38. Line G—G’, 4.3 miles long, extends southwest from Five Points. Line F—F', 37 °00’ 36°30’ 36 “00' CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE 120°30’ 120°00' E51 T Los Banos / Dos Palos / 3 / 3 0,1,0 / Me I1 0" o 0 a/ ,t ‘00 EXPLANATION 77777777777, Boundary of deformed rocks +100 Generalized line of equal distance between the base of the Corcoran Clay Member of the Tulare Formation and water level in wells tapping the lower zone, in feet Interval 100 feet. Areas of positive numbers indicate where artesian pressure causes the water level to rise above the base of the Corcoran, in wells. Negative numbers indi- cate where the water level is below the Corcoran and unconfined conditions exist. Based on maps showing the depth to the base of the Corcoran (figure 12) and the depth of the water level as ofMay 1960 Western boundary of the Corcoran Clay Member of the Tulare Formation 0 10 15 MILES O 5 1O 15 KILOMETRES 1 ‘~‘\.F:r.es~no/'“"-\,.__\/- m ‘31, Firebaugh endota 180 007* Kermanc Five Points \ m *500 | x PL ASANT Coalinga VALLEY Kettleman City f’l“ TULARE LAKE BED Base from US. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 34.—Art,esian head of the lower zone as of May 1960. E52 STUDIES OF LAND SUBSIDENCE 120°3o' l 15 120°00' 33 Los Banos 152 37°OO’— DOS Palos / ,' , sno _ ’ .k \frfL/ '----"\’\/ 0% / "a / Mewoza ’ 0")?! Firebaugh $090 ’0 $8’63€§ 00” /§Q'®Q9 1’ 10A 0 Mendota Cantua Creek 36°30’ — EXPLANATION Boundary of defortned rocks 400 Generalized potentiometric contour Shows altitude of potenfiometric surface of lower water-bearing zone. Con tour interval 50 feet, except the 25-foot line. Datum is mean sea level. Measurements, by US. Geological Survey, represent approximate high level for the 1 962-63 winter season TULARE LAKE a: . Kettleman BED O 5 10 15 MILES City 0 5 10 15 KILOMETRES 60 I 3 00 Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 35.—Water—level contours for the lower-water-bearing zone, December 1962, CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE E53 120°30’ 120°00' 33 I Los Banos 15 / / o , _ Dos 37 00 Palos / a \ ._.\_F_'r—B_SI:0/_‘__ 33 0} ’ w Ira \ fi/ ‘9‘ M\ / “40> / .50 Q" \ 49’ Firebaugh 0 $63 ’0 \ ‘V C/cf‘ \ 4‘ Q» 0 § \ lg? Q/ ' ’37 E endota 0/ 1° ' 180 76> Q; \ Kermanc J— 6‘ L As (O 5‘? § %0 41 ( \ w 8V \\ \ \‘ >0 p65 \ \\\ ’9 \ «47¢; \ \ \\ (,3 \ 4404/ \ \ .\ 00‘ \ \ \ — _ as \ \ “we . 0/ *9 Cantua Creek ~58? _ 36°30 — 6)» ’0 \ \ \ Lo 06‘ \ \1 ‘Sr l \ ( 94¢ ’< 9% \ \ x ( \ 62¢ ‘9 Five Points \ \ ~. 3300 \ \ fl; __ _ - _ \ \ ‘_ -L_ 9/0 . EXPLANATION 0 aa \ /’ < , , (’6‘ . Boundary of deformed [Y’Q 3; rocks ‘9 '3’; 450 Generalized potentiometric contour ,‘ Shows altitude of potentiometric surface of / .7 73. lower zone; dashed where approximately // ,9, ,0 .50 Ki located; contour interval 50 feet. Datum is a 0091’ \ trat- mean sea level. Measurements represent PLEASANT 6* 0rd approximate high level for the 1965-66 [ winter season Coalinga VALLEY / TULARE 5} f (@444 41/ / LAKE o 5 1o 15 MILES 4/ / 5% Kettleman BED 36°00, o 5 1o 15 KILOMETRES , 33 ‘6‘ City Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FxGURE 36i—Generalized water-level contours for the lower zone, December 1965. E54 30 I l Line of measurement along G-G SLOPE OF POTENTIOMETRIC O | SURFACE, IN FEET PER MILE EASTWARDIWESTWARD _, O | 1900 1920 1940 1960 FIGURE EXT—Change in slope of the potentiometric surface ofthe lower zone south- west of Five Points, 1906—66. Line of section shown in figure 33. 7.7 miles long, extends to the southwest from a point midway between Firebaugh and Mendota, but dis- tances of 4.0 and 5.6 miles had to be used for some periods. The location of the section lines are shown in figure 33. The head differential for each period along both lines has been corrected for the estimated post-1906 subsidence. Mendenhall, Dole, and Stabler (1916) estimated that the slope of the lower-zone potentiometric surface in 1906 was 2—5 feet per mile to the east. A value of 4 feet per mile to the east has been used in both figures. Both graphs indicate that the amount of underflow 30 I l I 20 e , . _ Line of measurement along F- SLOPE OF POTENTIOMETRIC SURFACE IN FEET PER MILE 10 — g / < / E / é, - / - E // E l£11900 19l20 19'40 1960 w FIGURE 38.—Change in slope of the potentiometric surface of the lower zone south- west of Firebaugh, 1906—66. Line of section shown in figure 33. STUDIES OF LAND SUBSIDENCE from the east side of the San Joaquin Valley has in— creased substantially since about 1916. Unfortunately, as of 1968, the hydraulic conductivities of the lower- zone deposits are not known so the amount of change in underflow cannot be computed. Along the span of section lines F—F’ and G—G’, the westward steepening of the potentiometric surface ap- pears to have ceased in the early 1960’s—most likely because a general equilibrium between underflow, water of compaction, and withdrawal may have been approached. The rate of steepening of the potentiomet- ric gradient decreased about a decade after the increase in total pumpage stopped (fig. 23). Part of the post-1960 change can be attributed to the fact that the 1962 and 1965 slopes were taken from maps of the winter high potentiometric level. The surface has a steeper slope in the summer than in the winter. Profiles indicating the changes in the configuration of the potentiometric surface in the northern and southern parts of the area are shown in figures 39 and 40. All the data, except the 1943 data, are for times of seasonal recovery highs. The May recovery high is almost the same as the December recovery high, and for some years in the southern part of the area, May water levels are higher than December water levels. The altitude of the potentiometric surface for the line of section between Tumey Hills and Mendota, measured six times between 1943 and December 1965, is shown in figure 39. A progressive deepening of the potentiometric surface is shown by the profiles. In 1943 most of the potentiometric surface was above sea level, but by 1966 the potentiometric level was as deep as 270 feet below sea level. The 1943 profile is symmetrical, but the 1953—65 profiles have varying degrees of asymmetry. The location of the troughs of the profiles have varied, but the trend has been an overall westward migration of the trough of the deepest water levels. The greater sep- aration of the lines of profile in the western part of the line of section shows that greater head declines occurred between the various periods of measurement in the western part than in the eastern part of the line of section. The altitude of the potentiometric surface for the line of section between Anticline Ridge and Fresno Slough, measured six times between 1943 and December 1965, is shown in figure 40. In contrast to the previous set of potentiometric levels shown in figure 39, the poten- tiometric levels have not deepened uniformly here. Most of the head decline occurred between 1943 and 1953. Since 1953 the overall trend has been toward a slow decline in artesian head, but the depth to water varies greatly for the individual years. All the profiles are asymmetrical and have steeper slopes in the west- ern parts of the line of section than in the eastern. As in CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE F 100' ' I “ SEA LEVEL 100' h “ 200' — — \ y/ o 2 4 6 MILES ‘ \ 090 IF I | I I l J — \ 0 2 4 6 KILOMETRES _/ VERTICAL EXAGGERATION X 211 300' FIGURE 39.—Change in the altitude of the lower-zone potentiometric surface, figure 39, the trough of deepest water levels has mi- grated to the west, and the largest amounts of post-1943 head decline have been in the western part of the line of section. The change in the potentiometric surface between 1943 and 1960 is shown in figure 41. The maximum head decline shown is northeast of the Big Blue Hills where the potentiometric surface had dropped more than 400 feet in the 17-year period—an average of about 25 feet per year. Areas of lesser head decline, such as along the road southwest of Five Points near Anticline Ridge, are largely the result of a low density of wells where less water has been pumped than in adjacent areas of more abundant wells. In general, the decline in head was only 50—150 feet in the eastern and northern parts of the area, but more than 300 feet of head decline was common in areas close to the Diablo Range. The amounts of head decline are in part a function of 1943—66, Tumey Hills to Mendota, Line of section F—F’ shown in figure 3. distance from the recharge area. The eastern and northern parts of the area are closest to the area of major recharge—the east side of the San Joaquin Val- ley. Very little recharge is derived from the Diablo Range, particularly lower-zone recharge. The areas near the Diablo Range have had the most severe head declines because they are farthest from the Sierra re- charge water and because they are adjacent to a moun- tain front that approximates an impermeable bound- ary. Much of the recharge water from the east is inter- cepted by wells before it reaches areas near the Diablo Range. In the southern part of the area, the maximum head decline is nearer Huron than the Diablo Range. The lower zone in the area between Huron and. the Diablo Range is receiving undetermined amounts of recharge from intermittent flows of Los Gatos Creek. The Corco- ran is poorly defined or absent in most of this area, thereby permitting recharge of the lower zone. The E56 150' — 100' r 50' ~ STUDIES OF LAND SUBSIDENCE SEA LEVEL 100' - 150' r 200' — \ / 2 4 l l I | l 2 4 6 KILOMETHES 6MILES O——O VERTICAL EXAGGERATION X 211 250' FIGURE 40.—Change in the altitude of the lower-zone potentiometric surface, 1943—66, Anticline Ridge to Fresno Slough. Line of section G—G’ shown in figure 3. 1951—65 change in depth to water-table map (fig. 26) shows that the area southwest of Huron has had the maximum decline in the water table in the study area. This indicates that water in beds that are stratigraphi- cally equivalent to beds in the upper zone east of Huron is moving down to partly recharge water withdrawn by the deep wells. Another reason for the lesser amounts of head decline in the area west of Huron, as compared to the areas adjacent to the Diablo Range farther north in the study area, is the lack of an impermeable boundary. In this area, the impermeable boundary is actually the south- west side of Pleasant Valley because ground water can move from Pleasant Valley to the San Joaquin Valley through the gaps in the foothill belt. In the area northeast of the Big Blue Hills and south- west of the town of Cantua Creek, the head declines in excess of 300 feet are due, in part, to the aquifers pene- trated by the irrigation wells. The wells in this subarea are perforated in the Tulare Formation below the Cor- coran and in the marine sands of the Etchegoin Forma- tion. Although fresh water has largely replaced the salt water in the marine sands, very little recharge reaches the sands compared to the amount of recharge to the Tulare Formation. The lack of significant recharge to the Etchegoin sands probably is the main reason why this part of the study area has undergone the maximum decline in head between 1943 and 1960. The change in altitude of the lower-zone potentiomet- ric surface between December 1962 and December 1965 is shown in figure 42. In marked contrast to large head declines that occurred between 1943 and 1960, the re- cent 3-year period has been one of rise, as well as de- cline, in the potentiometric level. The extremes within 37°00’ 33 CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE 120°30’ 120°00’ ‘ | E57 152 'u 15 \ Los Banos 36°30’ 36"00’ \ Firebaugh . JOA Mendota 180 RIVER Kernian . EXPLANATION Boundary of deformed rocks 10“ <0 ‘7 .150 4’0 Generalized line of equal water-level change for the lower zone Interval 50 feet. Chief sources of water-level measurements used for control: Pacific Gas and Electric Co. and US. Geological Survey Areas in which the lines for the 1960 map are drawn on minimum water levels that occurred between 1950 and 1958 41 Water levels in this area rose for several years prior to 1960 because water from Delta- Mendota Canal has in general replaced ground water for irrigation Western and eastern boundaries of the Corcoran Clay Member of the Tulare Formation , 0 0 10 15 MILES 5 10 15 KILOMETRES Base from US. Geological Survey Central 41 Kettleman TULARE LAKE BED Valley map, 1:250,000, 1958 FIGURE 41.—Decline in the altitude of the potentiometric surface of the lower mne, 1943—60, City E58 STUDIES OF LAND SUBSIDENCE 120°30’ 120°00’ 33 I 15 Los Banos 15 I / o , _ Dos 37 00 Palos / \fl/mx/“Rv I / 33 Delta / 0371‘ / Mendotc / 63% Firebau h ER V e o ’ g RIV € ‘9 Q ‘1' c?’ 0 Q (gs-1% QU‘N , $00 A Job FRESNO / r\n 4 “i 7 L 0/ 7'00 130 an \ 7 .S' r Kermano T 6% e '39,? O '2 \b’e ‘1 ( \ \D 6 V\ ) \ 222% ‘ Q9" 4’0 ~00 ’\ ( 4/ \ 0 s .9 \ 0/ o ‘9 C 36°30’ — ‘6 ,0 _ 9L 06 L o / 0 e _ ‘7¢ <( O 0 <0 EXPLANATION \. o, . ‘3‘ , 7777777777? 63 ,/ Boundary of deformed rocks -50 33, Generalized line of equal water-level change for the lower zone Interval 25 feet. Based on measurements made by U.S. Geological Survey and Calif- ornia Department of Water Resources Strat- ford Areas of more than 25 feet of head rise Western boundary of the Corcoran Clay Member of the Tulare Formation TULAHE ' r f (Q41 u LAKE o 5 1o 15 MILES "lg, , Q Kettleman BED 36000, 0 5 1o 15 KILOMETRES | , 9 <& | City Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 42.—Change in altitude of the lower-zone potentiometric surface between December 1962 and December 1965. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE the study area are 50 feet of head rise west of Firebaugh, and 75 feet of head decline southwest of Huron. Locally, in areas such as southwest of Huron, and adjacent to the Big Blue Hills, lower-zone head decline was continuing at rates similar to those in the early 1950’s—the period of maximum rates of head decline for much of the area. Between 1962 and 1965 pronounced head decline was occurring in only about 25 percent of the area. Areas of head rise of more than 25 feet totaled about 5 percent of the study area; the remaining 70 percent had little change in potentiometric level or underwent minor amounts of head rise. The areas of maximum head de- cline were farthest from the area of major recharge east of Fresno Slough. In the rest of the area, a rough balance between pumpage and sources of ground water ap- peared to have been achieved, as was noted in the dis- cussion of the change in potentiometric slope. SEASONAL FLUCTUATION OF THE POTENTIOMETRIC LEVEL The trend in seasonal changes in the lower-zone ar- tesian head is roughly the same throughout most of the Los Banos—Kettleman City area. After the summer, pumpage decreases during the fall as many crops are harvested. Some irrigation continues for the planting of winter grains. The winter recovery high occurs most commonly during the last part of December. Pumping during the first months of the year for preirrigation of summer crops causes the head to decline by the middle of March to almost the same level as the summer low. Little pumping occurs while the summer crops germi- nate, and by early May water levels in much of the area have recovered almost to the December high levels. Summer is the time of maximum pumping, and the lowest water levels usually occur during August. Thus, the typical seasonal trend of the lower-zone water levels has been to have two major fluctuations each year—low levels in March and August separated by periods of pronounced recovery that peak in May and December. The pattern of seasonal head decline between De- cember 1965 and August 1966 is shown in figure 43. In general, the trough of maximum seasonal fluctuation, about halfway between the topographic trough of the valley and the Diablo Range, is largely controlled by the density of well spacing. This is particularly true in the northern half of the study area. In the southern half of the area, the gross lithologic properties of the lower zone are important in influencing the extremely large amounts of seasonal fluctuation. A lithofacies map (Part 2, fig. 68), based on the mean resistivity of the lower-zone deposits corrected E59 to 100°F and 1,000 mg/l NaCl salinity, shows a remark- able similarity of pattern with the seasonal fluctuation map of figure 43. The arc of seasonal fluctuation in excess of 80 feet corresponds with an arc of minimum resistivity of the lower-zone deposits. Thus, the large seasonal fluctuations appear to be the result of the pres- ence of thick fine-grained deposits of low permeability. In order to get sufficient yields, many pumps have to be operated with drawdowns of 50—100 feet. Northwest of Tulare Lake bed, farmers prefer to operate the pumps in this fashion instead of drilling wells 2,500—3,000 feet deep to tap the deeper fresh-water-bearing deposits (figs. 12, 17). In the small area southwest of Mendota, seasonal fluctuation in excess of 80 feet is also influenced partly by lithology. This area is part of the area of intertongu- ing fine-grained facies of the Sierra and Diablo flood-plain deposits. It is also the area of lowest well- yield factors in the northern part of the study area (fig. 16). The seasonal fluctuation map indicates the variation in applied stress during a given year. In those areas of 10—20 feet of seasonal fluctuation, the maps of the potentiometric surface made at the times of minimum applied stress, such as December 1962 and December 1965, are useful in determining the relation between change in applied stress and compaction. However, in much of the area, seasonal head declines of 60—150 feet result in substantially greater stresses being applied to the lower-zone deposits during times of maximum pumping than during times of minimum pumping. For this reason, the critical maps and hydrographs used in this series of papers for studies of the interrelations of hydrologic and geologic factors are based on changes between summer water levels. The variation in seasonal fluctuation from east to west across the central‘part of the area is shown by the records of lower-zone observation wells 15/16—34E 1, 15/14—14J1, and 16/14—16N1 in figure 44. Well 34E1 shows a fairly consistent seasonal fluctuation of 10—15 feet, particularly since 1959. Few, if any, wells pump from the lower zone in the Vicinity. The seasonal fluctuation and the overall decline in artesian head at this site are chiefly the result of intensive lower-zone pumping farther west. Well 14J 1 is in an area which has moderately high density of wells and where nearly all the irrigation water is pumped from the lower zone. The 40—70 feet of seasonal fluctuation is typical of other lower-zone wells in the vicinity that are deeper than well 14J1. Well 16N1 is only a mile east of the Diablo Range. The 40—50 feet of seasonal fluctuation is less E60 37°00’ 36°30’ 36 °OO' STUDIES OF LAND SUBSIDENCE 120°30’ 120°00’ 33 j 15 Los Banos 152 / / _ Dos Palos / L~.\_If{efl'°/—..\,\’___\/_.v”\\_grver / 33 091,4 "$1 ”0’40,” 0 ’ 9%., Firebaugh Q ’0 egg ’0 9% 0‘3? 120 A001?! 0 o 10 FRESNO KS' 0/ 60\\f m n 4? Men 0% , H‘— o/ \ 8° \ .7 6' \ Kermanc J— 6) <6 was (0 2 We ‘” ( X m \\ 100 \\ )s \ (I 0 \ 5/1, ~ < 6‘ {a} \K Moll/0° w\_ 1 lo (”Vs 1‘36 _ 96‘ '9, Cantua Creek \fdg _ 9L 06‘ N 20 o 6‘ \ ’9 ‘o , \ 7¢ Q \ 0 62° 0 / ive Points \ Ga “\ k 120 r—‘\ “— ‘N ' ' EXPLANATION 0 “‘o I “ ' ’0 14a , . 7777777777 4, 33 '60 '\ / Boundary of deformed (06‘ °o I rocks A,“ 7% 120 4s \\ ‘ 2‘): Generalized line of equal water—level change for the lower water-bearing zone ‘ \ . 19 Interval is 20 feet, except for the 10-foot \ g \ \Westha n l .3 line. Chief sources of water-level measure- / / 7 9 '2- ments used for control: U.S. Geological / 9/1.. 0 H tone I x3 Survey and Pacific Gas and Electric Co. 0 (41’ \‘ Strat— "° to o ford PL SANT C; 0 Western boundary of the Corcoran Clay _ $0 ’0 Member of the Tulare Formation Gownga i {291/65 VALLEY Q ’8 <90 I ’00 TULARE 6‘ 524‘ LAKE 4144’ 0 5 10 15 MILES , ,y/( Kettleman BED 33 ( - 0 5 10 15 KILOMETRES / 6‘ Clty Base from U.S. Geological Survey Central Valley map, l:2$0,000, 1958 FIGURE 43.—Seasona1 decline in the altitude of the potentiometric surface of the lower zone, December 1965 to August 1966. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE 120 I l I | I | l I I | I | | I I | 140 — _l 16 — — o 15/16»34E1 180 — — 200 - ’ 220 300 320 - 34o — 360 _ 15/14-14J1, 1010 feet deep 380 — 400 k 420 720 740 - a 760 - 16/14-16N1, 2027 feet deep — 780 — - DEPTH TO WATER BELOW LAND SURFACE, IN FEET 800 | I I l l l l l | I l I I l | | FIGURE 44.—Variation in seasonal fluctuation of water levels in lower-zone wells in the central part of the Los Banos—Kettleman City area. than for well 14J 1, despite the fact that well 16N1 is farther from areas of potential recharge. The smaller fluctuation at well 16N1 most likely is due to a lower density of wells in the vicinity. There were no irrigation wells west or southwest of well 16N1 during the period of record. HISTORY OF HEAD DECLINE In an area as complex as the Los Banos—Kettleman City area, the history of head decline is highly variable. Factors influencing the patterns of lower-zone head de- cline, as shown by hydrographs, include the rate of agricultural development, changes in the types of crops grown, recharge, hydraulic conductivity of the aquifer materials, and the amount of imported surface water available. The trends of head decline within the area are separ- ated into long-term and short-term records; the long- term hydrographs show trends from as early as the 1920’s, and the short-term hydrographs show trends from the late 1940’s through 1965. Nearly all the data are from the Pacific Gas and Electric Co. Pumping levels were used because they are much more abundant than static levels. The drawdown between static and pumping levels remains essentially the same for a given well over a period of years. This is because the well yield must be sufficient to supply the crop requirements of the E61 fields being irrigated. If the yield declines because of head decline, a larger pump is installed, and the amounts of yield and drawdown for the well remain about the same as previously. Only those measure- ments made during times of widespread pumping were used. Winter high measurements were not used because not enough of them were available to show overall water-level trends within ranges of seasonal fluctuation as was done in figure 44. The use of occasional winter measurements would distort the overall trend in water levels. The use of summer and spring low pumping measurements wherever possible permits a smoother portrayal of the trends. Summer measurements also permit the trends to be based on the times of the year in which the potentiometric surfaces are at their lowest levels, maximum stresses are being applied to the aquifer system, and compaction rates are highest. The five long-term hydrographs shown in figure 45 represent different trends, from the northern part of the area in figure 45A, to the southern part of the area in figure 45C . Additional long-term hydrographs have been paired with subsidence graphs in Part 3. The 1932—66 lower-zone head decline near the Merced County line is shown in figure 45A (wells 12/ 12—34N1 and P1). The pre-1932 head decline in this area is estimated to be about 150 feet. A period of rapid decline ended in the late 1930’s. Between 1937 and 1951 the head declined only 25 feet. The rate of head decline increased between 1951 and 1954. Since delivery of Delta-Mendota Canal water in 1954, the head has con- tinued to decline, but at a decreasing rate. In contrast to the gradual decline in summer water levels since 1960, the winter levels have risen about 0—25 feet in the vicinity (fig. 42). The other hydrographs shown in figure 45A are for wells about 8 miles southwest of Mendota. Well 14/ 14—30E1 was one of the first wells to be drilled in this part of the township, but several miles to the northeast pumpage of lower-zone water had occurred prior to 1924. After World War 11 many additional wells were drilled to the southwest, as agricultural development expanded rapidly. Well 30E2 was drilled to replace well 3OE1. The rate of head decline was rapid before 1946, but it has been even more rapid since then. The 1937—63 head decline is almost 300 feet. The hydrograph in figure 458 shows more than 200 feet of head decline in the 1937—56 period for the area southeast of the town of Cantua Creek. The rate of artesian-head decline increased fairly steadily between 1937 and 1952, and during the period 1946—52, the head declined an average of about 23 feet per year. Since 1952 .;-’ E62 100 180 260 340 420 500 STUDIES OF LAND SUBSIDENCE «ex 180 \ l V l 1 2/1 2-34N 1, perforated 320-1152 feet 260 NM 0*“ +- \ u.| LIJ '4“ 340 Z \ 12/12-34 P1, perforated \ . 14/14~30E1 551-1057 feet 8 . < k‘ u. n: a 420 i O 14/14-30E2, 1234 2 feet deep < .J 3 O 500 J \ Lu m J Lu 5 A \ .1 580 o \. E E 3 300 ’\\ ‘1 17/16-18E1 perforated '9 6674615 feet I ‘\ I— E O 380 \\ 460 \ B \ 540 18/17-171N.\ \\ 19/18-3 N 1 , perforated 101 0-1900 feet 18/17-17Q.1\‘ \E \ \ \.\ \19/18-4G1 \ \1 feet deep 18/17‘17E1. 1301\ 19/18-3N2 perforated \ 706-2030 feet \\_\ \ ”N I \e 1920 19 30 1940 1950 19 60 FIGURE 45.—Long-term hydrographs of lower-zone wells. A, Northern part of area. E, Central part of area. C, Southern part of area. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE the potentiometric level has declined at a slower rate, as shown in figure 45B, and in the hydrograph for well 17/16—18Q2 (fig. 47). The composite hydrograph of three wells southwest of Five Points in 18/17—17 is shown in the bottom of figure 45C. Although water levels in these wells are, in gen- eral, representative of the lower zone, a small portion of the perforated intervals may be in the basal part of the upper zone. The 1923 pumping level suggests that the potentiometric surface was only 10—30 feet below its estimated 1906 position. The record indicates that the head has declined 400 feet at a fairly constant rate over a 40-year period—about 10 feet per year. The composite hydrograph of the three wells north of Westhaven in 19/ 18 (fig. 45C) shows a different pattern than that for the wells southwest of Five Points. North of Westhaven, it is apparent that water levels declined only moderately between 1918 and the end of World War II. After World War II the rapid development of nearby areas to the west and southwest caused the rate of head decline to accelerate. Since 1957, the trend in head decline has flattened. The measurements for the 1920’s are from the unpublished Haehl and Forbes re- port.'When pumping levels were only 100 feet below land surface, the potentiometric surface probably was about the same as in 1906. A similar long-term hydro- graph for wells a few miles farther south has been paired with a bench-mark graph and is shown in Part 3. Long-term records are not available for the area of heavy pumping from the marine sands of the Etchegoin Formation. An 8-year record for a well tapping the Etchegoin Formation adjacent to the Big Blue Hills is shown in figure 46. The nonpumping water levels in this well ranged between 800 and 940 feet below land sur- face. By the middle 1960’s, wells adjacent to the Big Blue Hills were pumping from depths of more than 1,000 feet (see Part 3). Monthly measurements made between May 1960 and February 1961 outline a sea- sonal head recovery of 60 feet. Between December 1965 and August 1966, the seasonal head decline was 45 feet. The overall trend of water levels during the 1960’s for this well has been a large and steady decline. From August 1960 to August 1967, the water level declined 64 feet—an average of 7 feet per year. More than 600 feet of artesian-head decline has oc- curred at the site of well 18/15—5E1. The altitude of the land surface at the well is 529 feet, therefore the August 1967 static water level was at an altitude of —402 feet. The trough of the San Joaquin Valley opposite the well _ site has an altitude of 180 feet. The potentiometric sur- face was at least 20 feet above the land surface in 1906. Mendenhall, Dole, and Stabler (1916) reported that the gradient of the potentiometric surface west of the valley E63 800 so 3) O l ‘ 880 - Well 18$/15E~5E1 depth, 2103 feet Water levels (D N O l 0 Winter high A Summer low DEPTH TO STATIC WATER LEVEL IN FEET l l l | I I l 960 1963 1964 1965 1966 1967 1968 | 1959 1960 1961 1962 FIGURE 46.—Hydrog'raph of irrigation well tapping the Etchegoin and San Joaquin Formations. trough was only 2—5 feet per mile. Assuming an initial gradient of 4 feet per mile to the east, the potentiometric surface was 80 feet higher (an altitude of +280 feet) at the well site than at the valley trough in 1906. Thus, in declining from about +280 feet to —400 feet, the poten- tiometric surface declined about 680 feet; if one as- sumed that no gradient was present in the potentiomet- ric surface in 1906, 600 feet of head decline occurred. The short-term trends of lower-zone pumping levels are shown in the 13 hydrographs in figure 47. These hydrographs have been placed on the map in order to facilitate comparison of the various trends and locations of the wells. Four of the wells—15/14—9E1, 20/ 17—33N1, 20/18—24D1, and 21/18—35N1—have had steadily de- clining water levels since 1951 or before. The continu- ing agricultural expansion to the southwest of wells 9E1 and 33N1 probably has influenced the trends in artesian head at these two sites. Well 35N1 is situated where little recharge can reach the well. No recharge is derived from the Kettleman Hills to the south and west, and the thick sequence of lake clays beneath Tulare Lake bed prevent recharge from the east. Recharge that might move towards the well from the north would be largely intercepted by other wells. The other nine hydrographs all show a decreasing trend in the rate of artesian-head decline. Well 12/1 1—13D2 is in an area that has had a reversal of pumping levels since 1958. The abrupt reduction in the rate of artesian-head decline between 1953 and 1959 is associated with the delivery of surface water in the Vicinity of the well. Since 1953 ground water pumped from well 13D2 has been used to supplement the surface-water supply. In 1959 a large area to the south of the well started receiving surface water (Bull “and Poland, 1974). The effect of surface-water imports both in 1954 and in 1959 is clearly shown in the hydro- graph of well 13D2. The other eight hydrographs that show a decreasing rate of artesian-head decline suggest a trend toward E64 37°00’ 36°30’ 36°00’ STUDIES OF LAND SUBSIDENC E 120°3o' 120.00, 3’ ' u I Los Banos I I — _ Dos Palos / / ~ ' ”‘9.” - -- ' ‘ Riv ," 200 I V ’ h v— ‘ '~/ K ‘er Madera 0e] 0‘ 4' 300 L J '9. 0° 1950 1960 $00 /'12/11—1302 o 0.", o ”lo, Firebaugh RIVER é: Q? 9 Q- 6" a $00 0"” Iééb/ 10A FRESNO 600 "\,-. Mendota ‘. H 80 , \ |_. 700 \ a so \ Ker-man J— 1950 1960 «go ‘1 \’ .15/12-2G1 ‘ 100 \\ / 15/14—9E1 \ \«x~ / 200 ’300 \\ 1950 1960 600 w \ \logeé 400 700 \ . 9 __ 100 1950 1960 16/1771631 50° 016/15-1901 H. 200\ — OCantua Creek ‘~ —l 600 1950 1960 1950 1960 a i _ 17/16-1802 ”“3“” QV/V \ /- 400 l EXPLANATION 06‘ 400 \ 20° .\‘~\19/18-26N1 J 5 o — 500 o \‘ f ' 1955 1965 Boundary of deformed 1 300 rocks 95° 1960 18/17-15M1' ‘ \19/18-35E1 1:: 400 L11 \\ I; 300 /\ E E 1940 1950 1960 LU 19“ 4°° 19/18-26N1 z 3 300 E - 19/18—35E1 ‘1 // 50° 19/17-31N ‘“ 400 O Huron YEARS 1950 1960 20/18-24D1 Hydrograph of selected well / K 0000 1500 ’ 20/17-33N1 .15/14-951 \ L2/. {fie/$1950 1960 ' 400 ‘ Locatlon of selected well 3%0‘5 400 \\ 500 .\ \ <¢‘,21/11335N1050\o o 5 10 15 MILES 60° \ l '4" 49/ 1950 1960 o 5 10 15 KILOMETRES 1 195° 196° a ,’ (<9 éKettleman City Base from 0.8. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 47 .—Trends of lower-zone pumping levels. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE equilibrium between pumpage and the various sources of water within the lower-zone aquifer system in most of the Los Banos—Kettleman City area. If the amount and distribution of pumpage within the area remained uni- form, eventually the decline in water levels would es- tablish a steep gradient that would permit sufficient recharge to the lower zone from the east side of the San Joaquin Valley to eliminate overdraft within the study area. Water levels would remain at low levels and would have large seasonal fluctuations in the areas of large lower-zone pumping, and the steep gradient of the potentiometric surface would be maintained around the borders of the study area. Table 3 and figure 23 show that the amount of total pumpage within the area has not increased since 1952. The maps of the potentiometric surface between 1926 and 1965 (figs. 31—33, 35, 36) show a progressive steep- ening of the potentiometric surface along the east side of the study area. Thus, the above figures and figure 47 all support the conclusion that a strong tendency toward reduction of overdraft within the lower-zone aquifer system has been occurring. SUMMARY AND CONCLUSIONS The 500—3,500 feet of unconsolidated to poorly con- solidated deposits that form the ground-water reservoir in the Los Banos—Kettleman City area consist of flood-plain, alluvial-fan, lacustrine, deltaic continental, and littoral and estuarine marine deposits. The sedi- ments were derived from both the Diablo Range and the Sierra Nevada. The stratigraphy of such diverse genetic units is complex, but a simple three-part hydrologic classification can be made of the deposits penetrated by wells. The upper zone extends from the land surface to the top of the principal confining clay. The upper zone, 100—900 feet thick, has a degree of confinement that ranges from unconfined in thick bedded sands to excel- lent confinement between extensive lacustrine clay beds. Much of the zone consists of lensing deposits in which the water is semiconfined. The primary aquifer consists of micaceous arkosic sands derived from the Sierra Nevada. The Sierra sands are almost 600 feet thick under the present valley trough but pinch out toward the west at distances of 5—15 miles from the eastern margin of the Diablo Range. Diablo alluvial-fan deposits make up most of the upper zone. Few wells tap the poor quality water in these deposits of low permea- bility. The upper-zone water, a calcium-magnesium sul- fate water, commonly contains 3,000—4,000 mg/l total dissolved solids. Water quality improves with depth, E65 and near the basal part of the zone, the total dissolved solids are about 1,500 mg/l. Most of the pumpage of upper-zone water is in the southeastern part of the study area and along Fresno Slough, south of the town of San Joaquin. A widespread diatomaceous clay stratum, deposited in a fresh-water Pleistocene lake 600,000 years ago, is the second hydrologic unit. The Corcoran Clay Member of the Tulare Formation extends beneath the entire study area, except for an area adjacent to the foothills in the southwestern part. The Corcoran is the principal confining layer throughout much of the San Joaquin Valley, and locally it separates waters of greatly differ- ing quality and head. The Corcoran provides effective confinement for the third hydrologic unit—the lower zone. The lower zone, which supplies about three-fourths of the ground water in the study area, ranges from less than 500 to more than 2,000 feet thick. Although the zone contains many lensing aquitards, the overall hydraulic continuity be- tween the basal and upper parts of the zone is good, except in the northern third of the area where a wide- spread clay layer acts as an effective separator within the lower zone. The lower zone consists chiefly of the alluvial-fan, flood-plain, and lacustrine deposits of the Tulare For- mation. In the southern part of the area, deltaic deposits are tapped also. Along the western margin of the valley, between the towns of Huron and Cantua Creek, wells are drilled still deeper to tap estuarine and littoral deposits of the San Joaquin and Etchegoin Formations. The alluvial-fan deposits, derived from the Diablo Range, consist of materials of low to moderate permea- bility. Individual beds within the Diablo flood-plain de- posits give this unit a moderate to high overall permea- bility. Well-yield factors indicate that the flood-plain deposits are 3—5 times as permeable as the alluvial-fan deposits. The Sierra flood-plain deposits have the high- est permeabilities because the sand beds are thicker, and they make up a greater porportion of a given section than do the Diablo flood-plain deposits. The thickness of the fresh-water-bearing deposits and the perforated interval of the lower zone both range from 400 to more than 2,000 feet, but rarely are they the same in a given part of the area. In some areas, sufficient yields can be obtained without drilling to the ‘base of the fresh water. Only LOGO—1,200 feet of the more than 2,000 feet of lower-zone fresh-water-bearing ' deposits are tapped northwest of Tulare Lake bed. Adja- cent to the Big Blue Hills, sufficient quantities of water cannot be obtained from the continental deposits, and E66 3,000-foot wells obtain part of their water from brackish-water-bearing marine deposits to depths of as much as 200 feet below the base of the fresh water. The total dissolved solids in the lower-zone water in most of the area west of the valley trough ranges from 800—1,500 mg/l, but locally they are more than 2,000 mg/l. The water is primarily a sodium-sulfate water with more bicarbonate than the upper-zone water. The chemical character of the water indicates that water derived from the Diablo Range has flushed the connate waters out of the marine and Sierra sands. Maximum concentrations of dissolved solids occur op- posite the mouths of Panoche and Los Gatos Creeks and in the area of maximum dependency of pumpage from the marine sands. Areas of low concentrations of dis- solved solids occur between the mouths of the large streams. Before the agricultural development of the central part of the San Joaquin Valley, the lower—zone poten- tiometric surface sloped gently towards the valley trough from both the Diablo Range and the Sierra Nevada. Because of the low permeability of the Corco- ran, upward movement of lower zone water probably was very slow; and as a result, the potentiometric sur- face was more than 20 feet above the land surface in the valley-trough area. Large-scale agricultural development has lowered the potentiometric surface on the west side of the valley to as much as 400 feet below sea level. Water-table conditions now exist below the Corcoran near the Di- ablo Range. The slope of the potentiometric surface has been reversed. By 1966, a belt only a few miles wide adjacent to the Diablo Range was still an area of eastern gradient for lower-zone water movement. Farther east, areas in which the potentiometric surface originally sloped eastward, locally had a westward gradient of as much as 40 feet per mile by 1960. Disruption of the natural flow system by man has resulted from the pumping of more than 1,000,000 acre-feet of irrigation water per year since 1950. In 1924, the total estimated pumpage was only 35,000 acre-feet. By 1945, pumpage was 370,000 acre-feet and by 1953, 1,200,000 acre-feet. Total pumpage has not increased since 1953. The increase in pumpage has closely paralleled the agricultural growth in the area from a few wells to irrigate pasture to a modern complex of large-scale diversified farming that occupies nearly all the area. Changes in the upper-zone water levels have not been pronounced in the northern and central parts of the area, but in the southeastern part of the area, where large amounts of upper-zone water is pumped, both the water table and the water levels in the confined aquifer system have declined. Locally the water table has de- STUDIES OF LAND SUBSIDENCE clined more than 300 feet, and elsewhere the artesian head at the base of the upper zone has declined more than 300 feet. North of Five Points, the water table has risen from less than 25 feet to more than 100 feet, and much of the area may be threatened with insufficient drainage for crops. In the northern area, water levels representative of the semiconfined zone have risen in some areas and have declined in others, depending on local variations in the amount of water pumped in the upper zone. The changes in the hydrologic environment have been the greatest in the lower zone. Flowing wells once were common along the trough of the valley. In other areas where the potentiometric surface initially was less than 100 feet below the land surface, static levels were at depths of about 500 feet by the 1960’s. Overall head declines of 300 to more than 400 feet are common in much of the area, and an estimated 600 feet of head decline has occurred next to the Big Blue Hills. The lower-zone aquifer system has responded to the changes imposed by man by developing a steep gradient in the potentiometric surface around the trough of max- imum pumping. In 1906, the potentiometric surface sloped 2—5 feet per mile to the east; by 1926, 6 feet per mile to the west; by 1943, 14 feet per mile; and by 1960, 30 feet per mile to the west. As the gradient became steeper and total pumpage stopped increasing, recharge from the east side of the San Joaquin Valley increased sufficiently to roughly balance the large overdraft from the lower zone. As a result, the rate of head decline has become progressively less since 1955 throughout most of the area. The records of many wells for the 1960—66 period show a seasonal fluctuation of 60—120 feet but less than 5 feet of year-to-year head decline. Most of the compaction has occurred in the lower zone as a direct result of the head decline that has occurred within it. Water-table changes also have affected the amounts of lower-zone compaction but only to a minor extent. Lower-zone applied stresses and compaction have been increased in areas of water-table rise and have been decreased in areas of water-table decline. Decline of the lower-zone water levels below the base of the Corcoran decreases the change in applied stress from 1.0—0.8 foot of water per additional foot of water- level decline. The processes of applied-stress increase are changed from that of seepage stress equal to head differentials, to those of loss of buoyancy and transfer of part of the contained water from a neutral to an applied-stress condition as the deposits are dewatered. REFERENCES CITED American Geological Institute, 1972, Glossary of geology: Washing- ton, D.C., Am. Geol. Inst. 805 p. CHANGES IN THE HYDROLOGIC ENVIRONMENT CONDUCIVE TO SUBSIDENCE Bull, W. B., 1964, Alluvial fans and near-surface subsidence in west- ern Fresno County, California: US. Geol. Survey Prof Paper 437—A, 71 p. 1972, Prehistoric near-surface subsidence cracks in western Fresno County, California: US. Geol. Survey Prof Paper 437—0, 85 p. 1974, Land subsidence due to ground-water withdrawal in the Los Banos-Kettleman City area, California—Part 2, Subsidence and compaction of deposits: U.S. Geol. Survey Prof. Paper 437—F (in press). Bull, W. B., and Poland, J. F., 1974, Land subsidence due to ground— water withdrawal in the Los Banos-Kettleman City area, California—Part 3, Interrelations of water-level change, change in aquifer-system thickness, and subsidence: U.S. Geol. Survey Prof. Paper 437—G (in press). Croft, M. G., 1972, Subsurface geology of the late Tertiary and Quaternary water-bearing deposits of the southern part of the San Joaquin Valley, California: US. Geol. Survey Water-Supply Paper 1999—H, 29 p. Davis, G. H., Green, J. H., Olmsted, F. H., and Brown, D. W., 1959, Ground-water conditions and storage capacity in the San Joaquin Valley, California: US. Geol. Survey Water-Supply Paper 1469, 287 p. Davis, G. H., and Poland, J. F., 1957, Ground-water conditions in the Mendota—Huron area, Fresno and Kings Counties, California: US. Geol. Survey Water-Supply Paper 1360—G, p. 409—588. Frink, J. W., and Kues, H. A., 1954, Corcoran Clay—A Pleistocene lacustrine deposit in San Joaquin Valley, Calif: Am. Assoc. Pe- troleum Geologists Bull., v. 38, no. 11, p. 2357—2371. Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1955, Proposed program for investigating land subsid- ence in the San Joaquin Valley, California: Sacramento, Calif, Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, Calif, open-file report, 60 p. 1958, Progress report on land-subsidence investigations in the San Joaquin Valley, California, through 1957: Sacramento, Calif, Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, Calif, open-file report, 160 p. Ireland, R. L., 1963, Description of wells in the Los Banos-Kettleman City area, Merced, Fresno, and Kings Counties, California: US. Geol. Survey open-file report, 519 p. J anda, R. J ., 1965, Quaternary alluvium near Friant, Calif, in Guidebook for Field Conference I, Northern Great Basin and California—Internat. Assoc. Quaternary Research, 7th Cong, U.S.A., 1965: Lincoln, Nebr., Nebraska Acad. Sci., p. 128—133. Johnson, A. I., Moston, R. P., and Morris, D. A., 1968, Physical and hydrologic properties of water-bearing deposits in subsiding E67 areas in central California: US. Geol Survey Prof. Paper 497—A, 71 p. Lofgren, B. E., 1960, Near-surface land subsidence in western San Joaquin Valley, California: J our. Geophys. Research, v. 65, no. 3, p. 1053—1062. 1968, Analysis of stresses causing land subsidence, in Geologi- cal Survey research 1968: U.S. Geol. Survey Prof. Paper 600—B, p. B219—B225. 1969, Land subsidence due to the application of water, in Varnes, D. J ., and Kiersch, George, eds., Reviews in Engineering Geology, Volume II: Boulder, Colo., Geol. Soc. America, p. 271—303. Lohmari, S. W., and others, 1972, Definitions of selected ground-water terms, Revisions and conceptual refinements: U.S. Geol. Survey Water-Supply Paper 1988, 21 p. Meade, R. H., 1967, Petrology of sediments underlying areas of land subsidence in central California: US. Geol. Survey Prof Paper 497—C, 83 p. 1968, Compaction of sediments underlying areas of land subsidence in central California: US. Geol. Survey Prof. Paper 497—D, 39 p. Mendenhall, W. C., Dole, R. R., and Stabler, Herman, 1916, Ground water in the San Joaquin Valley, Calif: US. Geol. Survey Water-Supply Paper 398, 310 p. Miller, R. E., Green, J. H., and Davis, G. H., 1971, Geology of the compacting deposits in the Los Banos-Kettleman City subsidence area, California: US. Geol. Survey Prof. Paper 497—E, 46 p. Ogilbee, William, and Rose, M. A., 1969, Ground-water pumpage on the west side of the San Joaquin Valley, Calif, 1962-66: US. Geol. Survey basic-data compilation, 7 p. Page, R. W., 1971, Base of fresh ground water (approximately 3,000 micromhos) San Joaquin Valley, California: US. Geol. Survey open-file report, 13 p. Poland, J. F., 1959, Hydrology of the Long Beach-Santa Ana area, California, with special reference to the watertightness of the Newport-Inglewood structural zone: U.S. Geol. Survey Water- Supply Paper 1471, 257 p. Poland, J. F., and Davis, G. H., 1969, Land subsidence due to with- drawal of fluids, in Varnes, D. J., and Kiersch, George, eds., Reviews in Engineering Geology, Volume II: Boulder, Colo., Geol. Soc. America, p. 187—269. Poland, J. F., Lofgren, B. E., and Riley, F. S., 1972, Glossary of selected terms useful in studies of the mechanics of aquifer systems and land subsidence due to fluid withdrawal: U.S. Geol. Survey Water-Supply Paper 2025, 9 p. Terzaghi, Karl, and Peck, R. B., 1948, Soil mechanics in engineering practice: New York, John Wiley and Sons, Inc., 566 p. Acknowledgments ,,,,, Alluvial fans __________________________________ 8 Alluvial-fan deposits ,,,,,,,,,,,, 12, 17, 23, 25, 27, 65 derived from the Diablo Range ,,,, 17, 23, 25, 65 permeability ______________________ ,_,, 17, 65 Anticline Ridge __________________________________ 23 Aquifer system, confined __________________ 6, 19, 66 wells ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 34 definition \ ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 19 lower zone ,,,,,,,,,,,,,,,,,,,,,,,, 22, 23, 65, 66 measuring equipment ,,,,,,,,,,,,,,,,,,,,,,, 9 permeable ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 17 primary ____________________________________ 65 semiconfined ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14 upper zone, micaceous sand ,,,,,,,,,,,,,,,,, 17 water levels, changes _______________ 39, 65, 66 Aquifer systems __________________________ 2, 6, 7, 8 definition of terms ,,,,,,,,,,,,,,,,,,,,,,,,,, 8 Aquitards _____________________________________ 22 semiconfined _______________________________ 14 Artesian head, lower zone ____________________ 22, 50 decline ,,,,,,,,,,,,,,,,,,,,,, 9, 23, 39, 61, 63, 66 Cantua ,,,,,,,,,,,,,,,,,,,,,,, 1 1 upper zone ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 66 Bench—mark surveys ________________________ 6, 7, 50 Bench marks, changes in altitudes ,,,,,,,,,,,,,,,, 9 Big Blue Hills ________________ 23,27, 32, 50, 63, 66 Boston Land Co ..... C California Aqueduct ____________________________ 2 California Department of Water Resources,,,_ 6, 8, 45 Cantua Creek ______________ ,,_, ,,,, 32, 40, 50 Cantua, core hole site _______ ,,,, 7 Cantua recorder site, annual unit compaction ,,,,,, 11 natural applied stress ,,,,,,,,,,,,,,,,,,,,,,,, 11 water table Casing-failure studies ,,,,,,,,,,,,,,,,,,,,,,, ,, 11 Ciervo Hills ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 32 Compaction ,,,, ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 6, 9 definition of terms 8 delayed ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 9 due to wetting _________________________ 9 measurement 6 rapid, geologic factors ,,,,,,,,,,,, saturated deposits stress factors buoyant support Compaction recorders ,,,,,,,,, mechanics of systems _____ multiple ,,, sites _____ Conclusions ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 65 Corcoran Clay Member, Tulare Formation _, 12, 17,19, 34, 43, 45, 50, 65 Tulare Formation, altitude of base ____________ 27 areal extent ,,,,,,,,,,,,, diatomaceous clay ________ flow system lacustrine sands lithology ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 19 principal confining layer ,,,,,,,,,,,,,, 19, 65 stratigraphy ____________________________ 19 thickness ,,,,, ___ 12, 19 unit compaction ,,_ 11 vertical permeability _ _______ 19 water-table decline ______________________ 43 INDEX [Italic page numbers indicate major references] Page Corcoran lake ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, E19, 65 Corcoran lake clay ,,,,,,,,,,,,,,,, 32 structure ,,,,,,,,,,,,,,,,,,,,,, ,, 19 thickness ,,.._ ,, 19 vertical permeability ,,,,,,,,,,,, 19 Core holes ,,,,,,,,,,,,,,,,,,,,,,,,,, 7 Core samples, saline water body D, E Definitions ,,,,,,,,, ,3 Delta-Mendota Canal ,,,,,,,,,,,,,, 40, 46, 61 Deltaic deposits ,,,,,,,,,,,,,,,,,,,,, 12, 23, 25, 27 derived from the Sierra Nevada ,,,,,,,,,, 23, 25 Diablo Range ,,,,,,,,,, 8, 9, 12, 17, 23. 25, 32,36, 65 alluvial-fan deposits ,,,,,,,,,,,,,,,,,, 17, 25, 65 flood-plain deposits ,,,,,,,,,,,,,,,,,, 25, 59, 65 head decline ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 55 lithology , ,,,,,,,,,,,,,,,,,,,,,,,,,, 8, 9 recharge ,,,,,,,,,,,,,,,,,,, 32 water ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 66 Diatomaceous clay ________________ 19, 65 Dissolved solids, concentrations ,,,,,,,,,,,, 29, 32, 66 Los Gatos Creek ,,,,,,,,,,,,,,,,,,,,,,,, 32, 66 lower zone ,,, ,,,,,,,,,,,,,,,,,, 29, 32, 66 Panoche Creek , ,,,,,,,,,,,,,,,,,,,,,,, 32, 66 upper zone variations Estuarine deposits, Pliocene ,,,,,,,,,,,,,,,,,,,,,, 12 Etchegoin Formation ,,,,,,,,,,,,,, 12, 23, 56, 63, 65 F Five Points ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 40 Flood-plain deposits ,,,,,,,,,,,,,,,, 12, 17, 23, 25, 27 derived from the Diablo Range ,,,,,,,,,,,, 25, 65 derived from the Sierra Nevada ,,,- 17, 23. 25, 65 lithology ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 25 micaceous ,_. , 17,25 permeability ,,,, 25,65 Flow system, lower zone, initial ,,,,,,,,,, , ,,,,,,, 34 natural ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 32, 66 man’s disruption __, ., 34, 66 Fossils, fresh—water ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 32 Franciscan Formation ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 8 Freshwater-bearing deposits ,,,,,,,,,, 12, 13, 27, 59 altitude of base ,,,, geologic sections , hydrologic units, lacustrine clay , lower unit, lower zone ,, thickness ,,, subsurface geology Tulare Formation, Corcoran Clay , ,, ,,, 12 Member upper unit ,,,,,,,,,,, upper zone ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, G Geologic studies, regional ,,,,,,,,,,,,,,,,,,,,,,,, 7 Gravel, Los Banos Creek ,,,,,,,,,,,,,,,,,,,,,,,, 17 Ground water, agricultural use ,,,,,,,,,,,,,,,, 2, 34 calcium concentrations ,,,,,,,,,,,,,,,, 17, 19, 65 definitions of terms ,, 8 depth ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 40 development, history ,,,,,,,,,,,,,,,,,,,,,,,, 34 dissolved solids, variation ,,,,,,,,,,,,,, 19, 65 irrigation ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 34, 36 magnesium sulfate concentrations ,,,,,,,, 17, 65 pumpage ______________________ 14, 36, 38, 39, 46 Page Ground water—Continued sodium bicarbonate concentrations ,,,,,,,,,,, E19 upper zone ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14 withdrawals, computation ,, , , ,,,,,,,,,,,,, 36 Ground-water levels, changes ,,,, ,,,,,,,,,,,,, 39 Ground-water reservoir, description ,,,,,,,,,,,,,, 12 general features ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 12 lower zone ,.. ,,,, 13, 14,19 hydrologic character ,,,,,,,,,,,,,,,,,,, 23 physical character ______ productivity ,,,,,,,,,,,,, pumpage ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14 water, chemical character ,,,,,,,,,,,,,,, 29 natural flow system_,, ,,,,,,,,,,,,,,,,,,,, 32 saline water body ,,,,, sediments, lithology ,,,,,,,,,,,,,,,,,,,,,,,, thickness ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Tulare Formation, Corcoran Clay Member ,,,, 19 upper zone ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14 physical character ,,,,,,,,,,,,,,,,,,,,,, 1 7 productivity ,,,,,,,,,,,,,,,,,,,,,,,, 14, I 7 sands water, chemical character ,, water-level changes ,,,,,,,,,,,,,,,,,,,,,,,,,, 34 H Head, decline ,_ ,, 34, 39, 43, 54. 55, 56, 59, 61, 63, 66 decline, Big Blue Hills ,,,,,,,,,,,,,,,,,,,,,,,, 66 history ,,,,,,,,,,,,,,,,,,,,,,,,,, ,,,. ,,, , 61 near the Merced County line ,,,,,,,,,, , 61 north of Westhaven southeast of Cantua Creek southwest of Five Points ,_ southwest of Mendota ,,,,,, west of Huron,, , ,_ ,,,,,,,, _,, differential ,,, .,, Huron, core hole site ,, Hydraulic continuity ,,,,,, ,,,, ,,,, , ,,, . Hydraulic gradient, lower zone ,,, ,,, Hydrologic environment, changes caused by man ,,,,,,, ,, .,,,,,,,,,, 34 changes caused by man, ground- water development, history , ,,.,,,,,,,,,, 34 ground-water levels, changes ,,.._,,,, , , ,, 39 ground-water pumpage. total, trends ,,,,, 36 lower zone ,,,,,,,,,,,,,,,,,,,, ,,, ,,,,,, 45 head decline, history ,,,,,,,,,,,,,,, 61 potentiometric level, seasonal fluctuation ,, ,,,, ,,,,,,,,,,, ,, ,,, 59 potentiometric surface changes ,,, ,,, 46 upper zone, confined ,,,, .,, ,,, ,,, ,,, 43 semiconfined ,,,,,,, ,,. ,,,, ,,, ,, ,,, 43 water table,, ,,,,,,,,,,,,,,, ,, ,,,,,, 39 Hydrologic system, San Joaquin Valley ,, ,,, .,,, 32 Hydrologic units ,,,,,,,, , , ,,,, ,,,,, 12, 13,65 1, K lnter~Agency Committee on Land Subsidence,, ,,,, 2 cooperative program ,,,,,,,,,,,,,,,,,,,,,,,, 6‘ Federal program , , ,, ,,, ,, 6 field program ,,,,,,,,,,,,,,,,,,, ,_ , 6 laboratory program ,,,,,, ,,, ,,, ,,,,,,, ,, , 7 Introduction ,,, ,,, ,, ,,, ,,,.,,,, ., ,, ,, , 1 Ireland, R. L,, cited ,.,,, ,,,,,,,,,, ,,,,,,, , 27 Irrigated land,,, , . , ,,, ,,, ,,,, ,, , .,,, ,,,., 36, 38 Kettleman Hills ,,,,,,, ,,, ,, ,,,,,,,,.,,,,, 32,63 Kings River, irrigation water ,,,,,,,,,,,,,,,,,,,, 45 E69 E70 Page L Laboratory program ,,,,,,,,,,,,,,,,,,,,,,,,,, E 7 Lacustrine clay." ,,,,,,,,,,,,,, 19 Lacustrine deposits 1 ________ 12, 17, 23 Lacustrine sands ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 17 Land subsidence ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 9 Lemoore site ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 44 Little Panoche Creek ,,,,,,,,,,,,,,,,,,,,,,,,,, 32 Littoral deposits, Pliocene ,,,,,,,,,,,, c. 12 Los Banos Creek, gravel ,,,,,,,,,,,, ._ 17 sediments ,,,,,,,,,,,,,,,,,,,, 1. 17 Los Banos—Kettleman City study area ,,,,,,,,,,, 2 alluvial-fan deposits ________ 12, 17, 23, 25, 27, 46 aquifer systems ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 7 boundary __________________________________ 2 compaction ______________________ 6, 9, 11, 46, 66 cultural features ____________________________ 2 deltaic deposits," flood-plain deposits ,, H. 12, 23, 25, 27 , 12, 17, 23, 25, 27 flow system, natural 1. ,,,,,, 32 fresh-water-bearing deposits ,,,,,,,,,,,,,,,,,, 27 thickness ____________________________ 27, 29 ground water ________________________________ 13 pumpage _______________________ 36, 38, 39 ground-water reservoir W ______ 12 head declines ,,,,,,,,,,,, _ 55, 59, 61 head differential _c, _. 43, 44 hydrologic environment ,,,,,,,,,,,,,,,,, 7, 66 hydrologic units ______________________ 12, 13, 65 irrigation water ,,,,,,,,,,,,,,,,,,,,,,,,,, 46, 66 lacustrine clay ______ 19 lacustrine deposits ,. _ W. l2, 17, 23 lower zone ,,,,,,,,,,,,,,,, 13, 19, 25, 29, 65, 66 artesian head _.,_ ,,,,,,,, 50 seasonal changes _. ,,,,,,,,,,,,,,, 59 compaction ,,,,,,,,,,,,,,,,,,,,,,,, 46, 66 ‘ confinement, extent ,,,,,,,,,,,,,,,,,,,,,, 32 perforated intervals ,,,,,,,,,,,,,,,,,,,,,,, 29 recharge gradient ,,,,,,,,,,,,,,,,,,,, 46, 66 stress, applied ,,,,,,,,,,,,,,,,,,,,, 50, 66 wells ,,,,,,,, , 36, 61, 63, 66 micaceous sand ,,,,,,,,,,,,,, 17 potentiometric surface , 34, 46, 54, 65 principal confining layer ______________ 12, 19, 65 pumpage ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 65, 66 recharge ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 55, 59 regional geologic studies ,,,,,,,,,,,,,,,,,,,, 7 saline water body ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 32 sediments ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 12, 14 lithology ,__ , 12, 17, 65 stress, applied, variation ,,,,,,,,,,,,,,, 59 subsidence ___________ fl" 2, 6, 7, 9 area ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 9 topography ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2 upper zone, micaceous sand ,,,,,,,,,,,,,,,,, 17 permeable aquifers ,,,,,,,,, , 43, 65, 66 ,,,,,,,, 34 water quality__ _______ 65 water, irrigation ,,,,,,,,,,,,,,,,,,,,,,,, 25, 66 water table ,,,,,,,,,,,,,,,,,,,,,,,, 39, 56, 66 well yields ,,,,,,,,,,,,,,,,,,,,,,,, 27, 59, 65 Los Gatos Creek ,,,,,,,,,,,,,,,,,, 32, 40, 43, 55, 66 alluvial fan, ancestral ,,,,,,,,,,,,,,,,,,,, 19, 40 dissolved solids ,,,,,,,,,,, ,3 32, 66 recharge ",1 d1 40, 55 Lower mne ,,,,,,,,,, W, 19, 65, 66 alluvial-fan deposits , 7,, 23, 27, 46 aquifer system ,,,,,,,,,,,,,,,, confined ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 19 artesian head ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 22, 50 chloride concentration ,,,,,,,,,,,,,,,,,,,,, 29 compaction ,,,,,,,,,,,,,,,,,, confinement, degree__ extent ,,,,,,,, deltaic deposits ..... dissolved solids, concentrations ________ 29, 32, 66 variations ______________________________ 29 flood-plain deposits ______________________ 23, 25 INDEX Page Lower zone—Continued flow system, initial ,,,,,,,,,,,,,,,,,,,,, E34, 66 fresh-water-bearing deposits, thickness ___. 27, 29 ground water ,,,,,,,,,,,,,,,,,,,, 13, 23,29, 65 irrigation ______________________________ 19 head declines ______________ 39, 46, 59, 61, 63, 66 hydrographs ___ ..... 61, 63 head differentials fl” , 22, 50, 54 hydraulic continuity, W, 22, 65 hydraulic gradient ,,,,,,,,,,,,,,,,,,,,,,,,,, 50 irrigation water ,,,,,,,,,,,,,,,,,,,,,,,, 46, 59 lithology ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 23, 65 perforated interval, thickness ____________ 27, 29 permeability ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 25, 65 pore-pressure decline ,,,,,,,,,,,,,,,,,,,,,,,, 29 potentiometric level, seasonal fluctuation ______ 59 potentiometric surface ,,,,,, 34, 46, 54, 56, 63, 66 productivity _____ 25, 29 pumpage ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14, 59, 63 pumping depressions ,,,,,,,,,,,,,,,,,,,,,,,, 46 recharge .............. 32, 34, 55, 59, 63, 65, 66 area ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 34 gradient "3 , 46, 66 stress, applied , _ 50, 66 seepage ,,,,,,,,, h, 50 surface water, imports ,,,,,,,,,,,,,,,,,,,, 63 thickness ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 29, 65 water, chemical character ,,,,,,,,,,,,,,,,,,,,, 29 salinity ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 29 sodium sulfate ,,,,,,,,,,,,,,,,,,,,,,,,, 29 temperatures ,,,,,,,,,,,,,,,,,,,,,,,,,,, 32 water levels H 39, 45, 46 decline ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 50 seasonal fluctuation ,,,,,,,,,,,,,,, 59, 66 water table ___________________________ 50, 66 yield factors ,,,,,,,,,,,,,,,,,,,,,,,,,, 25, 27, 65 M, 0 Meade, R, H,, cited ______________________________ 7 Mendota ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 34 core hole site ,, A 7 Mendota recorder site, water table ,_ H, 43 Miller, R. E,, cited ,,,,,,,,, n, 13 Monocline Ridge ,,,,,,,,,,,,,,,,,,,,,, Oro Lorna core hole site ,,,,,,,,,,,,,,,,,,,,, 7 Oro Loma recorder site ,,,,,,,,,,,,,,,,,,,,,,,,, 22 annual unit compaction _____________________ 11 P Pacific Gas and Electric Co ,,,,,,,, 7, 8, 36, 46, 50, 61 Panoche Creek, dissolved solids ,,,,,,,,,,,,,, 32, 66 Perched water ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 40 Pleasant Valley ,,,,,,,,,, 56 Potentiometric surface ,_ c _ - 46, 50, 63 altitudes ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 54, 56 between Anticline Ridge and Fresno Slough 54, 55 between Tumey Hills and Mendota ,,,,,,,,,, 54 lower zone changes ,,,,,,,,,,,, 34, 46, 54, 56, 66 northeast of Big Blue Hills ..... profiles ,,,,,,,,,,,,,,, slope _______ _,, 46, 50, 54, 66 Purposes of report "w". 7 R, S Recharge, Diablo Range ,,,,,,,,,,,,,,,,,,,,,, 32, 55 Kettleman Hills ,,,,,,,,,,,,,,,,,,,, 63 Los Gatos Creek ,,,,,,,,,,,,,,,,,,,,,,,, 40, 55 lower zone ,,,,,,,,,,,,,, 32, 34, 55, 59, 63, 65, 66 San Joaquin River ,,,,,,,,,,,,,,,,,,,,,,,,,, 34 San Joaquin Valley ,,,,,,,,,,,,,,,,, 55, 65, 66 References cited ,,,,, Russell Giffen, Inc _ Saline water body ,,, San Joaquin River ,,,,, San Joaquin Valley ____________________________ 2 geographic setting __ geosynclinal trough ,,,,,,,,,,,,,,,,,,,,, hydrologic system ,,,,,,,,,,,,,,,,,,,,,,,,,, 32 Page San Joaquin Valley—Continued recharge area _________________________ E34, 55 subsidence ____________________________ 2, 6, 7 underflow _________ 54 San Luis Canal _____ 2, 40 Sands, arkosic, micaceous __________ 14, 17, 23, 27, 65 micaceous, upper zone ____________ 14, 17, 23, 27 upper zone, dissolved solids ,,,,,,,,,,,,,, 19 permeability ________________________ 17 Santa Clara Valley ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 6 Sediments, buoyancy change A... Semiconfined aquifers ,,,,,,,,,,,, Semiconfined water ,,,,,,,,,,,,,,,,,,,,,,,,,, 40, 44 Shallow water, depth , ___ 43 Sierra Nevada _-, ______ arkosic sands, micaceous W, 14, 17, 23, 27, 65 deltaic deposits __________________________ 23, 25 flood-plain deposits ____________ 17, 23, 25, 59, 65 sands ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14, 39, 65, 66 Stress, applied ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2, 12 applied, computation _______________ confined zone, water-table change increase at Cantua ______________ variation ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 59 aquifer system, water-level change, basic theory 12 confined zone, magnitudes of components ,,,,,, 12 effective ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, hydrostatic ,,,,,,,,,,,,,,,,,,,,,,,,,,, , , seepage ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 12, 50 Study area boundaries , 2 Subsidence _________ 9 altitude, changes _ ______________ 6 corrections ,,,,,,,,,, 6 area adjacent to Big Blue Hills ,,,,,,,,,,,,, 23 central California ,,,,,,,,,,,,,,,,,,,,, 7 effects on canals ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2 Los Banos—Kettleman City area 1, _ 2, 6 measurement, change in percentage 1 __ 11 near-surface H, 9 rates ___________ 9 reference point changes ______ San Joaquin Valley _________ Summary ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 65 Surface water, deliveries by the Delta-Mendota Canal 46 imports ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14, 63 T Thickness, Corcoran lake clay ,,,,,,,,,,, lacustrine sands ,,,,,,,,,,,,,,,,,,,,,,,,,,, micaceous sands ,,,,,,,,,,,,,,,,,,,,,,,,,, 17 Tranquillity site ,,,,,,,,,,,,,,,,,,,,,,,,,, 43 Tulare Formation ,,,,,,,,,,,,,,,,,, 12, 17, 23, 32, 65 Corcoran Clay Member _ __,_ 12, 19 areal extent _____ flow system "fl lacustrine sands ,,,,,,,,,,,,,,,,,,,,,, lithology ___________________ principal confining layer ___. fi. 12, 19, 65 stratigraphy ____________________________ 19 thickness ccccc , 12, 19 unit compaction H __________ 11 vertical permeability , ,,,,,,,,,, 19 water-table decline ,,,,,,,,,,,,,,,,,,,,, 43 productivity ,,,,,,,,,,,,,,,,,,,,,,,,,, 23 upper zone ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 17 Tulare Lake bed ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 59, 63 Twenhofel, W. S., cited ,,,,,,,,,,,,,,,,,,,,,,,,,, 3 U US. Bureau of Reclamation _______________ 8, 40, 44 US, Coast and Geodetic Survey__ US, Geological Survey 3,, Upper zone ,,,,,,,,,,,,,,, alluvial—fan deposits ,,,,,,,,, aquifer, primary _____________ arkosic sands, micaceous ______ 14, 17, 23, 27, 65 head, decline _______________ differentials __________ irrigation wells .1 lacustrine sands___, Page Upper zone—Continued micaceous sands E14, 17, 23, 27, 65 permeability ___________ piezometers productivity ________________________________ 1 7 pumpage ________________________________ 43, 65 recharge ____________________________________ 34 seasonal fluctuation ______ __r 44, 45 semiconfined aquifer system thickness ________________ _ 65 water, chemical character ________________ 17, 65 calcium ,,,,,,,,,,,,,,,,,,,,,,,,,, 17, 19, 65 magnesium sulfate __________________ 17, 65 water table ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 14, 66 yield factors ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 17 W, Y Water, agricultural ,,,,,,,,,,,,,,,,,,,, 14, 34, 36, 38 brackish ,,,,,,,,,,,,,,,,,,,,,,,,,, 14, 23, 29, 65 calcium-magnesium sulfate ,,,,,,,,,,,,,,,,,, 65 chloride concentrations ,,,,,,,,,,,,,,,,,,,,,, 32 connate _____________________ 23, 66 Diablo Range _______ . ______________ 66 dissolved solids _____ 19, 29, 32, 65, 66 fresh ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 27, 29, 65, 66 irrigation ,,,,,,,,,,,,,,,,,,,, 25, 39, 45, 66 perched ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 40 Pliocene sands ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 32 productivity, lower zone, saline ,,,,,,,,,,,,,,,,,, sodium chloride ,,,,,,,,, sodium sulfate ,,,,,,,,,,,,,,,,,,,,,,,,,, 29, 66 surface imports ,,,,,,,,,,,,,,,,,,,,,,,, 14, 63 temperatures ,,,,,,,,,,,,,,,,,,,,,,,,,, 23, 32 Water-level recorder Water table ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, Wells, alluvium INDEX Water levels, changes ____________ confined zone ______ A, ,,,,,,,, 39 lower zone _________________ 39, 45, 50, 61, 63 measurements ,,,,,,,,,,,,,,,,,,, 7 periodic measurements ,,,,,,,,,,,,,,,,,,,, 6, 46 seasonal fluctuation ,,,,,,,,,,,,,,,,,,,,,, 39, 59 semiconflned zone ___________________ 39 upper zone ____________ 43, 44, 45, 66 altitude _ _ r decline ,,,,,,,,,,,,,,,,,,,,, 40, 43, 44, 56, 66 lower zone ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 50, 66 rise ,,,,,,,,,,,,,,,,,,,,, 40, 43, 66 upper zone A, ,,,,,,,,,,,,,,,,, 14, 66 artesian ,,,,,,,,,,,,,,,,,,,,,,,, u 34 head decline ,,,,,,,,,,,,,,,,,,,, 23, 34, 61 Big Blue Hills ,,,,,,,,,,,,,,,,,,,,,,,,,, 63, 65 brackish water ,,,,,,,,,,,,,,,,,,,,,,,,,, 29, 66 Cantua recorder site __ descriptions by Ireland _ 6 Etchegoin Formation r 23, 29, 56, 63 flowing ,,,,,,,,,,,,,,,,,,,,,,,, H 34, 66 fresh water ,,,,,, 56, 65, 66 base ,,,,,,,,,,,,,,,,,,,,,, 29 irrigation ,,,,,,,, 7, 17, 23,27, 34, 36, 39, 44, 56 Kreyenhagen Formation ,,,,,,,,,,,,,,,,,,,, 23 Los Gatos Creek area ,,,,,,,,,,,,,,,,,,,,, 27 lower zone ________ ,7 __ 22, 34, 36 head differentials , hydrographs ,,,,,,,, water levels, declines ,,,,,,,, yield factors ,,,,,,,,,,,,,,,,,,,,,,,, 25, 27 Mendota recorder site ,,,,,,,,,,,,,,,,,,,,,,,, 43 mixed zone ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 45 Page Wells—Continued near the Merced County line ,,,,,, north of Westhaven , ,,,,,,,,,,,,,,, northwest of Tulare Lake bed ,,,,,,,,,,,,, 59, 65 numbering system ,,,,,,,,,,,,,,,,,,,,,,,,,, 6 observation ,,,,,,,,,,,,,,,,,,, 7, 59 location __r 9 perforated ,,,,,,,,, 22, 27, 29, 39, 40, 43 permeability ,,,,,,,,,,,,,,,,,,,,,,, 17, 65 Pliocene deposits ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 23 saline water ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 32 San Joaquin Formation ,,,,,,,,,,,,,,,,,, 23 San Joaquin Valley ,,,,,,,,,,,,,,,,,,,,,,,,,, 63 seasonal fluctuations shallow ,,,,,,,,,,,,,,,,,,, southwest of Los Banos ,,,,,,,,,,,,,,,,,,,,,, 17 southwest of Mendota ,,,,,,,,,,,,,,,,,,,, 59, 61 Tranquillity site __ ,,,,,,,,,,,, 43 Tulare Formation , J, 23, 32, 56 unused ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 45 upper zone, yield factors ________ 27 water levels ,,,,,,,,,,,,,,,,,,,,,, 39, 40, 45, 50 water table ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 43 water temperature ,,,,,,,,,,,,,,,,,,,,,, 23, 32 west of Fresno Slough ,,,,,,,,,,,,,,,,,,,,,,,, 17 west of the San Joaquin River ,u ,,,,,,,,, 17 Westhaven site ,,,,,,,,,,,,,,,,,,,, 43 yields ,,,,,,,,,,,,, J 27, 65 Westhaven ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 34, 43, 63 Westhaven site ,,,,,,,,,,,,,,,,,,,,,,,,,, J” 43 Westlands Water District ,,,,,,,,,,,,,,,,, r," 8 Yearout site, wells, irrigation ,,,,,,,,,,,,,,,,,,,, 39 Yield factors ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 17, 25, 65 U. S.GOVERNMENT PRINTING OFFICE: 1975-0-689-905/10 PE 75' 7 DAY 775, V. 457* F Land Subsidence Due To Ground—Water Withdrawal in the Los Banos—Kettleman City Area, California, Part 2. Subsidence and Compaction of Deposits GEOLOGICAL SURVEY PROFESSIONAL PAPER 437—F Prepared in cooperation with the California Department of Water Resources Land Subsidence Due To Ground-Water Withdrawal in the Los Banos—Kettleman City Area, California, Part 2. Subsidence and Compaction of Deposits- By ‘NILLIAM B. BULL STUDIES OF LAND SUBSIDENCE GE Prepared in cooperation with the Calfornia Department of Water Resources OLOGICAL SURVEY PROFESSIONAL PAPER 437—F UN] TED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1975 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress Cataloging in Publication Data Bull, William B. 1930— Land subsidence due to ground-water withdrawal in the Los Banos—Kettleman City area, California. (Studies of land subsidence) (Geological Survey Professional Paper 437—E—G) Pt. 2 by W. B. Bull; pt. 3 by W. B. Bull and J. F. Poland. ‘ Includes bibliographies and indexes. CONTENTS: pt. 1. Changes in the hydrologic environment conducive to subsidence—pt. 2. Subsidence and compaction of deposits. [etc.] Supt. of Docs. No.2 1 19.16z437—F 1. Subsidences (Earth movementsy—California—San Joaquin Valley. 2. Aquifers—Califomia—San Joaquin Valley. 3. Water, Underground—California—San Joaquin Valley. 1. Miller, Raymond E. II. Poland,Joseph Fairfield, 1908— III. California. Dept. of Water Resources. IV. Title. V. Series. V1. Series: United States. Geological Survey. Professional Paper 437—E—G. QE75.P9 No. 437—E—G [GB485.C2] 557.3’08s [551.3’5] 74-28239 For sale by the Superintendent of Documents, US. Government Printing Office Washington, DC. 20402 Stock Number 024—001-02610 CONTENTS Page Page Glossary __________________________________________________ V Compaction of the ground-water reservoir——Continued Abstract __________________________________________________ F1 Field measurements of compaction—Continued Introduction ______________________________________________ 1 Shortening and increased protrusion of well Purposes ______________________________________________ 2 casings—Continued Acknowledgments ______________________________________ 2 Casing-failure study __________________________ F45 Subsidence of the land surface ______________________________ 2 Proportions of compaction occurring in the upper and lower - zones ____________________________________________ 46 Sources of vertical-control data ________________________ 4 . , . , . . . . Geologic factors influencing compaction of the unconsolidated Topographic mapping program of the US. Geological deposits 49 Survey ______________________________________ 4 . """""""""""""""""""""""""" Bench-mark survey program of the US Coast and Geo- Local relations """""""""""""""""""""" 49 . Overburden load __________________________________ 49 detic Survey ________________________________ 4 P t l 51 Changes in the altitude of the land surface ______________ 6 Be d1: ogy """"""""""""""""""""" 54 Tectonic movements ________________________________ 7 e 8ng “fl—"dulfl'ut—iHHTt """""""""""" 56 Apparent uplift of Anticline Ridge, 1962—63 ____ 7 1erra 0° 1,) ain ePOSI S """"""""""" - . Diablo alluv1al-fan depOSits ____________________ 57 Subs1dence due to Withdrawal of petroleum .......... 8 . . . - Diablo flood-plain dep051ts ______________________ 57 Near-surface subs1dence ____________________________ 8 . . . ~ - Sierra deltaic depOSits __________________________ 58 Subs1dence due to Withdrawal of ground water ______ 10 . . . . . Lacustrme depOSits ____________________________ 59 Extent and magnitude of subs1dence in the Los - Lateral extent ________________________________ 59 Banos—Kettleman City area ______________ 10 , . . - Comparison of bed-thickness factors ____________ 60 History of sub51dence __________________________ 19 . . , . Compaction characteristics ________________________ 62 Rate of subSidence ____________________________ 22 , . Regional relations ____________________________________ 63 Compaction of the ground-water reservoir __________________ 29 Age of the deposits ________________________________ 63 Field measurements of compaction ______________________ 29 Specific unit compaction of the lower-zone deposits __ 64 Types of compaction gages used ____________________ 29 Geologic factors influencing specific unit com- Analysis of friction in a compaction recorder ________ 31 paction __________________________________ 67 Cumulative compaction at multiple compaction-recorder Prior total applied stress __________________ 67 sites ________________________________________ 33 Stress-compaction products ________________ 70 Cumulative compaction at single compaction-recorder Mean lithology ____________________________ 76 sites ________________________________________ 36 Source and mode of deposition __________________ 79 Unit compaction at the multiple compaction-recorder Variation in excess pore pressure _____ __________ 82 sites ________________________________________ 38 Distribution of well-casing failures __________________ 83 Shortening and increased protrusion of well casings __ 41 Summary and conclusions __________________________________ 84 Shortening of an oil-well casing ________________ 42 References ________________________________________________ 87 Shortening of water-well casings ________________ 43 Index ____________________________________________________ 89 ILLUSTRATIONS Page FIGURE 1. Map showing bench marks, observation wells, compaction recorders, core holes, and lines of section referred to in this report ______________________________________________________________________________________________ F3 2. Map showing level-line network of the US. Coast and Geodetic Survey, 1963 ____________________________________ 5 3. Maps showing extent and times of principal leveling by the US. Coast and Geodetic Survey ______________________ 8 4. Graph showing apparent net uplift of Anticline Ridge along State Highways 33 and 198, between March 1962 and March 1963 ______________________________________________________________________________________________ 8 5. Graph showing change in altitude of bench marks in Pleasant Valley (T156), Anticline Ridge (W156), and the west edge of the San Joaquin Valley (Y156), 1933—66 ____________________________________________________________ 8 6—13. Maps showing: 6. Location of oil and gas fields in western Fresno County ________________________________________________ 9 7. Areas of major land subsidence in the San Joaquin Valley, as of 1963 ____________________________________ 11 8. Land subsidence due to artesian-head decline, 1920—28 to 1943 __________________________________________ 12 9. Land subsidence, 1920—28 to 1966 ____________________________________________________________________ 13 10. Land subsidence due to artesian-head decline, 1943—59 ________________________________________________ 15 11. Land subsidence, 1955—56 ____________________________________________________________________________ 16 12. Land subsidence, 1959—63 ____________________________________________________________________________ 17 13. Land subsidence, 1963—66 ____________________________________________________________________________ 18 III IV FIGURE 14. 15. 16. 17. 18—21. 22. 23. 24. 25—35. 36. 37. 38. 39. 40-44. 45. 46. 47. 48—52. 53—58. 59. 60. 61. 62. 63. 64. CONTENTS Graph showing distribution of intensity of subsidence, 1920—28 to 1966 __________________________________________ Graphs showing subsidence for selected bench marks __________________________________________________________ Profile of subsidence that has occurred since 1943, Tumey Hills to Mendota ______________________________________ Profile of subsidence that has occurred since 1943, Anticline Ridge to Fresno Slough ______________________________ Maps showing: 18. 19. 20. 21. Average yearly rate of subsidence, 1959—63 ____________________________________________________________ Average yearly rate of subsidence, 1963—66 ____________________________________________________________ Change in rate of subsidence between the 1943—53 and 1959—63 periods __________________________________ Change in rate of subsidence between the 1959—63 and 1963—66 periods __________________________________ Graphs showing subsidence rates for selected bench marks ______________________________________________________ Diagram of recording compaction gage ________________________________________________________________________ Diagrammatic sketch of a compaction- -recorder system with casing-cable friction __________________________________ Graphs showing. 25. 26. 2.7. 28. 29. 30. 31. 32. 33. 34. 35. Interpolation of part of the cumulative compaction record from well 16/15—34N1 __________________________ Compaction and subsidence at the Oro Loma site, 1958—66, and Mendota site, 1961-66 ............... Compaction and subsidence at the Cantua site, 1958—66 ________________________________________________ Decrease in the percentage of subsidence measured in the 0—2,000-foot depth interval at the Cantua site, 1959—67 ______-_,,--,---1,,,,,1111 ______________________________________________________________ Compaction and subsidence at the Westhaven site, 1962—66, and well 13/12—20D1, 1961—66 _______________ Compaction and subsidence at well 19/16—23P2, 1959—66 ________________________________________________ Mean annual unit compaction in three depth intervals at the Oro Loma site for 2-year periods, 1960—65 _____ Mean annual unit compaction in two depth intervals at the Mendota site for 2-year periods, 1962—65 ____ Mean annual unit compaction in three depth intervals at the Cantua site for 2-year periods, 1960—65 _____ Unit compaction in three depth intervals at the Westhaven site for 1-year periods, 1963—65 ________________ Decrease in annual compaction for selected depth intervals at multiple compaction-recorder sites __________ Photograph showing compressional rupture of an irrigation-well casing ___________________________________________ Graph showing relation of increased casing protrusion to casing diameter for observation wells that are not gravel packed __________________________________________________________________________________________________ Diagrammatic sketch of wells used for measuring water levels and compaction, wells 20/ 18—1 1Q2 and 11Q3 ________ Photograph'showing compaction gage and casing separation at wells 20/18—11Q2 (inner casing) and 11Q3 (outer casing) __________________________________________________________________________________________________ Graphs showing: 40. 41. 42. 43. 44. Shortening of 11%-inch casing, wells 20/18—11Q2 and 11Q3 ____________________________________________ Subsidence of well bench marks and reference bench marks within 17—193 feet of the well bench mark ______ Effect of pumping on differences of changes in altitudes of reference and well bench marks ................ Unit casing-failure ratio for 50-foot intervals above and below the Corcoran Clay Member of the Tulare Formation ________________________________________________________________________________________ Comparison of unit compaction at the Mendota, Cantua, and Westhaven sites and unit casing- -failure ratios in the same depth intervals of nearby irrigation wells ______________________________________________ Map showing proportions of compaction occurring in the upper and lower water- bearing zones ____________________ Graphs showing relation of applied stress, sorting, and particle size on void ratio and porosity of selected suites of samples of alluvial sediments from three core holes in the Los Banos—Kettlema’n City area ____'_ _______________ Electric log of the deposits at well 18/19-20P1 ____________________________________________________ ; _____________ Graphs showing bedding, lithology, and vertical permeability: I i 48. 49. . Sierra flood-plain deposits, Cantua site, depth 978—1,134 feet ____________________________________________ Diablo alluvial-fan deposits, Mendota site, depth 350—500 feet __________________________________________ 50. Diablo flood-plain deposits, Mendota site, depth 1,040—1,205 feet ________________________________________ 51. 52. Fine- grained facies of the Sierra deltaic deposits, Huron site, depth 2 ,,000—2 114 feet ______________________ Corcoran Clay Member of the Tulare Formation and adjacent deposits at the Mendota site, depth 600—721 feet __ Maps showing: 53. 54. 55. 56. - 57. 58. Maximum thickness of the perforated interval of the lower zone ________________________________________ Specific unit -compaction for the lower water-bearing zone, 1943—60 ______________________________________ Depth to the middle of the lower zoned“; _____________________________________________________________ Applied stress due to the unsaturated condition of the deposits above the water table as of 1951 __________ Seepage stress on the lower zone as of 1943 ____________________________________________________________ Total applied stress on the middle of the lower zone as of 1943 __________________________________________ Graph showing reduction of the effect of variable effective stress through use of compressibility-effective stress products for core samples from the Cantua site ____________________________________________________________ Map showing variations in stress-compaction products __________________________________________________________ Lithofacies map based on the mean corrected resistivities of the lower zone ______________________________________ Graph Showing variation in mean particle size with depth for alluvial deposits below the Corcoran in cores from the Mendota and Huron sites ________________________________________________________________________________ Graphs showing relation of mean corrected resistivity to the product of specific unit compaction and total applied stress, lower zone ________________________________________________________________________________________ Map showing relation of stress-compaction products to the sources and modes of deposition of the lower-zone deposits_- -_ Page F19 20 21 22 23 24 25 27 28 29 32 32 34 35 35 36 37 38 39 40 40 40 41 42 42 43 44 45 45 46 47 50 52 55 56 57 58 58 59 65 66 68 69 71 72 73 75 78 79 79 80 CONTENTS V Page FIGURE 65. Section showing relation of stress-compaction products to types of lower-zone deposits _____________________________ F81 66. Graph showing relation of well-casing failures to hydrologic unit and type of adjacent deposit _______________________ 84 TABLES Page TABLE 1. Summary of compaction-recorder installations ________________________________________________________________ F31 2. Annual compaction rates at multiple compaction-recorder sites ________________________________________________ 38 3. Variation in the deepest annual water levels for selected depth zones at the multiple compaction-recorder sites, 1959—63 ______________________________________________________________________________________________ 41 4. Proportions of compaction occurring in the upper and lower water-bearing zones ________________________________ 48 5. Amount of clay in deposits from Diablo and Sierra sources in the Mendota, Cantua, and Huron cores ______________ 53 6. Mean vertical permeabilities of the different types of deposits as determined from consolidation tests of samples in the $990 load range 400—800 lb in‘2 at the four core-hole sites ______________________________________________________ 56 . Summary of lower-zone weighted mean bed-thickness factors of aquitards for types of deposits and Inter-Agency Com- mittee core- -hole sites __________________________________________________________________________________ 60 Weighted mean bed-thickness factors of aquitards for lower- -zone deposits at Inter-Agency Committee core- h-ole sites 61 Mean consolidation characteristics of the Corcoran and the different types of lower- zone deposits in the load range 400—800 lb in‘2 62 GLOSSARY The geologic and engineering literature contains a variety of terms that have been used to describe the processes and environmental conditions involved in the mechanics of stressed aquifer systems and of land subsidence due to withdrawal of subsurface fluids. The usage of certain of these terms in reports by the US. Geological Survey re- search staff investigating mechanics of aquifer systems and land subsidence is defined and explained in a glossary published separately (Poland and others, 1972). Several terms that have developed as a result of the Survey’s investigations are also defined in that glossary. The aquifer systems that have compacted sufficiently to produce significant subsidence in California and elsewhere are composed of unconsolidated to semiconsolidated clastic sediments. The definitions given in the published glossary are directed toward this type of sedi- ments; they do not attempt to span the full range of rock types that contain and yield ground water. In defining the components of the compacting stresses, the contribution of membrane effects due to salinity or electrical gradients has been discounted as relatively insignificant in the areas studied. In our research reports, pressures or stresses causing compaction are usually expressed in equivalent “feet of water head” (1 foot of water = 0.433 lb in ‘2 (pounds per square inch)). A committee on redefinition of ground-water terms, composed of - members of the Geological Survey, recently issued a report entitled “Definitions of Selected Ground-Water Terms” (Lohman and others, 1972). The reader is referred to that report for definitions of many ground-water terms. Five terms used in this report which have not been defined else- where are given in the following list. APPARENT COMPRESSIBILITY. A time-dependent parameter derived from field observations that indicates the amount of shorten- ing, per unit thickness of deposits, per unit change in applied stress. Parameters such as specific unit compaction and stress-compaction products are apparent compressibilities because the degree to which applied stresses have become effective is not known. COMPRESSIBILITY-EFFECTIVE STRESS PRODUCT. The pro- duct of compressibility and effective stress, as determined by labora- tory consolidation tests. The resulting product is a true compressibil- ity for which the effects of variable effective stress have been largely eliminated. CRITICAL DEPTH. The depth below which friction between the casing and the adjacent deposits exceeds the shear strength of the casing. STRESS-COMPACTION PRODUCT. An apparent compressibility for which the effect of prior total applied stress has been removed. In this paper, the stress-compaction product was computed by multiply— ing specific unit compaction by total applied stress. The resulting product is only an apparent compressibility of the deposits, because the degree to which applied stresses have become effective is not known. SUBSIDENCE, NEAR-SURFACE. The vertical downward move’ ment of the land surface that occurs when moisture—deficient deposits compact as they are wetted for the first time since burial (Bull, 1964a). STUDIES OF LAND SUBSIDENCE LAND SUBSIDENCE DUE TO GROUND-WATER WITHDRAWAL IN THE LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2. SUBSIDENCE AND COMPACTION OF DEPOSITS By WILLIAM B. BULL ABSTRACT Pumping of ground water has increased the stresses tending to compact unconsolidated deposits by as much as 50 percent, thereby creating the world’s largest area of intense land subsidence in the” west-central San Joaquin Valley, Calif. As of 1966, 2,000 square miles had subsided more than 1 foot, and the area that had subsided more than 10 feet was 70 miles long. Maximum subsidence was 26 feet. Subsidence rates increased until the mid-1950’s when the maximum observed rate was 1.8 ft yr_ 1 (feet per year), but have decreased since then. During the 1963—66 period the maximum subsidence rate was only 1.1 ft yr_1. Subsidence due to artesian-head decline is of greater extent and magnitude than three other types of subsidence in the area. Tectonic subsidence is difficult to separate from other types of subsidence. Net uplifts of less than 0.1 foot have occurred at three places at the front of the Diablo Range. Subsidence due to pumping of petroleum appears to be minor. The Coalinga oil field subsided only 0.25 foot in 20 years. About 120 square miles adjacent to the Diablo Range is susceptible 'to near-surface subsidence, where compaction due to wetting of moisture-deficient alluvial-fan deposits has caused as much as 15 feet of subsidence. Subsidence of 3—10 feet is common. Subsidence due to artesian-head decline occurred first in the north- ern part of the area, where, by 1943, subsidence was as much as 10 feet. By 1963, 20 feet of subsidence had occurred in both the northern and southern areas. Maximum subsidence, as of 1968, was estimated to be 28 feet. Special compaction recorders in wells penetrating most of the aquifer system tapped by wells initially measured as much as 99 percent of the subsidence. Since 1963, most recorders have been measuring progressively less of the subsidence, which indicates that compaction due to pore-pressure decline is occurring at greater depths than previously. _3 Unit compaction of as much as 1.2x 10 feet per foot per year has been measured at the Cantua site. Casing-failure distribution indi- cates that amounts of unit compaction increase to depths of roughly 200 feet below the Corcoran Clay Member of the Tulare Formation in response to progressively larger head declines with depth. Below a depth of about 200 feet below the Corcoran, unit compaction decreases with depth, probably in response to minimal change of head decline with depth and to the decreasing compressibilities of the deposits caused by progressively greater prior effective stresses. Compaction mainly shortens water-well casings, but also causes increased casing protrusion above the land surface of as much as 10 percent of the compaction. Bench marks within 17—193 feet of active irrigation wells subside less than the tops of the well casings despite increased casing protrusion. Maximum compaction occurs at pump- ing wells, because they are points of maximum applied stress. In most of the area about 70-95 percent of the compaction occurs in the lower zone below the Corcoran confining bed. As much as 30—40 percent of the compaction occurs in the upper zone in the southern part of the area. Geologic factors that cause differences in specific unit compaction include total applied stress, lithofacies, and source and mode of deposition—factors that were assessed by removing the effect of prior load. The specific unit compaction of the lower-zone deposits, 1943—60, in the northern part of the area is four times that in the central and southern parts of the area, suggesting a marked difference in the compressibility of the deposits. About one-third of the apparent differ- ence in compressibilities between the northern and southern areas is real and is due to differences in total applied stress prior to 1943. Deeply buried deposits that have been subjected to large prior applied stresses are less compressible, per unit of additional stress increase, than are deposits at moderate depths. The other two-thirds of the compressibility difference is only appar- ent and is attributed chiefly to hydraulic differences between genetic types of deposits that affect the rate of expulsion of water from aquitards for a given applied-stress increase. When compared with the Diablo (derived from Diablo Range) and Sierra (derived from Sierra Nevada) flood-plain deposits, the Diablo alluvial-fan deposits have a higher clay content and are more poorly sorted, which results in lower permeabilities and slower consolidation rates. Fine-grained beds generally are thicker in the lacustrine and fan deposits than in the flood-plain deposits. (Respective mean bed-thickness factors are 61, 24, and 14, where bed-thickness factor is (aquitard thickness/2W). Thus, conditions in the alluvial-fan aquitards in the southern part of the area and thick lacustrine sequences in the central part of the area are favorable for development of large residual excess pore pressures and high values of ultimate specific unit compaction. These same conditions also are responsible, in part, for the lower apparent com- pressibilities (stress-compaction products) during the 1943—60 period in the areas of thick alluvial-fan and lacustrine deposits than in the areas of thick flood-plain deposits. Variations in the mean lithology (corrected mean resistivities) of the lower zone are not as important as either prior overburden load or mode of deposition in determining the apparent compressibilities of the deposits. INTRODUCTION By increasing the stress tending to compact the un- consolidated deposits by as much as 50 percent, man has created the world’s largest area of intense land subsid- ence in the west-central San Joaquin Valley. With- drawal of ground water for agriculture has caused more than 2,000 square miles to subside more than 1 foot. As F1 F2 of 1966, the area that had subsided more than 10 feet was 70 miles long, and the maximum subsidence was 26 feet. The land subsidence, compaction of the saturated deposits that caused the subsidence, and the geologic factors influencing the compaction—which are the top- ics of this paper—will be presented for one of four major areas of intense land subsidence due to ground—water withdrawal in California. This paper is the second of three reports discussing land subsidence due to ground-water withdrawal in the Los Banos—Kettleman City area, California. Part 1 (Bull and Miller, 1974) is a factual presentation of the hydrologic factors conducive to land subsidence in the study area. Part 3 (Bull and Poland, 1974) discusses the interrelations of water-level change, change in aquifer-system thickness, and the concurrent changes in land-surface altitude as well as the criteria for pre- diction of subsidence. The introduction to all three parts can be found in Part 1 (Bull and Miller, 1974). That introduction in- cludes descriptions of the extent of the study area and the geographic setting, as well as sections about the Inter-Agency Committee on Land Subsidence and the scope of the field and laboratory work for the Coopera- tive and Federal subsidence programs. The principal areas of land subsidence in California due to ground- water withdrawal and the topographic and cultural fea- tures of the Los Banos—Kettleman City subsidence area are shown in figures 1 and 2 of Part 1 (Bull and Miller, 1974). For a résumé of the hydrologic environment and the man-induced changes in the hydrologic environ- ment, the reader is referred to the summary and conclu- sions of Part 1. The boundaries of the Los Banos—Kettleman City study area, bench marks, observation wells, compaction recorders, core holes, and lines of section referred to in this report are shown in figure 1. The northeast bound- ary as shown in figure 1 is along the valley trough, but as of 1966, as much as 8 feet of subsidence had occurred east of the valley trough. Therefore, in much of the study, the 1-foot subsidence line (figs. 9, 14) was used as the east boundary of the subsidence system. The bulk of the information presented in this paper concerns the events before April 1966, which was a time of complete leveling of the bench-mark network by the US. Coast and Geodetic Survey (since 1970, the Na- tional Geodetic Survey, a component of the National Ocean Survey). Where post-March 1966 data are pre- sented and discussed, it is done only to present facts or concepts that cannot be demonstrated with the earlier data. PURPOSES The scope of this paper is to discuss the compaction of unconsolidated deposits and the resulting land subsid- STUDIES OF LAND SUBSIDENCE ence in the many different geologic and hydrologic environments present in the west-central San Joaquin Valley. Within this scope, the paper has three specific purposes. The first is to show the extent, magnitudes, and rates of subsidence due to artesian-head decline; to show the changes of these aspects during the agricul- tural development of the area; and to compare the ex- tent, magnitudes, and rates of subsidence due to artesian-head decline with concurrent subsidence caused by compaction due to wetting, withdrawal of petroleum, and tectonic activity. The second purpose is to describe the measurement of compaction, the propor- tions of subsidence being measured by compaction re- corders, and the rates and amounts of compaction occur— ring within specific depth intervals. The third purpose of this paper is to assess the geologic factors influencing compaction of the deposits of differing lithology, source, mode of deposition, and depth of burial. Both those geologic factors described in the literature and consid- eration of new factors will be included in the geologic appraisal of compaction. ACKNOWLEDGMENTS The cooperation of numerous ranchers, landowners, and companies is acknowledged for supplying essential information to the subsidence project and for giving permission to install and maintain wells and equipment for obtaining water-level and compaction information. Particular assistance was given by the Pacific Gas and Electric Co., Westlands Water District, and Russell Gif- fen, Inc. The financial cooperation of the California Depart— ment of Water Resources made this study possible, and information provided by the US. Bureau of Reclama- tion from core holes and observation wells contributed significantly to the essential data. This work could not have been completed without the discussions, interest, and assistance of many people who have been associated with the land-subsidence studies since 1956. I appreciate particularly the helpful discussions and review of the manuscript by the project chief, J. F. Poland, and my colleagues, G. H. Davis, B. E. Lofgren, and F. S. Riley. I enjoyed working together with R. L. Ireland and R. G. Pugh on a variety of jobs in the field and appreciate their extensive help in collec- tion and assembling of field data. Particular credit is due Mr. Ireland for his meticulous care and thoughtful foresight in the installation and operation of the equip- ment for recording compaction and water-level changes during the entire period of record. SUBSIDENCE OF THE LAND SURFACE Several parts of the Los Banos—Kettleman City area have subsided more than 20 feet, and subsidence rates LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 l3 120° 30' 14 F3 17 120°oo' 37°OO' Me On) Lorna site 01416 1-6 G EXPLANATION 77777; 7777/: Boundary of deformed rocks 36°30’ Boundary of the Los Banos- Kettleman City area .34 N1 Core/hole and well number A Compaction recorder; if more than one, number indicated inside symbol (9 Observation well and well number; if more than one, number indicated inside symbol 35N1 06N1 Irrigation well from which water-level rec- ord has been obtained and well number Xvesz Bench mark and number 0 0’ Line of section or profile shown in suc- ceeding illustrations 0 1O 15 MILES 0 5 10 15 KILOMETRES 36°00' 175(uses | 3 A'9 @‘A @s V earout site Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 1.—Bench marks, observation wells, compaction recorders, core holes, and lines of section referred to in this report. have exceeded 1 ft yr"1 (foot per year). The main pur- Three other types of subsidence also will be discussed to pose of this section is to discuss the extent, rate, and magnitude of subsidence due to artesian-head decline. indicate their extent, rate, and magnitude in relation to the areas of subsidence due to artesian-head decline. F4 SOURCES OF VERTICAL-CONTROL DATA The two main sources of vertical-control data are maps made by the Geological Survey and bench-mark altitudes of the Coast and Geodetic Survey. The Bureau of Reclamation and the California Department of Water Resources also have surveyed bench marks along canals and future canal alinements. TOPOGRAPHIC MAPPING PROGRAM OF THE US. GEOLOGICAL SURVEY The first detailed topographic mapping of 71/2-minute quadrangles in the Los Banos—Kettleman City area was done mainly during the 1920’s. Surveys for detailed topographic maps were made in the following periods: between latitudes 36°30’ and 37°00’, 1919—23; between 36°15’ and 36°30’, 1924—28; and between 36°00’ and 36°15’, 1926—33. These maps had a 5— or 10—foot contour interval based on planetable surveys. The Geological Survey was first confronted with the subsidence problem in the Los Banos—Kettleman City area in 1953—54 when a map revision program was undertaken (Inter-Agency Committee on Land Subsid- ence in the San Joaquin Valley, 1958, p. 33—35). Nor- mally a revision for the purpose of bringing culture up to date would not present many problems. However, the surveyors had difficulty in closing stadia traverses and in reconciling topography with cultural changes. It was apparent that a useful topographic map for engineering purposes would not result from a mere cultural revision. The situation was brought to the attention of the members of the Inter-Agency Committee, and it was agreed that completely new topographic maps were necessary to show the amount of subsidence that had occurred since the 1920’s, especially for large areas be- tween the existing level lines. The Coast and Geodetic Survey gave full cooperation to a coordinated program of establishing vertical control for the areas to be re- mapped topographically. The topographic mapping immediately followed the leveling of September- November 1955, and 28 quadrangles were remapped during the winter of 1955—56; by 1962, 43 maps within, or partly in, the Los Banos—Kettleman City area had been revised and then remapped where necessary. The contour interval for these maps ranges from 5 to 40 feet. A comparison of the maps made in the 1920’s and the 1950’s showed that more than 10 feet of subsidence had occurred over large areas and that the maximum sub— sidence was about 18 feet in an area west of Mendota. Because of the large areas between level lines prior to 1955, this comparative subsidence map is used, in part, for all the subsidence maps that portray subsidence prior to 1955. Maps that portray only post—1955 subsid- ence are based entirely on bench-mark control. STUDIES OF LAND SUBSIDENCE BENCH-MARK SURVEY PROGRAM OF THE US. COAST AND GEODETIC SURVEY The Coast and Geodetic Survey has been the key agency in fulfilling the following vertical-control ele— ments proposed by the Inter-Agency Committee on Land Subsidence in the San Joaquin Valley (1955, p. 16—17). 1. Maintenance of a basic network of first-order levels surrounding the San Joaquin Valley, with cross- ties between bedrock in the Sierra Nevada, Coast Ranges, and Tehachapi Mountains, and to ocean- tide gages. (This network provides an overall datum and helps determine the general stability of the local bedrock reference points.) 2. Establishment of a network of first- and second-order levels within the basic network to form a base for topographic mapping and special surveys, which will provide information on the extent of subsid- ence areas and on the development of new subsid- ence areas. 3. Periodic releveling of a comprehensive network of lines in the areas of known major subsidence to define the amount and rate of subsidence. (The Los Banos—Kettleman City area was releveled every 2 years between 1955 and 1959 and every 3 years between December 1959 and March 1966.) The level-line network of the Coast and Geodetic Sur- vey is shown in figure 2, which also shows the quad- rangle boundaries and numbers. Only part of the lines outside of the Los Banos—Kettleman City area are shown. Additions to this network have not been pro- posed except for short spur lines to compaction record- ers. The first Coast and Geodetic Survey leveling in the Los Banos—Kettleman City area was made in 1933 (prior levelings were made by the Geological Survey) and was followed by releveling or new leveling in 1935, 1942—43, 1947, 1948, and in every year from 1952 through 1968 except 1956 and 1961. In some of these years, the extent of the leveling was small because the work consisted mainly of establishing bedrock ties for work being done outside the Los Banos—Kettleman City area. The extent of the eight principal levelings is shown in figure 3. The complete subsidence network that was established in 1955 has been releveled four times, the latest being in the winter of 1966. Leveling accuracy is difficult in an area that subsides as rapidly as the Los Banos—Kettleman City area. At— tainment of precise results is hindered by movement of reference bench marks within the mountains and by subsidence of bench marks during the leveling of the valley areas. For purposes of adjusting the results of a leveling program, certain bench marks set in bedrock LOS BANOS—KE'I'I‘LEMAN CITY AREA, CALIFORNIA, PART 2 F5 120°30' 120°00’ 33 z 1; Los Banos 0 3 152 / : : 0) : 3 g ,0 371203 , s 371202 3/ 3712007400 000 000000000 9...]??5 00%000000 :000000000000000000000000000000000000 00000000/0'. a os ,_ , . ~.’\E[e£"£”~——\\,_\V,._/ ~\Igiver .9 Q: 33 : 0e, ’ : "3, "’ /8I '06 5 ¢ M: d = 2 Or 2 / a 102 0a,, . 5‘ 6 ’ I ‘3 Firebaugh \° 0 0 103 [0 Cf" / ’0 m 1 : K5 {gt-co éO I 2 ,— _°4_ .3— ) / IN “‘ $0 I'm—4' : I °e or“;U / Q" Q 1 0 %\ I Q / 08 _| 0 O ,6 104 a Mendota \ ' é: 7% 3 r 707—3 18° 1 6% Q; )0) 1*07, ._ «a Kermanc_ o w : 107 «9% 106 ‘S; 0 ‘ o O) (r - 0° \~ .9 m «o1 z e 4‘ 6 I 1° : 109 _l— I ’o = 69 J IL ‘\"° A 2 : tr \ 1 1 ’9 (6;, . 2 X 9‘9? I'— SI Pl \ \2} ‘— 1 44° 11’1|111_{_ 111 _I ~-—\\\\ 0 o - 361204 "4%. 0; 2 361201 3 $1 0 36°3O’L 0000000000("@00?/° 0000 0000000£ %C‘WS000000-0F 00 ’91. ° 6‘6 °° 112 ' .. o- e 11° 0 2.1.2— K ”r, 5 __. _ (w) 0 \ a m; 5 :1 g} ’7 0 — Five Points. I)\ F EXPLANATION $0 : I ‘~~ 105 .<<‘ - I—K: ‘— 77777777777 : o ’0, I z; I 70,07/ , 0 ‘— , Boundary of deformed : ’0 <5 I . I e rocks ' 9 33 " 105 : K110 -/ : (o 3"— — "_ ‘h _mI ' s '- 110 101 — . ,7/ \ :J I .— Level line that usually is leveled to first- : <40 I g 17.3 L.‘ order accuracy : , cl I ‘ 3; ,_ 3 ,3 \02 I "3| I I 0 ' ~ 101 1 106 -- | , 107 ‘- Level line that usually is leveled to second- : 105' .|1o7 u U 1 order accuracy : / / I Westhaverfl I i,” 361202 : 7 9 lo 8 Huron : 8 1 E 0000000000000 : ’00 7;; “a Location and name of oil 'J or gas field E. Coalinga I 1 .3 extension WesthavenO ' HuronO I 4 J Strat— / ‘Pleasant Valley 900 ford l (‘9 0‘ Q Guijarral Hills «25,969 / Q \0 {u‘o' / TULARE J l'tos . % Kettleman acal ' a North dome LAKE 5 ‘l 15 MILES 0 0 x / , Kettleman BED o 5 10 15 KILOMETERS 1 / 9 [ city 36°OO’ ‘ Base from U.S. Geological Survey Central Valley map, 1:250,000. 1958 FIGURE 6.—Location of oil and gas fields in western Fresno County. (From California Division of Oil and Gas, 1960), transmission towers, and buildings and has made the irrigation of crops difficult. Subsidence of 3—5 feet is common, and 10—15 feet of subsidence has occurred within small areas. The rate of subsidence is as much as 0.25 foot per day and is controlled partly by the rate at which the water front advances through the deposits. F10 Subsidence cracks—which are typical of this type of subsidence—are vertical fissures that may or may not have offset of the bedding on opposite sides of the crack. Near-surface subsidence results chiefly from the compaction of deposits by an overburden load as the clay bond supporting the deposits is weakened by water per- colating through the deposits for the first time since burial. Two requirements are necessary for compaction due to wetting to occur: first, that after much of the water has been removed from the deposits by evapo- transpiration, the moisture-deficient state of the de- posits be maintained by absence of percolation of water from rainfall or streamflow as the deposits are buried to progressively greater depths; second, that the deposits have enough clay so as to undergo a decrease in com- pressive strength when they are wetted for the first time after burial. Most of the known compaction due to wet- ting has occurred in the upper 200 feet of deposits. The amount of subsidence is dependent mainly on the overburden load, natural moisture conditions, and the amount and type of clay in the deposits. Test-plot data show that the compaction due to wetting varies directly with amount of overburden load under uniform gross lithologic and moisture conditions (Bull, 1964a, p. 48). The type, amount, and moisture condition of clay influence the amount of subsidence. The predominant clay mineral in the subsiding fans is montmorillonite (Meade, 1967, fig. 14), which is stronger, at a given moisture content, than other clay minerals (Trask and Close, 1958). Small fans (derived from the foothill belt of the Diablo Range) that are susceptible to subsidence usually have higher clay contents than nonsubsiding fans of the same size. The clay is derived from the marine sedimentary rocks of the Diablo Range. Soft clay-rich rocks predomi- nate in the drainage basins of subsiding fans; there, they underlie an average estimated 67 percent of the area as compared to an average 38 percent for the drainage basins of nonsubsiding fans. Fan deposits with low clay contents do not have enough dry strength to preserve voids supported by a sparse clay binder as the overburden load increases naturally; moreover, deposits with high clay contents do not compact much because the clay, even when wet- ted, partly supports the voids and because the clay swells. Maximum compaction due to wetting occurs at intermediate clay contents (Bull, 1964a). Detailed studies of near-surface subsidence, the de- posits that compact when wetted, and the source areas of the deposits have been made by Bull (1964a), and prehistoric near-surface subsidence is described by Bull (1972). Other studies, in conjunction with the planning and construction of the San Luis Canal section of the California Aqueduct, have been made by the California STUDIES OF LAND SUBSIDENCE Department of Water Resources and the Bureau of Rec- lamation. As a result of these various studies, the de- posits along the route of the San Luis Canal section of the California Aqueduct that were believed to be sus- ceptible to compaction due to wetting were preconsoli- dated by ponding. SUBSIDENCE DUE TO WITHDRAWAL OF GROUND WATER About a third of the San Joaquin Valley is subsiding because of ground-water withdrawals. The three prin- cipal subsidence areas are between the towns of Los Banos and Kettleman City, Tulare and Wasco, and Arvin and Maricopa (fig. 7). The extent and the magnitude of the subsidence as of 1962—65 are shown in figure 7. The total area within the 1-foot subsidence line is about 3,800 square miles. The Los Banos—Kettleman City area is not only the largest but is the most intense of the three subsidence areas —subsidence has exceeded 20 feet, as compared with a maximum of 12 feet for the Tulare-Wasco area, and 8 feet for the Arvin-Maricopa area. In general, the boun- daries of the three areas coincide with the areas of pumpage from confined and semiconfined aquifer sys- tems. Since 1955, the rate of subsidence has been ac- celerating in the vicinity of Hanford, between the Los Banos—Kettleman City and Tulare-Wasco areas. Post-1963 leveling indicates that the rate of subsidence has increased along the trough of the valley for 20 miles north of Mendota and that much of this area has sub- sided more than 1 foot. EXTENT AND MAGNITUDE OF SUBSIDENCE IN THE Los BANOS—KETTLEMAN CITY AREA The two periods of topographic mapping and the many relevelings of bench marks in the area permit assessment of the changes of the extent, magnitude, and rate of subsidence. Many subsidence maps have been made, but only the most pertinent maps are included in this report. The extent and magnitude of the early subsidence in the area are shown in figure 8, which was compiled by subtracting the 1943—59 subsidence from the 1920—28 to 1959 subsidence. The area of intense subsidence west of Mendota was mapped topographically in 1920, and about three-fourths of the area within the 2-foot subsidence line of figure 8 was mapped in 1920—21. The 2-foot subsidence line is close to, and parallels most of, the south, east, and north boundaries of the area irrigated with ground water as of 1937—42 (Pt. 1, Bull and Miller, 1974, fig. 21). Along the west side of the irrigated area, the 2-foot line is 2—6 miles west of the boundary of land that was being irrigated in 1937—42. In contrast to the 10 feet of subsidence that had occurred in the northern part of the area, little LOS BANOS—KE'l'I‘LEMAN CITY AREA, CALIFORNIA, PART 2 120° F11 119° 1 2 1 ° 1 | l l b .‘ o Merced Los Banos ‘8 . \ _ 37°— :(0 San Luis \ Reservoir \ % 7 \ o ’ \\ ‘0 07 LP) ’6 OMendota OFtesno 1° \ 1920 63 ° (5 KCantua Creek 5) \I ‘2 \ \\ 620 H/anford d‘ 1933- 622 TulareO \\ 36 o __ o Kettleman City _ EXPLANATION ‘ —" \ Outline of valley \ ) Drawn chiefly on boundary ‘\ ’\ of consolidated rocks < “‘ \ Line of equal subsidence Dashed where approximately 10- . o cated. Interval, in feet, variable 1‘0“ Hills 0 %———>—— 0 Yrs California Aqueduct A 1933 62 OBakersfield Period of vertical control / A\ Compiled from leveling of the 1926'65 \ U.S. Coast and Geodetic Survey ArvmO and topographic mapping by / / \ U.S. Geological Survey 3° / /::)’8 / / 9 19 210 . so 4'0 MILES '7z Maricopa o f/ o 10 2o 30 40 K lLOMETRES C?“ ‘\ oWheeler Ridge _ 35° — m l | | FIGURE 7 —Areas of major land subsidence in the San Joaquin Valley, as of about 1963. (From Poland and Evenson 1966 ence was minor. For eizample, bench mark PTSZlS, subsidence had occurred as of’1943 in the southern part, where agricultural development was limited. Even in north of Westhaven, subsided only 1.2 feet between the largest area irrigated with ground water, subsid- 1923 and 1947. F 1 2 STUDIES OF LAND SUBSIDENCE 120°30' 120°00’ 33 I Los Banos e r _ Dos 37 00 Palos / ~.r\£r,e£°/-s—m , J l “ KI???" ’Madera / 33 V}? e”? / ‘1 //’ Akmbb Co I ”9’ Firebaugh C190 ’0 ‘2 gosozge 6.1 A001“ 0 4; 10§ endota\ , (7 $0 130 , 6) o Kermanc ( 1. 4; O «a ‘\%o ? \‘\ (6, \ i \ %F% K ((4‘6‘" \ 44 e ‘2 04/00 “\n 4 [4’6 ’\ :1, 36°30’ — “/6 4/0 oCantua Cre {; 9L °¢~ \' O ‘a ’ \ ’9 (a! “ ‘74, Five Points \ EXPLANATION Boundary of deformed rocks 2 Line of equal subsidence Interval 2 feet. Compiled as the difference between the 1943-1959 subsidence map (fig. 10) and the 1920-28 to 1959 sub- sidence map (compiled chiefly as the sum of (1) a comparison of topographic map- ping by the U.S. Geological Survey done between 1920 and 1928 and in 1955 and (2) leveling of the U.S. Coast and Geode- VALLEY tic Survey in 1955 and 1959). The ,A estimated near-surface subsidence com- ’ ponent has been subtracted from total Huron TULARE subsidence ' 4'43.) (434’ LAKE 4 MI ES '1' ?_,_L_fil(;15 L x 17/“ Kettleman BED o 5 1o 15 KILOMETRES I / 9 ~9 1 City 36°00’ Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 8.;Land subsidence due to artesian-head decline, 1920—28 to 1943‘ The date 1920—28 was used for figure 8 and the The areas that were mapped prior to 1920 never have 1920—28 to 1966 map because nearly all the areas of subsided much, and the areas first mapped between early subsidence were surveyed between these dates. 1928 and 1933 did not subside much until the middle LOS BANOS——KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F13 120°30' lzoaoo, 33 i Los Bano 152 / / o I Dos 37 00 Palos “,\Er—e§:|_¢1,.__\ Madera 33 U) 9/, YZ‘ M at ca ’Iq’ Firebaugh\ $090 ’0 e <:» 00$ " é / é" O -' . I I'. Q C” - .° 12 ep\ 0 4 ‘. . 20 6‘ endota / 71/ ' 180 I 7Q 0 ' 22 \ ( 9; ' ' (g, Kermanc o ‘o . 1 \féab’ e x o Q \~ ‘9 26 " fl . u 'u.. 2?. x‘ A " , 1 \‘ 9/01, . .' Q‘s?“ 44 04,0 O C(ll‘l .. 6‘ - ... . o . . ' , 36°30’ — ’6‘ 9/0 . Cantua Creek “’L 06 : - ° 1 ' .. ’3; z :' °‘ e? EXPLANATION ,9 Q - m 7e / 6‘ Boundary of deformed <0 rocks 0 ’0 2 33 Line of equal subsidence 9(08 Interval in feet, variable. Compiled chiefly ,9, as the sum of (1) a comparison of (<3 topographic mapping by the U.S. Geologi- cal Survey done between 1920 and 1928 and in 1955, and (2) leveling of the U.S. Coast and Geodetic Survey in 1955 and / \ \) \6 g 1966. Controlled in part by leveling of / / g, 9\ . 1943 and 1959 / ,9 x , Hum 52. /°O< 7 I O / \ Strat- ................ . a <6 a ford Boundary of neat-surface subSIdence areas PL SANT as of 1961 Coalinga {:3 +’—‘>—— VALLEY San Luis Canal section of the California Aqueduct , TULARE ks} r4644 41 LAKE o 5 1o 15 MILES 441% Kettleman BED 36°00, o 5 1o 15 KlLOMETRES 1 / ’ 33 ‘6‘ 1 City Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 9,—Land subsidence, 1920—28 to 1966, 1940’s, as is indicated by the subsidence history of bench mark PTSZIS. The 1920—28 to 1966 subsidence map (fig. 9) shows the magnitude and extent of the long-term subsidence within the Los Banos—Kettleman City area. The basic pattern of the lines of equal subsidence is an elongate F14 oval. The area that has subsided more than 10 feet is 70 miles long, and the area within the 1-foot subsidence line exceeds 2,000 square miles. Maximum subsidence was about 26 feet at bench mark 8661, southwest of Mendota. Within the main subsidence area, smaller elongate areas of locally intense subsidence occur. The southern part of the area had subsided as much as 22 feet by 1966, largely as a result of the accelerated compaction of deposits between the mid-1940’s and the mid-1950’s. Near-surface subsidence occurred chiefly after 1950 and varied markedly within short distances. Local pockets of intense near-surface subsidence have not been included. Although some of the subsidence shown is the result of compaction due to wetting of alluvial-fan deposits, the amount is not large, and the trends of the lines of equal subsidence do not change upon entering or leaving areas of near-surface subsidence. The San Luis Canal section of the California Aqueduct passes through the areas of most intense subsidence, but between the intense subsidence areas the canal passes through an area that had subsided only 4 feet as of 1966. The 1943—59 map (fig. 10) shows only the subsidence due to artesian-head decline. The general pattern of subsidence is much the same as for the 1920—28 to 1966 map, but the maximum amounts of subsidence shown are 16 feet for both the northern and southern parts of the area. Because the dates of leveling control for this map are the same as the dates for the best available long-term water-level control, this map will be used later in this report to make a specific unit compaction map (fig. 56). The near-surface subsidence component was esti- mated and removed from the differences in altitude for 14 bench marks used in the construction of the 1943—59 map. Several lines of evidence were used to estimate the amounts of near-surface subsidence. Some of the bench marks, although they are adjacent to areas of 2—10 feet of near-surface subsidence, probably have not been subjected to near-surface subsidence because they are in areas such as cotton gins, oil pumping stations, and farm buildings that are removed from the effects of irrigation water. By plotting subsidence profiles along level lines in near-surface subsidence areas, it was apparent that the protected bench marks had subsided less than nearby bench marks known to have been affected by near-surface subsidence. In some cases it was possible to draw a profile of the deeper seated subsidence due to artesian-head decline by using bench marks that were assumed not to have been affected by near-surface subsidence. The history of irrigation within the area provided a second approach for estimating amounts of near-surface STUDIES OF LAND SUBSIDENCE subsidence. Surveys by the California Department of Water Resources and the Bureau of Reclamation provided information on how long the land had been irrigated and on the type of crops grown. Test holes drilled by these agencies provided information about the depth of the wetted front near some of the bench marks known to have been affected by near-surface subsidence. This information was used to make esti- mates of the thickness of the dry fan deposits wetted since 1943 and the clay content of the deposits. The relation between (1) overburden load and compaction due to wetting and (2) the effect of clay content on compaction due to wetting (Bull, 1964a, fig. 27, p. 48—63) were applied to the data to make estimates of the near—surface subsidence component at those bench marks known to have settled as a result of compaction due to wetting. With the establishment of the level-line network in 1955, which was designed specifically to provide control on land subsidence, maps could be made that were based entirely on the results of leveling by the Coast and Geodetic Survey. The 1955—66 map (fig. 11) shows that more than 12 feet of subsidence occurred during these 11 years (13.1 ft at bench mark 8661). In the northern part of the area, the area of most intense subsidence had moved 8—10 miles south since the 1920—43 period. Because topographic remapping of the areas of most rapid subsidence was done in 1955, the 1955—66 subsidence map is the most useful map, at the time of the writing of this report, for correcting the 1955 map altitudes within the subsidence area. The 1959—63 map (fig. 12) shows maximum subsid- ence was almost 41/2 feet and a 54-mile-long area that had subsided more than 2.5 feet. In general, the area in the vicinity of the Delta-Mendota Canal subsided less than 1 foot, indicating a deceleration of subsidence rate from prior years. The 0.5—foot subsidence line extended half way between Mendota and Kerman, and north of the Kings River in the vicinity of Highway 41, indicat- ing an acceleration of subsidence in the eastern part of the area when compared with the 1957—59 map (not included in this report). The subsidence during the next 3-year period is shown in figure 13. Although the same time interval occurred between the 1959—63 and 1963—66 periods of bench-mark leveling, the amounts of subsidence in the 1963—66 period were substantially less than during the 1959—63 period. Maximum subsidence was only 3 feet, and the area having more than 2.5 feet of subsidence, instead of being a continuous 54-mile-long area, consisted of four isolated areas. The maximum subsid— ence was near the town of Cantua Creek in the central part of the study area, instead of being southwest of Mendota as in previous years. The subsidence rate LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F15 120°30’ 120°00’ 33 I Los Banos 152 / / e , Dos 37 00 Palos / , ~.'\}T'_eé’19'“-—\x._\ , 33 Madera 0% 9 ”49‘ Ca 49’ Firebaugh +690 ’o ‘v 0° of Q ‘4 (m ’0 ‘. _\ a ' "I " \ 5’94, : . ‘\ ((061 . ' \ 4104/00 ' —\ (IA/6‘ I . 9 5‘ 2 fig . I __ o, '9; . M\ . Cantua Creek \‘ (3‘4 35 3° EXPLANATION ‘9»,— °o® ° \ r o ' ' 77777777777, 2 -' , \ Boundary of deformed ’9 (m ‘ rocks ‘7 Five Points o0 a 8 6‘ [—L: Line of equal subsidence o I “ Interval 2 feet except for the 1-foot line. ’0 33 h Compiled chiefly from leveling of the Q i U.S. Coast and Geodetic Survey in 1943 0s o and 1959, but in part extrapolated from HQ 0 ' leveling in 1947. Configuration between (6' :0 bench-mark control based partly on com- ’o , ‘° parison of topographic surveys made by D i the U.S. Geological Survey in 1920-28 \ ‘ - - . and 1955 / / \\ \ sthaveno Y, ................ , .. Boundary of near-surface subsidence areas / 9,01} Hg") 0 \ I (‘5. as ofJanuary 1960 a, 0641, o O '\ Stra The estimated near-surface subsidence com- PL SANT ,2\O 0', O ford ponem‘ has been subtracted from total , e O subsidence in these areas Coalmga 2 ‘3 Q55 5y 9 a VALLEY Qirxé San Luis Canal section of the California / Aqueduct I TULARE 4's ’r (434, 41 LAKE o 5 1o 15 MILES - 44", x /(< Kettleman BED 36°00, o 5 1o 15 KILOMETRES / , 33 6‘ l Clty Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 10,—Land subsidence due to artesian-head decline, 194&59. remained the same northeast of Mendota, but decreased markedly from the 1959~63 rate in the Vicinity of the Kings River, owing to the greater availability of surface-water imports (Pt. 3, Bull and Poland, 1974, fig. 49). Additional leveling was done during the winter of F16 STUDIES OF LAND SUBSIDENCE 12030 120.00, 33 I 52 Los Banos 152 / / 37° 0' D08 0 Palos / ‘-’\E':e§£g"‘—\xflq V,../~“¥Igi\v’er 33 (A 0e- , v a / ‘1 Manda,“ Ce / a?! Firebaugh Q \ 09 / \ Q o O 2 ———>——— " 7 San Luis Canal section of the California / ‘ TULARE Aqueduct , 4’s, \ ' ) 414 \Q LAKE D 5 10 15M|LES 4,67 K ttl n e ema 36°00, o 5 1o 15 KILOMETRES / ,’ 9 <4 ' City BED Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 13.#Land subsidence, 1963—66. 1968—69, when bench marks along the completed San a small part of the Los Banos—Kettleman City area. The Luis Canal were leveled with the rest of the network. graph of distribution of subsidence intensity (fig. 14) 1s The areas of most intense subsidence constitute only based on the 1920—28 to 1966 subsidence map and LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 28 l l r 24— ~ SUBSIDENCE, IN FEET 1600 0 400 800 1200 2000 AREA, IN SQUARE MILES FIGURE 14.—Distribution of intensity of subsidence, 1920—28 to 1966. includes areas that are northeast of the Los Banos —Kettleman City area as defined in figure 1. As of 1966, almost 2,000 square miles had subsided more than 1 foot, but only 50 square miles had subsided more than 20 feet. 7 The total volume of subsidence within the 1-foot subsidence line in the Los Banos—Kettleman City area between 1920—28 and 1966 was 8,500,000 acre-feet. This is the volume of water derived from compaction of the unconsolidated deposits and for the most part represents a permanent decrease in storage of the confined aquifer systems. However, because the com- paction has occurred mostly in the fine—grained aquitards, usable storage in the aquifers has not been reduced appreciably. HISTORY OF SUBSIDENCE Past subsidence in an area as large as the Los Banos—Kettleman City area is likely to be highly vari- able. Subsidence graphs show a variety of trends, and subsidence profiles show that in some places the loci of maximum subsidence have migrated. Nine graphs of cumulative subsidence are shown in figure 15. Bench marks in areas of ground-water pump- F19 ing at the time that the bench mark was established do not show abrupt changes in the slopes of cumulative subsidence plots. Examples would be bench marks F678, H237 (reset), and the three bench marks at Men- dota. Along the western and southern parts of the area, subsidence was minor until the agricultural expansion after World War II. For example, the plot of bench mark E220 southwest of Mendota shows little subsidence from 1935 to 1947 and then a large amount of subsid— ence distributed evenly over the two decades since that time. Marked changes in subsidence rates after 1947 also occurred at bench marks Q237, P692, and N692. At bench mark -V805, steepening of the slope of the cumulative subsidence plot occurred after 1953. At bench mark W805, which is only 1 mile south of V805, the slope of the cumulative subsidence plot steepened gradually during the period of record. The plot for bench mark L157 in the southeastern part of the area also shows the acceleration of the rate of subsidence after 1947. However, bench marks in this area show periods of little or no subsidence in 1956 and 1958, which is in contrast with the pattern of the bench-mark histories in the rest of the area. The reasons for variation of the rate of subsidence at bench mark L157 are discussed in detail in Part 3 (Bull and Poland, 1974). The amounts of subsidence can vary within short distances, as is shown by bench marks P692 and N692. These bench marks are only 1 mile apart, yet the total subsidence at N692 is about four times the 4% feet of subsidence at P692. Some bench-mark plots indicate a decreasing subsid- ence rate since 1950. The plot for N692 indicates a decreasing rate of subsidence, but the record at Men- dota shows a gradually increasing rate of subsidence since 1919. Two transverse subsidence profiles illustrate the his- tories of subsidence southwest of Mendota and Five Points. The locations of these profiles are shown in figure 1. Subsidence profile A—A’ (fig. 16) extends from the edge of the foothills of the Diablo Range to Mendota, passing through the center of maximum subsidence shown in figure 9. The series of profiles shows the differ- ent amounts of subsidence at seven times between 1943 and 1966. As much as 3 feet of subsidence occurred along the line of profile between 1935 and 1943 (fig. 8). From 1947 to 1957 the point of maximum subsidence migrated toward the southwest, and by 1966, 24 feet of subsidence had occurred at one point. Subsidence profile B—B' (fig. 17) extends from Anti- cline Ridge through Five Points to Fresno Slough. The maximum subsidence in the 1943—66 period was 18 feet. The profiles are highly assymetric as compared with those shown in figure 16. The persistent steepness of the F20 STUDIES OF LAND SUBSIDENCE 120°3o' 120000, ‘ 33 I Los Banos 1940 1950 1960 x233X o 2 370 I DOS 00 Palos / \F~« _ m “’7, 9’ Firebaugh 1940 1950 1960 1920 . 1930 1940 1950 1960 \ \ \ \ \ \ 1 40 20 ,‘o / \ 9 1950 1960 F\6781940 1950 1960 x\ \ o \ 4 \ \ 4 \\ 8 \ K/ \‘ H237 (reset) ‘~_.\ “We 36 °30' — o Cantua Creek a, o . ’5; 40 \( EXPLANATION Q7 (‘53 1940 1950 1960 19 195° 196° 0 0 7/77/7777 $620 2 \ \ 4 “FBEIEQCO Boundary of deformed ’27 \ 0 KINGS CQ rocks 9/0 7-H TIME,IN YEARS "of N69; \‘ Z l- u.| u.I \ O I“ 4 — LL U) / g E 1950 1960 K (I) 0 1930 1940 1950 1960 \ 4 \ 0 \ {825 \ 4 8 X0237 \ Q 8 \ Bench-mark number 12 W805 ’ and location 9 ’ 4 / TULAHE \ \8 / LAKE 0 5 10 15 MILES ’/ '/ / Kettleman BED 36°00, o 5 1o 15 KILOMETRES / I ° City Base from US. Geological Survey Central Valley map, 1:250,000. 1958 FIGURE 15,4ubsidence of selected bench marks, SUBSIDENCE, IN FEET OD; P661 12-— 16— 20— LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 April 1943 I l 175 ~(USGS) F21 24 N— 8 12 DISTANCE, IN MILES FIGURE 161—Profiles of subsidence that has occurred since 1943, Tumey Hills to Mendota. 16 20 F22 STUDIES OF LAND SUBSIDENCE Anticline Ridge N 0° Fresno 0’ rx 08 g Feb 1943 3 smug" 3' I Mar 1947 4 — _ I— 8 — — |.I.l Lu u. E |.i.i~ 0 Z u! D 5 m a 12 — _ 0 33° wk. i e 3’ 16 — 5"; _ 20 I | I I l 0 4 8 12 16 ' 20 24 DISTANCE, IN MILES FIGURE 17.—Profiles of subsidence that has occurred since 1943, Anticline Ridge to Fresno Slough. southwest side of the profiles is Suggestive of a sudden change in the compaction characteristics of the sedi- ments, or in the rate of Withdrawal of ground water, or both. RATE OF SUBSIDENCE Changes in the slope of cumulative subsidence graphs, such as those shown in figure 15, provide a general indication of changes in subsidence rate. In this section, the areal variations in subsidence rate will be discussed first, then the changes in subsidence rate, both regionally and at specific bench marks, will be discussed. The trends of most lines of average yearly subsidence rate for the 1959—63 period (fig. 18) are similar to the trend of the lines of equal subsidence of the 1959—63 subsidence map (fig. 12). However, in the areas of widely spaced lines of equal subsidence, such as be- tween Mendota and Five Points, the patterns of the lines of equal subsidence and the lines of equal subsid- ence rate are different. Subsidence rate maps are useful in that they permit the designers of engineering structures, such as canals, to see at a glance the mean amount of subsidence that has occurred each year during a period of record. If the same units are used, rate maps are also useful in com— paring the magnitude of subsidence occurring in differ- LOS BANOS——KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F23 120°30’ 120°00’ .3 | 5 | Los Banos 152 ’ _ ’ / 37°00, ‘ Dos / ,’ Palos ' ./\_Ff_efl£»~_\\___\ 1J~K¥Igiver ,/ ‘ ' ‘ ‘ Madera 33 "$7 ‘2- 00 V O 99 £5 0 0% 47 2° I Firebaugh RIVER g {so <3? FRESNO n l_. 180 \ Kerman J‘ 41 ) ’4‘2, (<06). . _,\~ "a {>96 36°30’ \4 ~I Five Points \ 0,25 EXPLANATION r—t — — - 7777777277, 6,0 I 7" ‘ , Boundary of deformed e 33 '. ,/ rocks <0 ' I 0.75 /~/,( I Line of equal rate of subsidence. Interval ('5‘ 3% 0.25 foot per year. Derived from figure 12 r" ooII-Ooc-nuo-no | w Boundary of near-surface subsidence areas / l I as of 1961 / / sthaven Ya / '9x’0< HuronO | E 5 a o I San Luis Canal section of the California as G‘s/’1’ ‘ Sftrat— AQueduct PL SANT 0C; 0 0rd Coalinga Q (fie/6:1“) VALLEY ' €be 4,. TULARE 4-5)} ($41 41 LAKE o 5 1o 15 M I LES 44"] }—_'—l_'—T_l—__.—J I Kettleman / 44 . BED 36°OO' o 5 1o 15 KILOMETRES / 33 6‘ Clty Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 18,—Average yearly rate of subsidence, 1959—63. ent areas. Figure 18 shows that the alinement of the and through one area that subsided between 1.25 and San Luis Canal—California Aqueduct passes through 1.50 ft yr‘1 during the 1959—63 period. During this several areas that subsided more rapidly than 1 ft yr‘1 period, 480 square miles subsided more than 0.5 ft yr‘ 1 7 F24 STUDIES OF LAND SUBSIDENCE 1 20° 30’ 120°OO’ 33 I Los Banos 152 / . l 37. . Dos 00 Palos / ---\E’F£'l°/-~—\\ 1I> “a Ca ’19! Firebaugh 0.25 (250 Mendota 180 I Kermanc J“ (D \_,\\ : "g 03,0 _\ ¢ 36°30’ _ . Cantua J39? Q fl . ‘3\ N, O “a \1 \ 0.) x 6‘ \ 0.75 Five Points \ EXPLANATION I .7,"~ , -: , /' Boundary of deformed ’ rocks I «r; 0.25 l :3“ Line of equal rate of subsidence V Interval 0.25 foot per year. Compiled from ' @ leveling of the U.S. Coast and Geodetic "sthaven ,' Survey, February-April 1963 and Feb- ‘23 wary-March 1966 551 a... .00 II I‘ .Strat_ . .. - ()0 ford Boundary of near-surface subs1dence areas, 0 ,0 as of 1961 % «25’ 0 ++ Q (9% San Luis Canal section of the California Aqueduct TULARE I Q LAKE 0 5 1 1 5 M I LES O 67“ Kettleman BED 36°00, o 5 1o 15 KILOMETRES 1 s 1 ‘ City Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 19.—Average yearly rate of subsidence, 1963456. and 63 square miles subsided more than 1 ft yr—l. The rate of subsidence during the most recent period of leveling, as of the time of writing of this paper, is shown in figure 19. Only a small area subsided at a rate greater than 1.0 ft yr—l, and the area of most rapid subsidence shifted from southwest of Mendota to southwest of the town of Cantua Creek. Comparison of the 1959—63 and 1963—66 subsidence rate maps reveals LOS BANOS—KETTLE‘MAN CITY AREA, CALIFORNIA, PART 2 120°30’ F25 120°00' 33 Los Banos 152 37°00’— 36°30’ — EXPLANATION Boundary of deforrned rocks 0.20 Line of equal increase in rate of subsidence Interval 0.20 foot per year, except for the 0.10 foot line. Compiled chiefly from lev- eling: of the U.s. Coast and Geodetic Survey in 1943, 1953, 1954, 1958, 1959, and 1963 Areas in which the rate of subsidence was , / less during the 1959453 period than dur— / ing the 1943-53 period Boundary of near-surface subsidence areas as of 1961 ——)——>— San Luis Canal section of the California Aqueduct PL 0 5 1O 15 MILES O 5 10 15 KILOMETRES ] Kerm an C _,\% ‘9 ‘x‘ a9 / ’0‘}, 064’ . Strat- ford SANT CoaUnga VALLEY TULARE LAKE . Kettleman _ BED City 36°OO’ Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 20,—Change in rate of subsidence between the 194I¥53 and 1959—63 periods a general decrease in subsidence rate that is discussed later (fig. 21). A 1943—53 subsidence rate map (not included in this report) was compared with the 1959—63 rate map to determine the changes in rate between early and recent periods. Figure 20 shows that the rate of subsidence increased in most of the Los Banos—Kettleman City area between the 1943—53 and 1959—63 periods. In most F26 of the area, the rate increased 0.1—0.4 ft yr—1 . In two areas, one southwest of Mendota and the other south- east of Huron, the subsidence rate increased more than 0.8 ft yr—l. The rate decreased in two areas, a small area east of the town of Cantua Creek and a large area between Los Banos and Mendota. The changes in the rate reflect changes in the many factors influencing increase in applied stress, compac- tion, and subsidence. The large area of decreased sub- sidence rate lies within the service area of the Delta- Mendota Canal. Although some of the wells in the ser- vice area continued to be pumped after large-scale canal-water deliveries began in 1953, the net effect was for the artesian head to decline less rapidly than before, or to rise slightly, thereby causing a decrease in the compaction rate of the deposits. Some areas were al- ready receiving surface water from other canals before the construction of the Delta-Mendota Canal. However, the area of decreased subsidence rate lies almost en- tirely within the area that has been receiving large amounts of surface water only since 1953. An area adja— cent to the north end of the Panoche Hills has been receiving canal water since 1959 and shows little change from the subsidence rate that prevailed in the 1943—53 period. In contrast, the adjacent areas to the southeast that did not receive any surface water under- went a doubling of subsidence rate. Most of the areas with a rate increase of more than 0.40 ft yr—1 were areas that were unirrigated before 1940 but that were developed agriculturally with the aid of ground water between 1940 and 1950 (Pt. 1, Bull and Miller, 1974, fig. 22). In these areas, the change in rate is due largely to the fact that large manmade ap- plied stresses persisted throughout the 1959—63 period, but were developed only during the latter part of the 1943—53 period. Subsidence rates in much of the area irrigated with ground water throughout both periods increased from 0.1—0.4 to 0.2—0.8 ft yr-l. The large increase in subsid- ence rates in areas already irrigated with ground water in 1943 probably is due to a combination of fac- tors. Factors contributing to an increase in subsidence rate would include increases in the rates of artesian- head decline for the zones being pumped and increases in excess pore pressures in the aquitards. Several aspects regarding the withdrawal of ground water were considered, but do not seem to explain fully the increased subsidence rate in those areas irrigated with ground water throughout both the 1943—53 and 1959—63 periods. The overall amount of ground water pumped within the area has not changed much since 1953 (Pt. 1, Bull and Miller, 1974, fig. 23). In general, the wells were perforated in the same intervals during both periods, which would indicate that the head de- S’I‘UDIES OF LAND SUBSIDENCE cline was occurring in the same zones during both periods. An increase in the rate of head decline within the area would explain the increase in subsidence rate, but pumping levels have been declining at a progres- sively slower rate in much of the area. The factor that accounts for the increased subsidence rates is increased excess pore pressures in the aquitards. Evidently, the head in the aquifers has been drawn down more rapidly than aquitard excess pore pressures could decay, and hence the differential be- tween the head in the aquifers and average excess pore pressures in adjacent aquitards has increased. The rate of subsidence is a function of this head differential. The change in subsidence rate between the two most recent periods of leveling of the bench-mark network is shown in figure 21. In contrast to the comparison shown in figure 20, subsidence rates during the 1963—66 period were less than during the 1959—63 period throughout most of the area. Within about 80 square miles in the northern part of the area, the subsidence rate had de— creased more than 0.25 ft yr—1 between the 1959—63 and 1963—66 periods. In the central and southern parts of the area, the subsidence rate decreased more than 0.25 ft yr—1 only in small local areas. The dashed line con- nects the outermost points of no change in subsidence rate between the two periods, but intersection of rate lines of the two maps show that isolated points of no change in rate occur within the dashed line. Some small areas of minor increase in subsidence rate in the south- ern part of the area were suggested by comparison of the two maps (figs. 18, 19), but in these areas the suggested increases in rate were less than 0.25 ft yr'l. The contrast between the trend of subsidence rates in figures 20 and 21 is the result of a decrease in the rates of increase of stress being applied to the aquifer system, as indicated by decreasing rates of artesian-head de- cline (Pt. 1, Bull and Miller, 1974, fig. 45). Rates of artesian-head decline have decreased markedly in re- cent years and have been accompanied by slight to mod- erate decrease in subsidence rates. Some of the geologic reasons for the greater decrease in subsidence rate in the northern part of the area are discussed in the section “Geologic Factors Influencing Compaction of the Un- consolidated Deposits.” Bar graphs of subsidence rates for five bench marks (fig. 22) show the changes in subsidence rate better than the changes in slope of the cumulative subsidence graphs of figure 15. Both the amounts, and patterns of changes of subsidence rate are highly variable in the different parts of the study area. 7 The record for bench mark 97.68 (USBR) shows in- creasing subsidence rates from 1937 to 1954 and de- creasing rates since then. The marked reversal in the trend of subsidence rate coincided with the delivery of 37°00’ 36°30’ 36°00' LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 120°30' 120°00’ F27 33 i Los Banos -@ Kermanc b “x 9 oCantua Creek \ “f: EXPLANATION Boundary of deforined ‘0 rocks 7% Area in which the subsidence rate during 1963-66 decreased more than 0.25 foot per year from the rate during 1959-63 Outer line through the points of no change in subsidence rate between the 1959-63 ’/ and 1963-66 periods Boundary of near-surface subsidence areas as of 1961 _>_—.>_ San Luis Canal section of the California Aqueduct TULARE LAKE 0 5 1O 15 MILES Kettleman BED o 5 1o 15 KILOMETRES i ' City Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 21.—Change in rate of subsidence between the 1959—63 and 1963.66 periods. Delta-Mendota Canal water to the area. The dotted line of best fit because it is based on equal areas above and showing the interpolated general subsidence rate is an integration of the bar-graph data. There is only one line below the line. The post—1963 line is tentative, for post- 1966 data are necessary to complete the integration. F28 STUDIES OF LAND SUBSIDENCE 12030 120000, 33 I Los Banos @ 152 / 3 7 °OO’ ‘.c\_’1j';:e§r£0/_\___ ‘ \ /~/"-\Igi3gr J; 0 . | I I I 1920 1930 1940 1950 1960 1970 RIVER 1N JOAQU r. I l | L. 1940 1950 Kerman r _ _ <56 \_3 I I I ~ \ 1950 1960 1970 51% \I 4 36°30'—— EXPLANATION oCantua Creek i; “I Boundary of deformed rocks Five Points ‘I Ill-I u: I I I < :5 01 >- u.I n: — — - o . z E 1 l I l '-“ I— 1940 1950 1960N70 9 Lu — — 3 (n LLI I I”; m u. I ' L1 57 3 E I I I m \ TIME,IN YEARS I I I I l Xwaos .- 37% Bench—mark number — -' - T and location I Strat— ........ ~ , ford fl." ”0- . U! I l l lnterpolated general 0 1950 1960 1970 L subsrdence rate 00’ o ’0 roe O s» 09 $436 TULAFlE LAKE o 5 10 15 MILES 44"] /(< Kettleman BED 36°00, o 5 1o 15 KILOMETRES 6‘ | ° City Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 22,—Histories of subsidence rates for selected bench marks, Subsidence rates have increased steadily since 1919 at Mendota. Some minor fluctuation of subsidence rate occurred during the middle 1950’s, and the rate in- creased the most rapidly in .the 1963—66 period. Bench mark S661 has subsided more than any other bench mark in the San Joaquin Valley. The altitude of this bench mark declined 24 feet in the 23 years prior to 1966. The rate of subsidence has not been uniform, LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 although, at first glance, the cumulative subsidence graph (Pt. 3, Bull and Poland, 1974, fig. 30) appears to have a fairly constant slope since 1947. The subsidence rate increased rapidly between 1943 and 1953 as ground water was pumped in the vicinity for the first time. The interpolated general subsidence rate line in- dicates that the maximum rate of subsidence was in 1954 and was more than 1.8 ft yfl. Since 1955, subsid- ence rates have been decreasing, and by 1965 the rate was only 0.7 ft yr“1. Bench mark S661 is in the large area of recent decrease in subsidence rate (fig. 21). At this bench mark, the subsidence rate decreased 0.51 ft yr“1 between the 1959—63 and 1963—66 periods. The increased subsidence rates at bench mark W805, in the southern part of the area, also are associated with agricultural expansion since 1947. In contrast with the record of S661, however, the rates .do not define a peak until 1964 (fig. 22). The record at bench mark L157, in the southeastern part of the area, shows three periods of little or no subsidence and two periods of subsidence rates of about 0.4 ft yr— 1. Subsidence in this part of the area since 1955 is influenced by changing proportions of the sources of irrigation water, which include surface water from the Kings River and ground water from above and below the Corcoran. COMPACTION OF THE GROUND-WATER RESERVOIR In the preceding section, most of the subsidence in the Los Banos—Kettleman City area was attributed to ex- cessive withdrawal of water from confined aquifer sys- tems. This section describes the compaction of the ground-water reservoir and compares the amounts of compaction and subsidence. The best information regarding the amounts, rates, and vertical distribution of compaction is obtained from specially drilled wells or unused irrigation wells that are equipped to measure shortening of the deposits be- tween the land surface and a designated depth. A second source of information is provided by studies of well- casing shortening and rupture that occur as a result of compaction. FIELD MEASUREMENTS 0F COMPACTION TYPES OF COMPACTION GAGES USED The methods of measuring compaction used by the Geological Survey have evolved from relatively simple to refined equipment that is adaptable to the problems encountered at individual locations. The basic type of recording compaction gage is shown diagrammatically in figure 23. A heavy weight is lowered to the bottom of the well on a 143—inch cable. Where possible, the anchor weight is set below the casing bottom to measure the vertical shortening of the deposits rather than the con- current shortening of the well casing. At the land sur- F29 :Recorder Sheaves mounted l in teeter bar /——Compaction tape ______ Steel table Counterweights Clamp—1| Bench mark J J— Concrete slab Cable, 1/8-inch stainless steel, 1 x 19 stranded, reverse lay Well casing, 4 to 13 inches Anchor weight, 200 to 300 pounds FIGURE 23.—Diagram of recording compaction gage. face, the cable. is passed over two ball-bearing sheaves and is counterweighted to keep it taut. The sheaves are mounted in a metal rack set on a l-foot-thick concrete foundation that does not touch the well casing. A mechanically driven hydrographic recorder (Stevens, type F) set in the rack is connected to the 1As-inch cable with a small diameter cable that is clamped to the main cable and passes over the drive pulley of the recorder. As compaction occurs, the concrete slab and the recorder move downward relative to the cable clamp, because (ideally) the length of the cable remains constant as the thickness of the aquifer system decreases. The move- ment of the recorder relative to the small-diameter cable rotates the recorder pulley and chart drum, pro- ducing a graph of compaction at a scale of 1:1. The principal limitation upon the accuracy of the system is friction between the well casing and the down-hole cable. Many improvements have been made since the first recorders were installed. In wells where the amount of friction between the casing and cable is small, an expanded-scale record is obtained directly in the field through the use of a second recorder linked to the first by an amplifying gear train. A 12- or 24—times expan- sion of the record is useful in observing the finer details F30 of the compaction record, provides more accurate meas- urements of short-term compaction, and permits de- termination of the times of changes from recorded com- paction to record expansion of the aquifer system. Friction in the above-ground components of the sys- tem has been reduced to a negligible level by mounting the sheaves in a teeter bar. As compaction occurs, the teeter bar tilts on a knife—edge fulcrum, but the sheaves do not rotate. The sheaves rotate when the bar is leveled each time the recorder is serviced. Errors caused by seasonal swell due to changes in surface moisture condi- tions have been largely eliminated by the use of con- crete and steel, instead of wood, in the tables and foun— dations. Changes due to seasonal soil swell have not been eliminated entirely, but can be measured when necessary. Compaction of the enclosing deposits shortens and destroys well casings. Slip joints installed in some compaction-recorder wells apparently have been suc- cessful in preventing or delaying major casing damage. The characteristics of the cable are of paramount importance. Even small unit changes in cable elonga- tion due to fatigue or untwisting are significant if they affect much of the length of a 2,000—foot cable. Changes in the position of the top cable clamp due to these factors cannot be distinguished from changes due to compac- tion unless special measurements are made. The effect of temperature changes is not considered important, because below a depth of a few feet the temperature remains uniform. The first cable used for compaction recorders in the study area consisted of 7 X 7 stranded 1/s-inch galvanized steel, but corrosion caused failure of cables at several sites within a few months. This cable was replaced with stainless steel, plastic coated, 7X7, 1Aa-inch stranded cable, which resisted corrosion, but had more casing— cable friction than the uncoated cable. Also, the cable tended to untwist as indicated by rotation of the coun- terweights. As of 1968, 1/s-inch, 1 X 19 stranded, un- coated, stainless steel, reverse-lay cable had been found the most desirable for compaction-recorder use. It re- sists corrosion, has low stretch and friction characteris— tics, and little tendency to untwist. The low tendency to untwist under load is due to the fact that the six strands about the center strand spiral in the opposite direction from the outer twelve strands. A different type of compaction gage was installed in well 15/13—35D5. It consists of a 11/2-inch pipe inside a casing. The bottom of the 11/2-inch pipe was set 7 feet below the bottom of the enclosing 4-inch casing. Changes in aquifer-system thickness are determined at monthly intervals by measuring the distance between the top of the Ilka-inch pipe and a steel frame bolted to a concrete foundation that encloses but does not touch the STUDIES OF LAND SUBSIDENCE 4—inch casing. Wells 20/18—11Q2 and 16/15-34N4, at the Westhaven and Cantua sites, also operate as a compaction-pipe type of gage. (See description of the Westhaven site under section "Shortening of an Oil- Well Casing”) The first compaction recorder was installed in Sep- tember 1955 in well 19/17—35N1. The site was an un- used irrigation well 2,030 feet deep, having 16-, 12-, and 9-inch casing. The compaction record from this installa- tion is shown in Part 3 (Bull and Poland, 1974, fig. 11). Attempts to install compaction recorders in the three core holes drilled in 1957 were unsuccessful. As an experiment and an economy measure to eliminate cas- ing costs, sidewall anchors were installed in core hole 12/12—16H1, which was uncased. The hole collapsed during installation of the equipment, even though it was filled with a special mud to inhibit caving. Later attempts to install compaction recorders in uncased holes 14/13—11D2 and 19/17—22J1, 2 used 1A-inch iron tubing to protect the cables. These compaction recorders were unsuccessful because of excessive friction between the tubing and cable and because of corrosion and cementation. By January 1968, 21 wells were providing informa- tion about compaction in the Los Banos—Kettleman City area. Groups of recorders with bottom-hole weights set at different depths are at 12/12—16H near Oro Lorna, at 14/13—11D west of Mendota, at 16/15—34N near the town of Cantua Creek, and at 20/18—11Q near West- haven. Twelve of the recorders operate in groups, and nine operate singly. Descriptions of the compaction-recorder installations are summarized in table 1, and their locations are shown in figure 1. Where possible, the anchor was set below the casing bottom, and, in the unperforated wells, the anchors were set as much as 49 feet below the bottom of the casing. In most of the perforated wells, however, the anchor weight was set on sand in the casing; in most of these the sand was brought into the well as a result of development to observe water-level changes. Attempts to bail the sand from the casing usually resulted in a continuing influx of sand through the perforations. However, useful compaction records are obtained because the casings are shortened almost the same amount as the sediments that encase them and because the amounts of compaction that do not cause casing shortening cause measurable increased casing protrusion above the land surface. Compaction that has occurred at the sites is shown in figures 26 through 32. Data from multiple compaction- recorder sites will be discussed first. Inverted bar graphs showing monthly compaction for most of the sites are given in Part 3 (Bull and Poland, 1974, figs. 13—17). LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F31 TABLE 1.—Summary of compaction-recorder installations Position of Anchor depth anchor Depth interval when above (+) or Perforated Corcoran Clay Casing installed below (—) interval Member Date Agency diameter Depth of (ft below bottom of (ft below (ft below Well installed drilled by— (in.) cased hole land surface) casing (ft) land surface) land surface) Remarks 12/12—16H2____ 2/26/58 (1) 4 964 1,000 736 None 379—465 Water-level records obtained from 12/12—16H5 (perforated interval 67(L712 fl) and 12/12r16H6 (perforated interval 77(L909 ft). 12/12—16H3__,_ 2/26/58 (1) 4 320 350 730 None 379—465 12/12-16H4M“ 2/26/58 (1) 4 470 500 —30 None 379—465 13/12—20D1 -___ 7/27/61 (2) 4 665 681 —16 425~665 30£L418 13/15—35D5 .1.. 5/13/66 (3) 4 433 440 *7 37i¥433 428—476 Compaction-pipe type of recorder. 14/12—12H1____12/10/64 (2) 6 936 913 +23 740—936 615~719 14/13—11D4 1111 9/28/60 (3)“) 8 774 780 76 714—774 625—700 Water level not re resentative of zone. 14/1&11D6 .___ 4/14/61 (3)0) 8 1,329 1,358 —29 1,133—1,196 625—700 Water-level recor s obtained also from 14/13—11D3 (perforated interval 180—240 It). 15/13—1 1D2 __,-12/28/64 (2) 6 960 958 +2 900—960 768-860 15/16—31N3 ,1" 3/23/67 (3) 6 595 596 71 497—587 585»648 Gravel packed; water-level records also obtained from 15/16—31N2 (perforated interval 667A747 ft). 16/15—34N1 __ (‘) 4 1,951 2,000 749 Not perforated 565—575 16/15—34N2 (‘) 4 66 703 ~43 Not perforated 565—575 16/1&34N3 (‘J 4 457 503 —46 Not perforated 565575 16/15—34N4,,,, 8/11/60 (”K“) 8 1,112 1,096 + 16 1,052—1,112 565—575 Water-level records obtained also from 16/15—34N5 (perforated interval 240-300 It). 18/16—33A1 ,,,_12/11/64 (2) 8, 6, 4 1,070 1,029 +41 85&1,070 781—805 18/19—20P2 ____ 3/24/67 (3) 6 577 578 —1 4974537 567—634 Water-level records obtained from 18/19—20P1 (perforated interval 647—687 It). 19/16—23P2 ,___ 4/30/59 (5) 13 2,406 2,200 (5) Unknown Not present 19/17—35N1,", 9/1/55 (7) 16, 12, 9 2,130 2,030 +100 SOB—2,130 860»870 Cable failed October 1960; casing broken; not repaired 20/18—6D1 __.,12/11/64 (2) 6, 4 1,007 867H +140 71&736 811—820 76(L835 8517872 20/18—11Q1-_._ 6/ 6/64 (4) 4 710 710 0 650—710 715745 20/18—11Q2 ,__, 8/16/62 (4) 11 (9) 8459 (9) 755—805 715745 Compaction-pipe type of recorder. 20/18-11Q3 __,, 8/16/62 (1°) 4, 11 2,004 1,930 (6) 1,8851325 715—745 lInter-Agency Committee on Land Subsidence in the San Joaquin Valley. 2US. Bureau of Reclamation. 3California Department of Water Resources. ‘U,S. Geological Survey. 5Shell Oil Company. ANALYSIS OF FRICTION IN A COMPACTION RECORDER The accuracy of the recorded compaction data is in large part dependent on the amount of friction Within the compaction recording system. Friction occurs both in the recording equipment above the land surface and between the cable and the well casing below land sur— face. However, friction in the recording equipment is negligible, in comparison to casing-cable friction. The inaccuracies resulting from casing-cable friction are minimized by large-diameter straight casings and through the use of cables with minimum friction characteristics and high elastic modulus (minimum stretch per unit length per unit tension). If the tension gradient due to the unit weight of the cable is neglected, the tension in a free-hanging cable may be considered uniform. However, a typical compac- tion cable does not hang freely, and the tension is ap- proximately uniform only in the parts of the cable sus- pended between points of frictional contact with the casing. Tension above the uppermost point of contact between cable and casing equals the counterweight. Below this point the tension is different in each sus- pended segment. Figure 24 illustrates, diagrammatically, a compaction- recorder system that has friction between 6Anchor set on cement plug in casing. 7Russell Giffen, Inc. ”Anchor set on top of 140 ft of 4-in. casing. 9Mid-depth of cement plug between 4—in. and 11-in. casing. "’Texaco Oil Company. the casing and the cable, owing to a bend in the casing. For simplicity, only the uppermost point of contact be- tween the casing and the cable is shown (B), and it is assumed that the cable does not touch the casing be- tween point B and the anchor weight. Actually, the cable may be partly or wholly in contact with the casing below point B. In the situation portrayed in figure 24, any change in aquifer-system thickness above pointB will be recorded accurately if friction in the above—ground components of the instrument is negligible. Above point B, constant cable tension is maintained at all times by the counter- weights. Below point B, cable tension will, in general, not remain constant. During compaction, cable tension be- tween B and C will decrease until the cable stress be- tweenB and C, plus the friction at pointB, is exceeded by .the cable stress induced by counterweighting above the land surface. Relative upward cable movement past point B will then occur, and concurrently stress in the cable between B and C will increase rapidly until fric- tion at B prevents further movement. The cable be- tweenB and C may never attain the same stress as the cable betweenA andB, as long as compaction continues. An opposite relation exists during times of net F32 Shaave Counten/veight A. land surface \/ \ \\’/ B, uppermost point of contact between cable and casing Well casing C, anchor weight FIGURE 24.—Diagrammatic sketch of a compaction-recorder system with casingcable friction. aquifer-system expansion. During expansion of the de- posits and well casing below point B, cable tension will increase until it exceeds the cable stress betweenA and B, plus the friction at B. Downward cable movement past point B will then occur, and stress in the cable between B and C will decrease rapidly until friction prevents further movement past point B. The cable be- tween B and C may remain more highly stressed than between A and B, as long as expansion continues. Expansion or compaction below the uppermost fric— tion point will not be recorded unless unbalanced cable stresses across that point exceed the friction at that point. Installations having little friction generate a moderately smooth and reasonably accurate compac- tion record. Installations with large amounts of friction generate a stepped compaction record, with most or all of the compaction recorded at times when differences in cable stress exceed the friction. If undisturbed, record- ers with large amounts of casing-cable friction may show no compaction for many months and then sud- denly record several tenths of a foot of compaction. STUDIES OF LAND SUBSIDENCE A partial solution to the problem of excessive friction is to change the stress on the cable artificially each time the instrument is serviced. This is done simply by push- ing the counterweights down about 1 foot, or less, and allowing them to rise gently as the force is relaxed. This operation temporarily increases the stress imbalance across friction points enough to allow the cable to move upward against friction, thereby removing those differ- ences in cable tension that have accumulated as a result of compaction since the last application of stress. When the cable comes to rest after relaxation of the load, a new vertical distribution of stresses will have been imposed in the cable. The difference between the old and new stress distributions is a measure of the compaction that has occurred since the last time the cable was loaded in the same way. If the periodic loading of the cable is done in a highly consistent way and if the elastic properties of the cable and the friction characteristics of the casing- cable contacts change little with time, then the vertical distribution of stress within the cable should be nearly the same after each loading. Thus the cable length cor- responding to this characteristic distribution of stress constitutes a nearly unchanging reference against which to measure compaction of the aquifer system. An example of a record from a compaction recorder with large amounts of casing—cable friction is shown in figure 25. The amount of friction within this well proba- bly is as severe as for any in operation and is caused by the use of a cable with high friction characteristics (plastic coated) in a deep well (2,000 ft) that has a small diameter casing (4 in.). During the first year of opera- tion, before the cable was stressed monthly, this instal- lation would record no compaction for 6 months and then would record more than 0.5 foot of compaction at one time. The record shown in figure 25 is stairstepped because compaction is recorded only at the time of each 3.0 I '— u: b'.‘ 2 3-5 _ lnterpolated general . . “ - compaction curve UnadlUSIEd field 2 data 9 I- U E 4. — 5 O O U 4.5 510MB .|F\M1A\M1.‘J\AIS‘O|N10 1960 1961 FIGURE 25.—Interpolation of part of the cumulative compaction record from well 16/15—34N1. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 monthly stress increase. For most of the record, an in- terpolated cumulative compaction curve can be drawn through the low points of the stairstepped record. When the cable appears to have been overstressed (mid-1961) or understressed (late 1961), the value for that month (or months) is omitted, and the amount of compaction for two or more months is combined, as shown by the dashed lines. The method is accurate for determining compaction that has occurred for periods longer than 2 or 3 months because the cable probably returns to a similar distribution of stresses after most monthly stress increases. CUMULATIVE COMPACTION AT MULTIPLE COMPACTION—RECORDER SITES Plots of cumulative compaction and subsidence for those sites where two or three compaction recorders are operating are shown in figures 26—28. The plots are interpretations of stairstepped records similar to that shown in figure 25, and the dashed parts of the record indicate where more than one month’s record has been combined. By mid-1968, 10 feet of cumulative compac- tion had been measured by one recorder. The unit com- paction of the deposits in the different depth zones is discussed later. Compaction and subsidence at the Oro Loma site in the northern part of the area are shown in figure 26. About 12 feet of subsidence occurred at this site between 1920 and 1966 (fig. 9). The maximum rate of subsidence was in 1954 (0.9 ft yr"1), and since then the rate has decreased steadily (fig. 22). The change in slope of the plot for bench mark 97.68 (USBR) reflects the decreas- ing subsidence rate for the 1958—66 period. The compaction anchors at the Oro Lorna site were set at depths of 350, 500, and 1,000 feet. The 1958—66 com- paction was less than half a foot for the two shallow recorders, but more than 2 feet of compaction occurred in the 0—1,000-foot interval. The large amounts of ap- parent compaction that occurred during the first 3 months of operation in 1958 probably were caused by initial cable stretch and foundation settlement. If the first few months of record are omitted, the total compac- tion in the upper 350 feet has been only 0.1 foot in the 7 years since 1958. . The plots for wells 16H3 and 16H4 show periods of apparent net expansion of the aquifer materials prior to 1963. Similar effects are noticeable for the plot of well 16H2, but they are not as obvious as in the records from the other two recorders because of the greater compac- tion rate. The expansion is not real, but is chiefly a combination of soil and lumber swell during the winter rainy season. In April 1962, the installations for wells 16H3 and 16H4 were rebuilt, using steel racks set on large concrete pads that are not in contact with the casings. Little apparent aquifer-system expansion has F33 occurred during the rainy season since the site was rebuilt. The recorder for well 16H2 was rebuilt in a similar fashion in October 1960. A seasonal effect is noted for some years in the com- paction record of well 16H2. For example, in 1963 the maximum compaction rate occurred in February and J uly-September—the months of large demand for irri- gation water. A comparison of the compaction in the upper 1,000 feet to the total amount of subsidence can be made by examining the record for well 16H2 and the plot for nearby bench mark 97 .68 (USBR). If all the subsidence were the result of compaction in the upper 1,000 feet, the two plots would parallel each other. The Oro Loma site has experienced a change in the amount of compaction being measured compared with subsidence, as is indicated by the divergence of the subsidence and compaction plots after 1961. During the period October 1958—October 1961, about 90 percent of the subsidence was the result of compaction in the upper 1,000 feet. The percentage decreased to about 55 per- cent for the period October 1961—October 1965 when about 45 percent of the compaction occurred below 1,000 feet. Compaction and subsidence plots for the Mendota site (about 8 mi west—southwest of the town of Mendota) are shown in figure 26. The site, which subsided about 23 feet between 1920 and 1966, is in one of the areas of most intense land subsidence in the study area. The rate of subsidence increased until the mid-1950’s and has decreased since then. The 1961—66 subsidence trend is shown by the plot of bench mark GW4. Compaction anchors at the Mendota site were set at depths of 780 and 1,358 feet. During the period shown in figure 26, 0.9 foot of compaction occurred in well 11D4, and 2.85 feet of compaction occurred in well 11D6. The Mendota site recorders were built using concrete pads and steel racks and do not show the effects of soil and lumber swell as noted during the first few years of record at the Oro Loma site. The compaction rate varies with the season. Both wells show a pronounced reduction of compaction rate during the winter months. The times of maximum com- paction vary from year to year, but in general roughly correspond with the times of irrigation in the summer and late winter-early spring. The lesser overall slope of the compaction plot for well 11D6 as compared with the bench-mark plot reveals that part of the subsidence is occurring below 1,358 feet. During the period September 1961—August 1965, about 69 percent of the subsidence occurred as compaction between the land surface and 1,358 feet, and about 31 percent of the subsidence was attributed to compaction of deposits below 1,358 feet. About 23 percent of the F34 STUDIES OF LAND SUBSIDENCE if); 0 Y Well 16H3, 350 feet deep\ 2 eyes"- / m- uJ l— - New cable — 9 Wk installed Well 16H4, 500 feet deep \Compacfioni U) ~ ----- m 1 _ 1 3 l- i _ "x Well 16H2, 1000 feet deep (0 w ISubsudence, \A I 61‘ — Bench *nark 97.68 (USEN-n\_n_ — _____ \"h gz 2 - - - E \ Compaction \7“ < _ _ n. \ g 3 0 , 1958 1959 1960 1961 1962 1963 1964 1965 1966 0 >— ~--\‘~ |— . “““““ \. /Well 11D4, 780 feet deep m \N‘ ‘ Coriipaction I “‘ LLI - - u_ T‘\,‘ \ ----- \ E 1.0 ._ _~ 13 \‘x/Well 1106, 1358 feet deep 2 5’ _ 2.0 K m \f\ Subgdence, m ' bench mark GW4 D U) \— 0: K O 3.0 2 9 I.— U 1‘ 4 o E . o \\, U 5.0 1961 1962 1963 1964 1965 1966 FIGURE 26,—Compaction and subsidence at the Oro Loma site, 195&66 (upper graph), and Mendota site, 1961456 (lower graph ). compaction occurred between the land surface and a depth of 780 feet, and 46 percent between depths of 780 and 1,358 feet. Compaction and subsidence plots for the Cantua site in the' central part of the Los Banos—Kettleman City area are shown in figure 27. About 19 feet of subsidence occurred at the site between 1924 and 1966, but more than 9 feet has occurred since 1957. The subsidence rate has been rapid and fairly constant since the early 1950’s. In 1958, compaction anchors were set at depths of 503, 703, and 2,000 feet. In 1961, an additional anchor was set at 1,096 feet in a well that was drilled primarily to obtain lower-zone water-level information. All the re- corders were rebuilt on concrete pads in April 1962. Records were interrupted when corrosion caused the galvanized cables to break in May 1959 in well 34N1 and in December 1959 in well 34N2. The record for the 0-1,096-foot depth interval in well 34N4 was termi- nated in June 1963 when attempts to repair casing breaks caused by subsidence failed. Separation of two casings (a compaction—pipe type of gage) has provided compaction information for the 0—900-foot depth inter- val for well 34N4 since February 1965. The casing for well 34N1 has not failed, apparently because of the slip joints placed at several depths, even though 10 feet of casing shortening had occurred by mid-1968. In contrast with the Mendota site, the Cantua site record shows less variation of compaction with the sea- son of the year, although in some years the compaction rate decreased moderately during the winter. The 2,000-foot recorder measures most of the sub- sidence that is occurring. For the period December 1959—December 1962, about 99 percent of the compac— tion was occurring in the upper 2,000 feet. About 10 percent of the compaction was measured above 503 feet, and about 26 percent of the compaction was measured above 703 feet. During the next 3-year period, De- cember 1962—December 1965, the amount of subsidence remained about the same. However, the 2,000-foot re- corder measured only about 88 percent of the subsid- ence, indicating that about 12 percent of the compac- tion was occurring below 2,000 feet. During this second 3-year period, about 8 percent of the compaction was LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F35 0 \ -\ \ Well 34N3, 503 feet deep \\ ‘\\ ——\4é_______ x \ w—«Q \\ 1.0 \QCompaction< Well 34N2 703 feet deep 0 \\ \ 2.0 H \fl\ M | 34N4, 1096 feet deep \_ q \ \‘\\ '- 3 0 \‘ l.u , \ u. 2 \ .. \\ in 4.0 0 Z Subsidence, / \ we‘fleizzge'pgoo w . 9 mm" mark 61°46 \\14 \ Casing repair 90 V 10.0 1958 1959 1960 1961 1962 1963 1964 1965 1966 FIGURE 27.—Compaction and subsidence at the Cantua site, 1958—66. measured in the upper 503 feet, and about 22 percent of the compaction was measured in the upper 703 feet of the deposits. The percentage of subsidence being meas- ured decreased still further during the March 1966—N0vember 1967 period, being only 79 percent of the subsidence. The decrease in the percentage of sub- sidence measured in the 0—2,000-foot depth interval at the Cantua site between 1959 and late 1967 is shown in figure 28. Three compaction recorders—two cable type and one pipe type—are operating at the Westhaven site in the southern part of the Los Banos—Kettleman City area. The instrumentation of well 20/18—11Q2 consists of a 4-inch pipe cemented inside an 1 l-inch pipe at a depth of 830—860 feet. Compaction is measured by observing the amount of shortening of the 1 1-inch casing as compared with a reference point on the 4-inch casing and adding the minor amounts of change in protrusion of the 11-inch casing. The construction of this abandoned oil 100 O |.I.I I 3 w < Lu 5 ._ u.l U 2 u.l 9 8 50 — — D m u. 0 Lu 0 — _ < ’— Z 3 E 0 l/ | /f l/ | l | l L 1960 1962 1964 1966 FIGURE 28.~—Decrease in the percentage of subsidence measured in the 0—2,000-f00t depth interval at the Cantua site, 1959—67. well is described in detail in the section "Shortening and Increased Protrusion of Well Casings.” F36 Compaction and subsidence plots for the Westhaven site are shown in figure 29. About 13 feet of subsidence occurred at the site between 1928 and 1963. The plot of subsidence in figure 29 is taken from two subsidence maps because vertical control was not extended to the site until the 1966 leveling. The amount of subsidence shown for the 4-year period probably is within 0.2 foot of the amount that would have been observed if a bench mark at the site had been surveyed, because a level line is located 1 mile west of the site. Compaction is being measured above depths of 710, 830, and 1,930 feet. All three plots show pronounced seasonal variations in the rate of compaction. Max- imum compaction rates occur in the summer and in late winter. Compaction virtually ceases in early winter and early spring. The plots of subsidence and of compaction in the upper 1,930 feet are nearly parallel, and probably more than 95 percent of the compaction is occurring above this depth. CUMULATIVE COMPACTION AT SINGLE COMPACTION-RECORDER SITES As of 1968, single compaction recorders were opera— ting at 9 sites throughout the Los Banos—Kettleman City area. Only two of the records are sufficiently long to warrant illustration in this report, and at most of the sites, bench-mark altitudes were not established until 1966. Well 13/ 12—20D1 was one of many wells drilled by the Bureau of Reclamation to obtain geologic and hy- drologic information along the alinement of the San Luis Canal. About 10 feet of subsidence has occurred in the area between 1920 and 1966. Leveling has not been extended to the site itself, but subsidence maps provide a fairly accurate estimate of the amounts and rates of subsidence because of level lines 1 mile to the west, and to the south of the site. The plot for well 20D1 (fig. 29) shows a steadily de- creasing compaction rate into 1965, but the excessive compaction rate in the first 3 months of record may be the result of initial cable stretch and foundation settle- ment. Consistent seasonal fluctuations of compaction are not readily apparent in the record from this well, and long-term and seasonal changes in artesian head of the upper part of the lower zone have been minor. The well is in an area of near—surface subsidence, and compaction due to wetting of unsaturated deposits has occurred in addition to the compaction of saturated de- posits. A Bureau of Reclamation evaluation of the amount of compaction due to wetting in a 230-foot well at the site indicates that virtually no net compaction due to wetting occurred during the 4-year period. Ap- parently, percolation of irrigation water has thoroughly wetted all the deposits above the water table. STUDIES OF LAND SUBSIDENCE o w: - _ 5 I \ T‘ . —‘ Compactiom _. l- \\ ‘ \4—‘1 WeII1101,710mm7\'~H H] n: in \ \Nefan ° ‘; 10 \ Companion . I --. g - I ‘ ' \ 102 830}. 7‘ _ u; Approximate subsldenca a». \1 all 1 . eat 5 o 20/18-110 from 1959-63 \ \ View 4 E . and 1963-66 subsidence \ . ‘ E D 2.0 maps \ L in \ . 8 S \\W_a|l1103,1933 \f etdee Ill 8 \ D \. 1962 1963 1964 1965 1966 o 1 Well 13/122001, 690 feet deep \\ Compaction . \‘ \ \ \. Approximate subsidence at 7 \ \ ,_ 13/12-2001, from 195963 “ \ and 1963766 subsidence ‘- \ \ maps ‘ I \~~. 1963 1964 1966 b x COMPACTION OH SUBSIDENCE, IN FEET .N o 1961 1962 FIGURE 29,~Compaction and subsidence at the Westhaven site, 1962436 (upper graph), and well 13/12-20D1, 1961—66 (lower graph.) Comparison of compaction with estimated subsidence for the period December 1961—December 1965 indicates that about 90 percent of the compaction during the 4 years occurred above 690 feet and that 10 percent of the compadtion occurred below 690 feet. Well 19/16—23P2 is an oil test abandoned in 1950, in which a cement plug has been set in the casing at 2,200—2,406 feet. Seven feet of subsidence occurred at the site during the 1928—66 period. The use of the well has provided the Geological Survey with the deepest compaction recorder in the study area. The 13%—inch casing greatly reduces the casing-cable friction. Despite the potential of the site, the recorder has had many problems. The recorder has been rebuilt several times, and the cable has been removed from the well five times because of corrosion failure or replacement or to make other changes in the equipment. In 1966, the recorder was rebuilt completely, using the most advanced equip- ment available, and since then a record of both aquifer- system compaction and expansion have been obtained without changing the cable stress by monthly oscilla- tions of the counterweight. The record of net expansion is discussed in Part 3 (Bull and Poland, 1974). Compaction at 19/16—23P2 and subsidence at bench mark Z888—about 500 feet southwest of 23P2—are shown in figure 30. Because of the months of recorded net expansion and the instrumentation problems, many of the monthly records have been combined and are shown by a dashed line. Casing shortening is being measured because the anchor weight is set at a depth of 2,200 feet on a concrete plug in the casing. However, shortening of the casing is virtually the same as the concurrent shortening of the deposits that encase it, as LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F37 0 \ E uJ \\ u. \ _z_ 1.0 ‘ u.i o \0~.D E \ ‘~D Compaction, 9 \\‘D“/well 19/16-23P2, 2200 feet deep (0 2.0 \ m \ D ‘\ w \“—— EL 0: Subsidence, \. ‘*\\ O bench mark 2888 ‘~\ 2 \_ O 3.0 N _ o . \\ '6 Cable failure \ \‘\\ E D \ \_ ____1 2 New cable \ 0 installed 0 4.0 "0 1959 1960 1961 1962 1963 1964 1965 1966 FIGURE 30.—Compaction and subsidence at well 19/16—23P2, 1959—66. is shown by negligible amounts of increased casing protrusion above the land surface. Consistent seasonal patterns of compaction do not occur at this site because the compaction is dependent to a large extent on the pumping schedule of well 23P1, about 500 feet to the southwest. Well 23P1 pumps more often during the winter months than most of the wells in the Los Banos—Kettleman City area. Comparison of compaction at well 23P2 and subsid- ence at bench mark Z888 suggests that compaction is being measured in excess of subsidence. During the period December 1959—December 1965, measured com— paction was about 122 percent of the subsidence at bench mark Z888. The compaction cable was not re- moved from the well between the times of leveling in March 1963 and March 1966. Compaction was about 120 percent of the subsidence during the 1963—66 period. Subsidence rates change rapidly from west to east in the vicinity of 23P2 (fig. 13). Less subsidence should occur at bench mark Z888 because it is 500 feet to the southwest of 23P2. Steep subsidence gradients are not uncommon in the Los Banos—Kettleman City area. An example would be the‘ subsidence of bench marks P692 and N692 (fig. 15), where bench marks 1 mile apart have subsided 4 and 16 feet, respectively. Post-1966 leveling substantiates the presence of a marked subsidence gradient in the vicinity of well 19/16—23P2. The bench mark in the concrete pad of the recorder site was first leveled in March 1966 and was releveled in March 1967 and December 1967. Neither of the post-1966 periods indicates that the measured com- paction exceeds subsidence. Measured compaction above a depth of about 2,200 feet is only slightly less than the subsidence. For the period from March 1966 to March 1967, the data indicate that about 98 percent of the subsidence is being measured. Thus the presence of abrupt lateral changes in subsidence rate have been verified at the site. The leveling record shows that from March 1966 to March 1967 about 20 percent more sub- sidence occurred at the compaction-recorder well than at bench mark Z888. In September-December 1964, the Bureau of Recla- mation drilled four wells, principally for the purpose of monitoring lower-zone potentiometric head changes along the San Luis Canal (wells 14/12—12H1, 15/13—11D2, 18/16—33A1, 20/18—6D1). The wells are 868—1,070 feet deep, and compaction recorders have been installed in them by the Geological Survey in order to provide information regarding the maximum amount of compaction that might be occurring in the upper water-bearing zone. The compaction recorders are operating satisfactorily, and the preliminary results from them are used in the discussion of compaction above and below the Corcoran Clay Member. (See sec- tion “Proportions of Compaction Occurring in the Upper and Lower Zones”) In 1965, the California Department of Water Re- sources drilled well 13/15—35D5, and in 1966, wells 15/16—31N2, 3 and 18/19—20P1, 2. The Geological Sur- vey has installed equipment to observe compaction and water-level changes in these wells. At each site, a well was drilled to the Corcoran and a compaction recorder was installed in order to measure the amount of com- paction between the land surface and the Corcoran. Total subsidence will be obtained by periodic leveling to a bench mark set in the concrete pad. These wells should help evaluate compaction rates in areas where ground water is mostly pumped from the upper zone. F38 UNIT COMPACTION AT THE MULTIPLE COMPACTION—RECORDER SITES The setting of compaction anchors at various depths at a given site affords a means of measuring the amounts of compaction occurring in the depth intervals between the anchors. The amounts of compaction per foot of deposits for each calendar year are given in table 2, and unit compaction for 1-year or 2-year intervals is shown for the multiple compaction-recorder sites in figures 31 through 34. The thickness values exclude deposits above the water table. Changes in the position of the water table have been minor during the period of record at all the multiple compaction-recorder sites. Although the percentage compaction for the various depth zones is shown to the nearest percent, it is proba- ble that the measurements are accurate to only within several percent. Errors can be introduced by initial cable stretch and foundation settlement, casing-cable friction, untwisting of the cable, and leveling to the bench mark. In general, the percentage compaction is more accurate at those sites with the most compaction. Amounts of unit compaction vary from 0 for the 350—500-foot interval at the Oro Loma site to 0.00115 foot per foot per year for the 503—703-foot-depth zone at the Cantua site (table 2). Amounts of unit compaction vary by as much as 100 percent between various years. Changes in unit compaction with depth for the Los Banos—Kettleman City area are the result of two factors—the increase in head decline to and across the Corcoran in much of the area and the decrease in com- pressibility with depth because of increasing prior overburden loads. Both upper- and lower-zone wells commonly are perforated in the first 100—200 feet below the Corcoran (Miller and others, 1971, pls. 3, 4), which suggests that this depth interval may have undergone STUDIES OF LAND SUBSIDENCE the maximum head decline. The combined effects of both factors should result in increasing unit compaction to a depth of a couple of hundred feet below the Corcoran and then decreasing unit compaction below that depth. It is not economically feasible to install a sufficient number of compaction recorders at any one site to define the change in unit compaction within the lower zone. However, the variation in unit casing-failure ratio (fig. 45) suggests that unit compaction decreases below a depth of about 200—400 feet below the bottom of the Corcoran. Variation in unit compaction above the Corcoran is a function of the degree of confinement as well as varia- tion in compressibility of the deposits. Compaction has not occurred in those deposits containing unconfined water where the position of the water table has not changed. With increasing depth, the upper-zone waters generally become better confined, and in the southern part of the area, good confinement is provided by several extensive lake clays above the Corcoran. Considerable variation in applied stress and unit compaction should be expected for the different lithologic and genetic units of the upper zone. The mean annual unit compaction in three depth zones at the Oro Loma site are shown in figure 31. The unit compaction was computed as the mean of two con- secutive calendar years to reduce the year-to-year vari- ation and to illustrate trends in unit compaction. The largest amounts of unit compaction have been in the 500—1,000-foot-depth interval which is entirely below the Corcoran Clay Member. A progressive and rapid decrease in unit compaction has occurred in this interval—~the values of unit compaction for the 1964—65 period are only one-third those for the 1960-61 period. The reduction of compaction rate within this depth in- TABLE 2.—Annual compaction rates Anchor Thickness Compaction (ft) of Well gig? folgh compacting ' ne msfilled 2(aft) 1959 1960 1961 1962 1963 12/12—16H3 ______ 350 0—350 1340 0.05 0 0.01 20.04 0.00 16H4 ______ 500 350—500 150 .10 .01 0 2 .0 .01 16H2 ______ 1,000 500—1,000 500 29 .30 .33 2 .16 .19 16H2 ______ 1,000 0—1,000 1990 44 .31 .34 .20 20 14/13—11D4 ______ 780 0—780 1660 ____ ____ .31 .20 23 11D6 ...... 1,358 780—1,358 578 ____ ____ ____ .45 25 11D6 ______ 1,358 0—1,358 11,238 ____ ____ ____ .65 48 16/15—34N3 ______ 503 0—503 1313 12 10 .08 .14 08 34N2 ______ 703 503—703 200 .23 12 .20 16 17 34N1 ______ 2,000 703—2,000 1,297 .86 72 .86 .71 71 34N1 ______ 2,000 0—2,000 11,810 1 21 94 1 14 1 01 96 20/18—11Q1 ______ 710 0—710 1650 __,- A--- ____ ____ ____ 11Q2 ______ 845 0—845 1785 ____ _-__ __-_ -_-- .32 11Q23 ______ 845 710—845 135 ____ __-- __-_ ____ ____ 11Q3 ______ 1,930 845—1,930 1,080 ____ __-_ -_-_ __-- .29 11Q3 ______ 1,930 04,930 11,870 ____ --__ ____ __-- .61 I 1Only saturated deposits included in the compacting thickness. Depth to water table in 1965 was 10 ft adjacent to 12/ 12—16H3, 120 it adjacent to 14/ 13—11D4, 190 ft adjacent to 16/ 1&34N3, and 60 it near 20/18—11Q3. zApproximate values. “Compaction measured as casing separation between well 20/18—11Q2 and well 20/18—11Q3 plus increased protrusion of casing of 20/18—11Q3. LOS BANOS—KET’I‘LEMAN CITY AREA, CALIFORNIA, PART 2 MEAN ANNUAL COMPACTION HECORDEHS UNIT COMPACTION, IN 12/12-16 FEET PER FOOT H3 H4 H2 0 20 4O 60 80x10'5 0 I T I 1965 water table I; w 500 - u. E .. I. Lower/H '— confining m 1000L clay -* a 1500 l L l i J l i 1962 and 1963 1960 and 1961 1964 and 1965 FIGURE 31.—Mean annual unit compaction in three depth intervals at the Oro Lama site for 2-year periods, 1960—65. terval has been largely responsible for the decreasing rate of subsidence indicated by bench mark 97.68 USBR (fig. 22). The mean unit compaction values in the upper two depth intervals at the Oro Loma site do not show a progressive change with time and have never exceeded half the unit compaction of the deepest interval. The largest unit compaction in the 10—350-foot-depth inter- val was during the 1962—63 period, and the largest unit compaction for the 350—500-foot interval was during the 1964—65 period. The amounts of compaction were only a few hundredths of a foot per year, at most, and never exceeded the amounts of compaction recorded in 1959. The mean annual unit compaction at the Mendota site is shown in figure 32. The unit compaction in the 780—1,358-foot-depth interval (table 2) ranged from 0.00043 to 0.00078 foot per foot per year for the 1962—65 at multiple compaction-recorder sites F39 MEAN ANNUAL UNIT COMPACTION, IN FEET PER FOOT COMPACTION RECORDERS 14/1341 o 04 06 o 20 40 so 80x10" l965 water table I I I ' I I I p— 3 500 IL E I. .— 3, 1000 o woo 1962 and 1963 1964 Ind 1965 FIGURE 32.~Mean annual unit compaction in two depth intervals at the Mendota site for 2-year periods, 1962—65. period. When the data are grouped into 2-year periods, a slight increase in the lower-zone compaction rate is suggested. The 0—780-foot-depth interval has had a de- creasing rate of compaction, and the rate of compaction in the 0—1,358-foot-depth interval, although variable, has been decreasing (table 2). The largest values of unit compaction in the study area have been measured at the Cantua site (fig. 33). Although the unit compaction for each depth interval is highly variable from year to year, the 1964—65 amounts are lessthan the 1960—61 amounts of compaction. The subsidence rate has decreased, and more compaction has been occurring below 2,000 feet in recent years, as was pointed out in the discussion of figure 28. The highest unit compaction has been consistently in the 503—703-foot interval, which includes the deposits im- mediately above and below the Corcoran Clay Member, and in the Corcoran, which is only 10 feet thick at this site. Compaction—Continued (fl) Interval Unit Compaction of (X 10‘5ft/ft) Corcoran Clay Member 1964 1965 1959 1960 1961 1962 1963 1964 1965 (depfttl; in 0.00 0.01 15 0 3 12 0 0 3 .02 .01 67 7 0 0 7 13 7 379—465 .17 .06 58 60 66 32 38 34 12 19 .08 ____ ___- ____ _-_c ____ ____ ____ 19 .10 ____ --_- 47 30 35 29 15 625—700 39 .35 ____ ____ ____ 78 43 68 ~ 61 58 .45 ____ ____ ___- ____ ____ _--- _-__ .10 .08 38 32 26 45 26 32 26 .17 .11 115 60 100 80 85 85 55 565~575 .83 .63 66 56 66 55 55 64 49 1.10 .82 ____ ____ _-__ ____ -0- ____ -___ ____ .26 ____ ____ ____ ____ _-__ _c__ 40 .34 .31 ____ ____ ____ ____ 41 43 39 ____ .05 ____ ___- ____ ____ ____ ____ 36 715—745 ____ _-__ ____ ___- 27 19 32 F40 MEAN ANNUAL COMPACTION RECORDERS UNIT COMPACTION, IN 16/15-34 FEET PER FOOT N3 N2 N1 0 20 4O 60 80 100x10“ I I | I I | l I | I I :1965 water table: 1 000 1500 DEPTH, IN FEET 2000 EXPLANATION 14-— 1960 and 1961 ______ 1962 and 1963 ............ 1964 and 1965 2500 1 I | I I | I I FIGURE 33.—Mean annual unit compaction in three depth intervals at the Cantua site {or 2-year periods, 1960—65. The unit compaction for the Westhaven site has been plotted for l-year intervals in figure 34. Trends in the rate of compaction are not readily apparent for the 3 years considered. The site is the only one that definitely shows larger amounts of unit compaction in the upper water-bearing zone than in the lower water—bearing zone, a subject that is discussed further at the end of the section “Casing—Failure Study.” Overall decrease in amounts of annual compaction for selected depth intervals at the multiple compaction- recorder sites is shown in figure 35. The data are from table 2 and plot with large amounts of scatter. Despite COMPACTION RECORDERS ANNUAL UNIT COMPACTION, 20/18-11 IN FEET PER FOOT 01 02 03 o 20 40 60 x10‘5 0 +_ IF—I7l—I_VIT_’ I :1965 water table II | ‘- I 5 I I I 500 — :I I - Corcoran Clay 1| I |_ Member II I In I I u_ __ ___,__r_a_lh I : —Z— 1000 — I I I ‘ I I I I" | l . LI.I I I I D I ‘. I I E 1500 - I I I ‘ I I I I I I I i I i 2000 | I I | l EXPLANATION 1964 1963 FIGURE 34.;Unit compaction in three depth intervals at the Westhaven site for l-year periods, 196$65. STUDIES OF LAND SUBSIDENCE 1.0 l | Cantua Creek site 703 to 2000' foot depth interval + + + 0.8 _ + + + IT. Lu + u. 0 6 _ Mendota sits _ g ' 0 to 1358-f00t depth interval 2‘ 9 ’— O < 0. E 0 U _I g 0-4 T‘ Westhaven site _ Z 0 to 850-foot depth interval 2 + < . \ + \ . + 02 _ Oro Loma site m 500 to 1000—foot depth interval 0 0 I I I 1960 1962 1964 FIGURE 35.;Decrease in annual compaction for selected depth intervals at multiple compaction-recorder sites. the scatter, the overall trend toward decreasing rates of unit compaction appears to be real. The rate of decrease in the amounts of annual compaction appears to be more rapid for the two sites in the northern part of the study area (Oro Lorna and Mendota) than for the two sites in the central and southern parts of the area (Cantua and Westhaven). Possible geologic factors influencing the differences in decrease of compaction rate are discussed in the section “Geologic Factors Influencing Specific Unit Compaction.” The decreases in compaction rate shown are not the result of hydrologic changes for at least three of the sites, as indicated by minimum poten- tiometric levels for the lower-zone aquifer system, dur— ing the periods of record in table 3. At the Oro Loma and Cantua sites, the maximum annual depth to water in lower-zone wells had a range of only 3 feet, and at the Mendota site, the range was only 7 feet during the period of record. About 26 feet of head decline occurred LOS BAN OS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 TABLE 3.—Variation in the deepest annual water levels for selected depth zones at the multiple compaction-recorder sites, 1959—63 Depth to annual low Compaction-recorder site water level, Beginning of and depth interval in feet, and year water-level (ft) High Low record Oro Lorna, 500—1,000 ______ 202, 1963 205, 1964 9/60 Mendota, 780-1,358 ________ 496, 1962 503, 1965 4/61 Cantua Creek, 703—2,000 __ 600, 1961 603, 1962 8/60 Westhaven, 0—850 __________ 450, 1963 476, 1965 19/58 1Potentiometric level at base of upper zone. at the Westhaven site after the compaction gage was installed, which may account, in part, for the low slope of the line showing decrease in annual compaction for the upper-zone depth interval at the Westhaven site in figure 35. SHORTENING AND INCREASED PROTRUSION OF WELL CASINGS Shortening and increased protrusion of well casings and the distribution of casing failures provide valuable information about the compaction of the water-bearing deposits. Compaction resulting from water-level change is deforming well casings throughout the Los Banos—Kettleman City area. More than 3,000 irriga- tion wells have been drilled during 50 years of expand- ing agricultural development, but only 1,100 active ir- rigation wells existed as of 1960 (Ireland, 1963). Most of the wells that have been abandoned or destroyed were damaged by the compaction of the sediments that en- case them. Compaction has caused tens of millions of dollars of damage to well casings. For example, in 1965 it cost about $30,000 to drill, case, and gravel-pack a 2,000-foot well (maximum water-well depth in the area is 3,800 feet). Where subsidence rates exceeded 0.75 ft yr“1 (fig. 18), the average well has been abandoned or has undergone extensive repairs after only about 8 years. In areas where subsidence rates have not ex- ceeded 0.5 ft yr‘l, many wells are still in operation after 15 years of use, but casing repairs commonly are neces— sary. An underwater photograph of a casing failure is shown in figure 36. The light source was suspended under the camera. Machine-cut slotted perforations can be seen at the top of the photograph, and the.circular cross section of the casing has been changed to a dis- torted oval. Compressional forces have ruptured the casing, and pebbles from the gravel pack can be seen on top of plates of sheared casing jutting into the well. Many water wells are ruptured in several places. Some ruptures can be repaired by swaging deformed parts of the casing and installing steel liners, but such repairs are costly. Frictional resistance between the casing and adj acent deposits is cumulative with depth. Nonelastic deforma- tion occurs after a critical stress is exceeded. The depth F41 FIGURE 36.—Compressional rupture of an irrigation-well casing. (Photograph courtesy of Laval Underground Surveys, Inc.) at which the critical stress is exceeded is a function of well factors such as mode of construction and casing diameter and strength as well as geologic factors such as lithology of the adjacent deposits and depth distribu- tion, magnitudes, and rates of compaction. Above the critical depth, the enclosing sediments may move downward relative to the casing and result in increased casing protrusion at the land surface. The combined effects of depth of the compacting. in- terval and casing diameter as related to increased cas- ing protrusion are shown in figure 37. The upper limit of increased casing protrusion (dashed line, fig. 39) for the various casing diameters shows a progressive decrease with increasing casing diameter. Thus, in the Los Banos—Kettleman City area, large-diameter (large sediment-casing contact area) casings may deform more readily than do small-diameter (small sediment-casing contact area) casings. The data are from compaction- recorder wells operated by the Geological Survey, and the data for only one well were plotted for each multiple compaction-recorder site. The period of measurement was from September 1965 to September 1966. None of the wells are gravel packed, and none were pumped during the measurement period. F42 60 I I r EXPLANATION 0 Steel casing 0 Steel casing with — . cement jacket 20* — O 0 .I/A l | 4 8 12 16 CASING DIAMETER, IN INCHES INCREASED CASING PROTFIUSION EXPRESSED AS PERCENTAGE OF COMPACTION FIGURE 37.— Relation of increased casing protrusion to casing diameter for observation wells that are not gravel packed. The range in amounts of increased protrusion for a given casing size is largely a function of the depth of the compacting interval. For example, well 12/ 12—16H2 (point A, fig. 37) is 1,000 feet deep, but 90 percent of the compaction occurs below 500 feet (fig. 31). During the period of measurement for figure 37, compaction appar- ently occurred entirely below the critical stress depth, and increased protrusion of the casing at the land sur- face did not occur, even though this well has a 4-inch casing. For most wells, some compaction due to water- level change occurs close enough to the land surface so that casing strength exceeds the cumulative casing- sediment friction and small amounts of increased cas— ing protrusion are noted. For three observation wells shown in figure 37, increased casing protrusion ex- ceeded 20 percent of the measured compaction. SHORTENING OF AN OIL-WELL CASING Observations of an oil-well casing at the Westhaven site (20/ 18—11Q3) show that even a heavy oil-well cas- ing encased in a cement jacket is too weak to resist the compressional force of the compacting sediments and is being shortened virtually in accord with the compac- tion. Instrumentation of the well has resulted in the obtaining of data about casing shortening and protru- sion, compaction, and water-level changes. Preliminary results were presented by Poland and Ireland (1965). When the oil test was drilled by the Texas Co. in 1957, a surface string of 11%-inch casing with a wall thick— ness of 0.44 inch was set from the land surface to a depth of 2,004 feet. The seal to prevent contamination of the fresh ground water was completed by pumping cement into the annular space around the casing. When the oil STUDIES OF LAND SUBSIDENCE test was abandoned, a cement plug was placed in the well between 1,930 and about 2,030 feet. The Geological Survey converted the blank casing into a dual water-level well in April 1958. The casing was gun perforated from 755 to 805 and 1,885 to 1,925 feet. Hydraulic separation of the two intervals was done by the following method. A four-inch pipe with a packer attached was lowered inside the casing to a depth of 860 feet. A cement plug was placed on top of the packer, thus sealing the space between the 4- and 11%-inch casings in the depth interval 830—860 feet. A diagram of the converted well is shown in figure 38. Initially, the 4-inch casing was suspended by a casing hanger resting on top of the 11%-inch casing. Four months after installation, the casing hanger appeared to be rising off the top of the 1 1%-inch casing, indicating shortening of the 11%-inch casing above the cement bond between the casings at a depth of 830—860 feet. The cumulative separation (top of the 11%-inch casing is below the top of the concrete pad in figure 39) was measured monthly, and by November 1969 the 11%-inch casing had been shortened 3.30 feet. Shortening of 1,930 feet of casing was measured, starting in August 1962, by setting a compaction anchor on top of the cement plug. Measurements of changes in the protrusion of the 11%-inch casing above the land surface were started in February 1963. The measurements just described made it possible to measure casing shortening for the depth intervals 0—845, 845—1,930, and 0—1,930 feet. Compaction to Distance from clamp on cable to top of steel rack decreases as ——’-] S—C dIstance from lower cement Reference clamp _I/ /plug to land surface decreases on cable '— n r/Casing hanger on 4-inch casing Counterweight/ / //Separation of 4 Inch and 11% ‘ Inch casmgs T—z-Protrusion of 11%-inch casings 4-inch'cesing . ‘ '21- '. '.-". 11%-inch casing with cement seal ' '- ' outside /Confining bed, 715-745 feet E \Gun perforations, 755-805 feet Packer and cement plug, 830—860 V feet Confined aquifer system un perforations, 1885-1925 feet nchor weight at 1930 feet, at lower end of compaction cable Cement plug, top at 1930 feet FIGURE 38.—Diagrammatic sketch of wells used for measuring water levels and compaction; wells 20/ 18—11Q2 and 11Q3. (From Poland and Ireland, 1965.) LOS BANOS—KE’I'I‘LEMAN CITY AREA, CALIFORNIA, PART 2 FIGURE 39.—Compaction gage and casing separation at wells 20/ 18—11Q2 (inner casing) and 11Q3 (outer casing). 1,930 feet was measured by movement of the land sur- face relative to the reference clamp on the cable; it was equivalent to the amount of increased casing protrusion above the land surface added to the amount of casing shortening. The results are shown in figure 40. The plot of increased protrusion shows a reversal of about 0.015 foot late in 1963. Most of the reversal was due to soil and lumber swell which raised the table that was used as a reference point to measure changes in the position of the top of the casing. A concrete pad was poured in May 1964, and reversals of increased casing protrusion have been minor since then. Between August 1962 and October 1965, the total compaction above 1,930 feet was 1.98 feet. The total shortening of the 11%-inch casing and its cement jacket from the land surface to a depth of 1,930 feet was 1.83 feet (1.98 ft minus 0.15 ft of increased casing protru- sion). Casing shortening was 0.92 foot in the 0—845-foot-depth interval (casing separation) and 0.91 foot in the 845—1,930-foot-depth interval (1.83 ft minus 0.92 ft). For the 3-year record plotted in figure 40, casing shortening was equal to 92 percent of the compaction. Roughly 95 percent of the subsidence is being measured by the 1,930-foot compaction recorder. (See end of sec- tion “Cumulative Compaction at Multiple Compaction- Recorder Sites”) The oil-well casing at 20/18—11Q3 had an increased protrusion equal to 8 percent of the measured compac- tion. Well 19/16—23P2 also is an abandoned oil test and has an increased protrusion equal to about 3 percent of the measured compaction. These values of increased protrusion are about the same as for water-well casings of similar diameter. F43 SHORTENING OF WATER-WELL CASINOS The main effect of compaction on well casings in the Los Banos—Kettleman City area has been to shorten the casings; amounts of increased protrusion have been minor. In contrast, in at least one subsiding area, Mex- ico City, observed protrusion of water-well casings has been as much as 18 feet in response to subsidence of about the same magnitude (Poland and Davis, 1969, p. 227-228 and pl. 6), showing that under certain physical conditions, the friction between the compacting sedi- ments and the well casing may not be sufficient to over- come the casing strength. However, in Mexico City, the observed protrusion of well casings almost as great as the total subsidence is believed to be due in part to the fact that wells are drilled using several casing sizes. The maximum protrusion is observed for inner casings separated from the formation for part of their length by outer casings of larger diameter. General information about the shortening of water- well casings in the Los Banos—Kettleman City area is available through bench-mark surveys made by the Coast and Geodetic Survey. During the mid-1950’s, many well bench marks were established by chiseling a cross on top of the well casings or casing hangers of active and unused irrigation wells. For about 40 of these wells, reference bench marks consisting of a standard disk set in a concrete post were established Within 0.1 mile of the wells. It has been demonstrated that bench marks on well casings are not stable even though the casing may ex- tend beneath the compacting sediments (Poland and Ireland, 1965). Also, increased protrusion of a casing above the land surface should not be considered a reli- able measure of either land subsidence or compaction. The unreliability of well bench marks stems from the fact that the proportions of casing shortening and in- creased casing protrusion are unknown, unless detailed measurements are made such as were described for the Westhaven site. Some useful generalities, however, can be made by comparing well bench marks and nearby reference bench marks. A comparison of 18 pairs of well and reference bench marks is shown in figure 41. These selected pairs included only those pairs in which refer- ence bench marks were 17—193 feet from the well bench marks, and excluded all those pairs of bench marks in near-surface subsidence areas. The surface casing diameter of the selected irrigation wells ranged from 12 to 20 inches. The periods between bench-mark surveys ranged from 2 to 9 years. The comparison in figure 41 shows that the amounts of subsidence at the well and reference bench marks are not greatly different, as is shown by the way in which the points plot close to the line of equal subsidence for F44 STUDIES OF LAND SUBSIDENCE 0 ii “Ugh (Dzqu 0.2 (—3”; i i E?“ 005E E n: L o 0-845faet o4~ — }_ LLI LU LL Ease — d E E l- m 0 04930fem I U) o E1.2— — (I) < o LEV _ 20 I J 1962 1963 1964 1965 FIGURE 40.—Shortening of 113/4—inch casing, wells 20/1&11Q2 and 11Q3. the two types of bench marks. From this can be stated that, in general, water-well casings in the Los Banos —Kettleman City area are being shortened in amounts roughly equal to the compaction of the deposits within the well depth. > The small amounts of increased casing protrusion make the measured amounts of subsidence at well bench marks less than the true amounts of subsidence. Where increased protrusion has occurred, all the points should plot below the line of equal subsidence in figure 41. Actually, 7 of the 18 points plot above the line, which means that some well bench marks subsided more than the reference bench marks despite the tendency of in- creased casing protrusion to reduce the amount of measured subsidence. Apparently, amounts of subsid- ence vary considerably for distances of less than 200 feet from wells. The plot shown in figure 42 was made to determine whether the pumping of wells had any relation to the variation of subsidence measured at well and reference bench marks. The differences of subsidence between the two types of bench marks were as much as 9 percent. The differences are influenced to a small extent by the amounts of regional subsidence gradients between the two bench marks. However, the effect of regional sub- sidence trends probably is negligible for distances of 17—193 feet. In every case Where the well was not pumped between levelings, the well bench mark sub- LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 6 I I | I I .— LlJ u.I _ _ u. 2 Q 0 ¥ ‘1: 4 — Subsidence of well bench — 2 mark equals subsidence I of reference bench mark 0 Z In to — _ _l I _l I.” O 3 LL 0 2 _ _ Lu 0 2 g 0 a — _ In D U) 0 I I I I L 0 2 4 6 SUBSIDENCE OF REFERENCE BENCH MARKS, IN FEET FIGURE 41.—Subsidence of well bench marks and reference bench marks within 177193 feet of the well bench mark. +5 I I I I I I I I I 2 5., ‘2"- 0 ° EXPLANATION u.IO 5E 0 0mg a}; o E (D n: g :9 Well pumped between I < < i: 3 levelings MP2 9: L2 em 0 Lu""II tux n: 0 U m 5 Well not pumped u. E E E o g between levelings OLD 0 ram ° 0 o o 3 D 3 Lu 0 l—u’n: —(0 PW” S 0 43:1: 0 g... E ofi‘gg E LUUJI- '5 034.; g I M §<° —x _ I2” 5 Ia U U E 12 20“! .c O -20 2 w .. 03$ .8 o s .1 Eu g LL; E o D -10 I I l I I I I I I 12 16 20 CASING DIAMETER, IN INCHES FIGURE 42.—Effect of pumping on differences of changes in altitudes of reference and well bench marks. o=well pumped between levelings; o:well not pumped between levelings. sided less than the reference bench mark. This can be explained in two ways: First, part of the compaction F45 adjacent to the well casing results in increased casing protrusion instead of subsidence; second, if a well has become unused within the past few years, the applied stresses in the prior drawdown cone near the well may still exceed the maximum stresses that have been ap- plied to the deposits beneath the reference bench mark. Where this situation exists, prior larger compaction amounts near the well may have made the deposits less susceptible to compaction, relative to the deposits be- neath the reference bench mark, during the period be- tween bench-mark surveys. This evidence suggests that because the wells are point sources of maximum applied stress, maximum compaction occurs at or near the wells and that differ- ences of subsidence between closely spaced bench marks near pumped wells should be expected. The magnitude of subsidence dimples around pumping wells should be larger than indicated in figure 42 because subsidence of well bench marks is reduced by any increased protru- sion that has occurred. For several pairs of wells, the increased protrusion was sufficiently large that the subsidence of the well bench mark was less than subsid- ence of the reference bench mark, even though the well was pumped between bench-mark surveys. CASING—FAILURE STUDY Many of the water-well casings that are ruptured by compacting deposits are repaired. Before repairs are attempted, a survey of the damage to the well casing commonly is made with an underwater camera to locate the damage and to evaluate the feasibility of repairing the casing break. A photograph of a casing break is shown in figure 36. A study of the types, distribution, and relation of casing breaks to the adjacent deposits has been made by W. E. Wilson (written commun., April 1968) in about 650 square miles of the study area be- tween townships 13 and 21 south. Selected parts of Wilson’s work are included here and in the section “Geologic Factors Controlling Compaction of the Un- consolidated Deposits” because they provide informa- tion about compaction that cannot be obtained by com- paction recorders. Wilson’s study included more than 1,100 reported casing failures in 275 irrigation wells. Most of the breaks were compressional types that resulted in the casing shortening. The data were obtained by the Laval Underground Surveys, Inc., and from pump company repair records. The vertical distribution of casing failures with re- spect to the Corcoran Clay Member of the Tulare For- mation is shown in figure 43. All the casing breaks have been included, and the number of failures per 1,000 feet of well casing surveyed is plotted for each 50-foot incre- ment above and below the Corcoran. The unit casing- F46 400 l 1 I 200 CORCORAN, IN FEET Corcoran Clay Member\ DISTANCE ABOVE TOP OF 200 400 600 800 DISTANCE BELOW BOTTOM OF COHCORAN, IN FEET 1000 ' ' ' 0 4 s 12 16 FAILURES PER THOUSAND WELL-FEET SURVEYED FIGURE 43.—Unit casing-failure ratio for 50-foot intervals above and below the Corcoran Clay Member of the Tulare Formation. (From W. E. Wilson, written commun., April 1968). failure ratio increases to a depth of about 200 feet below the bottom of the Corcoran. The depth to the base of the Corcoran within Wilson’s study area ranged from 500 to more than 900 feet. Below a depth of about 200 feet below the bottom of the Corcoran, the values of unit casing-failure ratio decrease. Part of the fluctuation of the plot below a depth of 300 feet below the Corcoran probably can be attributed to the decrease in footage of well casing surveyed at the greater depths. Only 20 percent of the total footage of well casing surveyed was at depths of more than 300 feet below the bottom of the 7 woran (W. E. Wilson, writtenicommun” April 1968). The vertical distribution 0—funit casing-failure ratio permits some useful general conclusions regarding the variation of compaction with depth in the Los Banos —Kettleman City area, if one makes the assumption that casing failures are most common in depth intervals that are compacting the most. From 300 feet above the Corcoran to land surface (depth interval ranges of 0—100 STUDIES OF LAND SUBSIDENCE to 0—600 ft), the sparseness of casing failures indicates that little compaction is occurring. Maximum unit com- paction is suggested in the interval between 50 feet above the Corcoran and 250 feet below the Corcoran. The unit casing-failure ratio for this interval is about twice that of the deposits above and below the interval. The Corcoran has a unit casing-failure ratio of only 5, indicating that the Corcoran either is not compacting as much as the deposits above and below it or that the clay does not grip the casing and gravel pack of the wells tightly enough to result in shortening of the casing equal to the shortening of the deposits of the Corcoran. The lower values of unit casing-failure occurrence be- low a depth of 400 feet below the bottom of the Corcoran suggest that deposits at these depths have a lower specific unit compaction than the deposits above them. Some reasons for the increasing and decreasing trends of unit casing-failure ratio are discussed in the section “Distribution of Well-Casing Failures.” Wilson found that the casing failures were most common in the areas that had subsided the most (W. E. Wilson, written commun., April 1968). A comparison of unit compaction at multiple compaction-recorder sites and unit casing-failure occurrences in the same depth intervals of nearby irrigation wells is shown in figure 44. At the Mendota and Cantua sites, the variation in unit casing-failure ratio agrees very well with the vari- ation in unit compaction for the same depth intervals. The agreement is not good at the Westhaven site. Cas- ing failures are more common per unit well foot sur- veyed in the lower zone, yet figure 34 indicates that the upper zone has the largest unit compaction. One expla- nation for this apparent anomaly is that the lower-zone deposits may grip the well casings more tightly than the upper-zone deposits. PROPORTIONS OF COMPACTION OCCURRING IN THE UPPER AND LOWER ZONES General information about the proportions of com- paction occurring in the upper and lower zones is avail- able at 12 compaction-recorder sites in the Los Banos —Kettleman City area. The upper zone is 300—900 feet thick, and the lower zone is 400—2,400 feet thick. The amounts of water pumped and the resulting compaction of the two zones vary greatly in the different parts of the area. Most compaction-recorder wells do not have anchors set in the top of the Corcoran. The main purpose of the Bureau of Reclamation wells along the San Luis Canal was to monitor lower-zone head changes. In some cases, a suitable sand was not found within 200 feet of the bottom of the Corcoran. The main purpose of the De- partment of Water Resources wells at the Yearout, LOS BAN OS—KE'I'I‘LEMAN CITY AREA, CALIFORNIA, PART 2 ‘ F47 MENDOTA SITE CANTUA SITE WESTHAVEN SITE 800 I | I | m I I I T I I I I I I I T b O O Corcoran COHCOFIAN, IN FEET OO DISTANCE ABOVE TOP OF 400 — — — — — — 800 — — — - E _ DEPTH BELOW BOTTOM OF CORCOFIAN, IN FEET 1200 — — — — — A I I I I I I I I I I I I I I I I I O 20 40 60 0 20 40 60 80 O 20 40 60 A. MEAN ANNUAL UNIT COMPACTION X 10,51963-65, IN FEET PER FOOT 800 I I I I I I r I I f fir I I I ‘F I I 5 O O Corcoran CORCORAN, IN FEET DO DISTANCE ABOVE TOP OF 400 - — — _ _ s aoo — — - — t _ DEPTH BELOW BOTTOM OF COFICORAN, IN FEET 1200 I— — — — — — I I I I I l I I I I I I I I I J I 0 4 8 12 0 4 8 12 16 0 4 8 12 3. UNIT CASING-FAILURE RATIO, IN FAILURES PER 1,000 FEET FIGURE 44,—Comparison of unit compaction at the Mendota, Cantua, and Westhaven sites and unit casing-failure ratios in the same depth intervals of nearby irrigation wells, A, Mean annual unit compaction, 1963—65. B, Variation of unit casing-failure ratio with depth, (From W. E. Wilson, written commun‘, April 1968.) Tranquillity, and Lemoore sites was to determine the shortening of the deposits between the land surface and proportion of compaction occurring above and below the the Corcoran. Total subsidence and lower-zone compac- Corcoran. The compaction recorders at these sites have tion are obtained as a result of periodic surveys of the anchors set near the top of the Corcoran to measure bench marks at the sites. F48 Estimates of the proportions of compaction occurring in the two zones are based on compaction-recorder data and bench-mark surveys. The proportions of subsidence in the two zones described in this section are based on information obtained since 1958, but the proportions are generally applicable for pre-196O periods, such as the 1943—59 period, because the proportions of water pumped from the two zones in the different parts of the area (based on well-perforation data) have not changed greatly since 1943. Estimated proportions of the com- pactiOn occurring in the upper and lower zones are given in table 4. The Corcoran has been included in the lower zone in this discussion. Several correction procedures were necessary to com- pute the rough estimates because the compaction an- chors were not set in the top of the Corcoran at most sites. Estimates at those sites where the well does not bottom near the top of the Corcoran may overestimate the proportion of upper-zone compaction by as much as 10 percent. Estimates of the unit compaction between an anchor and the top of the Corcoran were made as STUDIES OF LAND SUBSIDENCE 12/12—16H and 16/ 15—34N, the unit compaction was determined for the interval between the bench marks set above and below the Corcoran. At the single compac— tion sites where the anchor was set above or below the Corcoran, the unit compaction for the interval between the water table and the anchor was used to interpolate or extrapolate amounts of unit compaction in order to estimate the amount of compaction between the water table and the top of the Corcoran. Corrections based on these procedures provided estimates of the maximum proportion of compaction occurring above the Corcoran because values of unit compaction are larger for the lower zone than for the upper zone, except at the south end of the study area (figs. 33, 36). The proportions of compaction in the upper and lower zones given in table 4 and shown in figure 45 indicate that, in general, north of Cantua Creek less than 20 percent of the compaction occurs in the upper zone, but south of Cantua Creek about 30—40 percent of compac- tion is occurring in the upper zone. Northeast of the town of Cantua Creek, most of the water is pumped from follows. At multiple compaction-recorder sites upper-zone aquifers, which in that area yield the best TABLE 4,—Proportions of compaction occurring Period £5532“ Anchor depth figgi Depth to C(inmtgigglng well measuorfement :Eigé: inggllled belogi; (_— ) 22%? 5:33“? 13.25% 5311,1306) 13.2% 233309) Candi?” 1335 wages 12/12—16H3 __________ 10/61—10/65 379—465 350 +29 10 % 16H4 ,,,,,,,,,, 10/61—10/65 379—465 500 —121 10 % 13/12—20D1 __________ 3/66—11/67 304—418 690 —386 180 %0— 13/15—35D5 __________ 5/66—5/68 428—476 440 —12 10 33% 14/12—12H1 __________ 3/66—11/67 615—719 913 —298 190 13352—311 14/13—11D4 ________ 12/62—12/65 625—700 780 —155 120 ligéfl 15/13—11D2 __________ 9/65—9/66 768—860 958 —190 220 22;;3258- 15/16—31N3 __________ 3/67—3/69 585.648 596 —11 15 % 16/15—34N3 ,,,,,,,,,, 12/62—12/65 565—575 503 +62 190 ~%§‘E 34N2 __________ 12/62—12/65 565—575 703 —138 ...... 59% 18/16—33A1 __________ 3/66—11/67 781—805 1,029 —248 40 4L$ 18/19—20P2 __________ 3/67— 3/69 567—634 578 #11 15 %§7§ 20/18—6D1 ,,,,,,,,,, 3/66—11/67 811—820 867 —56 150 %:67 11Q1 __________ 12/64—12/65 715745 710 +5 60 M- 650 LOS BANOS—KE'I‘I‘LEMAN CITY AREA, CALIFORNIA, PART 2 quality water. Pore-pressure decline occurs in the lower zone mainly as a result of extensive lower-zone pump- ing in the vicinity of Cantua Creek. Southeast of Men- dota, saline waters occur in the upper zone but not in the lower zone, and the combined effects of lower-zone pumping and lower-zone head decline more than 5 miles to the southwest result in more than 90 percent of the compaction occurring in the lower zone. Within the Delta-Mendota Canal service area, the wells supple- menting the surface-water imports pump mainly lower-zone water. In addition, part of the head decline results from intensive lower-zone pumping to the south. Large proportions of lower-zone compaction occur at both the Yearout and Lemoore sites despite heavy upper-zone pumping at both sites. The upper-zone de- posits being affected by pore-pressure decline are only 200—350 feet thick and consist largely of sands which undergo little inelastic compaction (Pt. 3, Bull and Po- land, 1974). At the Lemoore site, the fresh-water bear- ing deposits below the Corcoran are more than 800 feet thick; the lower-zone head decline to the west appar- ently has decreased artesian head at the site sufficiently in the upper and lower water-bearing zones F49 to result in more than 80 percent of the compaction occurring in the lower zone. GEOLOGIC FACTORS INFLUENCING COMPACTION OF THE UNCONSOLIDATED DEPOSITS The geologic factors affecting compaction of uncon- solidated deposits can be evaluated on a local or re- gional basis. Within the Los Banos—Kettleman City area, sufficient data are available to assess the effect of overburden load, petrology, and bedding at core-hole sites and to assess areally the effect of prior total applied stress, age of the deposits, mean lithology, and source and mode of deposition on the susceptibility of the de- posits to compaction upon increase in applied stress caused by ground-water pumping. LOCAL RELATIONS OVERBURDEN LOAD The prior effective load on a given deposit partly determines the amount it has compacted in the geologic past and the potential for future compaction. In general, Subsidence during perio . Extrapolated Estimated 0f Maximurm compaction maximum measurement uppe 2:. e Measured between compaction (ft) “3:235:63“!th compaction anchor occurring M' , (ft) t5: 71f 333:6 ‘ Estimated; ”$21,123:; Corcoran Corcoran Bench-m ark figgallgég:%% compaction surveys subsidence {percent} map 0.05 0.01 0.06 1.30 ________ —5 95 .04 ________________________________________ .16 .12 .04 .29 ________ E 86 .03 0 .03 ,,,,,,,, .48 —6 94 .48 .20 .28 .99 ________ E 72 .52 . 12 .40 2 . 1 4: ________ H 81 . 16 .04 . 12 ,,,,,,,, .90 E 87 .20 ' 0 .20 ,,,,,,,, .63 Q 68 .26 . 14 .40 3.1 5 ________ E 87 .45 ________ __1 _____________________________ .33 .08 .25 .56 ________ i 55 14 .07 0 .07 77777777 .50 -~-— 86 .45 .04 .41 1.23 ________ E 67 .25 0 .25 _______ .60 4—2 F50 STUDIES OF LAND SUBSIDENCE 12030 120.00, 33 I 5 Los Banos 152 / / 37a 0' _ Dos 0 Palos / ~.'\_FI‘,L"J£—--—-\\__‘ ,JN‘KIgiver , 33 ' ‘ ‘ Madera 0%2 / / "$1 0 O 5 — 0 Me 35" 99 «V o // 0% Sc 20 9, - R V O ’— -\ \ \ Firebaugh RIVE é Q35” 9 4; $00 /0 \ <9 o 9 \ I“ “‘ (3’0 1 ‘90 AQU «3' o, ‘ 5 o 5 10 FagsNo ": 14 '. r‘ O 4 '3“ 86 ..’ Mendota . 6 / "77’ 3w, '. \ z — \ l... 7& O , . 19 180 , 94 18° ( 9;. Kerman . J‘ O “‘ ‘ ° 3; \ “5° 41 Q \ d‘ \" A A \ ( 32 x 5.. O E \‘ \ a ': "a 9:6 0 I _ 0/ ‘9, -' Can ua Creek ‘94 36 30 EXPLANATION c o ° \ — 9L 06‘ " -‘ ° 13 “ o '- .' — '3 I ‘9 1 2 : 87 \ \ , , . . Boundary of deformed ,9 ((c‘ "" \ I'OCkS ’74, \ ' Five Points \ Boundary of areas of near-surface subsidence / __ as mapped in 1961 \ ' 14 ff , 6 E \ ,/' o E ’ ’ ’ Approximate proportions of compaction in \A I we the upper and lower zones at compaction- KL Ls recorder sites, in percent F” Number above line is maximum upper-zone ! \ m compaction; number below line is mini< \\ J mum lower-zone compaction Westhaveno 83'; ——m—— s— \ Approximate line of equal proportion of E O) L Strat— lower-zone compaction to subsidence , O ford Interval 20 percent. Based on computed roe/O estimates of minimum lower-zone com- «3.990% paction at recorder sites, a map showing Q I‘ the proportion of irrigation water pumped / from the upper and lower zones, and the I TULAHE compressibility and thickness of the low- er- and upper-zone deposits 4, LAKE o 5 1o 15 M I LES 44/ IVQ Kettleman BED 36°00, o 5 1o 15 KILOMETHES l ‘6‘ City Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 45l—Pruportions of compaction occurring in the upper and lower water-bearing zones. amounts of prior compaction increase with depth be- Several lines of evidence show that the compressibil- cause prior applied stress increases with depth and be- ity of the deposits at the core-hole sites decreases with cause geologic time has been sufficient for applied stress increasing depth of burial. Two examples of the de- increases to become effective, even in thick clay beds. crease in compressibility with increasing effective LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 stress at the Cantua site, derived from one-dimensional consolidation tests of core samples, are discussed in conjunction with figure 59. The upper-zone deposits should be more compressible than the lower-zone deposits at the core-hole sites be- cause they have been subjected to less prior effective stress. Petrologic characteristics greatly affect com- pressibility, but samples from the core-hole sites do not show major petrologic changes with depth of the de— posits of a given source and depositional environment. The relation between prior effective stress and com- pressibility of the deposits in the upper and lower zones probably explains the higher unit compaction in the upper zone at the Westhaven site (fig. 34). The bulk of the deposits in both zones at the Westhaven site consists of Diablo alluvial-fan deposits, with minor lacustrine deposits (Miller and others, 1971). Hydrographs of the wells at the site (Pt. 1, Bull and Miller, 1974, fig. 14) show that the history of head change at the base of the upper zone is about the same as that in wells tapping different parts of the lower zone. In addition, the casings of many of the irrigation wells in the Vicinity of the Westhaven site are perforated for 100 feet or more above the Corcoran, indicating that withdrawal of ground water and head decline are common in the upper zone. Specific unit compaction in the upper zone at the Oro Loma, Mendota, and Cantua sites also probably exceeds the lower-zone specific unit compaction at the sites, but is not apparent in figures 31—33. The total compaction for the upper zone at these three compaction-recorder sites probably is small because (1) the proportion of the upper-zone deposits affected by substantial head de- cline is much less than in the southern part of the study area and (2) the change in applied stress has not been as large as in the lower zone. The factors affecting the relation between applied overburden load and unit compaction also are apparent in the plot of unit casing-failure ratio versus vertical distance from the Corcoran (fig. 43, and W. E. Wilson, written commun., April 1968). Unit casing-failure ratio increases to a depth of about 200 feet below the Corco- ran and then decreases with increasing depth for the rest of the lower zone. Wilson’s plot can be interpreted as follows if it is assumed that unit casing-failure ratio is related directly to the unit compaction of the adjacent deposits. For a given suite of deposits, unit compaction decreases with depth and increases with increasing pore-pressure decline. Pore-pressure decline is related directly to the amounts of water pumped from the de- posits and hence to the perforated interval of the wells. Most of the wells are perforated mainly in the lower zone, and many of the wells that tap mainly the upper zone also tap the uppermost 100—300 feet of the lower F51 zone (Miller and others, 1971, pls. 3, 4). Wells that tap both zones are most common in the southeastern, east- ern, and northern parts of the area. Thus, the pattern of unit casing-failure ratio shown in figure 43 is logical. The upper part of the plot reflects the dominance of progressively greater pumping of confined water to a depth of about 200 feet below the Corcoran. The lower part of the plot reflects dominance of the other compo- nent —decreasing compressibility of the deposits with depth because of the effect of the preexisting overbur- den loads and because of the moderately good hydraulic conductivity of the lower zone. A detailed assessment of the properties of core sam— ples from three sites in the Los Banos—Kettleman City area has been made by Meade (1968). Although the core samples reflect the selectivity of the coring process (more clays than sands are recovered), Meade’s analysis provides a valuable insight into the factors influencing void ratio and porosity of sediments underlying areas of land subsidence. The relation between the logarithm of applied stress at the time of coring and void ratio for 40 core samples consisting of clayey silt is shown in figure 46A. Meade segregated the cored alluvial sediments of the Los Banos—Kettleman City area into four lithologic groups to minimize the strong correlation between particle size and void ratio that also occurs in the suite of cores. The term “clayey silt” is based on Shepard’s (1954) classification. The gap in the plot between applied stresses of 20 and 35 kilograms per square centimetre reflects the differential in artesian head across the Cor- coran that exists in the northern and central parts of the area. The regression line shown in figure 46A suggests that for the alluvial clayey silts cored, the void ratio would decrease from about 0.8 to 0.6 upon an increase in applied stress from 20 to 80 kilograms per square cen- timetre. PETROLOGY Laboratory consolidation tests made by many work— ers have shown that, in general, clays are much more compressible than sands. On the basis of the large body of literature discussing the result of laboratory studies, it is only natural to assume that conditions in the field consist of (1) small amounts of chiefly elastic compac- tion that occur rapidly in sands and (2) large amounts of chiefly inelastic compaction that occur slowly in clays. These assumptions, although probably true in a gen- eral sense, have yet to be fully verified in the field. Furthermore, the state of knowledge about laboratory consolidation of sands is not nearly as well known as for clays because of the difficulty of fitting a sand sample into a consolidometer ring without disturbing the sam- ple to the extent that results are unreliable. Most of the deposits in the study area consist of thin beds that F52 l l I I l | I | I ll }— 1.o — z 2m S is <( ” rim 0: _ —n_ 0 8g 6 T I: > 0.5V O_‘ A LO 1 I I > 10 APPLIED STRESS, IN KILOGRAMS PER SQUARE CENTIMETRE SORTING (SO) 2 4 e 8 I | I l I l I | a 50 I— 23 3 is < > w t: ‘40 Eu. 9 0% O — 30 m 3 > 2.: o A 20 > VOID RATIO 1 J: O POROSITY, IN VOLUME PERCENT —3O 1 4 16 64 MEDIAN DIAMETER, IN MICRONS FIGURE 46.7Relation of applied stress, sorting, and particle size on void ratio and porosity of selected suites of samples of alluvial sediments from three core holes in the Los Banos 7Kettleman City area. Figures are from Meade (1968, figs. 1 10, 13A, 16); solid lines are the regression lines, dashed lines represent the 95 percent confidence limits. A, Relation between void ratio and applied stress for clayey siltsi B, Relation between void ratio and (Ms—1'75. quartile deviation QD = in silty sands. C, Relation between void ratio and median particle diamzter for all samples, contain clay. Compaction recorders have measured net change in thickness of suites of deposits. None of the compaction recorders have been positioned in pairs so as to measure specifically changes in the thicker lacus- trine silty clays and clayey silts such as the Corcoran. Because of the lack of quantitative information about the compaction of different lithologies in the field, many of the interpretations about compaction in subsidence areas are based on assumptions derived from laboratory investigations. Compaction of sands occurs as a result of elastic com- pression of the grains and by rearrangement of the STUDIES OF LAND SUBSIDENCE particles. Most of the laboratory studies about consoli- dation of sands have been made on clean quartz sands, and little work has been done on clayey sands, mica- ceous sands, and polymineralic sands. Meade (1968, p. 9—14) reviewed the work that has been done regarding the void ratio characteristics of sands, In brief, void ratio of sands decreases with increase in median diame- ter, decrease in sorting, decrease in the angularity of the grains, and increase in overburden load. Consolidation characteristics of sands that contain mica flakes are different from mica-free sands. The mica flakes act as elastic beams between some of the sand grains. Studies by Gilboy (1928) showed that only a small percentage of mica added to a clean quartz sand greatly increases the compressibility of the sand. The variable presence of mica in the sediments of the Los Banos—Kettleman City area may explain, in part, the variations in net specific unit expansion that have been observed at compaction-recorder sites. According to Meade (1967, p. 5), sands derived from the Sierra Nevada contain 2—5 percent of fresh-looking biotite in large flakes, and sands derived from the Diablo Range contain 2 percent or less of weathered-looking mica in small flakes. In his study of the fabric of sands, Meade (1968, p. 32—34) concluded that distortion of compressible grains such as mica flakes and fragments of partly weathered shales and metamorphic rocks contributed to the com— pressibility of the sands represented by the core sam- ples. He also concluded that the orientation of large mica flakes parallel to the bedding in the Sierra sands was more conducive to elastic changes‘in thickness of the deposits than the orientation of small mica flakes at roughly 45° to the bedding in the Diablo sands. Large mica flakes oriented parallel to the bedding should re- spond to an increase in applied stress by bendingaround the grains—an elastic type of movement that is easily reversed upon decrease in applied stress. Small mica flakes oriented at 45° to the bedding should respond to an increase in applied stress by allowing particles to slip past one another into a denser state of packing—an inelastic type of movement that is largely permanent. But, as Meade stated, the compressibility of both types of fabrics in micaceous sands provides a greater poten- tial compressibility than in mica-free sands. 7 IrfinAeral, silts are considered more compressible than sands, but not as compressible as clays, probably in part because the coarser silt fraction does not have sufficient surface area to absorb the large amounts of water typically absorbed by clays. Most well-sorted silts have larger void ratios than sands because of the great- er angularity of individual grains. The poorer sorting of some silts, as compared with sands, tends to result in a lower void ratio. LOS BANOS——KETTLEMAN CITY AREA, CALIFORNIA, PART 2 Detailed studies of the clay mineralogy of the sedi- ments of 101 samples, 85 from deep core holes and 16 from streams and alluvial—fan deposits to a depth of 7 0 feet, have been made by Meade (1967, p. 18—24). There is a uniform preponderance of montmorillonite in the clay-mineral assemblages from the Sierra (derived from Sierra Nevada) as well as Diablo (derived from Diablo Range) source terranes. Calcium is the principal ad- sorbed cation in the clays. The percent of adsorbed sodium increases with depth, but does not exceed 38 percent of the cations in any of the samples tested. From studies of samples from core holes at the Men— dota, Cantua Creek, and Huron sites, Meade (1967, p. 22, table 5) estimated that the amount of material finer than 3 micrometres represented the proportion of clay minerals in the cores. The mean of the material finer than 3 micrometres in the 305 core samples is 26 per- cent. The mean was adjusted by Meade (1967, p. 22) to 15 percent, as an estimate of the proportion of clay minerals in the sediments, because the coring process tended to recover more clays than sands. However, the 3-micrometre size is 1 micrometre smaller than the size generally recognized as being the size between clay- and silt-size material. Therefore, for purposes of general comparison in this paper, the mean percentages of ma- terial finer than 3 micrometres are considered to be roughly equivalent to the amount of clay-size material (less than 4 micrometres in the deposits at each site). The amounts of clay-size particles in the deposits of different source areas and depositional types at the three core-hole sites are summarized in table 5. Cores from the Diablo flood-plain deposits have the lowest clay content (21 percent), and the Sierra deltaic deposits have the highest clay content (32 percent). The mean clay contents of all the cores from the Diablo and Sierra sources are about the same—27 percent for the Diablo deposits and 25 percent for the Sierra deposits. Almost TABLE 5.—Amount ofclay in deposits from Diablo and Sierra sources in the Mendota, Cantua, and Huron cores Percent finer than 3 micrometres2 (mean) Number of Source and mode of deposition‘ samples Diablo: Alluvial fan __________________ 145 28 Flood plain ____________________ 37 21 All Diablo samples ____________ 182 27 Sierra: Flood Plain ____________________ 58 23 Deltaic ________________________ 16 32 All Sierra samples ____________ 74 25 Combined Diablo and Sierra: Lacustrine deposits ____________ 44 27 All cored samples ______________ 3305 26 1From Miller, Green, and Davis (1971, pl. 5). 2Data from Meade (1967, table 5). “Includes five samples for which the source and mode of deposition were not determined. F53 half of the samples are Diablo alluvial-fan deposits, which have a mean clay content of 28 percent. The 44 core samples taken from the lacustrine sands and clays represent both Diablo and Sierra sources. The lacus- trine deposits varied from clean littoral sands to silty clays; the mean clay content for the 44 samples was 27 percent. The presence of clay adds greatly to the potential compressibility of the deposits of the study area. All clays tend to adsorb water, and the amount of water adsorbed is directly related to the surface area per unit volume of clay. Water farther away from the clay parti- cles is not held as tightly as the water next to the clay minerals. Increase in applied stress removes the less tightly held water, causing a concurrent decrease in volume as water is expelled. The rate of expulsion of water from aquitards and aquicludes is also a function of clay content. High clay contents tend to decrease the permeability and favor development of large residual excess pore pressures for a given applied-stress increase and bed thickness. The fact that 7 parts out of 10 of the clay-mineral fraction consist of montmorillonite throughout nearly all the Los Banos—Kettleman City area is important. Because montmorillonite is very finely divided, it has a much larger specific surface than other clay minerals. Meade (1964, p. 6), in summarizing the studies of other workers, tabulated the following specific surface ranges in square metres per gram: montmorillonite, 600—800; illite, 65—100; and kaolinite, 5—30. Thus, montmorillon- ite can adsorb more water at a given applied stress and salinity than other clay minerals. This affinity for water permits montmorillonite to have a larger void ratio at a given effective stress than other clay minerals, and therefore more potential for compaction for a given in- crease in effective stress. The void ratio of montmorillonite also is dependent, in part, on the electrolyte concentration and the nature of the adsorbed cations. Meade (1964, fig. 1), in his review of the literature concerning the clay-water sys- tem, pointed out that stronger osmotic pressures (and therefore larger void ratios) are associated with low electrolyte concentrations. He also pointed out (fig. 11) that at low effective stresses (<10 kg per cm2), mont- morillonite saturated with sodium cations has a consis- tently larger void ratio than does montmorillonite satu- rated with calcium, magnesium, potassium, or al- luminum cations. One would conclude, therefore, that the clayey deposits at shallow depth within the study area would be even more susceptible to compaction if the predominant adsorbed cation were sodium rather than calcium. If the void ratio of a sample can be assumed to be a rough measure of potential compressibility, a strong F54 correlation between potential compressibility and par- ticle size can be demonstrated. Figure 46C is a plot of the logarithm of median diameter and void ratio for 135 samples selected from alluvial deposits at the Mendota, Cantua, and Huron core holes. The semilogarithmic regression line suggests that the void ratio decreases from almost 0.8 for a median diameter of 1 micrometre to 0.6 for a median diameter of 250 micrometres. Meade noted a significant simple correlation between void ratio and sorting of the cored sediments in the coarsest grained group of cores—the silty sands. The results of his regression analysis of void ratio and quar- tile sorting are shown in figure 46B. Meade (1968, p. 25) pointed out that the degree of sorting also decreases with depth, and so the regression reflects the effect of some other factor(s). The combined effects of the many physical and chemi- cal factors influencing compaction of clays is difficult to assess. In an important Statistical study, Meade (1968) made a multiple-regression analysis from core studies of the Richgrove site in the southern San Joaquin Val- ley of the pore volume, overburden load, particle size, clay-mineral type, type of adsorbed cations, total dis- solved solids in leachate, pH, orientation of the mont- morillonite flakes, and diatom content. He concluded that the effects of overburden load on the pore volume in the suite of sediments studied is completely obscured by petrologic factors, which were responsible for an in- crease of void ratio with inceasing depth. The pore vol- ume was most closely related to particle size, diatom content, and the proportion of adsorbed sodium. Other factors thought to have a direct or indirect influence on pore volume were the dominant proportion of mont- morillonite in the clay fraction, pH, and electrolyte con- centration. Although a similar study has not been made in the Los Banos—Kettleman City area, it is anticipated that the petrologic factors having a dominant influence on pore volume will not be greatly different from those defined by Meade. For example, the diatomaceous clays of the Corcoran lacustrine sequence characteristically have the maximum void ratios and compressibilities. BEDDING The bedding of the deposits is one of the most impor- tant geologic factors affecting the rate of compaction of unconsolidated sediments upon increase in applied stress. If one considers units that are 50 to more than 1,000 feet thick, a given type of deposit—such as the Diablo alluvial—fan deposits—4s surprisingly homogeneous: vertical and lateral changes in lithology occur gradu- ally for a given fan. However, if one considers units of Only a few inches or feet thick, abrupt changes in lithol- ogy are characteristic of all genetic types of the deposits. STUDIES OF LAND SUBSIDENCE The interlayering of thin-bedded compressible fine- grained sediments with permeable coarse-grained sed- iments has resulted in aquifer systems that compact rapidly and substantially in response to increase in applied stress. Variations from this typical condition occur within the study area. In those areas where most of the beds are consistently coarse grained, such as some sites near the Kings River, the values of specific unit compaction (fig. 54) are less than in the areas of hetero- geneous interbedding, presumably because the coarse- grained sediments are less compressible than clayey sediments. In those areas Where hundreds of feet of clayey deposits occur, such as northeast of the Big Blue Hills, the values of specific unit compaction also are smaller than in those deposits that have heterogeneous interbedding because the low vertical permeabilities of the thick clay beds result in slow compaction rates and small amounts of observed compaction. The time, t, necessary for a specified percentage of compaction to be completed in a clay bed can be esti- mated from the following equation, which is based on the Terzaghi theory of consolidation (Terzaghi and Peck, 1948, p. 241): Th2 t 2 cu where T = a dimensionless time factor that varies non- linearly with the percentage of compaction completed; h = the thickness, in feet, of the compacting layer. If it is being drained through both upper and lower surfaces, the half thickness is used; the consolidation coefficient, in square feet per year, which is determined as part of the one-dimensional consolidation test. The Terzaghi equation illustrates the importance of the thickness of compressible clay beds on the amount of time necessary for compaction to occur. The time re— quired for a stress to become effective varies directly as the square of the bed thickness. The variable thickness of the Corcoran within the study area can be used as an example to illustrate the importance of bed thickness. The Corcoran varies in thickness from less than 1 foot to more than 100 feet. Assuming homogeneity, that is the hydrologic properties are identical and that expulsion of pore water only occurs at the bottom, a 100-foot thick- ness of the Corcoran would require 10,000 times as long to undergo a given specific unit compaction as would the 1-foot thickness. Even 15-foot-thick clay beds may have sufficient residual excess pore pressures that they con— tinue to compact after water levels have risen more than 50 feet (Pt. 3, Bull and Poland, 1974). , Electric logs of the wells within the area pYoVide a means of evaluating the characteristic bed thicknesses CU: LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 of the different types of deposits. An electric log is shown in figure 47, and micrologs are shown in figures 48—52. An electric log of the upper-zone aquifer system at well 18/ 19—20P1 is shown in figure 47. Below a depth of 200 feet, the resistivity log reveals three thick clay beds at about 240 feet, 290 feet, and below 565 feet. Two of these clays have been shown to be of lacustrine origin (Croft, 1972), the deepest clay being the Corcoran. The rest of the section consists almost entirely of water- bearing sands. The resistivity log reveals only general information about the gross thicknesses of large units, but the spontaneous-potential log shows that many of the units that appear to be thick-bedded sands on the resistivity log contain beds of finer grained material, perhaps having lithologies such as silty sand or clayey sand. The beds of low resistivity on the spontaneous- potential log produce a negative deflection instead of the positive deflection commonly noted because of the relation of the mud and formation resistivities at this site. At the bottom-hole temperature of 21°C (694 ft), the mud resistivity was 1.68 ohm—metres (ohm-metres2 per metre). Apparently, the mud had a much lower resistivity than the formation resistivity, hence the clays show as deflections to the left and the sands show as deflections to the right on the spontaneous-potential log. In many of the electric-log surveys made in the study area, ground water is used to mix the mud, and as a result the resistivity contrast between the mud and the formation is so slight that the spontaneous- potential log is Virtually useless. Salt is added some- times to the drilling mud to produce a spontaneous- potential log with characteristics similar to the log shown in figure 47. The spontaneous-potential log of figure 47 shows that many of the beds in the Sierra flood-plain deposits be- tween depths of 300 and 500 feet have the following thickness characteristics. Most of the sand beds are thick bedded, being 10—30 feet thick. Within the sand sequences are beds that are interpreted as being clayey or silty sand and, in general, are less than 10 feet thick. Above a depth of 230 feet, the minute crenulations in the spontaneous-potential log suggest that the deposits are much more heterogeneous than the deposits in the depth interval from 300 to 550 feet. The deposits in the upper part of the log are interpreted as being alluvial- fan deposits derived from the Diablo Range such as those noted in nearby core holes. Detailed bedding of five different types of Sierra and Diablo deposits is shown in the micrologs (microinverse 1” X 1" logs) of figures 48—52.The figures represent selected parts from logs made in the Inter-Agency Committee core holes at the Mendota, Cantua, and Huron sites. Samples from the intervals shown have F55 SPONTANEOUS POTENTIAL IN MILLIVOLTS RESISTIVIIY, IN OHMSM/m (64-inch normal) — iii + o 50 E E I i 600 ( FIGURE 47.—Electric log of the deposits at well 18/19720P1. been studied petrographically by Meade (1967), and the genetic types of deposits have been correlated on a re- F56 gional basis by Miller (Miller and others, 1971). The resistivities of the logs have not been corrected to a common salinity and temperature. The percent of clay-mineral material is from Meade (1967, table 5), and the percentage of sand and vertical permeabilities are from Johnson, Moston, and Morris (1968). The solid arrows represent the reported depths from which the samples were collected. Discrepancies between the re- ported depths and the microlog depths, in general, are less than 2 feet. For many of the depths reported in the field, the position of the sample had to be estimated because 100 percent recovery was not obtained in many of the cores. Where discrepancies in depth are apparent, a dotted arrow has been added to indicate the bed from which the author believes the sample was obtained. The coefficients of vertical permeability for clayey sediments with permeabilities of less than 0.01 gal day‘ 1ft‘2 (gallon per day per square foot) obtained from a variable head permeameter are considerably higher than permeabilities obtained from consolidation-test data of adjacent core samples. The differences are due in part .to the unloaded condition and the use of water of different chemical character from the pore water in the permeameter tests (Johnson and others, 1968, p. 26). Therefore, the permeability results shown in figures 48—52 that are less than 0.01 gal day“1 per ft’2 proba— bly are higher than if the permeabilities had been com- puted from a time—consolidation test. To provide the reader a rough comparison of the verti- cal permeabilities of the finer grained beds from the various types of deposits, mean permeabilities from 27 consolidation tests are shown in table 6. Only results obtained from samples tested in the load range 400—800 lb in‘2 (pounds per square inch) were used. The mean vertical permeabilities shown in table 6 indicate that fine-grained lithologies from both the lacustrine and alluvial-fan deposits have low permeabilities compared with the flood-plain deposits. The Diablo flood-plain deposits had the highest mean permeability, which is TABLE 6. — Mean vertical permeabilities of the'different types of de— posits as determined from consolidation tests of samples in the load range 400—800 lb in ‘2 at the four core—hole sites Number Mean coefficient of permeability2 of (gal day ‘1 Source and mode of deposition‘ tests ft‘z X10’5l (ft day" X 10‘ 5) Diablo: Alluvial fan ______________ 10 1.7 2.3 Flood plain ______________ 9 5.7 7.6 Sierra: Flood plain ______________ 4 4.0 5.3 Combined Diablo and Sierra: Lacustrine ________________ 5 2.9 3.9 1From Miller,Green, and Davis (1971, pl. 5). 2Data from table 9, Johnson, Moston, and Morris (1968, p. 64, 65). Cubic feet times 7.48 equals gallons. STUDIES OF LAND SUBSIDENCE consistent with the high silt content and low clay con- tent of these deposits as compared with the fine-grained beds of the other types of deposits. The performance characteristics of the wells in the northern and southern parts of the study area indicate that major differences exist between the transmis- sivities of the flood-plain and alluvial-fan deposits. Most of the wells are designed and pumped in such a manner as to yield LOGO—1,500 gallons per minute. In the north— ern area (such as T. 13 S., R. 13 E.), only GOO—1,000 feet of perforated interval are needed to get sufficient yields, and seasonal lowering of the potentiometric level is only 40—60 feet. In contrast, wells in the southern area (such as T. 20 S., R. 18 E.) have. perforated intervals of 1,200»1,600 feet, and the seasonal lowering of the potentiometric level exceeds 100 feet. Comparison of yield factors of lower-zone wells tapping different types of deposits indicates that the flood-plain deposits are three to five times as permeable as the alluvial-fan deposits. SIERRA FLOOD-PLAIN DEPOSITS Bedding of the Sierra flood-plain deposits at the Cantua site is shown in figure 48. The sand beds are RESISTIVIIY, IN OHMS m/rn 0 10 20 0.007 (— 21 8 :<_ 370 ,»/“"’ <=— ‘ 95 1000 » —* E \ *— T 7 Z 163__) i E 88 LU {b :=——_ O < ‘E >— 3) >— 2 °°—» 1,--_ — < 0.005 _ 8 —| 49 3 _ A O 1050 .1 in m a ’_ :7 g :2 . i z > f l- _ b ’3 D 1100 — .1 Vertical ’ permeability in : Percentage sand gallons per dav =- Percentage clay Der'square fg —§ FIGURE 48.»—Bedding, lithology, and vertical permeability of the Sierra flood-plain deposits, Cantua site, depth 978—1,134 feet. LOS BANOS—KE'I'I‘LEMAN CITY AREA, CALIFORNIA, PART 2 thick. A 65-foot-thick sand section occurs between depths of 985 and 1,050 feet, but within the bed are two thin beds of fine-grained material—one that is 1 foot thick and one that is 2 feet thick. Despite the large thickness of the overall bed, numerous thin beds having resistivities in excess of 10 ohm-metres are common, indicating the presence of many beds that are coarser grained, or have lower clay contents than most of the sand section. The lower part of the log also reveals sand beds ranging in thickness from 10 to 30 feet. Beds of fine grained material as much as 9 feet thick occur also. The lithology of the finer grained units is not uniform, but instead consists of alternating beds of different lithologies that have a mean bed thickness of about 1 foot. The lithologies of the Sierra flood-plain deposits have a wide range of particle-size distribution. The sand beds consist of about 90 percent sand, with virtually no clay. The fine-grained beds consist of almost half clay with less than 10 percent sand. The sample from a depth of 981 feet was well sorted even though it contained 70 percent silt. DIABLOIALLUVIAL-FAN DEPOSITS Bedding of the Diablo alluvial-fan deposits at the Mendota site is shown in figure 49. The bedding of the fan deposits is highly variable. Characteristically, the sand sections do not exceed 20—30 feet, and sand beds that are thicker than 10 feet appear to be less uniform in lithology than the Sierra sands. Sands predominate in the Sierra flood-plain deposits, but fine-grained deposits predominate in the Diablo alluvial-fan deposits. The finer grained sections of the alluvial-fan deposits range in thickness from less than 1 foot to more than 50 feet, but like the fine-grained sections of the Sierra flood-plain deposits, considerable lithologic variation of individual beds occurs. The particle-size analyses indicate marked differ- ences between the Sierra flood-plain deposits and the Diablo alluvial-fan deposits. Instead of containing 90 percent sand, the sand beds of the fan deposits contain 40—60 percent sand, and the clay content of the sand beds is 10—20 percent, instead of being less than 10 percent as in the case of the Sierra sands. Similar percentages of sand and clay occur in the thick sequences of alluvial-fan deposits in the southern part of the Los Banos—Kettleman City area. The sands of the Diablo alluvial-fan deposits at the Huron site rarely contain more than 60 percent sand and generally have 6—20 percent clay (Johnson and others, 1968, table 4). The fine-grained beds in the alluvial-fan deposits contain large amounts of clay. The clay content of 61 percent for the sample at the 397-foot depth in figure 49 was the maximum noted for the samples taken from fan F57 RESISTIVI'ZFY, IN OHMS m/m 20 0 350 \47 18 400 0.00007 ( L 57 3 450 m 5 ~ 5: DEPTH, IN FEET BELOW LAND SURFACE 0.7 --—> _? (— Vertical permeability in gallons per day per square foot J’From consolidation test Percentage sand Percentage clay 500 FIGURE 49.ABedding, lithology, and vertical permeability of the Diablo alluvial-fan deposits, Mendota site, depth 350—500 feet. deposits in the upper 600 feet. Clay contents in the 30—50 percent range in the finer grained beds at both the Mendota and Huron sites are more common than clay contents of more than 50 percent. The coarse-grained Diablo fan deposits are less permeable than the coarse-grained Sierra flood-plain deposits. The effect of the generally poor sorting of the fan deposits (Meade, 1967, fig. 12) tends to make the sand beds of the fan deposits have moderate to low permeabilities. For example, the sample from a depth of 472 feet in figure 49 contained 47 percent sand, but had a vertical permeability of only 0.7 gal day‘1 ft’2. The minimum permeability measured (in a per- meameter) in samples from the fine-grained beds in the fanzdeposits at the Mendota site was 7 X 10‘5 gal day’1 ft— . DIABLO FLOOD-PLAIN DEPOSITS Bedding of the Diablo flood-plain deposits at the Mendota site is shown in figure 50. The Diablo flood-plain deposits have abundant thin clayey and sandy beds. Characteristically, 4—8—foot-thick beds of clayey materials are interbedded with sand beds that range in thickness from less than 10 feet to more than 50 feet. The electric logs indicate that more abrupt F58 RESISTIVIT2‘Y, IN OHMS m/m 0 10 20 1050 1 _ 12 ~ 18 0.0001 36 22 D 20 0.004 E?‘ 24 56 ’ :: 16 g 42 :_ «e——\_ 82 E 0.94 _ (i 9 3 I 14 D 7 1100 7 8 0.0006 :2 38 _ ———————— -) f 9—774k 7 Z > d 3 174‘...%>L<— 7 E 3 50 a: ‘— 84 m f 7 m 5 .— 2: _ uJ £<--/ 28 I.L| u. E 3— I‘ 1150 — :5 ’ '_ __ 1:. Lu 0 Vertical fr;— permeability Z Percentage sand in gallons per Percentage clay day per square 1200 A foot 7 FIGURE 50.—Bedding, lithology, and vertical permeability of the Diablo flood-plain deposits, Mendota site, depth 1,040—1,205 feet. changes in lithology occur in the Diablo flood-plain deposits than in the other types of deposits. Thin beds of clayey and silty materials within the thicker sand sections are much more common than in the Sierra flood-plain deposits, and the sand beds within the sand sections appear to be more variable in lithology than those in the Sierra flood—plain deposits. The lithology of the sand beds appears to be that of clean sands, as in the case of the Sierra flood-plain deposits. In many of the sand beds, the amount of sand-size material ranges between 80 and 90 percent, and the amount of clay minerals is less than 10 percent. Only one sample from a fine-grained bed had a clay content of more than 36 percent, and the maximum clay contents for most of the fine-grained beds were about 20—30 percent. However, the fine-grained beds do contain large amounts of silt. Half of the beds sampled (fig. 52) had silt contents between 40 and 68 percent. The laboratory permeabilities of the Diablo flood—plain deposits also are different from those for the other types of deposits. For the sand beds, the permeabilities appear to vary with the degree of sorting. Well sorted beds have moderate permeabilities, STUDIES OF LAND SUBSIDENCE but sand beds that contain more than 15 percent silt and clay tend to have moderate to low permeabilities. Three sand beds that contained 72—76 percent sand had vertical permeabilities of only 1—2 gal day‘1 ft—2. The mean permeability of the fine-grained beds is three times the mean permeability of the more clayey Diablo alluvial—fan deposits (tables 5, 6). SIERRA DEL'l‘AlC DEPOSITS Beds that are considered to be deltaic deposits (Miller and others, 1971) derived from the Sierra Nevada are shown in figure 51. The bedding of the fine-grained deltaic deposits at the Huron site is distinctive when compared with the bedding of the other types of de- posits. Thick beds of a dominant lithology do not occur; instead, alternating beds of silty clay and clayey silt seem to be typical of the Sierra deltaic deposits at this site. Between depths of 2,000 and 2,075 feet, the mean bed thickness is about 4 feet, but below 2,075 feet, the mean bed thickness is only 1 foot. To the east of the Huron site, the deltaic beds consist of thick bedded crossbedded micaceous arkosic sand (Miller and others, p. 107). The coarse-grained facies of the deltaic deposits is similar to the Sierra flood-plain deposits in that thick sand beds characterize much of the section. Most of the cores of deltaic deposits at the Huron site have less than 20 percent sand and 15—60 percent clay. The typical lithology of the cores is that of poorly sorted RESISTIVIEY. IN OHMSm/m 0 1o 20 2000 ”J ‘4 00006 ‘ 16 2 0__,-O 31 u. I D m _ D <2: __ _1 16 g 2050 i 14 '—‘ O —1 ”=— uJ ‘r— m i¢~ 10 ,_ _ 56 17 u] LU g u. 3 E E a. _ 2 4T?— 14 LL! 0 00 a? <——— 5—1 0 Vertical E7, 2100 _ permeability <3) * in gallons per — Percentage sand day per square Percentage clay foot ‘4 From consolidation test FIGURE 51.—Bedding, lithology, and vertical permeability of the fine-grained facies of the Sierra deltaic deposits, Huron site, depth 2,0001114 feet. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 mixtures of sand, silt, and clay. Most of the sand sec— tions were not recovered during coring. The permeabilities of both the silty clay beds and the clayey silt beds is low. For the five samples tested in a permeameter, the2 range in per—meability was from 4x10 4to 3X102 gal day 1f The mean of two permeabilities derived from consolidation tests in the 800—1,600- lb in 2load range was about 1X10 6gal day‘1 ft—2 LACUSTRINE DEPOSITS A microlog of the Corcoran Clay Member of the Tu- lare Formation at the Mendota site is shown in figure 52. Cores indicate that the Corcoran occurs between depths of 625 and 700 feet and that it is underlain by Sierra flood-plain deposits and overlain by Diablo flood-plain deposits. The 6-foot sand beds that occur immediately above and below the Corcoran may be equivalent to thicker lacustrine sands that Miller (Mil- ler and others, 1971) found associated with the Cor- coran south of the Mendota site The bedding of the Corcoran 1s closer to being massive than any of the other types of depos1ts The lower 20 feet of the Corcoran is distinctly coarser grained and of more uniform lithology than the upper 55 feet, as is indicated by both the electric and core logs. The coarser grained basal part is typical of the Corcoran throughout the study area. The typical sequence of the upper part is RESISTIVI‘IgY, IN OHMS m/m o ‘ 10 20 600 ,_ Percentage sand Percentage clay in U E 0.005 (_ A n: 40 D m S 1 <7. 650 # 47 a .1 0.004 1 _ _23 g c 32 3 S ._ 1 o I: g 37 I- U B} , E 1 (__ _ _, u. 32 E m (— _ , f <__ 31 I F n. "J 0 0000414 <— 4 D 700 — #——>' 25 1 Vertical _ permeability — <— % in gallons 0 per day per <—*' 1—9 square foot l/From consolidation test FIGURE 52.—Bedding, lithology, and vertical permeability of the Corcoran Clay Member of the Tulare Formation and adjacent deposits at the Mendota site, depth 600—721 feet. F59 alternating beds of silty clay and sand-silt-clay, which commonly are less than 1 foot thick. The lithology of the Corcoran and adjacent deposits, as indicated by the particle-size analyses, is as follows. In the upper part, the beds of silty clay contain more than 40 percent clay, and the beds of clayey silt contain 30—40 percent clay. The clayey silt in the lower one- fourth of the Corcoran contains about 25 percent clay. Sand was present in all the samples, but many beds have only 1 percent sand. The maximum sand content was 27 percent. The bed considered to be a lacustrine sand beneath the Corcoran is a clean well-sorted sand, containing 80 percent sand and only 3 percent clay. The permeabilities of the beds within the Corcoran are consistently low, having a permeability of about 5x10 3gal day 1f 2(mean of three permeameter tests) or about 4X 10 5 gal day‘1 ft 2 (mean of three consolidation tests, load range 400—800 lb in_2). Minimum permeabilities from consolidation-test re- sults of the Diablo fan deposits were about the same as the minimum permeability observed for a sample from the Corcoran. l.ATERAL EXTENT Lateral extent, as well as bed thickness, is important in determining drawdown and seasonal fluctuation in the vicinity of irrigation wells. Extensive aquifers—as compared to a lensing aquifer system of variable permeability—will tend to reduce drawdown at the wells and increase the seasonal head declines at the midpoints between the wells. The general lateral extent of four of the types of de— posits can be evaluated by study of their modern coun- terparts. Deltaic sediments are not being deposited in the San Joaquin Valley at the present time. The deposits with the most extensive bedding are the lacustrine clays and sands. One of the diagnostic fea- tures of lacustrine clays such as the Corcoran is their unbroken continuity over thousands of square miles. The thin beds within the lacustrine clays commonly extend for distances of more than several hundred yards. The lacustrine sands are a littoral facies formed by the winnowing action of waves. The sands extend over great distances because they are deposited chiefly during expansions and contractions of a lake. The flood-plain deposits consist mainly of point-bar deposits, overbank deposits, and quiet water deposits. A lensing nature is typical of these deposits, but consider- able lateral continuity of permeability is provided by adjacent point-bar deposits of similar permeabilities. The extent and thicknesses of the lenses probably are greater for the Sierra than for the Diablo flood-plain deposits because the perennial streams from the Sierra Nevada were larger than the perennial streams from the Diablo Range. - . F60 The modern Diablo alluvial-fan deposits lense more than the other types of deposits. Although individual beds may extend for more than 1,000 feet along the radial lines of deposition of a fan, the lateral extent along the fan contours generally is less than 500 feet. COMPARISON OF BED-THICKNESS FACTORS The Terzaghi theory of consolidation (see section “Bedding”) states that the time, t, needed to establish a specified degree of compaction (pore-pressure decay) in an aquitard that is being drained through both the upper and lower surfaces is a function of the half- thickness of the bed, h, t=c(h/2)2 The coefficient, c, is used for T/cv because variations in the time factor and the coefficient of consolidation are not considered in the following bed-thickness evalua- tion. This section evaluates the effect of bed thickness on the relative time needed for a specified percentage of compaction to occur in lower-zone aquitards at the four Inter-Agency Committee core—hole sites. The results of the study are summarized in tables 7 and 8. Micrologs (microinverse 1 inch X 1 inch logs) of the core holes were used to estimate quantitatively the ef- fects of differences in bed thicknesses for the suites of deposits at each core-hole site. The bed-thickness study also provided a way of assessing the relative times needed for attainment of equilibrium pore pressures for the different types of deposits. The procedure was as follows. The effect of tempera- ture increase with depth on resistivity was accounted for by drawing a drift line on the electric log, touching the left edges of the beds of minimum resistivity. Aquitard bed thicknesses were measured along a line that was parallel to the resistivity drift line and was offset sufficiently to be to the right of low resistivity beds in the Corcoran. Beds that extended to the left of the measuring line were classed as aquitards, and those parts of the mi- TABLE 7.-—Summary of lower-zone weighted mean bed- thickness factors of aquitards for types of deposits and I nter-Agency Committee core-hole sites Weighted mean Deposit or bed-thickness factor core hole Genetic type of deposit: Sierra deltaic ______________________ 11 Sierra flood plain __________________ 16 } E Diablo flood plain __________________ 11 Diablo alluvial fan __________________ 24 Lacustrine __________________________ 61 Core-hole site: Oro Loma __________________________ 16 fi— Mendota __________________________ 11 Cantua ____________________________ 34 — Huron ______________________________ 15 l 24 STUDIES OF LAND SUBSIDENCE crolog to the right of the measuring line were classed as being chiefly aquifer material. It is unlikely that the “aquitard” beds have sufficient permeability to be con- sidered aquifers. One way to illustrate the conservative approach used would be to check the amounts of silt and clay in the material classed as aquifer material. For example, in the depth range 1,265—1,342 feet in the Mendota core hole, both micrologs were to the right of the aquitard measuring line, and thus no aquitard beds were counted in this depth interval. The coring process recovered samples with the following amounts of fine-grained material (Johnson and others, 1968, p. A48): Depth (top of Percentage silt Percentage clay 0.5-ft sample) and clay <0.004 mm 1,269.5 __________________________ 46 24 1,271.0 __________________________ 29 16 1,284.0 __________________________ 14 8 1,293.0 __________________________ 46 21 1,300.0 __________________________ 38 21 1,312.0 __________________________ 75 25 1,319.4 __________________________ 37 17 1,330.8 __________________________ 35 19 1,339.5 __________________________ 83 21 The mean silt and clay content of the samples was 45 percent, and the mean clay content was 19 percent. It is apparent that some beds to the right of the aquitard measuring line have permeabilities characteristic of aquitards. The lateral extent of the ”aquifers” adjacent to the aquitards also may be important in controlling expul- sion of water from aquitards. If lensing reduces the permeability of the aquifers, but not to the extent of being equal or less than the vertical permeability of the aquitards, lateral changes in aquifer permeability are of little importance because water can be transmitted by the aquifers more rapidly than it can be expelled from the aquitards. If, however, clayey sand lenses are completely enclosed by aquitards, bed thicknesses (as measured on the microlog) are less than the effective thicknesses of the aquitards. The degree of lensing, in decreasing order of impor- tance, for the various types of deposits is alluvial fan, flood plain, deltaic, and lacustrine. It was considered unlikely that beds a few inches to 1 foot thick could maintain lateral hydraulic continuity to the nearest well (mean distance about one-half mile), particularly in the alluvial—fan deposits. Thus, intermediate- and high-resistivity beds less than 1 foot thick were included in the aquitard thicknesses. 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Weighted mean bed-thickness factors for the lower-zone deposits, based on the data from the four core holes, are sum- marized in table 8. The mean bed—thickness factors for the genetic types of deposits range from 1 1 for Sierra deltaic deposits to 61 for lacustrine deposits. Although low, the value of 11 for the deltaic deposits probably is higher than that for the coarser grained Sierra deltaic deposits to the east and southeast of the Huron core-hole site (the only site where this type of deposit was penetrated). The flood-plain deposits have a mean bed-thickness factor of 14, with thicker aquitards being present in the Sierra than in the Diablo flood-plain sequences. The thicker aquitards in the Sierra flood-plain deposits may be a function of larger rivers entering the area from the Sierra Nevada than from the Coast Ranges. Fine- grained deposits, such as would accumulate in oxbow lakes and in backswamp areas, should have been pro- portionately thicker along the rivers from the Sierra Nevada than along the smaller streams from the Coast Ranges. ' Diablo alluvial-fan deposits tend to have distinctly thicker aquitards than either the flood-plain or deltaic deposits. The bed-thickness factor of 24 results in part from the relatively large proportion of intermediate- resistivity beds less than 1 foot thick in the fan deposits. The thickest aquitards occur in the sequences of lacustrine sands and clays, as shown by the large mean bed-thickness factor of 61. The 86- and 75—foot Corcoran aquicludes at the Oro Loma and Mendota sites were not included, but the 3—14-foot—thick clayey beds within the Corcoran at the Cantua and Huron sites were included in the analysis of lacustrine bed thickness. Other factors being equal, the mean bed-thickness factors for the different types of deposits indicate the potential for residual excess pore pressures within the lower zone. Flood-plain or deltaic sequences should compact rapidly, but lacustrine sequences can be ex- pected to have maximum residual excess pore pres- sures. Alluvial-fan sequences are intermediate in the amount of time needed for pore-pressure equilibrium to be attained. The mean bed-thickness factors at the core-hole sites reflect the types of lower-zone deposits. The deposits at the four core-hole sites consist of two to four genetic types of deposits. The lowest bed—thickness factor is for the Mendota site, where 80 percent of the aquitard beds are in flood-plain deposits. The Oro Loma and Huron sites have similar mean bed-thickness factors, but greatly different types of de- posits. At Oro Loma, flood-plain deposits predominate, but lacustrine beds are present also. At the Huron site, Sierra deltaic deposits in the deepest 400 feet of the core STUDIES OF LAND SUBSIDENCE hole reduce the effect of 1,000 feet of alluvial-fan de- posits on the mean bed-thickness factor. At the Cantua site, flood-plain, alluvial—fan, and lacustrine deposits are abundant in the lower zone. All three types of deposits have many thick aquitards, re- sulting in a high mean bed-thickness factor. On the basis of mean bed-thickness factors, the Cantua site has greater potential for residual excess pore pressures than the other three sites. With only four sites evaluated in a 2,000-square-mile subsidence area, firm conclusions cannot be drawn re- garding the effect of areal bed—thickness variations on residual compaction in the northern and southern parts of the study area. However, the mean bed-thickness factors of 14 for the northern and 24 for the southern parts of the area agree with other evidence that sug- gests greater amounts of residual excess pore pressure in the southern part of the area. COMPACTION CHARACTERISTICS Laboratory tests made on 18 samples from the Cor— . coran and the various types of lower-zone deposits pro- vide some general information regarding the consolida- tion characteristics of the fine—grained beds in different genetic types of deposits. Table 9 gives the mean parameters of the compressibility (compression index) and the rate of consolidation (coefficient of consolida- tion) for the 18 consolidation tests. Most of the conclu- sions derived from the results of the tests should be regarded as tentative because of the small number of tests involved. The results indicate the following de- creasing order of compressibility for the fine-grained beds: lacustrine, Diablo flood plain, Diablo alluvial fan, and Sierra flood plain. The rate of consolidation for the suites of samples decreases in the following order: Di- ablo flood plain, Sierra flood plain, lacustrine, and Di- ablo alluvial fan. The consolidation tests suggest the following generalizations. The lacustrine deposits should un- dergo large amounts of compaction, but over long periods of time. The Sierra flood-plain deposits should undergo only moderate amounts of compaction, and the compaction should occur fairly rapidly. The Diablo TABLE 9.—Mean consolidation characteristics of the Corcoran and the different types of lower-zone deposits in the load range 400—800 lb in ‘2 [Samples from fine-grained beds at the four Inter—Agency Committee core-hole sites] Mean Mean Number compression coefficient of index? of consolidation Source‘ tests (CC ) (CU, in ftz/yr ) Diablo: Alluvial fan ,,,,,,,,,,,,,,,,,,,,,,,,, 6 0.37 81 Flood plain ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 6 .46 328.5 Sierra: Flood plain ,,,,,,,,,,,,,,,,,,,,,,,,,,, 2 .33 20.8 Combined Diablo and Sierra: Lacustrine deposits ,,,,,,,,,,,,,,,,,,, 4 .82 17.5 lFrom Miller, Green, and Davis (1971). 2From Johnson, Moston, and Morris (1968, table 9). 5Median instead of mean used because of one excessively large value. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 alluvial-fan deposits should undergo moderately large amounts of compaction, but long periods of time will be required for ultimate compaction to be achieved. The Diablo flood-plain deposits should undergo moderately large amounts of compaction, and the compaction should occur more rapidly than for either the alluvial— fan or lacustrine deposits. Evaluation of the bedding, lithology, permeability, and lateral extent of the five types of deposits discussed in figures 48—52 results in conclusions similar to those derived from the consolidation tests regarding the dif— ferent amounts and rates of compaction in response to increase in applied stress. The following interpretations should be considered as generalizations. The Sierra flood-plain deposits should compact the most rapidly because of their high permeability, but the total amount of compaction should be smaller than for the other types of deposits because sections of sand thicker than 50 feet that contain less than 10 percent clay are common. The presence of mica in the Sierra sands results in higher elastic and inelastic components of compaction than in sands containing no mica. The Diablo alluvial-fan deposits contribute substan- tially to the large amounts of compaction that have occurred in the southern part of the area because of the fine-grained compressible nature of most of the fan de- posits. The many coarser grained beds of varying thick— ness furnish a means of escape for the water being expelled from the slowly draining intercalated clay beds. However, the rate of compaction for a given in- crease in applied stress probably is less than for either the Sierra or Diablo flood-plain deposits. The combined effects of large amounts of clay, even in the aquifers, and the highly lensing character of the overall suite of fan deposits tends to retard the expulsion of water from the aquitards and create a condition favorable for large amounts of residual excess pore pressure. The Diablo flood-plain deposits have characteristics that are almost ideal for large amounts of compaction to occur rapidly. Large amounts of compressible clayey material are present, and most of the beds of clayey material are only 4—8 feet thick. Almost 90 percent of these aquitards at the core-hole sites were less than 9 feet thick (table 8A). Although they contain large amounts of silt and clay, the highly compressible fine-grained beds Within the Diablo flood-plain deposits have higher permeabilities than the fine-grained beds of the alluvial-fan deposits. Sand beds with good to moderate permeability, and having large lateral ex- tents, commonly occur between the clay beds, thus pro- viding ready avenues of drainage for the water expelled from the clayey beds. The fine-grained facies of the Sierra deltaic deposits might be expected to compact to a moderate extent over F63 a long period of time. The ultimate specific unit compac- tion of the Sierra deltaic deposits probably is less than that of beds with similar petrologic characteristics in the upper zone because of the large stresses that have been applied to the deeply buried deltaic deposits in the geologic past. The compaction characteristics of the Corcoran should be opposite to those of the Sierra sands. The Corcoran is highly compressible, but the rate of compac- tion is very slow because of the great thickness and low permeability of this lacustrine unit (Miller, 1961). The low permeabilities of even the clayey silt beds more than offset the tendency of good lateral extent of the beds to cause a more rapid rate of compaction. Pore pressures in the middle of the thickest lacustrine clay beds may not have declined much, despite the large declines in pore pressures in the aquifers above and below the Corcoran. Analysis of the compaction and water-level record at the Lemoore site suggests that compaction may continue at a very slow rate in lacus— trine clays after artesian-head recovery in the aquifers of 50 feet from the previous summer low. REGIONAL RELATIONS Areal variations in the age, prior total applied stress, mean lithology, and source and mode of deposition of the deposits are responsible for much of the areal variations in the amounts of compaction upon increase in applied stress caused by pumping of ground water in the Los Banos—Kettleman City area. Both the degree of varia- tion of these geologic factors and their effect on man- caused compaction and subsidence will be the subject of this section. AGE OF THE DEPOSITS The older deposits in the study area have had more time in which to undergo diagenetic changes, which have increased their ability to withstand further in- crease in applied stress. Diagenetic changes not only include sufficient time for the compaction of thick clay beds, but also cementation of the sandy deposits result- ing from precipitation of part of the dissolved solids from water passing through the deposits or from solu- tion of part of the grains at the points of contact and redeposition in the areas of lesser grain-to-grain pres- sure. Mineralogic changes occur also with changing pressure, temperature, and chemistry of the contained waters. Most of the Pleistocene deposits are considered to be unconsolidated, even though in part they are buried to depths of more than 1,000 feet. The Pliocene marine and continental deposits show more effects of time when compared with Pleistocene deposits of similar lithology. The clayey deposits, instead of being plastic when han- dled, are sufficiently brittle that samples will break F64 when struck with a hammer. The sandy deposits, in- stead of being loose, are sufficiently cemented that they are cohesive, but friable to the touch. Lenses or con- cretionary nodules of calcareous sandstone are com- mon. The degree of lithification of the Pliocene water- bearing deposits is not advanced, however, and weath- ered outcrops of Pliocene materials commonly appear to consist largely of unconsolidated materials. The following stratigraphic and descriptive informa- tion about the deposits tapped by water wells in the study area is summarized from Miller, Green, and Davis (1971): Formation Age Lithology Depositional environment Tulare ,,,,,,,,,,,, Pliocene and Sand, silt, Continental—alluvial fan, Pleistocene. and clay. flood plain, lacustrine, deltaic. San Joaquin ,,,,,,,, Pliocene ............ Clay, silt, Marine and continental. sandstone. Etchegoin1 ________ Pliocene ,,,,,,,,,,,, Sand and silt, Marine, fluviatile, blue to lacustrine. brown. Kreyenhagen ,,,,,, Eocene and Organic, Marine. Oligocene. siliceous shale. ‘Upper part tapped by water wells south and west of Cantua Creek (town). A map showing those parts of the area where wells tap the pre-Tulare marine and continental Pliocene de— posits is shown in Part 1 (Bull and Miller, 1974, fig. 15). Two such areas are present adjacent to the foothills of the Diablo Range—one opposite the Panoche Hills and the other opposite the Big Blue Hills and Anticline Ridge. In the northern area the wells are shallow, some of them reaching the Kreyenhagen Formation at depths ~. of only 1,200 feet, and the bulk of the water pumped by the wells is derived from flood-plain deposits within the Tulare Formation. In the southern area, wells as deep as 3,500 feet tap the marine sands of the Etchegoin and San Joaquin Formations. Most of the ground water pumped within 5 miles of the Big Blue Hills probably is derived from these Pliocene deposits. Amounts of subsidence have been minor where wells derive‘ most of their water from the Etchegoin Forma- tion or other pre-Tulare Pliocene deposits. The artesian head has declined as much as 500 feet in the area adja— cent to the Big Blue Hills, but only about 1 foot of subsidence has occurred. The low specific compaction of these deposits indicates that the Pliocene deposits are much less compressible than the deposits of the overly- ing Tulare Formation. Part of the reason for the sharp decrease in subsidence on the west end of profile B—B’ of figure 17 may be attributed to the fact that the wells derive their water in part from pre-Tulare formations. SPECIFIC UNIT COMPACTION OF THE LOWER-ZONE DEPOSITS In evaluating the long-term relations between change in applied stress and compaction, Bull (Pt. 3, Bull and Poland, 1974) derived a specific compaction map of the lower zone for 1943—60. In making the map, STUDIES OF LAND SUBSIDENCE the following factors were evaluated: (1) the one compo- nent of stress change caused by lower-zone artesian- head decline, (2) the three components of stress change caused by change in the position of the water table, and (3) total subsidence for the period and the proportion of subsidence that was due to lower-zone compaction. Compaction of the lower zone in the 1943—60 period was estimated, utilizing the observed proportions of com- paction occurring in the lower zone in the 1960’s (fig. 45; see also section “Proportions of Compaction Occurring in the Upper and Lower Zones,” paragraph 3). The specific unit compaction of the lower-zone de- posits can be computed by dividing the specific compac- tion by the thickness of deposits undergoing pore- pressure decline. The perforated interval of the lower zone is used for this purpose. The maximum thickness of the lower-zone perforated interval is based on the well tabulation compiled by Ireland (1963), which lists the perforated-interval data for wells drilled before 1962. Since 1960, fewer wells have been tapping the brackish waters that occur at the base of the lower zone, but the tabulation is an excellent source of information regard- ing the distribution of perforated intervals of pumping wells during the 1943—60 period. The maximum thickness. of the perforated interval of the lower zone is shown in figure 532. The thickness of lower-zone deposits being tapped ranges from less than 400 feet to more than 2,400 feet. The general pattern is one of overall increasing thickness of perforated inter— val toward the southwest. Thicknesses of more than 1,800 feet occur in the areas of pumpage from the Etch- egoin Formation. In the Vicinity of Fresno Slough and Kings River, the thickness of fresh-water-bearing de- posits extends below the base of the perforated interval (Miller and others, 1971, pl. 4), but wells can obtain a sufficient yield without penetrating the full thickness of fresh-water-bearing deposits. Pore—pressure decline may be occurring below the base of the perforated inter- val in the vicinity of Fresno Slough and Kings River as a result of the large amounts of water being pumped from the deeper aquifers farther to the west. An example of this type of head decline is shown at the Yearout site by Bull (Pt. 1, Bull and Miller, 1974, fig. 24). The specific unit compaction map for the lower zone, 1943—60, is figure 54. The values would represent the variation in compressibility of the lower-zone deposits if pore-pressure equilibrium had existed throughout the aquifer systems in 1943 and 1960. The specific unit compaction ranges from about 0.5 to more than 10.0X10—5 ft‘1 (foot per foot of aquifer-system thick- ness per foot of increase in applied stress). Because of the complexity of the many factors used in computing regional specific unit compaction, the purpose of the 2Same as figure 18, Part 1; construction of map described in Part 1 (Bull and Miller, 1974). LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F65 2030’ 120.00 33 I 52 Los Banos 152 / / a I _ Dos 37 00 Palos / ~—’\_F_":e§10/"~-—\\__\ ,._/‘~‘¥I§iver , ‘ ’ ‘ ‘ Madera 33 e / V; I re / ¢ 0° V O hdo" 99 5 0 0a,? Q 20 / ’ Firebaugh RIVER 3‘? $0) 09° {3 l 400 0 § Q50 AQU 43- 09 " ‘900\ 0 FRESNO n O ,0 M endota (V 716 _/—\’ m l 130 \‘ L <3)(O 9% A ch? ‘3. Kerman . J" ‘3; :3 \fq’o 41 Q S \ m x \ \ § ‘ ‘5 \ «‘00 \ \ ‘ \‘ A \ \ \ \ \\ \\ \ \ ’00 "o \ \ t 2% \ \e \‘ (e " \ % \ \ k MOM-)0 /A \\ ‘ ’\ x 4 _ We F \ ’\ 3,06 36 :30: __ 96‘ 9,0 Cantua Creek \\ \4 \ _ 9L o<6 ‘4. \ N, \ O \ \ \ s? \\ \ x ’9 (0‘ :3 ) w “ ‘74, / / fa <38 % - Five Points \ ‘ 2200 h - . \ 06‘ 2400 ‘3 — — — — - EXPLANATION ( /’ 77777277777, Boundary of deformed roc ks Generalized line of equal maximum thick- ness of the perforated interval of the low- er zone for wells drilled before 1962. Short dashed where approximately located; . Strat- long dashed for thickness below estimated ford stratigraphic equivalent where Corcaran is absent. Interval 200 feet Western boundary of the Corcoran Clay Member of the Tulare Formation TULARE LAKE 0 5 1O 1 5 MI LES Kettleman BED 36°00’ O 5 1O 15 KILOMETRES 1 City Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 53.—Maximum thickness of the perforated interval of the lower zone map should be to illustrate general variations rather than to show precise values of specific unit compaction. In the southern and central parts of the study area, values of specific unit compaction generally are be- tween 1 and 3 X 10—5 ft‘l, but in the northern part of the area values of specific unit compaction generally exceed F66 STUDIES OF LAND SUBSIDENCE 120°3o' 120000, 33 1 Los Banos 152 / / 37°00'» D05 Palos / ~.a\_€r_emv-—a / 33 m Del!a / ‘ZL Meade,” Ca ,1” Firebaugh Qgfip l0 2 ‘0 C%é 00 V“ e o IQ? 0/ O 4, Mendota (7 71° Q‘o 130 ,' 6} 9;, 4} V .. Kermanc O “‘ \ e ’ 1; Jae (( H m \‘:,V e, _ ‘ A .3, (I \/ ‘\ ’< 476“ ‘ (6‘ \‘ 44 ‘~ O'VOo “\\_ ([4] ’Kflg‘ 36°30’ — 0/6 9/0 oCantua Creek \4 91— Ge o a \ \ ,5) (d, 2.5 ‘7¢ 1.5 Five Points \ 06‘ \0-5 {0 N e, I O 33\ e(% \ EXPLANATION ,7, u («5‘ 773;;737337 \ :3 Boundary of deformed \ / \9 l rocks / 1 . 2.5 / / \ Westhaven l . . . / Generalized line of equal compaction per / 9/0 Hurono . unit increase in applied stress per unit a 00:41, ) thickness (maximum perforated interval PL SANT 00.) of the lower zone). lnterval,in feet per / $0 ’00 foot squared x10? varies Coalinga (veg/0Q, VALLEY offgé Western boundary of the Corcoran Clay Member of the Tulare Formation k ’ \ TULARE 4‘) r4641 LAKE o 5 1o 15 MILES 4497 F—w—L—r—T—L——" , IQ .Kettleman BED 36°00, o 5 1o 15 KILOMETRES // 33 .9 I City Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 54l—Specific unit compaction for the lower water-bearing zone, 1943—60. 3 x 10‘5 ft—l; northeast of the Delta-Mendota Canal, Thus, the most important feature of the map is a values of specific unit compaction generally exceed distinct indication that the deposits in the northern part 10 X 10—5 ft‘l. of the area apparently are four times as compressible as LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 the deposits in the central and southern parts of the study area. The maximum value of the line of equal specific unit compaction for the northern part of the study area is four times that for the southern part of the area. Means of specific unit compaction from a 91-point grid also show a fourfold difference when a subarea north of the north boundary of township 16 south is compared with a subarea south of that boundary. Most of the rest of this section will be devoted to consideration of various geologic and hydrologic factors in an attempt to determine whether the deposits in the northern part of the area are indeed more compressible or whether other factors such as the rate of compaction of different genetic types of deposits are important in causing the contrast in specific unit compaction in the northern and southern parts of the study area. GEOLOGIC FACTORS INFLUENCING SPECIFIC UNIT COMPACTION PRIOR TOTAL APPLIED STRESS One of the geologic factors that might cause the lat- eral variation in specific unit compaction is the varia- tion in stress that was applied on the lower—zone de- posits in the northern and southern parts of the area before the 1943—60 period. In the northern part of the area, the depth to the base of the lower zone ranges from about 1,000 feet to about 2,000 feet, whereas in the central and southern parts of the area, the depth to the base of the lower zone ranges from about 1,300 to about 3,000 feet. The difference in depths to the base of the lower zone suggests the hypothesis that in the central andsouth- ern parts of the area, the greater prior total applied stress has already compacted the deposits to such an extent that they are less compressible per unit increase of additional applied stress than the deposits in the northern part of the area. The effect of prior total ap- plied stress on compressibility of the deposits at the Westhaven site was discussed in the section “Overbur- den Load,” paragraph 3. This hypothesis can be evaluated by determining the total applied stress on the middle of the lower zone and then by taking the product of the total applied stress on the middle of the lower zone and specific unit compaction to largely remove the effect of prior total applied stress. The depth to the middle of the lower zone is shown in figure 55. The middle ofthe'lower zone was selected as a reference surface on which to define the total applied stress as of 1943—the beginning of the 1943—60 period used for computation of specific unit compaction. Max- imum depths to the middle of the lower zone are the same in the northern and southern parts of the area —about 1,500 feet. In the central part of the area, max- imum depths exceed 2,000 feet in the area of pumpage F67 from the Etchegoin Formation. The minimum depths to the middle of the lower zone are less in the northern part of the area—600—800 feet—than in the southern part of the area—800—1,000 feet. The depth would be roughly proportional to the total applied stress on the middle of the lower zone if the entire section were saturated and if no confining beds were present to cause potential head differentials. Be— cause unsaturated deposits and confinement exist in the study area, corrections have to be made to figure 55 to derive the total applied stress on the middle of the lower zone. The gravitational stress of the saturated deposits is roughly equal to 1 foot of water per foot of thickness. The total applied stress of the deposits above the water table is about 1.8 foot per foot (assuming a mois- ture content of 0.2 the volume). The additional stress due to the unsaturated condition of the deposits above the water table is shown in figure 56. The lines of equal applied stress were computed by multiplying the thick- ness of deposits above the water table, as of 1951, by 0.8. The lack of saturation of these deposits results in a correction factor that locally increases the stress on the middle of the lower zone by more than 200 feet of water. The component of increased applied stress is minor in the northeastern part of the area, but in much of the area, the stress was 50—200 feet of water greater, as of 1951, because of the large thicknesses of deposits above the water table. The difference in applied stress on the lower zone resulting from differences in the position of the water table between 1951 and 1943 is minor. Although a water-table map is not available for 1943, spot checks indicate that the position of the water table was within 40 feet of the 1951 position. Although 40 feet of water- table change would cause 32 feet of stress change in the water-table aquifer as a result of change of the satu- rated condition of the deposits, the net effect of water- table change on the total applied stress on the lower zone is minor. The change in seepage stress resulting from water-table change more than offsets the stress change due to change in saturation of the deposits. The net effect is only 0.2 foot of water per foot of change in position of the water table (Pt. 3, Bull and Poland, 1974). Forty feet of water-table change would cause only 8 feet of net change in applied stress on the lower zone. If the maximum error introduced by using the 1951, instead of the 1943, water-table data is 10 feet of net stress change on the lower zone, it can be readily concluded that the magnitude of the error is insignificant compared to the 200-foot interval used for the 1943 total applied stress map (fig. 58). The other correction component that needs to be ap- plied to figure 55 to get the total applied stress on the middle of the lower zone is the seepage stress caused by F68 STUDIES OF LAND SUBSIDENCE 120°3o' 120.00, 33 I 5 Los Banos 15 / / 37°oo'— D05 / , Palos N / ‘—’\E’L¢flg”‘—'\\___\ ,J ~¥1§iVer , 33 ’ " Madera 0” / ”2 o ”’ o O ”adore 6b" m g: C Q ’ 0"" Firebaugh RIVER é? <59? 0 Q3- Q-Og ’0 0% ‘ “8) %é AQU‘N /QQ' o9 " 1000 10 1711133110 Mendota O ‘6 <7 7% ’200 a \ L 0( 9;. Kermanc I“ O 6‘ ’3 0 («n ’ A 2% (<69. 4'0 4/ 004/ /\ [Vs F 36°30’ — 0’6‘ '9 .— ‘L Ge . O " e ' Q’ ( '9 <0. v¢ 06‘ _ _ 0,0 °< EXPLANATION <16 77777777777, Boundary of deformed rocks I 1000 ' . . W th Line of equal depth to the mlddle of the \\°s “mo ' ‘23, lower zone Hurono I )2 Interval 200 feet. Compiled from map of \ J ‘ 32:;- half the thickness of the lower zone and 9 map of the depth to the base of the / $0 00 Corcoran Q)“: 09 _ _ _ , v X3399 Western boundary of the Corcoran Clay ’ Member of the Tulare Formation /k I TULARE 9r ' as Q LAKE 4’41 O 5 1O 15 MILES WIYQ Kettleman BED 36,00, 0 5 1o 15 KILOMETRES / 1’ G 4s l - City Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 55.—Depth to the middle of: the lower zone. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 120° 30’ 120°OO' F69 33 l Los Banos Dos o l,— 37 00 Palos 33 "3, '1» Cg”?! \ Mendota 36°30’ EXPLANATION ‘9 ’ Boundary of deformed rocks 50—— Line of equal applied stress due to the un- saturated condition of the deposits above the water table as of 1951 Dashed where approximately located. In- terval, in feet of water, varies. The applied stress is the sum of two components; an added stress due to lack of bouyant support equal to 0.6 foot per foot of un- saturated deposits, and an added stress due to the weight of water contained in the unsaturated deposits equal to 0.2 foot per foot of unsaturated deposits. The total applied stress of the deposits above the water table is 1.8 feet of water per foot of unsaturated deposits, but this map excludes the component of stress due to bouyant weight of the grains. Depth to the water table information is from Davis, Green, Olmsted, and Brown (1 959, fig. 16 ) 0 5 1O 1 Kl METRE 36900, 0 5 1o 5 LO 3 l 15MILES ~.—\_Er_e~m -« Firebau gh , J ‘ - ‘ \lgiver . ' ‘ ’ Madera J oAQUm Kermanc o Cantu. Creek _,\% \\%4 x K'\ . 0 Five Points \ \ Huron o Westhaven o (P 24’ 6‘ \ ofl-_._____ Kettleman City TULARE LAKE BED Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 56.—Applied stress due to the unsaturated condition of the deposits above the water table as of 1951. F70 head differentials between the water table and the potentiometric surface of the lower zone. The 1943 posi- tion of the lower-zone potentiometric surface was used to define the magnitude of the seepage stresses present in the area at the beginning of the 1943—60 period. The water level in wells tapping the lower zone rises as much as 500 feet above the base of the Corcoran, and before 1925 the artesian head was sufficient to cause wells to flow in the eastern part of the area (Pt. 1, Bull and Miller, 1974, fig. 21). However, by 1943, the poten- tiometric surface was below the water table throughout the area, and the resulting seepage stress on the lower zone was caused by, and equal to, the head differential between the water table and the potentiometric surface of the lower zone. The seepage stress on the lower zone, as of 1943, is shown in figure 57. Seepage stress exceeded 100 feet of water in most of the area and locally was more than 200 feet of water. The areas of maximum seepage stress coincide with the areas of maximum pre-1943 pumping of ground water—about midway between Fresno Slough and the Diablo Range. Not all the increase in stress applied to the lower zone as of 1943 had become effective in the fine-grained beds of low permeability at that date. Head differentials occur in the area west of the Cor— coran also, as shown by comparison of the position of the water table and water levels in wells perforated to depths of more than 2,000 feet. Variations of head differentials occur more abruptly in the area west of the Corcoran than in the rest of the area where the Cor- coran is present to provide uniform confinement for the lower zone. The total applied stress on the middle of the lower zone was obtained by adding the stress components shown in figures 56 and 57 to lines of equal depth to the middle of the lower zone, multiplied by 1.0 foot of water per foot of deposits. The combination of these three maps, figure 58, shows that the total applied stress on the middle of the lower zone, as of 1943, ranged from 600 to 2,200 feet of water. Throughout most of the area, the total applied stress was 1,000—1,800 feet. The amounts of total applied stress are about the same in the north- ern and southern parts of the area, except that the area west of Firebaugh is the area of lowest total applied stress in the study area west of the valley trough. The total applied stress in the central part of the area, where wells tap the Pliocene deposits, is almost one-third greater than the maximum amounts of stress that occur to the north and south. The lines of total applied stress were not extended west of the Corcoran, but the total applied stress in the area to the west of Huron seems to be in a narrow range between 1,600 and 1,800 feet of water. STUDIES OF LAND SUBSIDENCE STRESS—COMPACTION PRODUCTS The purpose of making the total applied stress map was to assess the influence of variation in prior applied stress on the apparent compressibility of the various types of deposits. The stress was determined as of 1943. The amounts of estimated compaction and increase in applied stress were obtained for the 1943—60 period. The effect of prior total applied stress on specific unit com- paction for the 1943—60 period was removed by multi- plying the specific unit compaction by the total applied stress. The validity of the use of such a product needs to be examined critically. The use of a simple product of total applied stress and specific unit compaction assumes that an arithmetic linear relation exists between com- pressibility and effective stress. Laboratory consolida- tion tests show that compressibility decreases with in- creasing effective stress. The exponential decrease in compressibility with in— creasing effective stress for both the laboratory and field ranges of stress for two consolidation tests is shown in figure 59. The compressibility plots are from J. F. Po- land (written commun., 1968), and I have added com- pressibility-effective stress products to the plots to show how the effect of variable effective stress can be almost eliminated. Sample A is the test result for the Cantua site that has the most extreme change of compressibil- ity-effective stress product with increasing effective stress. The sample for case A was taken from a thin bed within the Corcoran lacustrine sequence. The compressibility-effective stress products for sample A range from 0.133 to 0.280, showing that for the laboratory (and extrapolated) range of stresses, the use of products does not eliminate the effect of different effective stresses. Although a 110 percent difference is shown by the two extreme compressibility-stress prod- ucts, a substantial reduction in the effects of different effective stresses has been made because the difference in the compressibilities of the two points is 3,600 per- cent. The results of case B are for a sample that is much less compressible than sample A but which has a compressi- bility that probably is greater than the lower-zone clayey sands from the Cantua site for which consolida- tion tests were not made. The change of compressibility- effective stress products is much less than in case A; only a 7-percent change in the products occurs between the end—point values of 0.026 and 0.028. Thus, for de- posits having compressibilities similar to that of sample B, the use of compressibility-effective stress products eliminates most of the effect of different effective stress- es, even for the extreme range of load used in the laboratory. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 1 20 ° 30' F71 120°oo' 33 ” l Los Banos 37°00'— 33 Meadow Ca "’9’ \ I50 36°30’— ’6‘ EXPLANATION Boundary of deformed rocks 150 —— Generalized line of equal stress on the lower zone resulting from artesian-head decline Interval 50 feet of water. Dashed lines indi- cate the head differentials in the area southwest of the Corcoran. Compiled from a map showing the lower-zone potenfiometric surface as of 1943, and a water-table map based on 1951 measure- ments supplemented with pre- 1951 data. The seepage stress has been approxi- mated by using the head differential in- dicated by the position of the water table and potentiometric surface Western boundary of the Corcoran Clay Member of the Tulare Formation 0 5 10 15M|LES O 5 1O 15 KILOMETRES ] ‘ fi. \ Enema ,. _ \-__\ w ‘9 Firebaugh Mendot I 180 , l / Madera Kermanc \ Cantua Creek ’9’ ’o 0 < a. 6w SANT Coalinga VALLEY _,\d% 9 Y TULARE LAKE Kettleman BE City D 36°OO’ Base from U.S. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 57.~Seepage stress on the lower zone as of 1943. The reason that compressibility-effective stress prod- ucts almost eliminate the variations due to effective stress is that the slopes of the lines in figure 59 are close to unity. If the slopes had been substantially different from unity, exponential corrections (rather than simple products) would have been necessary to reduce the ef- F72 120°OO’ 33 I 52 Los Banos 152 / / 3 7 ° ’ — Dos 00 Palos / ~,r\E{e§_fl£—-——\\‘A IJN‘xlgiver , 33 ‘ ‘ ‘ Madera 091,0 / qéz‘ o / 0 V 0 / ehdotq 800 6‘ 99 [5‘ C.) s, 00\ 0 § / ‘2 Firebaugh 31V ER g <5? ‘29 7000 (3‘ Q-C’o ’0 <9 c e é £90 1200 JO A0111“ «3- 0/ FRESNO n O 4 140” Mendota 1 L1 / 7 . L 76, ‘2, 18° no \ (o 9?“ /’6‘00 Karma“ r ’S— \\ 41 ’(( H m \4 \ 000 “9%, ’00” (<06;— . M04, '9 \“’\ 0(2 )7 00 \. I’Vs 00 ’\ 5% o '9 C\ntu reek \‘ (:96 36°30’ — ’99 ’00 a a \ _ L 6‘ 3.. ‘n 0% \ 0° 4> <0 \ Q, 74/0 / 00:0 <0 m9 ‘a o, - % O EXPLANATION e A (06‘ Boundary of deformed ((5. rocks \ 1600 Line of equal total applied stress on the / middle of the lower zone, as of 1943 / / Interval 200 feet of water. Based on maps / 1"? showing the depth to the middle of the 0004’ lower zone, thickness of the deposits ‘2‘ 6‘ above the water table as of1951, and the P'- SANT seepage stress on the lower-zone as of C oalinga {:3 1943 VALLEY Western boundary of the Corcoran Clay Member of the Tulare Formation 4- TULARE e,» 4841 LAKE o 5 1o 15 M I LES “4/,y / /(( Kettleman BED 36°00, 0 5 1o 15 KILOMETRES / 33 6‘ 1 City STUDIES OF LAND SUBSIDENCE 1 20 ° 30' Base from US. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 58l—Total applied stress on the middle of the lower zone as of 1943. F73 LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 .36 55an 2: EE‘. 315$ 28 .5. 3252:; mmuhm ciaocbwkazfimmmoafioo :3 $5 .3525 mmwhm 252$» £2an we 38¢ «:80 :ozosvwmldm nxbofl IUZ. wm<30m Ema wDZDOm Z. .wwwIFw w>_._.Umu_u_w nor "or / «Pi >335 05 / E 333 3:93 .39 *0 33.05 / utoumE E:E_xw_>_ VN >20 0m Hzm @N Her—um acoogom 32 8.9530 .< 3 >20 mm Em R 2.8 «cecal 32 mm? .590 .m cmnoa Had SBHONI auvnos NI'ALI'IIEISSEUdWOD F74 fect of variable effective stress. If we let my be the compressibility and Fe the effective stress, then mv =cPe". The values of n (the rate of change of ml, with respect to Pe) generally are only slightly less than 1.00. The max- imum departure from unity for all the samples tested from the Cantua site is that of sample A. An appraisal of the changes of stress-compaction fac- tors under field—not laboratory—load ranges is neces- sary to complete the assessment of the validity of the approach used in this paper. The maximum possible error introduced by assuming a linear compressibility- effective stress relation can be estimated by using the maximum historic increase of total applied stress that has occurred at the Cantua core-hole site. The increase in applied stress is the result of 400 feet of head decline since about 1900 and, if taken a short distance below the Corcoran, indicates that a 52-percent increase in ap- plied stress has resulted from man’s change in the hy- drologic environment. At the GOO-foot depth at the Can- tua site, the applied stress has increased from 330 to about 500 lb in“2. By taking the extremes of compressi- bility (case A), and increase in applied stress, it can be seen that a change in the products of 0155—0167 occurs—an indication that only 92 percent of the effect of different stresses has been removed. However, in the case of less compressible materials (case B), 99.4 per- cent of the effect of different applied stresses has been removed. Thus, it is concluded that the use of stress- compaction products in this paper does not entirely eliminate the effects of variation in total applied stress within the study area but that more than 90 percent of the effects of variation of total applied stress are re- moved. The stress-compaction products will be used in this paper to evaluate the effects of prior total applied stress, mean lithology, and source and mode of deposition on variations of specific unit compaction between the northern and southern parts of the area. The products are apparent compressibilities, for which the effect of , prior total applied stress has been largely removed. The products are only apparent compressibilities because the degree to which applied stresses have become effec- tive is not known precisely. The product of lower-zone specific unit compaction and the total applied stress on the middle of the lower zone is shown in figure 60. As in the case of the specific unit compaction map (fig. 54), the maximum values of stress-compaction products occur in the northern part of the area. The maximum value of the line of equal stress-compaction products for the northern subarea is twice that for the southern subarea (south of township 15 in fig. 1). Means of stress-compaction products from a STUDIES OF LAND SUBSIDENCE 91-point grid indicate a 24-fold difference between the northern and southern subareas. Thus, the difference in apparent compressibility between the subareas appears to have been decreased by removing the effect of prior total applied stress. The amount of change, however, varies greatly in both subareas. Locally, the apparent compressibility has been decreased 50 percent in the northern subarea and increased 100 percent in the southern subarea, when changes in the apparent compressibility indices at selected points are compared with the mean indices of the other subarea. At other locations, little or no change in apparent compressibility resulted from the use of stress-compaction products instead of specific unit com- paction. Thus, the effect of prior total applied stress is important at some locations, whereas at others the ef- fect of prior stress on apparent compressibility is com- pletely obscured by petrologic factors. A similar conclu- sion was reached by Meade (1968) regarding the factors affecting change of void ratio with depth at the Richgrove core-hole site in the southern San Joaquin Valley. The mean values of specific unit compaction and stress-compaction products for the two subareas sug- gest that the overall difference in apparent compressi- bility between the subareas has been reduced from four- fold for the specific unit compaction to 21/2-fold for the stress-compaction products. Thus, in a general sense, it is concluded that roughly one-third of the compressibil- ity difference between the subareas is the result of dif- ferent prior total applied stresses. The remaining two- thirds of the compressibility difference is ascribed to variations in lithologic and geologic factors. Both the specific unit compaction and the stress- compaction products probably are anomalously high in the extreme northern part of the area because of the low values used for the thickness of the lower zone. Field evidence from compaction recorders indicates that the values of thickness of the perforated interval of the lower zone that are less than 700 feet are too low, but information is not available to indicate the true thick— ness of deposits subject to pore-pressure decline in the area. For example, the 1,000-foot depth for the deepest recorder at the Oro Loma site was selected as being representative of the deepest well perforations in the Vicinity, but comparison of compaction and subsidence (see section “Cumulative Compaction at Multiple Compaction-Recorder Site,” paragraph 7) shows that only 55 percent of the compaction was occurring in the depth interval 0-1,000 feet in 1961—65. The other 45 percent of the compaction was occurring in the deposits below 1,000 feet, due to pore-pressure decline resulting from upward leakage or in response to large artesian- head declines in deep aquifers to the south. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 F75 120°30’ Los Banos 37°OO’ 4104/0 C20» EXPLANATION 6‘ 36°30’ Boundary of deformed rocks \V -1 Products of the lower-zone specific unit compaction for the 1943-60 period times the total applied stress on the middle of the lower zone, as of 1943, X10? Based on maps of lower-zone specific unit com- paction and total applied stress on the middle of the lower zone Subarea discussed in text 0 10 15M|LES E—Qv—r'L——‘ 0 5 1O 15 KILOMETRES Base from US. Geological Survey Central Valley map, 1:250,000, 1958 36°OO’ ~-'\_I~:r.e~s"° —-~—~\ ,J‘“\st:vsr_fl 120°00’ ’Madera ' 5 Q) {3- FRESNO ”\ n |_‘ \ Kerman TULARE LAKE. kettleman BED FIGURE (SQ—Variations in stress—compaction products The problem of lack of knowledge about the max- imum depth interval in which pore-pressure decline is occurring along the fringes of the study area does not invalidate the conclusions mentioned. Values of specific unit compaction of 5X 10"5 and stress-compaction products of 8X 10—2 (figs. 54, 60) occur in the middle of F76 the large area of intense subsidence southwest of Men- dota where lower-zone aquifer-system thicknesses are 1,200 feet (fig. 55)—almost the maximum for the north- ern part of the area. The removal of the effect of prior total applied stress in the central part of the area reveals several interest- ing aspects regarding the apparent compressibility of the deposits. Extremely low values of specific unit com- paction (fig. 54) occur adjacent to the Big Blue Hills. By removing the effect of prior total applied stress on the deposits of this subarea, the values on the products map of figure 60 are no longer anomalously low, but are in the same range—l—ZX 10‘2—as about half of the area south of the town of Cantua Creek. The removal of the anomaly adjacent to the Big Blue Hills suggests that the Pliocene marine deposits would be only slightly less compressible or would have about the same general cdmpressibility as the Diablo alluvial-fan deposits south of the Huron-Westhaven area if the prior total applied stress had been equal. If a map showing variation in ultimate specific unit compaction (the true compressibility of the deposits) could be prepared and the total effective stress were entirely the result of differences in prior effective stress, such a map would show little variation in the values of products in areas of uniform geologic and lithologic conditions. Although figure 60 utilizes transient specific unit compaction, little variation in the products occurs in those areas of similar geologic conditions. In the central part of the study area (subarea A in figure 60), the stress-compaction products occur in a very narrow range, despite large differences in total applied stress, as of 1943. The work maps used in the construction of figure 60 show that the range of values for the products in this 100-square-mile subarea range only from 2.4 to 2.8x 10—2, even though the prior total applied stress on the middle of the lower zone ranges from 1,000 to 2,000 feet of water. The specific unit com- paction for the same area decreases progressively with increasing total applied stress. The removal of the effect of prior applied stress eliminates the trend shown by the specific unit compaction and indicates that if it were not for differences in prior applied stress, the deposits within the subarea A would compact the same amount per unit of head decline. The situation described sug— gests that the deposits within subarea A in figure 60 should be similar geologically. Sierra flood-plain de- posits are the dominant lower—zone type of deposit in all of subarea A. The western extension of the subarea north of the town of Cantua Creek coincides with the area of maximum western extent of thick Sierra flood-plain deposits and is north of the ancestral allu- vial fans of Los Gatos and Cantua Creeks and south of the Panoche Creek fan. The Sierra flood-plain deposits STUDIES OF LAND SUBSIDENCE intertongue with alluvial-fan deposits in the northwest and southeast corners of subarea A. MEAN LITHOLOGY Another geologic factor that might be responsible, in part, for the fourfold difference of specific unit compac- tion (fig. 54) in the northern and southern parts of the study area is the overall lithology of the deposits. The particle-size analyses of the samples from the core holes should be used with caution for such purposes because of the tendency of the coring equipment to recover the cohesive fine-grained deposits but not the incohesive coarse-grained deposits. More complete and unbiased information can be ob- tained through electric-log studies of the lower zone. A resistivity map of the lower-zone deposits was made to evaluate the effect of lithologic variations on the com— pressibility of the deposits within the study area. Three important types of data are available in all parts of the study area to make a lithofacies map based on electric logs. Abundant electric logs can be obtained readily. The salinity and chemical character of the lower-zone waters can be assessed as a result of a chemi- cal sampling program made in 1951 (Davis and Poland, 1957). The water temperatures at the discharge points of the wells are determined at the times of each pump-efficiency test made by the Pacific Gas and Elec- tric Co. Additional temperature information is availa- ble from the bottom-hole temperatures obtained at the times that the electric logs were made. Thus, Within the Los Banos—Kettleman City area abundant information is available to make a lithofacies map based on the mean resistivity of the lower zone, using electric-log data that are corrected for the effects of regional variations in salinity, chemical character, and temperature. Resistivity logs, instead of spontaneous-potential logs, were selected for the lithofacies study because of the lack of definition that is typical of the spontaneous-potential logs in this area. The mud used in drilling a new well usually is mixed with ground water from a nearby irrigation well; there- fore, there is little contrast between the mud and forma- tion resistivities, and the spontaneous-potential log ap- proaches a straight line in which deflections do not occur for either the sand or clay beds. The lateral resistivity log with a 19-foot spacing be- tween electrodes was used for the lithofacies study. The short- and long-normal resistivity logs were not used because small variations in resistivity were unimpor— tant in a study of mean resistivity of the entire lower zone and because the lateral log minimizes the effect of drilling mud resistivity. Most of the drilling mud resis- tivities, at 38°C, ranged from 3 to 6 ohm-metres, but the extremes in mud resistivities ranged from 1 to 20 ohm-metres. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 The temperature correction was based, in nearly all cases, on the temperature of the water being pumped from irrigation wells and ranged from 21 to 43°C. The coolest water temperatures were for wells along Fresno Slough, and the hottest water temperatures were for wells that tap the sands of the Etchegoin Formation opposite the Big Blue Hills. Two corrections had to be made for variations in the chemical character of the lower-zone water. A salinity correction was made, using standard charts provided by the Schlumberger Co. However, the Schlumberger charts are for NaCl solutions, and the typical lower- zone water is a sodium sulfate water (Davis and Poland, 1957). By using a procedure outlined by Schlumberger, correction factors were computed and applied to chemi- cal analyses of lower-zone waters from different parts of the study area. The calculations showed that the resis- tivity of the lower-zone waters was only 072—07 6, the resistivity of the NaCl solutions of comparable concen- tration. Therefore, a correction factor of 0.75 was ap- plied to the dissolved solids values used in all the salin- ity corrections. The salinity of the lower-zone water at each electric— log site was estimated from a map of the dissolved solids for the study area (Pt. 1, Bull and Miller, 1974, fig. 19). The estimated dissolved solids at the 110 electric-log sites ranged from about 700 to 2,000 mg 1‘1 (milligrams per litre). An NaCl salinity of 1,000 mg l‘1 was used as a standard for the study. The mean resistivity of the lower zone based on elec- tric logs, and corrected to 38°C and 1,000 mg 1‘1 NaCl salinity, is shown in figure 61. A general guide to the lithologies of the resistivities can be made by comparing the particle-size analyses and electric-log corrected re- sistivities at several core-hole sites. Thick clay beds such as the Corcoran or the fine-grained beds associated with the Etchegoin Formation have corrected resis- tivities of about 3—4 ohm-metres (values that may be too low if the pore water in the clays has a higher salinity than the water pumped by the wells). At the other extreme, clean well-sorted coarse-grained sand beds have a corrected resistivity of 20—25 ohm-metres. Thick beds consisting of fine- to_coarse-grained sand have a corrected resistivity of 10—15 ohm-metres. Silts and clayey sands have corrected resistivities of about 4—10 ohm-metres. The low mean resistivities that prevail throughout most of the study area are indicative of the clayey nature of most of the compressible deposits that have compacted to cause the large amounts of subsid- ence within the area. The lithofacies map also shows why SOD—2,000 lineal feet of casings have to be perfo- rated in most of the wells in order to obtain sufficient water for irrigation. The mean resistivity of the lower zone shown in figure F77 61 reveals some interesting lithofacies variations within the study area. Although fine-grained deposits occur throughout most of the area, the deposits in the northern part of the area appear to be less clayey than the deposits in the southern part of the area. The central part of the area appears to have deposits with an inter- mediate amount of clay. In four parts of the study area, the lithofacies map shows a strong correlation between increasing resistiv- ity (coarser deposits) and the areas where sediments were introduced into the area during the course of dep- osition. Coarse-grained deposits are most common where Panoche and Los Gatos Creeks and the San Joa- quin and Kings Rivers entered the study area. The bands of equal range in resistivity are concentric about the points of discharge into the San Joaquin Valley of the ancestral streams of Panoche and Los Gatos Creeks. The lines of equal sums of the determined con- stituents (approximately the dissolved solids) also are concentric about the ancestral mouths of Panoche, Los Gatos, and Cantua Creeks (Pt. 1, Bull and Miller, 1974, fig. 19), which might suggest, at first thought, that an incomplete salinity correction was made for parts of the area in preparing figure 61. This is not the case. Chemi- cal analyses were available for lower-zone wells throughout the study area. Furthermore, the lines of equal mean resistivity (fig. 61) cut across the lines of equal dissolved solids (Pt. 1, Bull and Miller, 1974, fig. 19). For example, in figure 61, the 7.5 mean resistivity line near the town of Cantua Creek passes through areas where the dissolved solids for lower-zone waters ranges from less than 800 mg 1‘1 to more than 2,000 mg 1‘1 . The 10.0 mean resistivity line opposite the mouth of Panoche Creek passes through areas that range from less than 1,000 to more than 2,000 mg 1‘1 dissolved solids for the lower zone. It is concluded that the sources of pre-Corcoran coarser grained deposits from the Di- ablo Range were also the source of younger waters of high dissolved solids that largely replaced the waters originally contained in the deposits. The results of particle-size analyses of core-hole sam- ples agree With the lithofacies map, even though a larger proportion of finer grained than coarser grained deposits were recovered in the coring process. Variation in mean particle size with depth for the deposits cored below the Corcoran at the Mendota and Huron core sites is shown in figure 62. The lithofacies map in figure 61 indicates that the lower-zone deposits at the Mendota site are slightly coarser than the deposits at the Huron site. The particle-size data shown in figure 62 show that many of the cored sediments at the Mendota site are as fine grained as those at the Huron site, but samples with mean particle sizes of more than 125 microns are much more common in the Mendota core than in the Huron F78 STUDIES OF LAND SUBSIDENCE 120°30' 120°00’ 33 i Los Banos @ ’ / a ,_ Dos 37 00 Palos / _ L,'\Ff€{n_‘7/-‘-.\.\’___~/‘_,’ 33 (P 06/10 Y1; Uta 12/12-16H 1 Ca ”W Firebaugh UIN 10” FRESNO \\\§/ K n Mendota |_| |_. 180 \ Kermanc J" 36 °30’ — EXPLANATION ,y I ( 77777777777, 6:7 <9 Boundary of deformed ¢ rocks (’20 >10 7 5-10.0 N 5.0-7 5 fl 7 / 4/69 2.5-5.0 0641’ Mean resistivity of the lower zone, in ohm- PLEASANT metres; based on electric logs, and cor- rected to 38°C and 1000 milligrams per Coalinga litre NaCl salinity VALLEY .14/13—1 1 D1 Core hole for data in figure 62 TULARE 4's,» ('84, 41 LAKE 4 MILES ’V 0 5 1O 15 / A0“ Kettleman BED 36°00, o 5 1o 15 KILOMETERS 1 / 33 6‘ 1' , City core. Meade (1967, p. 12) concluded that “the sediments from the Huron core are generally finer grained, less Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 61.—Lithofacies map based on the mean corrected resistivities of the lower zone. well sorted, and less skewed than the sediments from the Mendota core.” ' LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 MEDIAN DIAMETER, IN MICRONS 1 8 62 500 I I | I I I I I o I 0 8 00 0 Q o o o _ . '30. o _ O . O O O :3 O . 0000 _ O . o. o _ O O O. . O o o _ g Q o O A o o 5%. o .0 o _ g Q _ O . . OO 0 o o. o I. — o _ I.I.I . . 00 O 500 w 0 LL 0 o o 0 z 0 0 d) _ _ o 00 _ . . O 00 i O O .029 O u: 00 o o _ O U ': “ ‘5 ‘ .0 . o In _ .: _ I . I- . ' g _ o . . _ _I Lu 0 . In 0 I — o. — 1000 E o w 0 D o _ . _ o o o — . o _ o . o — . EXPLANATION — O Mendota site — o a Huron site I I I l I I I I I I 1500 FIGURE 62.—Variation in mean particle size with depth for alluvial deposits below the Corcoran in cores from the Mendota and Huron sites. (Data from Meade, 1967, p, 13,) A comparison was made between the overall lithology (mean resistivity) and the stress-compaction products for the lower zone. Because of the marked difference in apparent compressibility in the northern and southern parts of the area, the northern-area data were plotted separately from the data for the rest of the area. Data for all points north of township 16 (fig. 63A), for which the products shown in figure 60 exceed 2.5x 10‘2 (from work map), are plotted in figure 63A, and data for the points for the central and southern parts of the area are plotted in figure 63B. The large amounts of scatter in figures 63A and 633 show that variation in gross lithology, as indicated by F79 1 0 I I I I I o . A 0 s o o 0 ° 0 8- o . .1 o 6* ' . _ N o O I ;( '° 0 . a) ' ' 5— 4— o g _ U D ' g o D 2 ' - L 2_ - Z 9 l- O < n. o I l l | l l g 2 4 6 8 10 12 14 16 L.) MEAN HESISTIVITV, IN OHM-METERS § 6 l l | I I: B I- m o . o 4* ' ' — o e c o n ‘ .u . "" ' a: . : . o 2— . . a one . u o — n ' . . o . o . 0. ° .- . o. 0 ' I I I I 2 4 6 8 1O 12 MEAN RESISTIVITY, IN OHM-METERS FIGURE Sit—Relation of mean corrected resistivity to the product of specific unit compaction and total applied stress, lower zone. A, North of township 16. B, South of township 15. the mean resistivity of the lower zone, is not important in causing the fourfold variation in specific unit com- paction from 1943 to 1960 between the northern and southern parts of the area (fig. 54) or the twofold varia- tion in the stress—compaction products (fig. 60). The deposits in the northern part of the area are slightly less clayey than the deposits in the southern part of the area, but the twofold differences in the apparent compressi- bility of the deposits in the two subareas cannot be explained by variations in overall lower-zone lithology. Mean lithology may be highly significant in evaluating ultimate compaction amounts, but where aquitards have large residual excess pore pressures other factors, such as the thickness of a bed of a given lithology, are more important than average lithology. SOURCE AND MODE 0F DEPOSITION The third geologic factor to be considered as a possible cause of the variation in specific unit compaction in the northern and southern parts of the study area is the relation of the sources of the lower-zone deposits, and their modes of deposition, to the apparent compressibil- ity of the deposits. Different types of deposits inter— tongue with each other in much of the area, but the deposits can be grouped in three classes. The three categories of deposits shown in figure 64 are largely from Part 1 (Bull and Miller, 1974, fig. 16). F80 STUDIES OF LAND SUBSIDENCE 120°30' 120°00' Los Banos 37°OO’ .r~/"‘\@i”§'_» / .,—\ lingo/p.“ Madera FRESNO r-\ H Kerm an 36°30’ EXPLANATION Boundary of deformed Diablo and Sierra flood-plain deposits, mi- nor lacustrine and Diablo alluvial-fan de- posits Diablo alluvial-fan deposits, and Sierra flood—plain and deltaic deposits Sierra flood-plain deposits 4 Generalized line of equal product of lower- zone specific unit compaction and total applied stress on the middle of the lower zone, x 10’. Interval varies TULARE LAKE O 10 15M|LES i—‘V—l—TéA—‘ O 5 10 15 KILOMETRES Base from US. Geological Survey Central Valley map, 1:250,000, 1958 “((8 Kettlem an BED 36°OO’ FIGURE 64,77Relation of stress—compaction products to the sources and modes of deposition of the lower-zone deposits. The northern area of Diablo and Sierra flood-plain Diablo flood-plain deposits predominate near the Diablo deposits has the maximum apparent compressibility, as Range and the proportion of Sierra flood-plain deposits indicated by the lower-zone stress-compaction products. increases toward the east. East and north of Mendota, LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 flood-plain deposits from the San Joaquin River consti- tute virtually all the lower-zone deposits tapped by wells. In the southern part of the study area, most of the lower-zone deposits consist of alluvial-fan deposits. Near the Diablo Range, virtually all the lower zone consists of alluvial—fan deposits, except in those areas of pumpage from the Pliocene marine deposits. Farther to the east, Sierra flood-plain and deltaic deposits become increasingly more important in the basal part of the lower zone. Toward the north, Diablo and Sierra flood-plain deposits become progressively more com- mon. In the vicinity of the town of Cantua Creek, alluvial-fan, lacustrine, and deltaic deposits, as well as marine sediments, are present. The unit that includes alluvial-fan deposits has only half the apparent com- pressibility (as indicated by the stress-compaction products) of the flood-plain deposits in the northern part of the area. The Sierra deposits show considerable variation in apparent compressibility. South of the town of San J oa- quin, the apparent compressibility of the lower-zone deposits, as indicated by the products map, ranges from less than 1 to about 3 X 10—2—an apparent compressibil- ity that is less than the compressibilities in either of the two subareas adjacent to the Diablo Range. Most of the deposits in the southern part of the belt of Sierra F81 flood-plain and deltaic deposits were deposited by the Kings River. In the northern part of the belt of lower-zone Sierra flood-plain deposits, the apparent compressibilities tend to be about the same as for the Diablo flood-plain deposits to the west. Most of the Sierra flood-plain de- posits in this part of the subarea were deposited by the San Joaquin River. The lithofacies map in figure 61 indicates that the lower-zone deposits in the vicinity of Mendota have a higher resistivity (less clay) than the lower-zone deposits of the Kings River farther south. Prior discussions concluded that about one—third the fourfold difference in the values of specific unit compac- tion 'in the southern and northern parts of the study area was the result of actual differences in compressibil- ity due to the lesser prior applied stress in the northern part of the study area. The coincidence between the area of Diablo and Sierra flood-plain deposits and the area of high values of the stress—compaction products in the northern part of the area indicates 'a strong correlation between genetic class of deposits and compaction per unit head decline for stresses applied during the 1943—60 period. The relation of the apparent compressibility (stress- compaction products) of the lower zone to the genetic classes of deposits is shown along a longitudinal profile of the study area in figure 65. Maximum values of ap- PRODUCT OF SPECIFIC UNIT COMPACTION TIMES TOTAL APPLIED STRESS x102 Upper zone 000990 o,o,:,o.o,oooo Saline water body 0 ...‘a,.¢wv~ oooodfibooo I®%%¢” .. VERTICAL EXAGGERATION X26 SEA LEVEL 0 2 4 GMILES l—v—H—l—l o 2 4 6KILOMETRES EXPLANATION Sierra flood-piain Corcoren Clay Member of the E WA deposits Tulare Formation 15-34N1 Diablo floodplain deposits, in— terbedded with Sierra flood- plain deposits near well 16/ Diablo alluvial-fan deposits and Sierra flood-plain and deltaic deposits Marine sediments FIGURE 65.-Relation of stress-compaction products to types of lower-zone deposits. F82 parent compressibility occur in the northern part of the area, where Diablo flood-plain deposits constitute nearly all the lower zone along the line of section. The apparent compressibility decreases in the central part of the area. Stress—compaction products in the northern part of the area are about 8X 10—2, but in the central part of the area, the products are only about 3x 10’2. The marked decrease of stress-compaction products of the deposits in the central part of the area coincides with marked changes in the source and depo- sitional environment of the deposits tapped by wells. Coarse-grained Sierra flood-plain deposits constitute more than 400 feet of the lower zone (fig. 65), and below the Sierra flood-plain deposits are intermixed Sierra and Diablo flood-plain deposits. In addition, the Pliocene marine deposits of the Etchegoin and San J oa- quin Formations are heavily pumped to the west. The increase in the proportion of sand, with increasing proportion of Sierra flood-plain deposits and the inclu- sion in the section of the deeply buried partly consoli- dated Pliocene marine deposits, account for the de- crease in apparent compressibility in the central part of the study area. As much as 20 feet of subsidence had occurred in the central part of the area as of 1966, but figure 65 shows that the large amounts of subsidence that have occurred are not the result of large values of unit compaction per unit change in applied stress during a given period of time such as the 1943—60 period. Instead, the large amounts of subsidence that have occurred south of Can- tua Creek are the result of large pore-pressure declines in more than 2,000 feet of lower-zone deposits. Southeast of well 16/ 1 5—34N1, the apparent compres- sibility shown in figure 65 increases to about 5x 10—2. Deposits from many sources occur in this area also, but Sierra flood-plain and deltaic deposits make up much of the lower zone. Diablo alluvial-fan deposits overlie the Sierra deposits, and the marine littoral and estuarine deposits underlie the Sierra deposits. In contrast to the deltaic deposits shown in figure 51, the Sierra deltaic deposits in this part of the area have extensive sand beds. The marine sediments are not tapped by wells along the line of section south of the northernmost limit of the lens of brackish water. In the southern part of the area, wells are able to obtain sufficient quantities of water without having to tap the Pliocene marine section or the fresh-water— bearing deposits in the basal part of the overlying Tu- lare Formation. Although these deeper deposits contain fresh water, as indicated in figure 65, wells in the south- ern part of the area generally are not perforatedvmore than 100 feet below the bottom of well 20/ 18—1 1Q3 (fig. 65). The alluvial-fan deposits derived from the Diablo Range predominate within the interval tapped by irri- STUDIES OF LAND SUBSIDENCE ‘ gation wells along the line of section. The proportion of alluvial-fan deposits constituting the lower-zone de- posits increases to the southeast and is coincident with a decrease in apparent compressibility from 4 to 2 x 10—2. VARIATION IN EXCESS PORE PRESSURES Several lines of evidence indicate that the various genetic types of deposits differ in their ability to retain excess pore pressures because of the characteristics of their source materials and their modes of deposition. The following summary indicates that the Diablo alluvial-fan deposits should be Slower to attain pore- pressure equilibrium after a given head decline than the Diablo and Sierra flood-plain deposits: Evidence based on laboratory tests of'core-hole samples 1. Particle-size analyses of 145 samples from alluvial- fan deposits and 95 samples from flood-plain de- posits indicate mean clay contents of 28 percent for the alluvial-fan samples and 22 percent for the flood-plain samples. 2. The alluvial-fan deposits are more poorly sorted than the flood-plain deposits (Meade, 1967, p. 12). 3. Mean vertical permeabilities for 23 samples, as de- termined by consolidation tests in the load range of 400—800 lb in_2 indicate that the fine-grained beds of the fan deposits are less permeable than the fine-grained beds of the flood-plain deposits. In gal- lons per day per square foot, the mean permeabil- ity values were 1.7 for the fan deposits and 5.7 and 4.0 for the Diablo and Sierra flood-plain deposits. 4. Mean values of the coefficient of consolidation, CD, for 14 samples tested in the load range of 400-800 lb in_2 indicate that the fine-grained beds of the alluvial-fan deposits consolidate at a much less rapid rate than the fine-grained beds of the flood-plain deposits. The mean values of cu ft2 yr—1 were 8 for the fan deposits and 28 and 21 for the Sierra and Diablo flood-plain samples. Field evidence 1. Study of the micrologs of the different types of de- posits shows that the Diablo alluvial-fan deposits generally have thicker beds of fine-grained mater- ial than the flood-plain deposits. Weighted mean bed-thickness factors of aquitards penetrated by the four Inter-Agency Committee core holes were 24 for the alluvial-fan deposits and 14 for the flood-plain deposits. 2. Mean well yield factors (Pt. 1, Bull and Miller, 1974, fig. 16) for the types of deposits range from 1 to 4 for fan deposits and are 9 and 11 for Diablo and Sierra flood-plain deposits. The slow water expulsion rate from the fine-grained beds of the alluvial-fan de- posits is, in part, responsible for the perforated LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 2 intervals of 1,200—1,600 feet and drawdowns of 100—120 feet in the southern part of the area. In contrast, the wells of similar yield in flood-plain deposits commonly are perforated for 600—1,000 feet and have drawdowns of 40—60 feet. Thus, conditions in the alluvial-fan aquitards in the southern part of the area have been favorable for de- velopment of large residual excess pore pressures and high values of ultimate specific unit compaction. The same conditions also are responsible, in part, for the lower apparent compressibilities (stress-compaction products) in the alluvial-fan deposits than in the flood-plain deposits during the 1943—60 period. The hypothesis of more rapid dissipation of excess pore pressures in the northern subarea can be checked by examining the changes in compaction rates. at four compaction-recorder sites. The decrease in mean daily compaction rates at the four sites is shown by Bull and Poland (Part 3, fig. 40, 1974). The mean-daily- compaction—rate plots may be represented by a general exponential equation of the type y =cemx, in which c and m are determined by the data for each site. Taking the Cantua site data as an example, the equation for the plot of mean daily compaction rate (y) and the time since mid-1961 in years (x) is y=0.0028e_0'096x. Computation of the values of m for the four regression lines for the sites gave the following results: Cantua site, —0.096; Mendota site, —0.21; Westhaven site, —0.091; and the Oro Loma site, —0.18. Although these values of m are approximations, a rough twofold con- trast in m values is apparent for the compaction- recorder sites in the northern and southern subareas. The contrasts between the northern and southern areas regarding aquitard thickness and mean daily compaction rates imply that, as of 1967, larger excess pore pressures for a given head decline existed in the lower-zone deposits of the southern than the northern subarea. The magnitudes of the above contrasts is about the same as the magnitude of contrast in stress— compaction products (fig 60). Mean daily compaction rates might also be affected by the proportions of aquitards in the lower zone. The core-hole sites had the following percentages of aquitards in the lower zone: Oro Lorna, 41; Mendota, 23; Cantua, 69; and Huron, 55. The means for the two pairs of core holes in the northern and southern subareas are 32 and 62 percent, respectively. (The difference between these means is significant at the 0.88 probability level.) Thus, an inverse relation apparently exists between the compaction rates and the proportions of the lower zone F83 comprised of aquitards. This further underscores the effect of aquitard thickness on recorded compaction for an aquifer system that does not have a steady-state pore-pressure distribution. It is concluded that the source and environment of deposition is at least as important a geolOgic factor as the prior applied stress in determining the rate and amount of subsidence Within the Los Banos—Kettleman City area. The combination of extensive permeable sand beds and intercalated clayey beds that generally do not exceed 8 feet in thickness provide an ideal geologic environment for the rapid expulsion of large amounts of water from the fine-grained beds to cause the large amounts of subsidence during the 1943—60 period. One-third of the difference between the appar- ent compressibility (specific unit compaction) in the northern and southern parts of the area is real and is due to differences in prior total applied stress as of 1943. The other two-thirds of the difference is indeed only apparent and is attributed chiefly to hydraulic and pet- rologic differences between genetic types of deposits that affect the rate of expulsion of water from aquitards upon increase in applied stress. The effects of the mean lithology of the lower zone are not considered nearly as significant as either the effect of total applied stress or bed thickness of the sediments laid down under differ- ent modes of deposition. DISTRIBUTION OF WELL-CASING FAILURES Studies of well-casing failures have provided useful information about the distribution of casing breaks in the different types of deposits. Figure 66 shows the variation of casing-failure occurrences for the upper and lower zones and for the various types of deposits. In the upper zone, most of the casing failures have oc- curred in the basal part of the zone, where pore-pressure declines have been greatest. In general, the casing fail- ures are most abundant in the lower zone because, as a unit, it has undergone more compaction than the upper zone. West of the Corcoran in the southwestern part of the area, the unit casing-failure ratio is intermediate between the ratios for the upper and lower zones where the Corcoran is present. The Diablo alluvial deposits have an overall casing failure ratio that is similar to that of the Corcoran. The Sierra sands have the highest casing-failure ratio of any of the types of deposits. The abundant casing failures opposite the Sierra sands probably are not indicative of a higher unit compaction in sands than in clays. They may be related in part to the removal of sand adjacent to the casing during the course of pumping. Removal of the sand providing lateral support for the well casing would provide potential weak sections that could be ruptured as a result of compressive stresses that were caused by F84 compaction of overlying and underlying fine-grained deposits. Upper zone Lower zone West of Corcoran Diablo alluvial deposits Sierra sand deposits Corcoran Clay Member 'All zones Other deposits I III I 0 2 4 6 810 UNIT CASING-FAILURE RATIO, IN FAILURES PEFI THOUSAND FEET FIGURE fie—Relation of well—casing failures to hydrologic unit and type of adjacent deposit. (From W. E. Wilson, written commun, April 1968.) SUMMARY AND CONCLUSIONS Changes in the altitude of the land surface in the Los Banos—Kettleman City area have been caused by com— paction due to wetting of moisture-deficient alluvial-fan deposits, withdrawal of petroleum, and tectonic move- ments, but have been caused mainly by ground-water withdrawal. Two main sources of vertical-control data were used. The Geological Survey made surveys for detailed topo- graphic maps of the entire area during the 1920’s and in 1955. Comparison of these maps provides regional sub- sidence information prior to 1955. Although the Coast and Geodetic Survey levelings provide valuable infor- mation as early as 1933, the establishment of a level- line network in 1955 and subsequent relevelings to specifically evaluate land subsidence provided a means of obtaining detailed information about the extent, magnitude, and rate of subsidence. During the last million years, parts of the adjacent Coast Ranges have been elevated more than 2,000 feet, and parts of the San Joaquin Valley have subsided about 1,000 feet as a result of tectonic movements. Tec- tonic movements are continuing today, but at very slow rates compared with the rate of manmade subsidence. The amounts of intermittent uplift of parts of the moun- tain front are small and are superimposed on long-term subsidence due to nontectonic causes. About 0.1 foot of net apparent uplift of the crest of Anticline Ridge oc- curred between 1962 and 1963. Subsidence due to the withdrawal of petroleum is minor in extent and magnitude and occurs, in part, in those areas of subsidence due to withdrawal of ground water. Bench marks on Anticline Ridge that are set in formations older than the fresh-water-bearing forma— tions indicate about 0.25 foot of net subsidence due to withdrawal of petroleum from the Coalinga oil field since 1943. STUDIES OF LAND SUBSIDENCE Near-surface subsidence occurs within about 7 per- cent of the areas affected by subsidence due to artesian-head decline. About 130 square miles have subsided or would subside if irrigated. Subsidence of 3—10 feet is common, and 10—15 feet of subsidence has occurred locally. Near-surface subsidence results from the compaction of deposits by an overburden load as the clay bond sup- porting the voids is weakened by water percolating through the deposits for the first time since burial. The amount of compaction due to wetting is dependent mainly on the overburden load, natural moisture condi- tions, and the type and amount of clay in the deposits. The amount of compaction increases with an increase in the overburden load, but most of the near-surface sub— sidence has been caused by compaction in the upper 200 feet of deposits. For compaction due to wetting to occur, the alluvial-fan deposits must remain moisture- deficient after burial, and the deposits must have sufficient clay so that they undergo a decrease in strength When water percolates through them for the first time. Both the magnitude and extent of subsidence due to artesian-head decline are greater than near-surface subsidence. The pattern of subsidence is an elongate oval, in which the area (as of 1966) that had subsided more than 10 feet was 70 miles long. More than 1 foot of subsidence had occurred in 2,000 square miles of the Los Banos—Kettleman City area and the adjacent areas east of the trough of the valley. Maximum subsidence of 26 feet occurred southwest of Mendota between 1920 and 1966, and the maximum subsidence rate of a bench mark during this period was 1.8 ft yr_1. Intense subsidence occurred first in the northern part of the area. By 1943, as much as 10 feet of subsidence had occurred west of Mendota, but less than 2 feet of subsidence had occurred in most of the southern part of the area. The area of intense subsidence expanded after the middle 1940’s as a result of rapid agricultural de- velopment during and after World War II. By 1963, more than 20 feet of subsidence had occurred in both the northern and southern parts of the area. During the 1959—63 period, 480 square miles were subsiding more than 0.5 ft yr_1, and 63 square miles were subsiding more than 1.0 ft yr_1. Histories of subsidence rates are highly variable in the different parts of the area. In general, subsidence rates were 0.1—0.8 ft yr‘1 greater during the 1959—63 period than during the 1943—53 period. The area be- tween Los Banos and Mendota was the only large area in which the subsidence rate decreased between the two periods. Subsidence rates increased until 1954, when deliveries of water from the Delta-Mendota Canal re- duced the amount of ground water pumped, and have LOS BANOS—KET’I‘LEMAN CITY AREA, CALIFORNIA, PART 2 decreased since then. Subsidence rates have increased steadily at Mendota and to the northeast, and south of Huron until 1963. In the area between Kettleman City and Fresno Slough, years of little or no subsidence occur between years of as much as 0.4 foot of subsidence. Since the middle 1950’s, subsidence rates have re- mained fairly constant or have decreased slightly in most of the area. During the 1963—66 period, only a few square miles were subsiding more than 1 ft yr’l. Compaction gages, consisting of anchors set near the base of the fresh-water-bearing deposits and connected to the land surface with l/s-inch cables inside well cas- ings, have been measuring as much as 99 percent of the compaction that is causing the subsidence. The propor- tion of the subsidence that is being measured is decreas- ing at most compaction-recorder sites, indicating that compaction is occurring at greater depths than previ- ously. At the Oro Lorna site, the percent of subsidence that is being measured by the 1,000-f00t compaction recorder has decreased from about 90 to 55 percent. At the Cantua site, the percentage has decreased from 99 to 78 percent. Seasonal variations in the rate of compaction occur at most sites, but are not well defined at some sites such as the Cantua site. Subsidence rates tend to be greatest during the late winter and during the summer—the times of maximum demand for irrigation water from the ground-water reservoir. The use of several compaction recorders at one site provides a means of measuring the unit compaction in the intervals between the depths at which the anchors are set. Annual unit compaction has varied from zero for the 350—500-foot depth interval at the Oro Lorna site to 1.2x10‘3 foot per foot per year for the 503—703-foot depth interval at the Cantua site. Variation of unit compaction with depth for the Los Banos—Kettleman City area is largely the result of two components—the decrease in compressibility of the de- posits with depth because of the increase in prior effec- tive overburden load and the variations in the amounts of head decline that have occurred as a result of pump— ing. Perforated-interval data suggest that the amounts of head decline increase with depth to about 200 feet below the Corcoran and then remain about constant or decrease slightly with further increase in depth. The casing-failure data indicate that unit compaction in- creases to a depth of about 200 feet below the Corcoran because the trend of greater head decline with increas- ing depth dominates over the decreasing compressibil- ity of the deposits with increasing depth. Below a depth of about 200 feet below the Corcoran, the effects of decreasing compressibility of the deposits dominate, and unit compaction decreases with increasing depth. Water- and oil-well casings are being shortened in F85 amounts about equal to the amount of compaction of the deposits, even if they are encased in cement. For wells ranging in size from 4 to 13 inches that are not gravel— packed, resistance to compaction decreases with in- creasing casing diameter. Increased protrusion of the well casings above the land surface is common, but is less than 10 percent of compaction for most water wells. The use of tops of well casings as subsidence bench marks and the measuring of increased protrusion to obtain amounts of compaction are not reliable unless the proportions of casing shortening and increased cas- ing protrusion are known. Comparison of the subsidence of well bench marks and reference bench marks 17—193 feet from the wells indicates that casings of pumped wells subside more than reference bench marks despite increased protru- sion of the well casings. Maximum compaction occurs at, or near, pumping wells because they are point sources of maximum applied stress. Compaction has damaged or destroyed hundreds of well casings where subsidence rates have been more than 0.5 foot per year for more than 5—10 years. Wells in areas where subsidence rates are less than 0.5 ft yr—1 commonly last 10—20 years, but repairs of well casings in such areas of lesser subsidence rate are common. Most of the compaction is occurring below the Corco- ran; only 5—30 percent of the compaction occurs above the Corcoran in most of the area. As much as 30—40 percent of the compaction occurs above the Corcoran in the southern part of the area. The rates, amounts, and distribution of subsidence within the Los Banos—Kettleman City area are highly dependent on regional variations of geologic factors influencing the compaction of unconsolidated deposits. The poorly sorted and clayey nature of many of the sands tends to increase the compressibility of the sands within the study area. The presence of large fresh- appearing mica flakes in the sands derived from the Sierra Nevada increases the potential for inelastic com- paction and the potential for an elastic expansion or compaction of the aquifers. The deposits of the study area contain about 20 per- cent of clay—size material, which consists mainly of montmorillonite with calcium as the principal adsorbed cation. Except for the uppermost 300 feet of the Oro Loma core, about 7 parts out of 10 of the clay minerals are montmorillonite (Meade, 1967). The presence of large amounts of montmorillonite clay adds greatly to the compressibility of the deposits upon change in effec- tive stress, as compared with kaolinite or illite clays. In general, the younger deposits are less consolidated than the older deposits. The partly consolidated nature of the older deposits may be due to large prior overbur- den loads, but time also has been important in F86 influencing the degree of compaction or cementation of the deposits. The Pliocene marine deposits are notice- ably more consolidated than the Pleistocene deposits. The Pliocene clayey deposits, instead of being plastic, are sufficiently brittle that samples will break when struck with a hammer. The Pliocene sandy deposits, instead of being loose, are sufficiently cemented that they are cohesive, but friable. The’specific unit compaction for the 1943—60 period was determined for the lower zone. The specific unit compaction was based on (1) the subsidence during the period, (2) the proportions of post-1960'lower-zone com- paction in the various parts of the study area, (3) the change in applied stress on the lower zone as a result of change in lower-zone artesian head and change in the position of the water table, and (4) the thickness of the lower-zone deposits that have undergone large head decline. The most important aspect of the lower-zone specific unit compaction is that the values of specific unit com- paction are about four times larger in the northern than in the central and southern parts of the area. The geologic factors that were evaluated to determine the causes of areal variation in specific unit compaction were prior total applied stress, mean lithology, and source and mode of deposition of the different genetic types of deposits. The applied overburden load that was computed was the total applied stress on the middle of the lower zone at the beginning of the 1943—60 period. The components of the total applied stress included (1) the buoyant weight of saturated deposits, (2) the geostatic weight of deposits and contained water above the water table, and (3) the seepage stresses caused by head differentials resulting chiefly from artesian-head decline. The com- ponent of total applied stress on the middle of the lower zone that was present in 1943 owing to the buoyant weight of saturated deposits ranged from 800 to 1,800 feet of water for most of the area, but locally the applied stress resulting from this component was less than 600 feet or more than 2,000 feet. The lack of buoyant support for the deposits above the water table and the weight of water contained in the unsaturated deposits were responsible for an additional load in 1943 that was equal to 50—200 feet of water in most of the area. By 1943, artesian-head decline had lowered the potentiometric surface of the lower zone below the water table in all parts of the area. The result was an increase in applied stress on the lower zone. As of 1943, seepage stresses of. 100—200 feet of water‘were being applied to the lower zone in most of the study area. The three components of applied stress resulted in a total applied stress on the middle of the lower zone as of 1943 of 600-2,200 feet of water, but in most of the area STUDIES OF LAND SUBSIDENCE the range of total applied stress was 1,000—1,800 feet of water. The effect of prior total applied stress on lower-zone specific unit compaction for the 1943—60 period was largely removed by multiplying specific unit compac- tion by total applied stress. The resulting product is an apparent compressibility of the deposits. By removing the effects of prior applied stress about a third of the fourfold difference in specific unit compaction between the northern and southern parts of the area was re- moved. Removal of the effects of prior stress eliminated the area of anomalously low values of specific unit com— paction adjacent to the Big Blue Hills. In a 100-square-mile area underlain chiefly by Sierra flood-plain deposits, the removal of the effects of prior total applied stress that ranged from 1,000 to 2,000 feet resulted in almost uniform stress-compaction products that ranged only from 2.4 to 2.8x10‘2. It is concluded that prior applied stress is an impor— tant factor in determining the compressibility of a de- posit of a given lithology in response to unit increase in effective stress. Compaction-recorder data at the Westhaven site substantiate this conclusion. Values of unit compaction for the alluvial-fan deposits are larger at shallower depths than at greater depths, where much of the upper zone has undergone head declines of similar magnitude to those in the lower zone. Variations in the overall lithology of the lower zone were evaluated by making a lithofacies map based on the mean electric-log resistivities corrected to 38°C and 1,000 mg 1‘1 NaCl salinity. The lithofacies map indi- cates that the deposits in the northern part of the area are coarser grained than the deposits in the southern part of the area. The low resistivities that prevail in most of the study area confirm the presence of abundant fine-grained material noted in core samples. The coarser grained deposits in the lower zone are most common where the ancestral streams of Panoche and Los Gatos Creeks and the San Joaquin and Kings Riv- ers entered the study area. Plots of mean resistivity and stress-compaction pro- ducts of the lower zone have a large degree of scatter. A relation between mean lithology and apparent com- pressibility does not exist. Although laboratory tests indicate that clays are more compressible than sands, a parallel relation could not be demonstrated for the amounts of compaction that occurred for different mean lithologies between 1943 and 1960 in response to the increase in applied stress during the same period. Ap- parently, insufficient time was available during the period for large amounts of compaction to occur in those sections of the lower—zone containing large amounts of clay. The areas having large amounts of sand are inter- preted as having compacted rapidly, but the total LOS BANOS’KETTLEMAN CITY AREA, CALIFORNIA, PART 2 amount of compaction was less than for areas having intermediate amounts of sand. Consideration of the mode and source of deposition of the lower-zone deposits (Miller and others, 1971, p. 25—33) revealed that the northern part of the area con- sisted mainly of Diablo flood-plain deposits and that the southern part of the area consisted mainly of Diablo alluvial-fan deposits. The eastern part of the area has lower-zone deposits that consist chiefly of Sierra flood-plain and deltaic deposits from the Kings River in the south and Sierra flood-plain deposits from the San Joaquin River in the north. The area of highest apparent compressibility of the lower-zone deposits coincides with the area of Diablo flood-plain deposits and Sierra flood-plain deposits de- rived from the San Joaquin River. Several lines of evidence indicate that the bedding of the deposits is an important geologic factor controlling the magnitude and rate of compaction computed for the 1943—60 period. The Diablo flood-plain deposits contain abundant and laterally extensive sand beds between fine-grained beds 4—8 feet thick. In contrast, the alluvial-fan deposits have a higher clay content and are more poorly sorted than the flood-plain deposits —characteristics that result in minimum per- meabilities and consolidation rates for the fine-grained beds of the fan deposits. Fine-grained beds generally are thicker in the fan deposits (mean bed-thickness factor of 24) than in the flood-plain deposits (mean bed-thickness factor of 14), where the bed-thickness factor equals (aquitard thickness/2)? Thus, conditions in the alluvial-fan aquitards in the southern part of the area have been favorable for de- velopment of large residual excess pore pressures and high values of ultimate specific unit compaction. These conditions also are largely responsible for less unit compaction per given amountof increasein applied stress in the southern part of the area between 1943 and 1960. Thus, evaluation of several geologic factors indicates that the apparent fourfold higher compressibility (specific unit compaction) of the lower-zone deposits in the northern part of the area is part real and part appar- ent. About a third of the apparent difference in com- pressibility is real and is due to lesser amounts of total applied stress prior to 1943 in the northern areas. Most of the other two-thirds of the difference is only apparent. It is apparent because it can be attributed chiefly to geologic differences, such as thickness of bedding, that control the rate of expulsion of water from aquitards upon increase in applied stress in deposits of markedly different modes and sources of deposition. REFERENCES American Geological Institute, 1960, Glossary of geology and related F87 sciences [2d ed.]: Washington, DC, Am. Geol. Inst, Natl. Acad. Sci-Natl. Research Council, 325 p. with 72 p. supp. American Society of Civil Engineers, 1962, Nomenclature for hy- draulics: Am. Soc. Civil Engineers, Manual and Repts. on Eng. Practice, no. 43, p. 85. Bull, W. B., 1964a, Alluvial fans and near-surface subsidence in western Fresno County, California: U.S. Geol. Survey Prof. Paper 437—A, 71 p. 1964b, Geomorphology of segmented alluvial fans in western Fresno County, California: U.S. Geol. Survey Prof. Paper 352—E, p. 89—129. 1972, Prehistoric near-surface subsidence cracks in western Fresno County, California: U.S. Geol. Survey Prof. Paper 437—0, 85 p. Bull, W. B., and Miller, R. E., 1974, Land subsidence due to ground- water withdrawal in the Los Banos—Kettleman City area, California—Part 1. Changes in the hydrologic environment conducive to subsidence: U.S. Geol. Survey Prof. Paper 437—E, 71 p. Bull, W. B., and Poland, J. F., 1974, Land subsidence due to ground- water withdrawal in the Los Banos—Kettleman City area, California—Part 3. Interrelations of water-level change, change in aquifer-system thickness, and subsidence: U.S. Geol. Survey Prof. Paper 437—G, 62 p. California Division of Oil and Gas, 1960, Pt. 1, San Joaquin— Sac- ramento Valleys and northern coastal regions, in California oil p and gas fields, Maps and data sheets: 493 p. Carpenter, D. W., 1965, Pleistocene deformation in the vicinity of the Mile 18 pumping plant, in Guidebook for Field Conf. 1, Northern Great Basin and California—Internat. Assoc. Quaternary Re- search, 7th Cong., USA 1965: Lincoln, Nebr., Nebraska Acad. Sci. p. 142-145. Croft, M. G., 1972, Subsurface geology of the late Tertiary and Quaternary water-bearing deposits of the southern part of the San Joaquin Valley, California: U.S. Geol. Survey Water- Supply Paper 1999—H, 29 p. Davis, G. H., and Green, J. H., 1962, Structural control of interior drainage, southern San Joaquin Valley, California, in Geologi- cal Survey research 1962: U.S. Geol. Survey Prof. Paper 450—D, p. D89—D91. Davis, G. H., Green, J. H., Olmsted, F. H., and Brown, D. W., 1959, Ground water conditions and storage capacity in the San Joa- quin Valley, Calif: U.S. Geol. Survey Water-Supply Paper 1469, 287 p. Davis, G. H., and Poland J. F., 1957, Ground-water conditions in the Mendota—Huron area, Fresno and Kings Counties, California: U.S. Geol. Survey Water-Supply Paper 1360—G, p. 409—588. Frink, J. W., and Kues, H. A., 1954, Corcoran Clay—A Pleistocene lacustrine deposit in San Joaquin Valley, Calif: Am. Assoc. Petroleum Geologists Bull., v. 38, no. 11, p. 2357—2371. Gilboy, Glennon, 1928, The compressibility of sand-mica mixtures: Am. Soc. Civil Engineers Proc., v. 54, p. 555—568. Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1955,Proposed program for investigating land subsidence in the San Joaquin Valley: Sacramento, Calif. open-file report, 160 p. 1958, Progress report on land—subsidence investigations in the San Joaquin Valley, California, through 1957: Sacramento, Calif, open-file report, 160 p. Ireland, R. L., 1963, Description of wells in the Los Banos—Kettleman City area, Merced, Fresno, and Kings Counties, California: U.S. Geol. Survey open-file report, 519 p. Janda, R. J., 1965, Quaternary alluvium near Friant, California, in Guidebook for Field Conference I, Northern Great Basin and California—Internat. Assoc. Quaternary Research, 7th F88 Cong. USA 1965: Lincoln, Nebr., Nebraska Acad. Sci., p. 128—133. Johnson, A. 1., Moston, R. P., and Morris, D. A., 1968, Physical and hydrologic properties of water-bearing deposits in subsiding areas in central California: U.S. Geol. Survey Prof. Paper 497—A, 71 p. Lofgren, B. E., 1960, Near-surface land subsidence in western San Joaquin Valley, California: Jour. Geophys. Research, v. 65, no. 3, p. 1053—1062. 1968, Analysis of stresses causing land subsidence, in Geologi- cal Survey research 1968: U.S. Geol. Survey Prof. Paper 600—B, p. B219—B225. 1969, Land subsidence due to the application of water, in Varnes, D. J., and Kiersch, George, eds., Reviews in En- gineering Geology, v. 2: Boulder, Colo, Geol. Soc. America, p. 271—303. Lohman, S. W., and others, 1972, Definitions of selected ground-water terms—revisions and conceptual refinements: U.S. Geol. Survey Water-Supply Paper 1988, 21 p. Meade, R. H., 1964, Removal of water and rearrangement of particles during the compaction of clayey sediments—review: U.S. Geol. Survey Prof. Paper 497—B, 23 p. 1967, Petrology of sediments underlying areas of land sub- sidence in central California: US. Geol. Survey Prof. Paper 497—C, 83 p. 1968, Compaction of sediments underlying areas of land sub- sidence in central California: US. Geol. Survey Prof. Paper 497—D, 39 p. Miller, R. E., 1961, Compaction of an aquifer system computed from consolidation tests and decline in artesian head, in Geological Survey research 1961: US. Geol. Survey Prof. Paper 424—B, p. B54—B58. Miller, R. E., Green, J. H., and Davis, G. H., 1971, Geology of the STUDIES OF LAND SUBSIDENCE compacting deposits in the Los Banos—Kettleman City subsid- ence area, California: US. Geol. Survey Prof. Paper 497—E, 46 p. Poland, J. F., and Davis, G. H., 1969, Land subsidence due to with- drawal of fluids, in Varnes, D. J ., and Kiersch, George, eds., Reviews in Engineering Geology, v. 2: Boulder, Colo., Geol. Soc. America, p. 187—269. Poland, J. F., and Everson, R. E., 1966, Hydrogeology and land sub- sidence, Great Central Valley, California, in Bailey, E. H., ed., Geology of northern California: California Div. Mines and Geol- ogy Bull. 190, p. 239—247. Poland, J. F., and Ireland, R. L., 1965, Shortening and protrusion of a well casing due to compaction of sediments ina subsiding area in California, in Geological Survey research 1965: US Geol. Sur- vey Prof. Paper 525—B, p. B180—B183. Poland, J. F., Lofgren, B. E., and Riley, F. S., 1972, Glossary of selected terms useful in the studies of the mechanics of aquifer systems and land subsidence due to fluid withdrawal: U.S. Geol. Survey Water-Supply Paper 2025, 9 p. Prokopovich, N. P., 1963, Hydrocompaction of soils along the San Luis Canal alignment, western Fresno County, California, in Ab- stracts for 1962: Geol. Soc. America Spec. Paper 73, p. 60. Sharpe, C. F. S., 1938, Landslides and related phenomena: New York, Columbia Univ. Press, 137 p. Shepard, F. P., 1954, Nomenclature based on sand-silt-clay ratios: Jour. Sed. Petrology, V. 24, p. 151-158. Taliaferro, N. L., 1943, Geologic history and structure of the central Coast Ranges of California: California Div. Mines Bull. 118, p. 119—163. Terzaghi, Karl, and Peck, R. B., 1948, Soil mechanics in engineering practice: New York, John Wiley & Sons, Inc., 566 p. Trask, P. D., and Close, J. E. H., 1958, Effect of clay content on strength of soils: Coastal Engineering Conf., 6th, Florida 1957, Proc., v. 6, p. 827—843. A Page Age of deposits ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, F63 Alluvial-fan deposits, bedding ,,,,,, 54, 55, 57, 82, 87 casing failure __ 83 clay content _______________________________ 53 compaction ,,,,,,,,,,,,,,,,,,,,,,, 62, 63, 83, 87 compressibility _______________________ 76, 82, 83 consolidation ____________________________ 62, 63 lateral extent ,,,,,,,, H 60 lower-zone constituent moisture condition .1 ,,,,,,,,,,,,,,, 10, 14 permeability ________________________________ 56 stress-compaction product ___________________ 76 Westhaven site _____________________ ",1 51 Anticline Ridge ______________________ 7, 8, 19, 64, 84 Apparent compressibility, defined _ Applied stress, clay content compaction _________ lithology ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 83 lower zone ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 86 water-table change ,,,,,,,,,,,,,,,,,,,,,, 45, 57 Aquifers H" _________________________ 10, 19, 60 19, 26, 60,62, 63,79, 82, 87 H 6, 8, 14, 26, 84, 86 Aquitards H, Artesian-head decline , _____________________ 10 B, C Bedding of deposits ,,,,,,,,,,,,,,,,,,,,,,,,,, 54, 87 Bed-thickness factors ________________________ 60, 87 Bench marks ,,,,,,,,,,,,,,,,,,,, 4, 14, 19, 43, 45, 85 Big Blue Hills ________________________ 55, 64, 76, 86 California Aqueduct ,,,,,,,,,,,,,,,,,,,, 10, 14, 23 Cantua Creek ________________ 7, 14, 24, 26, 48, 76, 81 Cantua site, bed thickness ,,,,,,,, 62 casing failure ,,,,, compaction ______ .W 34, 38, 39, 40, 46 compressibility ,,,,,,,,,,,,,,,,,,,,,,,,,, 70, 74 equipment ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 30, 34 pore pressure ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 83 subsidence ,,,,,,,,,,,,,,,,,,,,,,,,, 34, 35, 85 water-level change ,,,,,, 40 Casing-cable friction _________________ 31, 32 Clay __________________ 10, 53, 59,63, 83, 84, 85, 87 Coalinga oil field ______________________________ 8, 84 Coast Range orogeny ,,,,,,,,,,,, Coast Ranges ,,,,,,,,,, Coefficient of consolidation __, Compaction __________________ _ 2, 10,29, 83, 84 Compaction, applied stress change ________________ 70 lower zone ,,,,,,,,,,,,,,,,,, 46, 64 measurement ___, ___________ 32, 33, 36, 38 relation to consolidation ,,,,,,,,,,,,,,,,,,,,, 62 relation to geologic factors _________________ 49 relation to well casing ____________________ 43, 44 upper zone Compaction recorder ,,,,,,,,,,,, 29, 33, 36, 38, 46, 85 Compressibility, apparent, defined .. v applied stress ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 74, 83 clay ________________________________________ 53 compaction ______________________________ 38, 85 effective stress ___________________ fine-grained beds _ lithology _________ lower-zone deposits , ____________ 87 overburden load __________________________ 50, 85 INDEX [Italic page numbers indicate major references] Page Compressibility-effective stress product, definedfiw v Compression index ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, F63 Compressional forces ,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 41 Consolidation , 51, 62, 70, 85 Terzaghi theory ,,,,,,,,,,,,,, , 54, 60 Consolidation coefficient Continental deposits ,,,,,,,,,,,,,,,,,,,,,,,,,,, 63 Corcoran Clay Member of the Tulare Formation 7, 38, 39, 46, 47, 54, 59, 63, 70, 77 Critical depth ________________________________ 41 defined ____________________________________ v D Damage caused by subsidence ____________________ 8 Damage to wells ______________________ 41, 42, 45, 85 Deltaic deposits _______________ 53, 58, 61, 63, 81, 82 Delta-Mendota Canal __,, ____________ 14, 26, 49, 84 Deposition ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 79, 87 Diablo alluvial~fan deposits, bedding ,,,,,, 54, 55, 57 casing failure __ clay content ,,,_ compaction ,,,,,,,,,,,,,, 60, 62 compressibility , We 76, 82, 83 consolidation ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 62, 63 lateral extent stress-compactiq‘n product ,,,,,,,,,,,,, Westhaven site ,,,,,,,,,,,,,,,,,,,,,, Diablo flood-plain deposits, bedding , clay content compaction , , compressibility ,,,,,,,,,,,,,,,,,,,,, deposition ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 80 lateral extent ____________________________ 59 permeability ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 56 Diablo Range ______________________ 7, 10, 64, 70, 81 Diagenetic changes ,,,,,,,,,,,,,,,,, ___ 63 Drawdown ,,,,,,,,,,,,,,,,, E, F Effective stress ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 51, 7O Elastic compaction ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 51 Electric log __- ,,,,,,,,,,,,,,,,,,,,,,,, 55, 57, 76 Equipment____ ,,,,,,, 29, 31, 33, 36, 37, 38, 42, 85 Etchegoin Formation __________________ 8, 64, 67, 77 Expansion "W Firebaugh W, Five Points fiflw; ___________________________ 19, 22 Floodplain deposits, bed thickness ,,,,,,,,,,,,,,,, 62 bedding ,,,,,,,,,,,,,,,,,,,,,, 55, 56, 57, 82, 87, clay content ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 53 compaction ,,,,,,,,,,,,,,,,,,,,, compressibility A deposition ___ lateral extent stress-compaction product ,,,,,,,, Fresno slough ,,,,,,,,,,,,,,,,,,,,, 19, 64, 70, 85 Friction in equipment ,,,,,,,,,,,,,,,,,,,,, 30, 31 G, H, I, J Geologic factors, relation to compaction ,,,,,,,,,, 49 relation to specific unit compaction __________ 67 Ground-water withdrawal -, 1, 7, 10, 33, 45, 57, 67, 84 Hanford ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 10 Page Head decline ________________ F6, 38, 59, 64, 70, 85 Helm oil field ,,,,, __ ,,,,, 8 Huron _________________ 26, 85 Huron site ,,,,,, H” 57,58, 62 Inelastic compaction ____________ lrrigation _____________________ J acalitos Formation ,,,,,,,,,,,,, 8 K, L Kerman ______________________ __ 14 Kettleman City ________ 10, 85 Kings River ,,,,,,,,,,,,,,,,,,,,, 15, 29, 64, 81, 86 Kreyenhagen Formation _______________________ 64 Lacustrine deposits ,,,,,,,,,,, H, 56, 59, 62, 63, 81 Laguna Seca Hills ____________________________ 7 Land surface movement ,,,,,, 6 Lateral extent of beds ____________________________ 59 Lemoore site ________ ._ 49, 63 Level-line network _ ,,,,, 4, 10, 14, 26 Lithology ___________ 54, 57, 58, 59, 76‘, 83, 86 Little Panoche Creek ____________________________ 7 Los Banos _______________________________ 10, 26, 84 Los Banos—Kettleman City, location ___ 2 Los Gatos Creek _________________________ 76, 77, 86 Lower zone, artesian head decline , ,,,,,, 86 compaction _______________ 39, 46 deposition _ ______ 87 deposits __________________________ 51, 64, 79 lithology ____________________________________ 76 specific compaction ______________________ 74, 86 Mapping program, ,_ _ Maricopa ,,,,,,,, Marine deposits Mendota eeeeee 14, 19, 22, 26, 28, 49, 85 Mendota site, bed thickness ______________________ 62 casing failure ______________________________ 46 compaction ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 33, 39 equipment ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 30, 33 lacustrine deposits ,fi 59 micrologs __ permeability pore pressure _________________________ subsidence ,,,,,,,,,,,,,,,,,,,,,,,,,,, water-level change ,,,,,,,,,,,,,,,,,,, Mica ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 51, 63, 85 Micaceous arkosic sand , _,. 58 Micrologs ___- ,,,,,,,,,,,,,,, 60 Moisture condition ,,,,,,,,, 10, 14, 84 Monocline Ridge ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 7 Montmorillonite __________________________ 10, 53, 85 O, P Oro Lorna site, bed thickness A. ,,,,,,,,,,,,,,, 62 compaction ,,,,,,,, e, 33, 38, 39, 74 equipment _____________________________ 30, 33 pore pressure ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 83 subsidence ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 33, 85 water-level change _______________________ 40 Overburden load ,,,,,,,,,, _ 10, 49, 84 Panoche Creek ,,,,, . 7, 76, 77, 87 Panache Hills ,,,,,,,,,,,,,,,,,,,, F90 Page Particle-size analyses ,,,,,,,,,,,,,,,,,,,,,,, F77, 82 Permeability ,,,,,,,,,,,,,,,,,,,,,, 57, 58, 59, 63, 82 Petroleum withdrawal ,,,,,,,,,,,,,,,,,,,,,,,,,, 7 Petrology ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 51, 74 Pleasant Valley 8 Pore pressure ______________ 26, 51, 54, 62, 79, 82, 87 Potentiometric level V ,,,,, 6, 56, 70, 86 Previous work A” 4 Purposes ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2 Q, R, S Quality of lower-zone water ,,,,,,,,,,,,,,,,,,,,,, 77 Rate of compaction ,,,,,,,,,,,, 33, 36, 38, 40, 83, 85 Rate of consolidation ____________________________ 62 Rate of subsidence ,,,,,,,, 2, 6, 8, 9, 10, 19,22, 33, 84 Resistivity ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 55, 76, 77, 86 Reversal of subsidence rate ,,,,,,,,,,,,,,,,,,,,, 26 Richg‘mve site ,,,,,,,,,,,,, 7-- 54 Salinity of the lower»zone water ,,,,,,,,,,,,,,,,, 77 San Joaquin ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 81 San Joaquin Formation ,,,,,,,,,,,,,,,,,,,,,,,,, 64 San Joaquin River ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 86 San Joaquin Valley ,,,,,,,,,,,, 1, 7, 8, 10, 28, 59, 84 San Luis Canal ,,,,,,,,,,,,,,,,,,,, 10, 14, 18, 23, 37 Sand ,,,,,,,,,,, 52, 57, 59, 63, 83, 85 Seepage stress H, _________________________ 67, 70 INDEX Page Sierra deltaic deposits W .,_, F53, 58, 62, 63, 82, 87 Sierra flood-plain depOSits, bedding" 55, 56, 82, 87 bed thickness ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 62 compaction ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 63 deposition ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 80 lateral extent _____________ 59 stress-compaction product _,__ ,,,,,,,,,,,,, 76 Silt ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 52 Sorting of the fan deposits H 57 Specific-unit compaction ,,,,,,,,,,,, 51, 54, 63, 64, 86 Stress-compaction product H 79, 80, 82, 86 defined ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, v Subsidence ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2, 82 damage ____________________________________ 8 near—surface ,,,,,,,,, 8, 14, 84 defined ,,,,, w,‘ v relation to petroleum withdrawal , 8, 84 relation to tectonic movement _____ "e. 7 relation to well-casing shortening ________ 37, 44 relation to withdrawal of ground water ,,,,,,,, 10 Surface-water imports ,,,,,,,,,,,,,, 15, 26, 27, 29, 84 T, U, V Tectonic movement ,,,,,,,,,,,,,,,,,,,,,,,, 6, 7, 84 Terwghi theory of consolidation ,,,,,,,,,,,,,, 54, 60 U. S. GOVERNPDINT PRINTING OFFICE: 1975-0-689-905/12 Page Thickness of' beds ______________________ F54, 64, 83 Tulare ,,,,,,,,,,,,,,,,,,,, 10 Tulare Formation 7, 8, 64, 82 Tulare Lake basin ,,,,,,,,,,,,,,, 7 Unconsolidated deposits _________________ 19, 49, 63 Unsaturated deposits ,,,,,,,,,,,,,,,,,,,,,,,,,,, 86 Uplift of Anticline Ridge ______________________ 7, 84 Upper-zone compaction ,,,,,,,,,,,,,,,,,,,,,,,, 46 Upper-zone deposits," ___ 51 Vertical-control data , h, 4 Void ratio ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 51, 54 / W, Y Warthan Canyon ________________________________ 7 Wasco ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 10 Well-casing failure ,,,,,,,, H 45, 51, 83 Well-casing shortening and protrusion ,,,,,,,,,,,, 36, 41, 42, 43, 85 Westhaven ,,,,,,,,,,,,,,,,,,,,,,,,,, Westhaven site, compaction , equipment ,,,,,,,,,,,,,,,,,,,,,,,,, 30, 35, 42 head decline ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 41 overburden load ,,,,,,,,,,,,,,,,,,,,,,,,,, 51 pore pressure ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 85 subsidence ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 35 Yearout site ________________________________ 49, 64 Qpi75' 7 DAY I! v.4'57' 5 \ Land Subsidence Due To Ground-Water Withdrawal in the Los Banos—Kettleman City Area, California, Part 3. Interrelations of Water-Level Change, Change in Aquifer-System Thickness, and Subsidence GEOLOGICAL SURVEY PROFESSIONAL PAPER 437—G Prepared in cooperation with the California Department of Water Resources Land Subsidence Due To Ground-Water Withdrawal in the Los Banos—Kettlernan City Area, California, Part 3. Interrelations of Water-Level Change, Change in Aquifer-System Thickness, and Subsidence By WILLIAM B. BULL and JOSEPH F. POLAND STUDIES OF LAND SUBSIDENCE GEOLOGICAL SURVEY PROFESSIONAL PAPER 437—G Prepared in cooperation with the California Department of Water Resources UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1975 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress Cataloging in Publication Data Bull, William B. 1930— Land subsidence due to ground-water withdrawal in the Los Banos—Kettleman City area, California. (Studies of land subsidence) (Geological Survey Professional Paper 437—E—G) Pt. 2 by W. B. Bull; pt. 3 by W. B. Bull and J. F. Poland. Includes bibliographies and indexes. CONTENTS: pt. 1. Changes in the hydrologic environment conducive to subsidence.~pt. 2. Subsidence and compaction of deposits. [etc.] Supt. of Docs. No.: I 19.16z437—G 1. Subsidences (Earth movementsF—California—San Joaquin Valley. 2. Aquifers—Califomia—San Joaquin Valley. 3. Water, Underground—California—San Joaquin Valley. 1. Miller, Raymond E. II. Poland,Joseph Fairfield, 1908— III. California. Dept. of Water Resources. IV. Title. V. Series. V1. Series: United States. Geological Survey. Professional Paper 437~E—G. QE75.P9 No. 437—E—G [GB485.C2] 557.3’O8s [551.3’5] 74—28239 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, DC. 20402 Stock Number 024—001—02611 CONTENTS Abstract __________________________________________________ Introduction ______________________________________________ Purposes of report ____________________________________ Definition of terms ____________________________________ Acknowledgments Analysis of stress changes tending to cause compaction ______ Stress change due to change in seepage forces __________ Stress change due to fluctuation of the water table ______ Buoyancy effects __________________________________ Effect of specific retention in the unsaturated zone __ Equation summing change in applied stress ____________ Combined effect of man-induced stress changes tending to cause additional compaction of the lower zone ____ Interrelations of water-level change, change in aquifer-system thickness, and subsidence ____________________________ Relation of subsidence to artesian-head decline __________ Relation of changes in aquifer-system thickness to change in artesian head Elastic and inelastic changes in aquifer-system thick- ness ________________________________________ Page G1 2 2 2 4 4 4 5 5 5 6 6 8 8 11 11 ILLUSTRATIONS FIGURE 1. Map showing location of bench marks, observation wells, compaction recorders, core holes, and lines of section re- ferred to in this report ____________________________________________________________________________________ Page Interrelations of water-level change, etc—Continued Relation of changes in aquifer-system thickness, etc—Con. Elastic and inelastic changes, etc—Continued Relation of monthly compaction to water-level change ________________________________ G13 Relation of compaction and expansion to change in artesian head __________________________ 17 The Lemoore site __________________________ 18 The Yearout site __________________________ ' 21 Well 19/16—23P2 __________________________ 22 Relation of lower-zone compaction to change in applied stress ______________________________________ 27 Criteria for the prediction of future subsidence ______________ 35 Timelag of compaction ________________________________ 35 Conditions before delivery of canal water ______________ 37 Computation of aquifer-system pore-pressure decay __ 44 Conditions after delivery of canal water ________________ 49 Summary ________________________________________________ 57 References ________________________________________________ 60 Index ____________________________________________________ 61 Page G3 2. Diagrams showing the effect of water-table change on lower-zone applied stress __________________________________ 7 3. Profiles of subsidence and artesian-head decline, 1943—66, Tumey Hills to Mendota ______________________________ 9 4. Profiles of subsidence and artesian-head decline, 1943—66, Anticline Ridge to Fresno Slough ______________________ 9 5—10. Graphs of subsidence and artesian-head decline near bench mark: 5. GWM59 ______________________________________________________________________________________________ 9 6. B1042 ________________________________________________________________________________________________ 10 7. 8661 ________________________________________________________________________________________________ 10 8. H237 (reset) __________________________________________________________________________________________ 10 9. N692 ________________________________________________________________________________________________ 10 10. PI‘SZIS ______________________________________________________________________________________________ 11 11. Graphs of subsidence, compaction, and artesian-head decline near Huron ________________________________________ 12 12—18. Graphs showing relation of: 12. Annual compaction rates to change in artesian head at the Oro Loma site ________________________________ 13 13. Monthly compaction to lower- -zone water- level change at the Mendota site, well 14/13—11D6 ________________ 14 14. Computed virgin compaction to lower- -zone water- level change at well 14/13—11D6 ________________________ 15 15. Monthly compaction to lower- -zone water- level change at the Cantua site __________________________________ 16 16. Monthly compaction to lower- -zone water-level change at well 19/16—23P2 ________________________________ 16 17. Monthly compaction to lower- z-one water- level change at the Westhaven site, 20/18—11Q2, 11Q3 ____________ 17 18. Aquifer- s-ystem compaction or expansion to water- level change, well 18/19—20P2 __________________________ 19 19. Stress- strain plot for well 18/19—20P2 __________________________________________________________________________ 20 20—23. Graphs showing relation of aquifer- s-ystem compaction or expansion to water level change: 20. Well 13/15—35D5 _______________________________________________________________________________________ 22 21. Well 19/16—23P2, February—July 1967 __________________________________________________________________ 24 22. Well 19/16—23P2, March 14—April 13, 1967 ______________________________________________________________ 25 23. Well 19/16—23P2, summer 1964 ________________________________________________________________________ 26 IV FIGURES 24—29. CONTENTS Maps showing: Page 24. Change in applied stress on the lower zone resulting from change in the position of the water table, 1943—60-- G28 25. Increase in applied stress on the lower zone resulting from artesian-head decline between 1943 and 1960 ___ 30 26. Increase in total applied stress on the lower zone, 1943—60 _____________________________________________ 31 27. Estimated compaction in the lower zone, 1943—59 _______________________________________________________ 32 28. Specific compaction of the lower zone, 1943—60 _________________________________________________________ 33 29. Depth to lower-zone pumping level, summer 1965 _____________________________________________________ 38 30. Plots of cumulative subsidence and subsidence rate for bench mark 8661 _______________________________________ 39 31. Map showing number of feet of lower-zone head decline associated with each foot of subsidence, 1943—60 ___________ 40 32. Map showing specific subsidence, 1943—59 _____________________________________________________________________ 41 33—39. Graphs showing: 33. Applied-stress increase and subsidence relations at bench mark GWM59 _________________________________ 42 34. Applied-stress increase and subsidence relations at bench mark H237 (reset) _____________________________ 42 35. Applied-stress increase and subsidence relations at bench mark P’I‘S218 _________________________________ 43 36. Changes in the mean daily compaction rate of deposits for selected applied stresses _______________________ 45 37. Decrease in the mean daily compaction rate in the 703—2,000-foot-depth interval at the Cantua site _________ 46 38. Estimated time needed for residual compaction to occur after mid-1961, 703—2,000-foot-depth interval, Cantua site ______________________________________________________________________________________ 47 39. Decrease in the mean daily compaction rate of the lower-zone deposits at the multiple compaction-re- corder sites _____________________________________________________________________________________ 48 40. Map showing areas to receive water from the San Luis Canal section of the California Aqueduct _________________ 51 41. Maps showing the effect of delivery of Delta-Mendota Canal water on subsidence rates in the northern part of the Los Banos—Kettleman City area ______________________________________________________________________ 52 42. Graphs showing interrelations of subsidence rates, artesian-head decline, and surface-water imports near Stratford and Lemoore __________________________________________________________________________________ 53 43. Map showing estimated annual subsidence rates in the Los Banos—Kettleman City area in 1970 if summer lower-zone water levels rose 60 feet and the seasonal fluctuation were reduced to 10—20 feet ________________ 55 TABLES Page TABLE 1. Variation in net specific unit expansion during a period of seasonal head recovery at well 18/19—20P2 ________________ G21 2. Estimated annual subsidence rates in the Los Banos—Kettleman City area if summer lower-zone waterlevels rose 60 feet and the seasonal fluctuation were reduced to 10—20 feet ______________________________________________ 54 STUDIES OF LAND SUBSIDENCE LAND SUBSIDENCE DUE TO GROUND-WATER WITHDRAWAL IN THE LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3. INTERRELATIONS OF WATER-LEVEL CHANGE, CHANGE IN AQUIFER-SYSTEM THICKNESS, AND SUBSIDENCE By WILLIAM B. BULL and JOSEPH F. POLAND ABSTRACT By increasing the stresses tending to compact the deposits by as much as 50 percent, man has created the world’s largest area of intense land subsidence in the west—central San Joaquin Valley, Calif. As of 1966, more than 2,000 square miles had subsided more than 1 foot, and the area that had subsided more than 10 feet was 70 miles long. Maximum subsidence was 26 feet. The increase in stress caused by pumping of ground water can be expressed in feet of water. A seepage stress of 1 foot of water occurs for each foot of head differential resulting from either artesian-head change or change in water-table position. Stress increase resulting directly from artesian-head decline has caused most of the compaction and subsidence. Each foot of water-table change also causes a 0.6-foot stress change because of removal or addition of buoyant support of the deposits within the interval of water-table change and a 0. 2-foot stress change because of part of the pore water being changed from a neutral-stress condition to an effective-stress condition, or vice versa. The effect of water-table change is to alter the grain-to-grain stress in the unconfined aquifer by $0.8 foot of water per foot of water-table change. The effect of water-table change on stress in the deeper confined zones is to alter the stress by only :t0.2 foot of water because the seepage-stress change more than offsets the sum of the two other stress changes. Changes in aquifer-system thickness may be both elastic (are re- versible and occur with minor time delay) and inelastic (are irreversi- ble and occur with large time delay). As of 1966 excess pore pressures existed in many of the aquitards and net aquifer-system expansion occurred briefly or not at all, but elastic changes did affect the monthly amounts of measured compaction. Compaction rates were maximal during times of head decline because elastic compaction is additive with virgin compaction, and compaction rates were minimal during times of head rise because expansion is subtractive from virgin com- paction. In the study area, the elastic component of seasonal compac- tion varies from less than 5 to about 90 percent. The percentage depends not only on the lithology and permeability of the deposits, but also on the magnitude and rate of increase of present applied stress as compared with past effective stress maximums and durations. Three concurrent processes are tending to change aquifer-system thickness during times of applied-stress decrease—elastic expansion with no measurable time delay (presumably chiefly of the aquifers), delayed elastic expansion (presumably chiefly of the thin aquitards and the outer parts of the thick aquitards), and virgin compaction (presumably of the thick aquitards and aquicludes). Compaction due to decay of excess pore pressures may still occur in thick clay beds after 60 feet of head recovery in adjacent aquifers, but only 1 foot of head recovery may be needed to reverse the trend from recorded compaction to recorded net expansion, even when water levels are near historic lows. The approximate modulus of expansion (net specific unit expansion) of the upper-zone aquifer system at the Lemoore and Yearout sites is about 3.5 X 10’6ft”1 (foot per foot of aquifer-system thickness per foot of decrease in applied stress). Dur ing a period of seasonal head recovery at the Lemoore site, the net specific unit expansion varied from 0.6 to 3.6 X 10"5ft’1 as the rates of residual compaction and nondelayed and delayed expansion varied concurrently with changes in the magnitude and rate of applied-stress decrease. 7 Little time is needed to raise pore pressures in many of the aquitards. Compaction ceases when aquifer pore pressures rise to equilibrium with the maximum pore pressure in a contiguous aquitard, thus preventing further expulsion of water. Further pore- pressure increases in the aquifers are transmitted fairly rapidly into the aquitards because their specific storage in the elastic range is small. The prediction of subsidence is largely empirical, and reasonable predictions can be made only if the rates and magnitudes of future applied-stress changes can be predicted accurately. The time- dependent nature of the pore-pressure decay in the aquitards and aquicludes greatly complicates estimates of compaction for heterogeneous aquifer systems. Most of the subsidence since 1960 has been the result of prior applied-stress increases. In many of the thick beds of low permeabil- ity, the applied stress has not yet become effective because of insufficient time for pore pressures in the aquicludes and aquitards to reach equilibrium with the head in the aquifers. Determination of the rates and changes of rates of residual compaction is important in the prediction of subsidence. The rate of decrease of aquitard-aquifer pore-pressure differentials can be evaluated at some sites through study of change of mean daily compaction rates for selected applied stress levels. In the 7 03—2,000-foot depth interval at the Cantua site, the relation between mean daily compaction rate (y) and time (x) for the 1961—67 period is y=0.0028e‘0'096‘". Because increase in applied stress was negligible from 1961 to 1967, the decrease in the post-1961 rate of daily compaction can be used to estimate future residual compaction. A 10-percent decrease in re- sidual compaction rate had occurred as of mid-1962 and 45 percent as of 1968, and a 90-percent decrease is predicted by about 1986. assum» G1 G2 ing a hydrologic environment similar to that of the 1961—67 period. Exponents of similar equations for other compaction-recorder sites indicate that the rate of pore-pressure decay is twice as rapid in the northern as in the southern part of the study area. Importation of surface water has resulted in alleviation of subsi- dence in the Delta-Mendota Canal service area and in the vicinity of Stratford and Lemoore. Deliveries of water from the San Luis Canal section of the California Aqueduct should result in widespread allevi- ation of subsidence. INTRODUCTION By increasing the stress tending to compact the un- consolidated deposits by as much as 50 percent, man has created the world’s largest area of intense land subsid- ence in the west—central San Joaquin Valley. With- drawal of ground water for agriculture has caused more than 2,000 square miles to subside more than 1 foot. As of 1966, the area that had subsided more than 10 feet was 70 miles long and included 500 square miles; max- imum subsidence was 26 feet. Water-level changes in the aquifer systems have in- creased the applied stresses and have caused acceler- ated compaction of the deposits. Detailed knowledge of the interrelations of water-level change, change in aquifer-system thickness, and the concurrent changes in the altitude of the land surface is necessary for a better understanding of the mechanics of aquifer sys- tems and the compaction of sediments, as well as for the development of criteria in predicting future land subsidence. This paper is the third of three reports discussing land subsidence due to ground-water withdrawal in the Los Banos—Kettleman City area, California. Part 1 (Bull and Miller, 1974) is a factual presentation of the hy- drologic factors conducive to land subsidence in the study area. Part 2 (Bull, 1974) contains basic data and interpretation about the land subsidence and compac- tion that have been measured in the area and discusses geologic factors influencing the amounts, rates, and dis- tribution of compaction. The introduction to all three parts, in Part 1 (Bull and Miller, 1974), includes descriptions of the geographic setting of the study area, the formation and objectives of the Inter-Agency Committee on Land Subsidence, the scope of the field and laboratory work for the coopera- tive and federal subsidence programs, and brief sum— maries about land subsidence and compaction. For a summary of the hydrologic environment, and the man- induced changes in the hydrologic environment, the reader is referred to the summary and conclusions of Part 1 (Bull and Miller, 1974). The principal areas of land subsidence due to ground-water withdrawal in California and the topographic and cultural features of the Los Banos—Kettleman City subsidence area are shown in figures 1 and 2 of Part 1 (Bull and Miller, 197 4). STUDIES OF LAND SUBSIDENCE The boundaries of the Los Banos—Kettleman City study area, bench marks, observation wells, compaction recorders, core holes, and lines of section referred to in this report are shown in figure 1. The northeastern boundary as shown in figure 1 is along the valley trough, but as of 1966, as much as 8 feet of subsidence had occurred east of the valley trough. Therefore, in much of the study, the 1-foot subsidence line of 1920—28 to 1966 (Pt. 2, Bull, 1974, fig. 9) was used as the east boundary of the subsidence area. PURPOSES OF RE PORT The overall purpose of Part 3 is to relate water-level changes to changes in thickness of the aquifer-system skeleton in the west-central San Joaquin Valley. This goal consists of three purposes. The first is to review how grain-to-grain stresses are changed by water-level changes. The analysis of stresses has been discussed by ‘ Lofgren (1968), but a modified method of applied-stress computation is used in this study. The second purpose is to show the effects of change in applied stress on aquifer-system thickness. Three components of change in aquifer-system thickness are discussed. The third purpose is to provide criteria for predicting future sub- sidence in the study area and to assess the reliability of the possible ways of predicting future subsidence. The bulk of the information presented in this paper concerns events that occurred before April 1966, which was the time of a complete survey of the bench-mark network by the US. Coast and Geodetic Survey (now National Geodetic Survey of the National Ocean Sur- vey, National Oceanic and Atmospheric Administra- tion). Post-March 1966 data are presented and dis- cussed only to present facts or concepts that cannot be demonstrated with the earlier data. DEFINITION OF TERMS The geologic and engineering literature contains a variety of terms that have been used to describe the processes and environmental conditions involved in the mechanics of stressed aquifer systems and of land sub- sidence due to withdrawal of subsurface fluids. The usage of certain of these terms in reports by the US. Geological Survey research staff investigating mechanics of aquifer systems and land subsidence is defined and explained in a glossary published sepa— rately (Poland and others, 1972). Several terms that have developed as a result of the Survey’s investiga- tions are also defined in that glossary. The aquifer systems that have compacted sufficiently to produce significant subsidence in California and elsewhere are composed of unconsolidated to semicon- solidated elastic sediments. The definitions given in the published glossary are directed toward this type of sed- LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 R. 10 E. II 12 13 120°30’ 14 15 16 I7 120°OO’ R.19 El 33 I I I I I I 152 Lot Banos I I I I 152 ’ I I I | | | I | I | I | | I _ _____I_____ I____ __I _’__ _| _______ | _______ | _______ o I I I Dos I l | 37 00 | Palos X It; I m I' I ~-\£r§9{-I/—~ VI‘f 9‘: I I / 33 I I I | w 394% ____I I Y7, _| _______ | _______ I GEL'EIIEI_ _____ I_ __‘— I I C; e site | I I I (' I ’1 0t I I I” / I 2 qsI-n s h I II II I ’ I II "I Firebaugh I O | | I 669-17— — 25¢;1I- —————— 1i ——————— III — — —+ ——————— IL —————— —+ ——————— | l «’cg'ooéeo I I I ’ I ' é‘ T ; (n E m —— \ i 0 U, 11-: W“ “——~\—\ APW E a Guntard A. B. C \ APb+AP : m 600 1 I ' 34600 n. D o 200 400 o 200 o 200 400 < NEUTRAL STRESS, IN FEET OF WATER FIGURE 2.—Effect of water-table change on lower-zone applied stress. A, Water table and lower-zone potentiometric surface at same level, B, Water table lowered, potentiometric surface constant. C, Water table raised, potentiometric surface constant. All stresses in feet of water; based on assumed porosity of 0.40, specific gravity of 2.70, and specific retention of 0.20 by volumePs : applied stress due to dry weight of unsaturated deposits;Pb : applied stress due to buoyant weight of submerged deposits; Pw 2 applied stress due to weight of contained water in unsaturated deposits; J =seepage stress; AP=change in total applied stress from condition A. G8 buoyancy effects tending to lift the grains in the section that has been submerged, and 20 feet of the decrease is the result of transfer of the pore water from an applied- stress to a neutral-stress condition. The 100 feet of water-table rise also caused a head differential across the aquiclude that has resulted in a downward seepage stress of 100 feet. The net effect of the three water-table components of stress change applied to the top of the lower-zone aquitard is to increase the applied stress by 20 feet of water. The net effect of stress change on the lower-zone de- posits per unit change in the position of the water table will be minor. Changes in stress resulting from buoyancy changes and changes in the stress condition of the contained water are more than offset by the change in seepage stress that also results from change in the position of the water table. A net change of applied stress on the lower zone of 0.2 foot of water per foot of water—table change is the resultant of the three compo— nents tending to change the applied stress. If the con— tained water above the water table is not taken into account, the net change in applied stress would be 0.4 foot of water—twice as large as it should be. During 1951—65, local water-table declines caused as much as 40—70 feet of water applied-stress decrease on the lower zone. Locally, change from a confined to a water-table condition below the Corcoran Clay Member of the Tulare Formation has decreased the rate of applied-stress increase from 1.0 to 0.8 foot of water per additional foot of lower-zone water-level decline. INTERRELATIONS OF WATER-LEVEL CHANGE, CHANGE IN AQUIFER-SYSTEM THICKNESS, AND SUBSIDENCE Part 1 (Bull and Miller, 1974), Part 2 (Bull, 1974), and the preceding section of this paper have discussed the hydrologic environment, the stress changes caused by changes in the hydrologic environment, and the com- paction of the ground-water reservoir and resulting land subsidence. The purpose of this section is to show the interrelations of change in applied stress caused by changes in the positions of the potentiometric surfaces including the water table, decrease or increase in aquifer-system thickness, and land subsidence. In most of the area the decline in artesian head ap- proximates the increase in stress, expressed in feet of water, tending to compact the lower-zone deposits. Changes in the position of the water table have been minor at most observation-well sites during the periods of record. Also, about 5 feet of water-table change causes a net change in applied stress on the confined zones that is equivalent to only 1 foot of change in artesian head. Therefore, the plots of change in artesian head shown in figures 3—23 are representative of the general changes STUDIES OF LAND SUBSIDENCE in applied stress (in feet of water) that have occurred in the deposits in which the wells are perforated. First, the records from two lines of section and specific sites throughout the area are interpreted. Then, the regional change in applied stress on the lower-zone de- posits that has resulted from changes in the positions of the potentiometric surfaces of the lower zone and the water table is analyzed for a 17—year period as the basis for a specific compaction map of the lower zone. RELATION OF SUBSIDENCE TO ARTESIAN-HEAD DECLINE A comparison of the regional declines in land-surface altitudes and the artesian head of the lower zone be- tween 1943 and 1966 is shown in figures 3 and 4. The plots showing change in head do not extend as far southwest as the plots showing change in the land- surface altitude, because the area near the foothills of the Diablo Range had not been developed agriculturally in 1943 and hence no head measurements were made west of those shown. Profiles of subsidence and artesian-head decline be- tween Tumey Hills and Mendota are shown in figure 3. The subsidence profiles reveal a slightly asymmetrical change in the altitude of the land surface. The profiles of artesian-head decline roughly parallel each other, but do not have the same overall configuration as the subsi- dence profiles. The profiles of head decline show pro— gressively larger amounts of decline to the west, whereas the subsidence profiles have a pronounced re— versal about midway along the line of section. By 1966 a maximum of 24 feet of subsidence had occurred since 1943 where the head had declined only 190 feet; farther to the southwest, only 14 feet of subsidence had occurred where the head had declined 350 feet. The profiles of subsidence and artesian-head decline between Anticline Ridge and Fresno Slough in figure 4 reveal a history that is roughly similar to that shown in figure 3. The subsidence profiles show a markedly asymmetrical change in land-surface altitude. The profiles of head decline parallel each other in the east half of the line of profile, but show a marked divergence in the west half. The 1955 head—decline profile is similar to the subsidence profile in that it reverses its trend and is asymmetrical. The trough of the head-decline profile is 1—2 miles southwest of the trough of the subsidence profile. By 1966, the head-decline profile did not show a reversal, but instead had an overall trend of increasing depth to the west. The subsidence maximum of 18 feet occurred where the head had declined 200 feet, but 5 miles to the southwest only 3 feet of subsidence had occurred where the head had declined 275 feet. It is readily apparent from figures 3 and 4 that al- LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 A April 1943 A’ I | Sam. 1955 SUBSIDENCE, IN FEET 3 oo 1 1 .- CD | 20— _ M 24_ 1 ay1943 *i -0 Ma 1955 0 — y —50 5 3F ._ _ 2+- Dec.1965 10° <31 (7)11. — —150 E; Eu; _ —2oo Lug 58 — —250 N 0:0 “a” — —300 o _| | I | o 4 8 12 16 2o350 DISTANCE, IN MILES FIGURE 3.~Profiles of subsidence and artesian-head decline, 1943—66, Tumey Hills to Mendota. though subsidence is associated with head decline, the quantitatiVe relation between cause and effect varies within the study area. For example, the subsidence/head-decline ratio varies along the line of profile 3 from 0.12 to 0.04, and the ratio varies along the line of profile for figure 4 from 0.09 to 0.01. Geologic reasons for the variability of the subsidence/head de- cline ratio are discussed in Part 2 (Bull, 1974). Comparisons of subsidence and change in artesian head are shown for selected bench marks and nearby wells in figures 5—10. The ratio of the water level to the subsidence scales is 20:1. The hydrographs consist of selected measurements that represent times of maxi- mal applied stress during the intensive pumping periods of late winter and summer. Description of the G9 8 Feb. 1943 3' 0 l 1 Nov.1955 4_ 1— LIJ LU LI. 3 8‘ of 0 Z UJ 912— V) [D D U) 16— M 20* ay1943 —O Q < LIJ 2 ~50 I,’_ Em _ 77100 at May 1955 ”i—JZ _ —150 Em Lug 2.1 * Dec. 1965 -200 08 gr: 2 «250 u E ‘3 l l l i o 4 8 12 16 20300 DISTANCE, IN MILES FIGURE 4.7Profiles of subsidence and artesian-head decline, 1943766, Anticline Ridge to Fresno Slough. six sites is from north to south, and the locations of the bench marks and wells are shown in figure 1. Subsidence and artesian-head decline near bench mark GWM59, 15 miles west of Mendota, are shown in figure 5. Subsidence rates increased between 1940 and 1955, and since then have undergone a slight, but con- I 1940 1950 1960 3 o d '- 300 1 r I 0 ED .1 3 Bench mark GWM59 E 14; LL We|l13/12-22N1 L“ a z perforated 400- u. _, — 400 1223 feet 5 E o W “I 32 ' ° 2 LL 5 n: E? 3 500 Well 13/12-2201 1° 9 tn perforated 602- g E g 1090 feet 3 I j J 1 m L' 600 LIJ 0 FIGURE 5,—Subsidence and artesian—head decline near bench mark GWM59. G10 tinuing, decrease. The water—level record reveals a parallel history of accelerating, then decelerating, rate of decline. Since 1960, summer low water levels have undergone little decline, while the subsidence has con— tinued at a moderately rapid rate. Subsidence and artesian—head decline near Mendota are shown in figure 6. This site provides the longest bench-mark record of subsidence in the Los Banos— Kettleman City area. The overall trends of both the subsidence and water-level plots have been toward gradually increasing rates of subsidence and head de- Cline. Subsidence and artesian—head decline 10 miles southwest of Mendota are shown in figure 7. Bench STUDIES OF LAND SUBSIDENCE mark 8661 has subsided more than any other bench mark in the San Joaquin Valley, even though the period of record extends only as far back as 1943. Rapid com- paction has destroyed well casings within a few years. Thus, the records from several wells are necessary to show the trend in water levels. Both the rates of subsid- ence and head decline have decreased since the mid-1950’s. Subsidence and artesian-head decline near bench mark H237 (reset), 6 miles northwest of Cantua Creek, are shown in figure 8. Well 16/15—6N1 was one of the first wells drilled in the vicinity of the bench mark, and the water-level record during the early 1940’s indicates that little head decline occurred during initial agricul- tural development. Between 1944 and 1961, the ar- tesian head declined rapidly, and since 1961 the head has continued to decline but at slower rates than previ- ously. The rate of subsidence increased until about 1960 and has been roughly constant since then. Subsidence and artesian-head decline southwest of Five Points are shown in figure 9. The head-decline 200 I I l 0 E E u! 0 Bench mark H237 LL 4 z E E f”. —| u! 300— ‘5 U m LL 2 > 2 Well 16/15-6N1 \ Lu ‘1", - perforated _D_ 0 8 396-1673 feet 3 E < 400— —10 :> n. u. w E n: D D 0.0) Well16/14-102 O D perforated 663- I‘2 500— 1610feet _ I <1 ._ _| n. Lu 0 600 ' ' ' 1940 1950 1960 1970 3 O _l N m l— o _. Hui 0 | l l l E ”>1: Bench mark 174 Bench mark Y661 ”u: U] -— Z 3.; "’0' Park“ 5 —. 2 0 31042 LL“, E If Well 13/14-3501 z 2 I 200 1100 feet deep 10 U1 3 :2 Well 14/15-18E2 9 “- ‘0 perforated 525- ‘8 O D 888 feet 3 ’— Z 300 l ' ' l ' 15 a, I: 1920 1930 1940 1950 1960 1970 l: Lu 0 FIGURE 6.—Subsidence and artesian-head decline near bench mark B1042. 200 1 I 0 l— Lu Bench mark 5661 m u. E . 300 - - 5 m 2’ Well 14/13-26N1 LL perforated n; 525-1409 feet 8 o 400 7 v 10 ,_ 2 Lu < m J u. g E 0 ~ u: d 500 1 —15 S 3 Well 14/13-26N2 m LU perforated 831- 9 > 1703 feet (I) Lu m _l 3 to 600~ —2o (0 E SE Well 14/13-26E2 3 perforated 809- 0- 1526 feet 0 1 ,_ 700— 25 I '- u. u: D 800 if ' l 1950 1960 1970 FIGURE 7.—Subsidence and artesian-head decline near bench mark 8661. FIGURE 8,—Subsidence and artesian-head decline near bench mark H237 (reset). 300 —r Bench mark N692 Well E O J Lu :1: l- 18/16722R1 _. 3 40071839 feet -5 5 Lu u. deep Lu > 2 u. 5 ". z (D L” _ 3% 50° " —1o 8 “- “- Well 18/16-2202 5 g g perforated 702- D u. w 2020 feet (.5 O D m i— z 600 ~ — 1 5 D I < m .— _.l n. Lu 0 | | | 20 7001940 1950 1960 1970 FIGURE 9.#Subsidence and artesian-head decline near bench mark N692. LOS BAN OS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 trend is similar to that shown in figure 8, although the head decline since 1940 has been about 90 feet greater near bench mark N692 than near bench mark H237. The subsidence histories of the two bench marks are similar until 1960, but since 1960 the rate of subsidence at bench mark N692 has decreased slightly, while that at bench mark H237 has been constant. Subsidence and artesian-head decline near West- haven are shown in figure 10. Wells in the vicinity of this bench mark provide the longest record of head decline in the Los Banos—Kettleman City area. The water-level record begins in 1918, and the bench-mark record begins in 1923. The rapid decline in artesian head between 1947 and 1953 coincided with a period of marked agricultural expansion after World War II. The subsidence rate increase after 1947 coincided with the increased rate of head decline. The relation between subsidence and the change in applied stress on the lower-zone deposits is discussed for three of the preceding sites with reference to figures 33—35. 100 r fir r I Wel|19/18-28F1 perforated 222- 2065 feet Well 19/18-14D1 perforated 750- 1690 feet 200— 300— _ Well 19/18-28E1 perforated 700- A 0 4°0— 2010 feet Bench mark PTS21S 500 — DEPTH TO PUMPING LEVEL BELOW LAND SURFACE, IN FEET 600 l 1920 l 1930 l 1940 L 1950 l 1960 l - 01 O SUBSIDENCE, IN FEET 0 FIGURE 10.—Subsidence and artesian-head decline near bench mark PTSZIS. RELATION OF CHANGES IN AQUIFER-SYSTEM THICKNESS TO CHANGE IN ARTESIAN HEAD The history of subsidence, compaction, and changes in artesian head near Huron from 1954 to 1960 is shown in figure 1 1 by means of graphs of subsidence of the land surface at B889, compaction in a well 2,030 feet deep as recorded by shortening of a cable anchored at the bot- tom of the well (Lofgren, 1961), and change in head as recorded by a float-type water-level recorder on well 19/18—27M1. The compaction record was the result of the first attempt to measure compaction in the study area. A good record was obtained from mid-1955 until the fall of 1960, when the cable of the compaction recorder failed because of corrosion. Attempts to install new equipment were unsuccessful. Bench mark B889 and well 19/17—35N1 are close together about 1%; miles G11 north of Huron, but well 19/18—27M1 is about 5 miles east of the compaction-recorder site. Wells suitable for water-level recorders were not available nearer the compaction recorder. The plots of subsidence and compaction in figure 11 are about parallel, indicating that most of the compac- tion causing the subsidence occurred above the depth of the compaction anchor at 2,030 feet. From October 1955 to January 1960, measured compaction was 85 percent of the total subsidence as observed by releveling of the nearby benchmark. The hydrograph for well 19/18—27M1 reveals an overall rate of head decline of about 8 ft yr‘1 (feet per year). Superimposed on the long-term trend are seasonal fluctuations of 40—70 feet. Comparison of the compaction and water-level plots shows that maximum compaction rates occur during seasons of declining head. Compaction rates are small or net compaction ceases during seasons of rising ar— tesian head. The trends of annual compaction rates and lower- zone artesian-head decline at the Oro Loma site near the Delta-Mendota Canal are shown in figure 12. The amounts of annual compaction measured by a cable- type recorder anchored at 1,000 feet in well 12/12—16H2 decreased from 0.44 ft yr’1 in 1959 to 0.08 ft yr'1 in 1965. The water level in well 12/12—16H6 indicates that the summer low water levels have been almost the same since 1960 but that the recovery of the water levels during the winters has become progressively less. Hence, the seasonal fluctuations decreased from 23 feet in 1960 to 9 feet in 1965. The compaction shown in figure 12 is virgin compac- tion occurring in the thicker more clayey aquitards and ' aquicludes that still are characterized by residual ex- cess pore pressures. The decrease in annual compaction rates reflects a progressive decrease in pore-pressure differences between aquifers and aquitards in the aquifer system as water drains to the more permeable strata. ELASTIC AND INELASTIC CHANGES IN AQUIFER-SYSTEM THICKNESS Not all virgin compaction is inelastic. A small part of the virgin decrease in aquifer-system thickness is elas- tic. The next two sections will describe some aspects of elastic compaction and expansion of the aquifer system, as well as virgin compaction, in response to change in applied stress as indicated by change in artesian head. The following modification of Jacob’s (1940) equation 1for the coefficient of storage provides a convenient way to visualize the relative importance of the elastic and inelastic components of compaction due to artesian— head decline: Q ._. N) STUDIES OF LAND SUBSIDENCE t; 360 m J “' LLI Z > \ " LU “In 358 Q < \ g ”a; \ /$ubsidence, bench mark 3889 }— Z 4 Lu 0: LL! 2 O i (D 0 <12 2 u: m 352 }_ Lu LU u. tion, well 19/17-35N1 Z i 9 '6 3 280 < O D. _J 2 u.l O m o 'u‘, m 320 “1 u "L < z u. - n: ‘ D 1:: Lu m 360 I- o <( Z 3 < 0 _| y‘drograph, well '_ 19/18-27M1 I 400 g. n. LIJ 0 1956 1957 1958 FIGURE 11.——Subsidence, compaction, and artesian-head decline near Huron, Inelastic Elastic components component Total water _ Expansion + Compression + Compression + Compaction from storage of water of aquifers of aquitards of aquitards per unit decline in head S = 'Ymn/E + 7m /E + 'Ym /E + 77713- t w 1 s 2 c 2 c 7 is the specific weight of water, n is the mean porosity of the aquifer system, m1 is the thickness of the aqui— fers, m2 is the thickness of the aquitards, m is the thickness of the aquifer system, Ew is the bulk modulus of elasticity of water, E s andEc are the moduli of elastic- ity of the aquifers and aquitards respectively, and [3 c is the modulus of compressibility for the inelastic compac- tion of the aquitards. Assumptions for this equation are that the aquifer system consists of uncemented granu- lar material and that the release of water from all parts of the aquifer system is instantaneous. These assump— tions are met for the first three terms of the equation. Because a timelag exists for the compaction of aquitards, the field determination of the fourth term is only an approximate minimum value. The water that is obtained from storage as a result of head decline is obtained from the elastic expansion of the water contained in the pore spaces and the compres- sion of the aquifer-system skeleton containing the water. The following example compares the general mag- nitude of the storage components yielded as a result of artesian-head decline for well 19/16—23P2: St =mn/Ew+7m1/Es +7m2/Ec+ ym2 ’Bc .- 36x10'3=(1.0 + 2.5 + 32)x10-3. The component of 1.0x 10’3 is the amount of water released from storage per unit head decline as a result of expansion of water, assuming a porosity of 0.4, a thick- LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 180 ell12/12-16H6 190 200 DEPTH TO WATER BELOW LAND SURFACE IN FEET 210 ANNUAL COMPACTION RATE, IN FEET PER YEAR, FOR THE 0-1000>FOOT DEPTH INTERVAL, WELL 12/12 16H2 01959 1960 1961 1962 1963 1964 1965 FIGURE 12.—Relation of annual compaction rates to change in artesian head at the Oro Loma site. ness of 1,800 feet, and 3 X 105 lb in—2 for the modulus of elasticity for water. The component of 2.5><10-3 is an estimate of the minimum amount of water released from storage per unit head decline as a result of elastic compression of the aquifers and aquitards within the 1,800-foot thick- ness and thus combines the second and third terms of the original equation. The estimate is based on the mean recorded net expansion measured during 18 periods of ,head recovery in which recorded expansion exceeded 0.01 foot. It is assumed that elastic compres- sion is equal to elastic expansion and that change in thickness in the elastic range of deformation is linear with change in effective stress. As will be discussed later, amounts of recorded expansion generally are less than amounts of actual expansion because of concurrent delayed compaction in beds with residual excess pore pressure. Thus, the value of 2.5><10_3 should be re- garded as a minimum. The inelastic component of 32 X 10—3 (the fourth term of the equation) is an estimate of the minimum amount of inelastic compaction of the aquifer system per unit head decline. The amount is based on the total subsid- ence that has occurred at well 19/16—23P2 as of 1966 G13 minus the estimated elastic compaction that has oc- curred for the historic increase in applied stress. About 8 feet of inelastic subsidence has occurred as a result of 250 feet of increase in applied stress. Continued record- ing of compaction during times of nonrising water levels, when potentiometric levels are above the his- toric low levels at well 19/16—23P2, indicates that the applied stress has not become fully effective in the finer grained parts of the aquifer system and that ultimate amounts of compaction have not occurred yet. Thus, the value of 32X 10‘3 should be regarded as a minimum. The thickness of the deposits affected by changes in applied stress was estimated on the basis of the follow- ing information. The compaction anchor is set at a depth of 2,200 feet in well 19/16—23P2. Pumping of well 19/16—23P1, about 500 feet from the recorder well, con- trols to a large extent changes in applied stress at the compaction-recorder site. The casing of the gravel- packed irrigation well is perforated from 660 to 2,155 feet below land surface. It is assumed that the draw- down in the irrigation well affects the artesian head for aquifers below a depth of about 400 feet. Hence, the storage components are based on an estimated thick- ness of 1,800 feet. For the example at well 23P2, most of the water derived from storage is yielded by inelastic compaction of the aquifer system. The amount of water yielded by elastic compression of the aquifer system is at least two or three times that yielded by elastic expansion of the water. Inelastic aquifer-system compaction has pro- vided at least 32 times the amount of water of expan- sion. The estimates of the components of the storage coefficient in those parts of the study area where large amounts of land subsidence have occurred indicate that less than one-tenth of the long-term compaction of the aquifer system is the result of elastic compression. A similar conclusion was reached by Poland (1961). It will be shown later, however, that in one area of minor subsidence, the elastic component of compaction ac- counted for most of the compaction during a 6-month period. (See end of section “The Yearout Site”) RELATION OF MONTHLY COMPACTION TO WATER-LEVEL CHANGE The monthly compaction that has been recorded at four sites is compared with the record of change in lower—zone water level in figures 13—17. The times of the measurement of the compaction usually are 28 days apart, but range from 26 to 32 days. The amount of compaction measured since the previ- ous Visit to the recorder site is dependent on several factors other than the change in aquifer-system thick- ness. Casing-cable friction at most sites makes it neces- G14 sary to stress the cable manually during each Visit. Manual stressing of the cable overcomes the friction that may prevent recording of compaction. The cable is stretched more than the amount of compaction that occurred during the month, but if friction characteris- tics remain the same from month to month, cable stresses between and below the points of contact bet- ween the casing and the cable should return to approx- imately the same tensions after each manual stressing. Examination of many records indicates that the friction characteristics of a given recorder system do not change noticeably with time. A more important source of error for a given measurement is the variation in the indi- vidual mode of manual movement of the counter- weights. However, little variation is apparent between the results obtained from a single operator from month to month. Errors introduced into measurements of compaction by individual differences in stressing are not cumula— tive and are compensated for in succeeding measure- ments. As the total amount of measured compaction accumulates during a period of several months, the ratio of error to total compaction decreases. No attempt has been made to compensate for possible errors introduced into the measurements of a single month. Where the measurement of a given month ap- pears to be in error, the amount of measured compaction is simply added to the compaction of an adjacent month and a mean value is shown for the combined periods. In addition, all records of apparent expansion of the aquifer system have been removed by averaging the measured expansion with the measured compaction of an adjacent month, or months. Recorded expansion was removed because it was not possible at some sites to separate objectively the records of net expansion that result from head recovery from the records of apparent expansion that are the result of operator error. STUDIES OF LAND SUBSIDENCE At some sites, such as the Oro Loma site, friction was large and the operator error was large compared to the small amount of monthly compaction. For this reason, the evaluation of the monthly compaction record for the Oro Loma site is not included; instead, annual compac— tion rates and water-level changes at Oro Loma are shown in figure 12. At the four other sites (see figs. 13—17), friction was small or the amount of operator error was small com— pared with the large amounts of monthly compaction being measured. The records from these sites provide useful information about the changes in compaction rates as related to the changes in applied stress, as indicated by changes in water level. The relation of monthly and bimonthly compaction to lower-zone water-level change for 1961—66 at the Men- dota site is shown in figure 13. The water-level record is continuous, and the time of measurement of the com- paction is at the end of each period shown. Casing-cable friction is moderate in well 14/13—11D6. Most of the compaction is recorded when the cable is stressed. The total recorded compaction is the sum of the relative cable movement during the period and the relative cable movement resulting from cable stressing at the end of the period. The general relation at the Mendota and other sites is that the maximum amounts of monthly compaction are recorded during times of declining head. During times of rising head, the amounts of monthly compaction commonly are less than half the maximum values, even when water levels are within 20 feet of historic low levels. As a result, the inverted bar graph in figure 13 gives the general impression that most of the compac- tion occurs before seasonal low water levels have oc- curred. The pattern just described is interpreted as being the result of elastic compaction and expansion of the aqui- _ a / tr ° -0.05 U 0.10 Compaction www Water level FOOT DEPTH INTERVAL, IN FEET DEPTH TO WATER BELOW LAND 1961 1962 1963 SURFACE, IN FEET MONTHLY COMPACTION IN THE 0-1358- 1964 1965 1966 FIGURE 13.#Relation of monthly compaction to lower-zone water-level change at the Mendota site, well 14/ 13—11D6. tersanddfinaammdstissupermmmmuno aquicludes. Most elastic changes in thickness otths aquiierwstessareassumsdtoherapidasdlisearin resmnsetoohangehuapphflsucss. Wirgincosnpaction ratesshouldteuorerapidattinaesot‘lowwaterlevels thanattiEesoihighwaterlevelshecamtheapM WW tmmtdmmgumoiapflmdmdwmdastm expansion is subtracted irons vugin compaction. An estimated elastic component was renamed toss the recorded values otthe 1% record hr wéll Misuse at the Mendota site to evaluate the validity of the hregoing interpretation..it The elastic changeswereestimatediorthosedemsitsassumedto besutficiostlypermeahletohavelittleornotimedelay tor thickness changes during times of apflliedfiress mange. GoreshomtheMendotasitesuggestthatthe sandy bposits undergoing elastic changes consist chiefiyofsands silts andthinaheddedclapeymnds. A totaloflldteetofclayeydepositswasnotincluded in the computation ofelastic change in thickness because ofthetimeneededtoexpelwaterfromaquitardsupon increase in applied stress. Also, those aquitards within which virgin compaction was continuing would corn tinue to expel wawr during times ofdecrease in applied stress The core record indicates that 540 fleet ofsandy deposits occur in the W interval between the base ofthe Oorcoran Clay Member at adepthof’WOOfeetand the anchor depth of 1.358 fact An additional so that of sand is in that part ofthe upper none that is mumed to be compacting to cause about 19 percent of the subsid‘ ence during 1963-661 The pattern of computed montth virgin compaction for the 1968 data mim depending on the values as signed to specific unit expansion for the 600 feet of sandy deposits within the compacting interval Low values, such as 1 6261041?1 reduce the variation in compaction between the periods but tend to retain the general pattern of figure 13» where maximum compae tion values occur before the times of maximum applied stress A specific unit expansion of 5.0»«10’532‘1 was tried, but resulted in 3 of the 6 months of water-level decline being associated with assigned amounts of elas- tic compaction that exceeded measured compaction for those months Thus, a specific unit expansion of 5 0X10'6ft‘ ‘1 is above an upper limit for assigning a reasonable value of specific unit expansion An intermediate value between the extremes of 1.6 and 5.0x 10‘6ft‘1 appears to be reasonable for the pun ‘hshouflhrmgnizedthatdumthesewonalmcandladcfi‘mleadtorthe aquiferstheboundaries within theaouitardsbatweenexpandingandcompactingthichncs sesamconstnntlychanging.. sis V moievaluatisggrosschasmimthepattermofl monthly and bimonthly compaction Acmrdimglby 8:3 mammoth imammmmtmw omansion columns, usingthisassumptim. would he 33>X11©45>I; .— , 480 _ L“ . u 9. u: 14 '6 ,_ Lu u. \ .V (“E m 2 520 0.20 m I 5‘ ‘ 5* "u n. . 1" U ‘ s 0 Lu < < 560 - VNO record due to casing rupture > 0 g :3 l N -' l- o 3 W '15 O l; ‘0 600 i u Water level, well W z 8 l- 0 16/15-34N4 o a. z E 3 El 640 1960 1961 1962 1963 1964 1965 1966 FIGURE 15.—Relatiun of monthly compaction to lower-zone water—level change at the Cantua site. i 8 O / 3' E 2 ° 3 i l 0.05 “1 , I Z l l ‘ Compaction ‘ A l- -_ l i l l 0 10 E :(l g .— ~ U l ‘ 1 -~ l m l m . z > 0 LLI 1 1 l ' 0 II S E l l l 1: ,‘i‘ m z 480» | ‘y ‘ ‘ 0.15 2 z E :1 : I“. g -l {1‘ A hj E ; I- a 52071, ,3, if ll ,ggit : 7, g 1 . _ _, ”#2 o +- < <( WE " : ‘ : .:‘ . r o a] g E ‘1 I °\ I 3 . >_ O .2 I N I | ‘. . '98 560* «4 Water eve ‘ ‘ g is I D l [— o ,_ l 2 u. 3:3 600 0 D -J 1960 1961 1962 1963 1964 1965 1966 E LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 1959 Subsequently, the surface string of 13_ %- inch s-gun perforated The well was used as .an irrigation, uge1L for several years. , 1 _ The mode f: operation of the compaction recorder at th1s s1te has not. been as consistent as at the other sites Problems with therable have, been frequent, andthe cable haditobereplamd fivertimes during the per-iodzof ,.¢ record-showninéfiguro :16.- ‘The well-casingdiameter is '2 1.113:imheS;s.whichfiresults> in less easing-cable:.gf-r—iction gthamifétheeasing diameter‘was smalienfloweveriex— 'DEMPtefor3131489811011“.since-Augusti966é- Mien-has been : sufficient-119 require c,ab1e_stressing,at eashmisitrPrior :toéAugust19‘66, monthly-amounts of eomp‘actiontend‘ed :tvobe‘»erraticrd1£ring,,.thoseaperiOdS:Whaligthei cable :was anot'streSSed": during each servicing; of the installation. ">""Appai‘eriti'eiipansion‘of theiaquifer syStenir has oc- (21111919111911 19116423132311111 has beenrem0ved from the ‘record'ShoWn'in'figdre 16'in order to be consistent With' that type of presentation shown in figures 13— 17 A float-Operated water- level recorder has been used in the same well t ohtain a record of the artesian head. Partsohthe-recordi;particularly, in 1961,.- a-re missing tee-991661111 ite‘iidéhoy'iof the-float to be caughtgbet'we‘en ‘théiachfiiifiotihnifiééhleii and ‘the - casings: The " sharp 'fluctoéiionh'iii Water ievel reSult from the intermittent pumping ‘61: irrigation Well 19/16—23P1 about 500 feet southwest oi the? observation Wei} ‘ Se’Veral' general fizature's ’of the records shown in i’fifi'fiéflfi are zipparent. The times of mmimum meas- ‘ 91911116111113; oompaction occnifmostly‘adufiing timhs‘of ‘ foot occurs 'diiriiig times of- rapid arteSIan' head'deciine which? suggests that most of these largecxrnont'hly duiits ofooinpacnon are the resuit of eiastic’wmpac- tron silage thicknesses of depos1t's. Comparison of the compaction and water-level records-ifs Ebetter"during 51116151111161, when 'th’e‘iiclablewas‘istressedi‘ateach visit, 391191199“ d‘aringfiie's and 1966, thari during periods in ‘Wh'ihh’ #11? cable Was arely stressed such as during 1963 211161964 v 7 ‘ Né’attémp‘txhhs Been? made t6 separate the elastic and 3911*ng éorifiaoiihhtsiofcompactlon 1n the 19/16—23P2 rec- » 01611666616 6f théifrequent equipment changes and the inconsistehs semssmg of the cable The fiela‘t'iiiii’ (ifmmpaction to lower- -zone water- level rchaii’ghs afi 13116E Westhaven site is shown in figure 17. Both this Watér- level and compaction records are based oirnfionthlyl hieasurements The compaction recorder 1s 5descr1bed 15y Poland and Ireland (1965) The- amounts of monthly compaction were small. Most of the compaction occurred during times of declin- ’ ing Water'levels, and little net compaction was meas- ured during times of rising water levels. G17 6 n 031- * .. 'TLIJ ' cm 31' , / _ ‘ uJ11. om, —~ “1,2 I2 J“ 7 ’__ ,mué. ’7 ., ~.: . 2—1 m 2 Compaction, well _ < n: __ sons—11163 z > mm . Om 1:)— 0:7 —Lu << 360— _ 5,. :5: ~ , g , -,~ . <12. 0 u. 4.3: 4‘ A; . fl-EI 0’ 0° \ CL" 550 K/n \f .\ “\1/1 w //\ . you: 12' ‘ >0 ”Lu <_440—' \ — .Jh ’D'J‘ ' ' Water levei wéi‘l -' VI 0 I— , . 20/181102 1,, . 28 , 480 . , o : 31963 4964 ‘11‘965;g 2 quns 17 —Relation of monthly compaction to lower— —'zone water- leVei change at the West- haven site, 20/18—11Q2 11Q3 RELATION or COMPACTioN ANn EXrANSION TO CHANGE 1N ARTESIAN HEAD The records of monthly compaction in the preceding section indicated that thickness changes within the elastic range greatly affect the pattern of ' short-term recorded oompaction of'ithe‘taquer'system. However. ' the-’ex‘cessikie‘irictioh?atirnost‘sites'and the low sensitiV» 9 ity“ of thelgraphica‘lganalysisfof figures 13— 1:7. permit only general interpretationSEzThree" sites within the study area have sufficiently'iow*‘friotiorithat the records can be used to obtain quantitative‘f'estimates about the mechanics of the aquifer systems. The net expansion characteristics of the aquifer- system skeleton can be ' approximated in some cases and the types of inelastic processes can be? identified} 1 :1 "risi'r'fg Maxi-mos: MOnthly'cohipaciiio n? (3661301011 -% “és'ti‘mates asbeing’orrly general approximations. Even -‘ at sites where changes‘in aquifer-system thickness are iThe‘reader-'isichiitioned‘ to regard the quantitative beingimeasufred Eaccurately, two types of questions arise - regarding the Water-level data. First, in a heterogene- 'ou's> aquifer system, “What is the interval that is being affected by the head changes indicated by the water— ' level record?” Where additional data are available, the water-level records of nearby irrigation wells are com* pared with the observation—well record to see if they are similar and if the times of water-level change coincide with the times of aquifer-system compaction or expan- sion. In the absence of these cross-checks, it is assumed that the water-level record is representative of the aquifer system. The second question is, “What are the variations in pore pressure in the aquifers and aquitards within the thickness of deposits opposite the perforated casing?” This question cannot be resolved unless piezometers are installed in many aquifers and aquitards. It is assumed that the water-level record represents an integrated pore-pressure distribution for the aquifers and that the pore pressures in the aquitards not only lag behind the pore-pressure 618 changes in the aquifers but also have less seasonal fluctuation than pore pressures in the aquifers. Excess pore pressures in the central parts of the thicker aquitards may have no seasonal fluctuation, only a van iable rate of decay, depending on the magnitude of the hydraulic gradient to contiguous aquifers. Therefore, the general purposes of this section are to provide some gross approximations of the physical con- stants of the aquifer systems, to illustrate techniques of relating water-level change to change in aquifer system thickness, and to provide tentative interpret» tions of the figures and tables of this section. Most of the following interpretations are based on the classical hydrodynamic theory of soil consolidation (Teraaghi and Peck, 1948, p. 283—942), Field compac- tion and waterlevel records help veribi parts of the theory of consolidation of clays that has been developed through laboratory investigations. Also, field studies can add to those aspects of the theory that cannot be tested in the laboratory. Eleven compaction recorders in the study area have recorded net expansion during water-level rise, The records of net expansion fi‘om three of the sites are presented in this section. Water-table changes are neg‘ ligible at all three sites during the periods ofrecord, and so the artesian-head chanw are the only causes of the appliedustress changes. THE Lmoons Sire Excellent records of aquifer-system compaction and expansion and the associated watenlevel changes have been obtained from well ism—sore, about 10 miles northeast of Westhaven. This upper-lone well taps the confined aquifer system above the Gorcoranl A float-operated recorder monitors water-level changes through a perforated interval 497—537 that below the land surface, The well is 577 feet deep, has a flit-inch casing, and has a reverse-lay stainless steel cable that does not require stmssing when the charts are changed on the 1:1 and 24:1 recorders. The depth range of deposits affected by the change in recorded artesian head has been estimated from an else tric log of well 18/19—20P1 (Pt. 2, Bull, 1974, fig, 47) and from the water-level record in a nearby well 260 feet deep. The electric log indicaws that a continuous sand occurs between depths of 294 and 665 feet, which is confined by lacustrine (Croft, 1972) clay beds at depths of 277—294 and 565-577 feet The lower clay is the upper part of the Comoran. Nearby well 18/19—2133 is perfo- rated in the depth interval 220—260 feet and has a water level that is 40—50 feet higher than the level in well ,18/19—201’2 but fluctuates annually about 45 feet, Thus, substantial long‘term arwsiandiead decline has oc- curred to at least as shallow a depth as the base of a clay STUDIES OF LAND SUBSIDENQE bed between depths of 280 enmi- ' ‘ , fluctuations are sufficiently'iarge ‘ a . ' ., _ . , paetion and expansion in the sand j‘i. _ and 977 ibetForpurposesofthia t;- ' _ . penetrated by well 18/194093» x. ‘ ' , «a expanding is estimated to be bet’r‘ii ( " , .r foet=a thicltn‘ess arse? feet the-e ’ t- ;-. three clay'beds afibcted byh‘ead , a; “ ‘~ The watenlevel record ofwelltw ’L ’ the applied‘astress changes dtthevs , continuityexists in thethieltsa ‘ n' V the depths of 294 and 865 {tote ,. percent of the aquifer material “V '. a 1 thickness, The aquifbr between'dep ,1, ' A fast is only as {bet thick, The rate and? g; .- < changes differ moderately from MW aquifer below the 284‘fbot depth, and it is ,Thliiewn ’..that both aquifbrs undergo head declines during'the late winter and summer and have rising heads earnest: autumn, Changes in aquifensystem thickness-"during regional water-level recovery are shown in await; which in- cludes the summer low water level of'ildj feet and the winter high water level of 157 fbet The'wdtenlevel recovery needed to record not expansion generally is ’ only 1-2 feet The fact that only 1 foot of applied-stress decrease was needed to initiate net aquifer-system ex- pansion when the depth to water was 214, 201, and 169 feet shows that the emote virgin compaction ofthe beds was small. Virgin compaction may continue at a slow rate in a few tens offeet ofclay beds during times of water-level rise, when most of the deposits are expand- ing. The net mault is recorded expansion almost as soon as applied stress starts to decrease, Furthermore, the lefbot rise in water level needed to reverse the trend from compaction to net expansion indicates that the amounts of casing-cable friction and lag in the recorder system are minimal. In a major contribution, Riley (1969) developed a graphical method for plotting field measurements of water-level change and compaction as stmss-strain curves. Under favorable circumstanm, these can be used to obtain quantitative values for gross elastic stor- age and compressibility parameters and other charac- teristics of compacting aquifer systems. A stress-strain plot for well 18119-20192 is shown in figure 19, Consecu- tive periods of repeated applied-stress inmase and de- crease produce a series of loops, or nearly parallel seg- ments, that are displaced with increasing time toward the right side of the plot as a result of cumulative inelas- tic compaction. Cumulative compaction between two dates can be determined along any line of equal applied stress. The descending segments of the stress-strain plot are . of particular interest because they mpregcntlihe times ‘ a 35‘3 Leemeexmemm emmhehmmmehme 919 .7. 11‘ 1. u 7 1 . 1 777 7’7 7 '7 1 7 7 7 7 1 7 7 7 7 ° 32; -e.m E "“3 SE 7 , I V“""‘V .‘ 2‘ .1. ' ‘ " ,M, g . . ., ‘ , , . ‘ ‘ a . g ::., J g3 % 1me _.; 1w: 8 7 ‘ ‘ "we I g M ‘ e01“ , i e . .. s ;‘ E gee; « tee ‘ . a .' .1 !. f ,_ " I; 1..“ ‘ ‘7"‘“‘~ ‘ “OF; 1 1 .. 1 . v eh 1.11 X ,, ,, <7 ,, 11 7 ,, , 7 » 1 , , ,, , , ill ,, , , I ; figteeerr , j Newmheg I em I mm I Eimw, ,, ,, RS7: , , , , ,, ,, , , , , , gee hem MWermmmwmetWtommhwm MIN/1W. eteet eeethreeetemexeeheiee The meen eleeeefthe lewehpetteefthe deeeehdihelihehe meyiideehheeeeef W the Whig??? efthe edeifee WWW‘R e11 eeeeiheexpen= eye WWthemeleheeheWhmhemeleh Lame This 1e the meet et‘ the eteteee ., 4, Whetehleteeleetteheeheheeetthe eehhh ,, eeehvmm Theneteheeiheehit 121310-53 —__==ee>x1e-he-1 e47; fleet thie tethe Went eteeeeihe etmee ettlrihhtehle te eleetmeeeeheeeftheeeehhedeyetemehetetee _ ehdrhihelimheeftheeletetehet wt ht timeeeteeeel eeehedetteee thetiethe he he the lettet‘thedeeeehdihelhhh (The? end 441%?) e112 te the rieht e? the deeeeedihe limb (Wile/£8 end wee/gee Theee yer1et1ene een he 931 Bleihed hy dimeee ”111, the tetee efdeleyed eheheee thet ere eeeezeihe 1n the eeem eyetem. The greatest eeheitiyity efthe etteeenetueie plet 11; in determining the mimete eleetie meeertiee et‘the aquifer eyeteme. h Wm! preeeeure that '11 eeeeitjiye 111 determining mam ehm (he 18) will he need te deeerihe the hydmdyeemie peeeeeeee end te exp!eiih, the mietiene 111 the etxeee-etxein plet, Heme leehewetheetheteefvemetmmtheretee end tyeee e? tame-delved eheheee eh eeuiiee-eymm thiekneee. The neviehe dim eheut the reletjien e? mehthly eemeeefien te teeter-level eheneee ehewed the W eff eleetlie eheheee en mended eempeetien demett‘meeefehehemeehhhedetxeeeehdeeheeehe eeeeteed thet meeh etthe thnhheeeeheeeelihheehe 1%? heheetie It‘ehthethtehheeeeheneeeweteeleetteeed G20 ‘ STUDIES OF LAND SUBSIDENCE 220 | | Note: Date (month/day/year) .9/10/67 = 210 . “ . 09/27/67 0 '8/30/67 0 03/24/67 010/4/67 .10/30/67 1 , 200 7/2/68 0 '1— . E Lu 0 w <12 u. 9 z D i a 2 Lu , J; ‘2 . ° < EL . . _‘ . _‘ a a 190 ' — m 0 11/19/67- I- 2 ‘0 < D _J 0 LL! " 3 , ' o 5‘ 3 11/26/67 / g g 2/26/68 Z n: o z “J LL! 0 1 o 2180 ' — E 3 ° I o 0 ,.. 12/4/67- LL I 5/8/67. 0 o E 4/19/67 LL! 5: 3 ° 0 >- W m 170 ~ 12/20/67. '2/10/63 05/4/67 160 /2/3/68 ~ 01/26/68 ‘ ' 150 I H l —3 0 +4 +8 COMPACTION, IN FEET X10_z FIGURE 19,—Stress-stmin plot for well 18/19»20P2, (Modified from Poland, 19693, p‘ 19.) occurred Without‘time‘ delay; the eXpansion and‘com-r change represented by the waterJevelfrecord.‘ Only ‘a: pactionEplot would parallel the plot of applied—stress small part efthe tWO plots isparallel—Iiear the 1754001: LOS BAN OS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 depth-to-water part of the record, At deeper water levels,. convergence of the plots from September into. December is interpreted as being the result of continu- ing virgin compaction that is concurrent with elastic, expansion. The result is that net expansion is less than . if virgin compaction were not continuing. Atrising water levelsabove 175 feet, theldivergence of the plots is interpreted as being the result of delayed-expansion. Delayed expansion may have been occurring at deeper . water levels also, but was masked by large rates of virgin compaction. » , The relative magnitudes of convergence and di-Q vergence at selected times are shown by the dimension- . lesslnumbers in figure 18. The rate of convergence is ~ more, rapid during times of deep thanshallow water levels, indicating that virgin compaction rates. are larger during times of larger applied stress.‘ The large rate of convergence during the period of declining water levelsearly 1n February as compared , with the divergence ratespreceding the start of head . declin‘e indicates that time-delayed compaction was oc-‘ curring at water levels of less than 170 feet. It cannot be determined if part of the .delayed compaction is i~nelas-~ tic, because eitherelasti-c or inelastic compaction would cause the convergence patterns in figure 18. Three thick , clay beds are influenced by water-level changes in well 18/19—20P2. Apparently, one or more of the beds is sufficiently thick and of sufficiently low diffusivity to retain excess pore pressures after 57 feet of head recov- ery from the summer low water level of 214 feet. These excess pore pressures have resulted from years of cumulative head decline. The linear plot for the same time period in figure 19 suggests that most of the change in aquifer- -system thickness at water levels above 170 feet is elastic. It should be kept in mind, however, that concurrent delayed compaction and delayed expansion tend to offset each other to an unknown degree that varies with applied- stress level. The presence of delayed expansion shows that three concurrent processes are tending to change aquifer- system thickness during times of applied- stress decrease—elastic expansion with no measurable time delay (presumably chiefly of the aquifers), delayed elas- tic expansion (presumably of the thin aquitards and outer parts of the thick aquitards), and Virgin chpac- tion (presumably 0f the thick aquitards and aqui- eludes). It is assumed that the rates of elastic change in the aquifers occur linearly and thatinelastic compac— tion rates decrease and delayed expansion rates in— crease with decreasing applied stress. The amounts of delayed eXpansion at the Lemoore site cannot be esti- mated, because virgin compaction was occurring at the same time. However, it appears that during times of high water levels the rates of delayed expansion exceed G21 the rates of virgin compaction, for a given. rate. of applied- stress decrease Variations in net specific unit expansion during the seasonal decrease in applied stress, are shown in table 1. Tina LE 1.——Variation in net specific unit expansion during a period of seasonal head recovery at well 18/19—20P2 I Depth. 1 Water-level Mean rate of Recorded net Specific unit , to water rise water-level rise expansion expansion ‘ (ft) (ft) (R per day) (111 ’ (x10- 611-1 1967 ' ' ‘ Sept. 20 ".1", 214 0 _ . Sept} 22 -4", 211.5 - 2.5 ' , 1.2 0.0005 , 0.6 . ' 9.5 l ‘ ‘ 1.1 ~ .006 . 1.8 . ‘ 4.0 .8 .003 72.2 . 6.5 V .6 ‘ -' .004 1.8 D ‘ 1 . . 5.0 > .6 .004 - 2.3 D .0. , Dec. 4 11111111 177.0 13.0 .8 - .013 2.9 D ,,,,,, 77.0 7 . Dec.‘ 18 ______ 169.7 73 ,5 .009 » 3.5" . Do ______ 169.7 . 1968 . .. , , Jan, 10 ______ 159.0 10.7 .5 .012 . 3.2 Do ,,,,,, 159.0 . » ‘ . . « Jan. 21 ...... 157.0 2.0 ,2 .0025 3.6 The mean rates of water-level rise were 1.2 feet per day . immediately after the summer low water level, but de- creased to 0.2 foot per day for an 11-day period preced— ing the winter high waterlevel. Most of the periods had mean rates of water-level rise of 0.6—0.8 foot per day. The values of net specific unit expansion for the nine, intervals of head recovery at well 18/19—20‘P2 given in ' table 1 form a logical sequence when'considered in a context of the combined effects of decreasing rates of water—level rise (decreaSe in applied stress), concurrent decrease in virgin compaction rates, and increase in delayed eXpansion rates. Table 1 shows that net specific unit expansion reaches a value of 3.5 X 10—6 more than 1 month before the winter high water level. Low values of net specific unit expansion occur during the three periods after the summer low water level, even though the rates of head recovery are the most rapid during these periods. The low values of net specific unit expan- sion are interpreted as being the result of rapid rates of virgin compaction. Between October 8 and December 18, the rates of water-leVel’rise are roughly constant, but the values of net specific unit compaction increased from 2.2x 10—6 to 3.5x10‘6ft‘1. This increase can be attributed largely to a decrease in the rate of Virgin compaction with decrease in applied stress and to an increasing rate of delayed expansion. THE YEAROUT SITE Monthly compaction and expansion and water levels have been measured in upper-zone well 13/15—35D5, about 4 miles east of Mendota. The 4-inch well casing is perforated opposite Sierra micaceous sands and silts at depths of 373—433 feet. The bottom of a pipe-type com- paction gage is set in the upper part of the Corcoran at a depth of 440 feet (Pt. 2, Bull, 1974, table 1). (3M mmwwmfladmwm iim lhg (lifwdlll Ila/115435511311 (mmmdfwmm)m wwwmtmmmmwmmmm. mwm 11mm (Wffltm wwmm zamfl Wmmwnmw W). Wmdftfim WIWRWWWMWMMWW mmmmm.mm,wmwmmn W111 1131/115amn Wmmifimmmmm dike EWMM and mm tflham lim 111m amaznmwmkemmmmwammw wmmmmmflwmm «if tfihe (Emma mow mm With: Mm WWW Minimum mvwdlll 1153/th. Fur rpm- mwmmmm,mmmmmwwm mamammammmmwmam. mmuhwmaayflmwnmmmmaa wmwww. ’mhe nmfiihlly mm W m “181111 IKE/11554831193 Wm time mm W iim wmmmm§11m.Mthmm- WIWWMWWMWW wmwmnmwmmumwwu mm mm W kiln 11m. W W elf WW mmawevell WW 23113“ mutt iii: The mm (Iii mmdlwell and WW- WWfilifl/flfififlfimmmfin www.mwmwmmmmm, mffmmmflhs. memmwmmtmmmm ammmmwmmwnwm HWM.MHW,WWWWW (mmfiljifiiimmmiimtflhfiqfimss ,_ (0%” (cm WWGMW AIME ' mWW as WWW! WM we» Qéé‘ffi fé WATER EEEQW LAMB wfififié, 1W féfi E g g s g mums Zia—dadlddimidfzaquifbrmyflwmwmmwwuhmpdnfimnlm Wrimdwhmge. wdll wwwm WWWW MWWWMW©meW- mmmmwmmmmnm—mw ammw‘. M film we W afis mm Wmmmmmmmmm mwmmmwmmmhw mmwmmmmnmmm iis W mm m W min W at We Ywuttés‘mifim mmmmm quaasynwfiw ,,mfi&.11%b. Mm (b‘ftfiha WW W W at W831 Ila/11W mm. MAW %, 11%,M AWLAW,%MWWWM&W mmmnwmam,mmmamm- menmm.mawma 11%, mm 114;, um, ammumhwdlmm W W by a 1m W Mm mm mmmmmJAmmmmme Wmmmwmmmw mm,@mm D F 540 V.’ LIJ Lu 1: .— u.| uJ < “- E 9 E 3 0 ui 0 Z _ o /‘ < ‘2: 550 - E 3 3 LL! U) I Q I- Z w < o .1 E g n A .1 0 560 T J 0.12 E _l < 53 E tr Lu E Water level 0 < <2: 3 I O 570 U l- u. I 0 E a g < 0 E m 580 b A 590 '. Feb Mar Apr May June July 1967 FIGURE 21.#Relation of aquifer-system compaction and expansion to water—level change in well 19/16—23P2, February-July 1967‘ levels and elastic expansion of the aquitards. to-grain stress, even when net compaction is continuing The time lag at the reversals from compaction to within some aquitards. When the aggregate expansion recorded expansion is due to the mechanics of the of the aquifers and thinner aquitards exceeds aggregate aquifer system and to the mechanics of the recorder. shortening of the thicker aquitards still compacting, net Elastic expansion is concurrent with decrease of grain- expansion of the aquifer system will occur. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 G25 0 — A Compaction, well 19/16-23P2, 1:1 scale A : %V \——V : _ _ 0.05 550 0 Well 19/16-23P2, 24:1 scale / Aquifer- Aquifer- / system system compaction expansion / ’— Lu u.I / “L 2 o l- j -_ In L” 560 / 0.0083 2 I- Lu 0 < LL _. 2 2 Q 0 _. z m E I; 3 / E < u. I: ~ CC 9; 3 o as w s D _ 53 A / S D _I < E E / l N 1 A °' _I O 570 . 0.0167 2 “L _I < ) O l 0 < LU m E z I: / LI.I — I- Lu 1": / w 0 < >. z "3 I 0 Lu 0 l- Well 19/16-23P2 E u. I D 0 E 0 Lu l.I.I < 2' I: 0 > m a: \(water level \ 0| co 0 I \ \ L 0.0250 l I I | | | I I I I I 00333 590 I I I I I I I I I I I I 15 25 10 March April 1967 FIGURE 22.—Relation of aquifer-system compaction and expansion to water-level change in well 19/16—23P2, March 14—April 13, 1967, Expansion will not be recorded, however, until the direction of movement of the recording equipment has been reversed. When a system that has casing-cable friction is recording compaction below the uppermost point of contact between the casing and the cable, cable tension is reduced below that point. The counterweights move down relative to the concrete pad, when the cable tension is reduced by an amount that exceeds friction in the system. On the other hand, expansion is recorded after cable tension has increased to the point where friction is overcome and the counterweights begin to rise. The amount of movement needed to reverse the loaded gear train in the recording equipment is negligi- ble compared with the amount of movement necessary G26 to change cable stresses in a system where casing-cable friction is significant. Because of the mechanical lag in the recorder system, the water levels at which net expansion is first recorded are higher than when the net expansion first occurred. For the periods of aquifer-system expansion shown in figure 21, net expansion was first recorded when the water level had risen about 10 feet, but net expansion probably had begun earlier. The proportions of elastic and virgin compaction probably changed during periods of declining poten- tiometric levels. For the period of record shown in figure 21, the proportion of elastic to virgin compaction, per unit decline in head, probably was largest when water levels were higher than 550 feet and probably was smallest when water levels were lower than 580 feet. STUDIES OF LAND SUBSIDENCE The initial stages of rapid compaction that? coincided with the rapid declines in water level that occurred from the 547 -foot depth to water in April and the 535-foot depth to water in May probably are largely elastic. As water levels continued to decline, a progressively larger number of beds within the aquifer system began to contribute to the virgin component of compaction. The relation of aquifer-system compaction and ex- pansion to water-level change at well 19/ 16—23P2 dur- ing a typical summer pumping season is shown in figure 23. The nearby irrigation well was pumping during the entire summer, except for a 12-day period in May and a 4-day period in September. Again, the times of recorded compaction coincided with times of increasing applied stress, and the times of recorded expansion coincided with times of decrease in applied stress. However, the 500 Expansion \ /"_ \ // ‘x H I \ -0.1 01 N O ,____________J “‘\ n_.__.___‘ I \\\/Compaction ‘ 0.1 Water level / SCALE OF CHANGE IN APPLIED STRESS AS INDICATED BY DEPTH TO WATER BELOW LAND SURFACE, IN FEET 01 U1 0) b O O AOUIFER-SYSTEM COMPACTION OR EXPANSION, IN FEET 0.3 580 April May June July August September 1964 FIGURE 23.—Relation of aquifer-system compaction and expansion to water-level change, well 19/1&23P2. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 curves of change in applied stress and change in aquifer-system thickness do not show the parallelism of the plots in figure 22. The plots in figure 23 suggest that much more friction was present in the recorder system in 1964 than during the period shown in figure 22. Many of the apparent differences between figures 22 and 23 can be explained by comparing the differences in the equipment used to measure changes in aquifer- system thickness for the two time periods. Such a com— parison also illustrates the need to manually stress the compaction cable at each monthly visit at some recorder sites. A 1Aa-inch stainless steel 7 X7 stranded uncoated cable was used during the period of record shown in figure 23. The cable had twice the stretch characteris- tics (B.E. Lofgren, April 22, 1968, written commun.) of the reverse-lay cable used during the period of record shown in figure 22. Therefore, before installation of the reverse-lay cable, larger changes in aquifer-system thickness were necessary during expansion to increase cable tension below the uppermost friction point sufficiently to overcome the casing-cable frictidn. Although expansion was recorded many times at the site, net recorded expansion exceeded 0.01 foot only 18 times during the 1962—67 period. Maximum recorded expansion was 0.094 foot. The following data and in- terpretations pertain to the above 18 times of expan- sion. The delay between the start of water-level recovery and the start of recorded expansion is a function of the rate of applied-stress decrease, the difference in cable stress above and below the uppermost casing-cable fric- tion point at the start of applied stress decrease, the magnitude of cable-casing friction, and the stretch characteristics of the cable. The delay ranged from 38 hours for vinyl-coated cable (large stretch and friction properties) to 6 hours for the reverse-lay cable (low stretch and friction properties). The associated water- level recoveries were 21 and 6 feet, respectively. The number of hours between the start of water-level recovery and the start of recorded expansion does not seem to be related to the depth to water at the beginning of water-level recovery. For example, the six times in which 7—10 hours of water-level recovery occurred be- fore recorded expansion started were associated with initial water levels ranging from 545 to 587 feet below the land surface. The specific unit expansion of the 18 times when recorded expansion exceeded 0.01 foot ranged from 0.6 to 3.1X10‘6ft‘1. The presence of delayed compaction indicates that minimum values of net specific unit ex- pansion are being obtained for the amounts of expan- sion and applied-stress decrease that occurred after ex- pansion was first recorded. It is concluded that the mean value of 1.4><10”6ft”1 for the 18 times is a minimum G27 value for the net specific unit expansion and that a representative value for the 1962—67 period may be larger than 2.0x 10‘6ft‘1. RELATION OF LOWER-ZONE COMPACTION TO CHANGE IN APPLIED STRESS Regional applied-stress increases have resulted from the changes in the positions of the lower-zone poten- tiometric surface and the water table. The algebraic sum of stresses caused by these two types of regional water-level change provides information regarding the increase in lower-zone applied stress during a selected 17-year period. Then, by estimating the lower-zone compaction, the specific compaction (compaction per unit applied-stress increase) can be derived. The specific compaction map relates the estimated compaction to the observed change in applied stress on a regional basis, thus permitting examination of the effect of hy- drologic (other than long-term water-level change) and geologic factors on compaction. The period between 1943 and 1960 was selected as the interval to appraise the specific compaction. The period is sufficiently long to eliminate some short-term factors that might affect the results of a 3- to 6-year appraisal. The 1943—December 1959 subsidence map (Pt. 2, Bull, 1974, fig. 10) shows only the subsidence that has re- sulted from artesian-head decline. The earliest wide- spread water-level control within the study area is based largely on measurements made by the Pacific Gas and Electric Co. in 1943. Most of these measurements were made during the summer pumping season. The 1960 water—level map (Pt. 1, Bull and Miller, 1974, fig. 33) also is based on measurements made largely during the summer pumping season. Some recent maps have many control points, but are based on water-level measurements made at the time of winter high water levels. Thus, the 1943—60 period fills the requirements of being long and having good control regarding changes in the position of the potentiometric surface and altitude of the land surface. The regional change in total applied stress on the lower zone was determined as a result of the seepage- stress change, the gravitational change resulting from the gain or loss in buoyancy of the grains caused by water-table change, and the gravitational change re- sulting from the change of pore water from a saturated to an unsaturated condition, or vice versa. The change in applied stress on the lower zone result- ing from change in the position of the water table be- tween 1943 and 1960 is shown in figure 24. For those areas that were developed agriculturally by 1960 but not in 1943, the water table was assumed to have re- mained constant until irrigation began. Electric logs of the first water wells drilled within a given part of the G28 STUDIES OF LAND SUBSIDENCE 12030 120000 33 I 152 Los Banos 152 / / 37 "OO’ —— Dos Palos / ’ 1.» Freya/R.“ >_ ,"\_{Ziver _ 33 \A “/— ‘f ‘ ‘ Madera / (D 091;” / '2 00 V O Mend 4' C) a", 99 ‘0 O / ca”? - ‘19 ‘2 / Firebaugh RIVER équ’ 0‘90 Q / @Q'C/O 90 I0 U114 é $60 A0 /Q— 0/ I» :0 FRESNO r\-l_l 0/ 4 Mendota l, \ L ‘7 180 <5? Kerman J— ‘ d- x? 41 1 51369 36°30’ — Cantua Creek \{3 _ EXPLANATION g 06 "K 0 T W s, r J \ ’ (r \ \ Boundary of deformed ’27 in _Q F' P . \ rocks ‘ ~30 ' we omts [b0 ‘ ‘ ‘40 a.) K __ _ _ _ .50 (0 ° [_—.\—— , Line of equal change in applied stress on the 9/ I 7 (A lower zone resulting from change in the 0 , 9 ,0 . / position of the water table, in feet of 9% ‘ \ X water '6‘ ,y I Q Interval 10 feet. Based on maps showing Q‘s 1% change in the position of the water table, We, 1951-65 and 1962-65, a map showing the \ ‘2 a history of increase of irrigated area, and \ 9‘ \ ' 193 changes in the position of the water table po\ \fi ,’ as indicated by electric logs of wells /\‘°’o \ \ 95‘ aveno \73_ drilled in the 1940’s and the early 1960’s. Huron \ I :5. A O _\ v0 Strat- ’: ‘30 O) \ ford Western boundary of the Corcoran Clay As ANT / x.)oo /O Member of the T ulare Formation / 96010 L - Coalinga 9/?) Q— 90 AVALLEY Q {9 \ ’ / TULARE \ //v$ \ , > ' f 9‘71, 4, LAKE 44/ 0 10 15 MILES , a,“ Kettleman BED 36°00, o 5 1o 15 KILOMETRES 1 / e (s I City Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 24.—Change in applied stress on the lower zone resulting from change in the position of the water table, 1943—60. area provided valuable information about the position graphs from shallow wells and from maps showing the of the water table at the onset of irrigation. The rates of position and change of the water table during much of water-table change were derived largely from hydro- the 17-year period. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 Within the areas of near-surface subsidence (Pt. 2, Bull, 1974, fig. 10), little change in the position of the water table has been noted. Within these areas, the moisture-deficient deposits apparently absorbed most of the moisture that percolated below the root zone during the 1943—60 period. This moisture added above the water table increased the applied stress on the lower zone. However, because the quantity is small and is unknown, this increment of stress increase was not included. The change in applied stress on the lower zone that has resulted from change in the position of the water table between 1943 and 1960 is small. The total range in applied-stress change is 100 feet, from about +25 feet to —75 feet, but the stress change for more than 90 percent of the area is within :20 feet of water. Water-table rise is characteristic of most of the area east of the west boundary of the Corcoran Clay Member of the Tulare Formation. In much of the area, water- table rise has caused less than 10 feet of increase in applied stress on the lower-zone deposits. In the small area southwest of Mendota, about 20 feet of increase in applied stress has occurred as the result of 100 feet of water-table rise. Large water-table declines occurred in all the area west of the Corcoran because of pumping of wells perfo- rated 400— 1,900 feet below the water table. Water-table decline extended as much as 5 miles east of the west boundary of the Corcoran aquiclude and may have influenced the rates of water-table rise for even greater distances to the east. The areas of maximum water- table decline coincide with the areas in which vertical permeability in the upper zone is greatest. The max- imum decrease in applied stress on the lower zone was 70 feet, southwest of Huron, and was the result of 350 feet of water-table decline. The good vertical permeabil- ity of the deposits southwest of Huron has permitted recharge from streamflow with a high concentration of dissolved solids to move down into the main ground- water body (Davis and Poland, 1957, p. 459). The change in applied stress on the lower zone that has resulted from lower-zone artesian-head decline is equal to the head decline in feet of water. The decline of the lower-zone potentiometric surface from 1943 to 1960 (fig. 25) represents the increase in applied stress as a result of the component, which is large compared with the stress increase resulting from water-table change. Areas of applied-stress increase of 300 feet are wide- spread, and locally the applied stress increased as much as 400 feet. The change in total applied Stress on the lower zone is the algebraic sum of the data shown in figures 24 and 25. Artesian-head decline has occurred throughout the area during the 1943—60 period. The net water-table G29 component has been added to the head-decline compo- nent in areas of water-table rise and has been sub- tracted imareas of water-table decline. Figure 26 shows the 1943—60 total applied-stress increase, which ranges from 75 feet in the northern part of the area to a max- imum of 350—400 feet near the Big Blue Hills. The general pattern of the map conforms to the change in artesian head because change in head is the dominant component. Except for the area between Huron and Westhf'ven, the maximum increase in applied stress is near t}; west boundary of the study area, which is the side of least ground-water recharge to the lower zone. Not all the land subsidence, however, is the result of compaction of the lower-zone deposits. Information from 12 compaction-recorder sites in different parts of the area provides estimates of the amounts and propor- tions of compaction occurring above and below the prin- cipal confining bed—the Corcoran. The minimum pro- portion of compaction occurring in the lower zone ranges from about 95 percent at the Oro Loma site in the northern part of the area to about 58 percent at the Westhave-n site in the southern part of the area. North of the road between Five Points and Anticline Ridge, more than 80 percent of the compaction occurs in the lower zone, except within a small area near Fresno Slough where most of the pumpage is from the upper zone. The proportions of compaction in the two zones (Pt. 2, Bull, 1974, fig. 45) are based on post-1958 information, which is considered applicable for the 1943—59 period because the proportions of water pumped from the two zones (based on well-perforation data) apparently have not changed materially since 1943. The compaction isopleths for the lower zone (fig. 27) for the 1943—59 period were derived from the 1943—December 1959 subsidence map, using the infor- mation noted. The values of lower-zone compaction for most of the area are nearly as large as the amounts of land subsidence due to artesian-head decline during the period (Pt. 2, Bull, 1974, fig. 10). However, the amounts of lower-zone compaction are considerably less than subsidence along most of Fresno Slough and south of the Five PointseAnticline Ridge road. The overall trend of maximum amounts of lower-zone compaction increases northward from the vicinity of Huron to the area southwest of Mendota. The ratio of the lower-zone compaction (fig. 27 ) to the lower-zone increase in applied stress (fig. 26)—specific compaction—is shown in figure 28. In a general sense, compaction of unconsolidated deposits increases with increasing applied stress. One purpose of computing the compaction per unit change in applied stress is to gain an insight into factors, other than long-term change in applied stress, that may affect the amounts of compac- G30 37°00’ 36°30’ 36°00’ STUDIES OF LAND SUBSIDENCE 120°30’ 120°00' 33 I 152 \ Los Banos 152 . ' ' / .' .- / _ : : Dos / , Pa‘los .: ,oo \E’F§"°/—--»___r.\,_f . D .. / 33 '. 0 <0 qq Vi Ca), ' . 9’ Firebaugh C1 / ‘1' O - ' '. Secs/($01“ " - 5") " A {rs-O, ’ 200 "W JO 0 4 ’00\Mendota / 71’ 763 00 ( I» ‘0 O ’3; ( (m EXPLANATION “4,6 - 9% ’9, ' L Boundary of deformed ’9 rocks Q 300 ’27 (‘9 ¢ Generalized line of equal increase in applied stress on the lower zone due to artesian- head decline between 1943 and 1960, in feet of water Interval 50 feet. Based on map showing the maximum decline in the altitude of the potentiometric surface at the lower zone, 1943-1960 (pt 1, fig. 41) O nuucuunoocoon Area in which the lines for the 1960 map ‘ are drawn on the basis of minimum water levels that occurred between 1950 and 1958 Water levels in this area rose for several years prior to 1960 because water from the Delta-Mendota Canal has, in general, replaced ground water for the irrigation Western and eastern boundaries of the Corcoran Clay Member of the Tulare Formation O 5 10 15MILES O 5 10 15 KILOMETRES . Kettleman City TULARE LAKE BED Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 25,—Increase in applied stress on the lower zone resulting from artesian-head decline between 1943 and 1960‘ 37°00' 36°30’ 36°00’ LOS BAN OS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 G3 1 120°30’ 33 l 152 Los Banos 152 l / _ Dos / Palos \fw.s"0/~--.\/_~~ fix’\_8_iver ‘ 33 v Madera V5 0e14, / ‘2’,“ 00 ‘2' O Me’ldo, 99 ‘5 O a,“ 0 § / 9’ Firebaugh RIVER §V (5° table 1 943-60 0 5 0 5 10 EXPLANATION ’9 Boundary of deforrned rocks 250 Line of equal change in applied stress on the lower zone, expressed in feet of water Interval 25 feet. Map was derived from maps showing lower-zone artesian-head decline and change in the position of the water 10 15 KILOMETRES TULARE LAKE 15 MILES Kettleman BED Crty Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 26.—Increase in total applied stress on the lower zone, 1943—60. G32 STUDIES OF LAND SUBSIDENCE 120°30' 120°00’ 33 I 152 Los Banos 152 / / 37°oo' — Plain / os Free/«u ._ x'\_zeim / 33 I \—— V .J“ l _ Madera / M 9% C? Y' 0 Mb” Q D on, 99 so 0 Carl?! F. b h R V to? 2 ire aug RIVE € ‘0 Q {3- Q9: ’0 "3909 4 J A FRESNO 6 F3 0 ‘° endota Lj / 7 8 \x L 7 7’0 ,0 130 <9 0 Kerman J— (O a“ ‘3. 12 41 I (( m 2,, r /\ 5/7, \ << ’5‘;— \- x s \ 440 __\ 4’0 04/4, d> s °¢ 36°30’ — 0/6 ’9/0 antua Creek \‘Pf‘ _ fib 99 ~\ I EXPLANATION ’( 2 ,9 (d, K9 2 Kt :::::::::::' ’ FivePoints Boundary of deformed O rocks (6 ' —— " “ ‘ 8 Generalized line of equal compaction in the 33 lower zone 6‘08 Interval 2 feet, except the I-foat line. Map A,/( based chiefly on the 1943-59 subsidence (5‘ map, the estimated proportion of upper- and lower-zone compaction at 12 com- $4 0 paction-recorder sites, and a map showing 9 the variation in the amount of water / \ pumped from the lower water-bearing // / ) zone. Maps showing depth to the base of 9,012 the Corcoran and thickness of the lower Q 06‘6" . Strat- water-bearing zone were used also PLEASANT Coalinga Q VALLEY TULARE 4“» f 9% LAKE .q o 5 1o 15 MILES ’V / &’<( Kettleman BED o 5 1o 15 KILOMETRES / 33 s City 36°00’ ‘ Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 27,—Estimated compaction of the lower zone, 1943—59. tion. If there were no variation in the other factors values of specific compaction would be characteristic of affecting lower-zone compaction and the history of the entire area. However, a pronounced anomaly is applied-stress increase was similar regionally, uniform readily apparent in figure 28. The specific compaction of LOS BANOS—KET’I‘LEMAN CITY AREA, CALIFORNIA, PART 3 G33 120°30’ 120°00’ 33 I 152 Los Banos 152 / / o I _ Dos 37 00 Palos / F reggo/Hu __ ,/’\_giver 33 \A’ V “f ‘ “ ‘ Madera m e ‘9‘ 00 V O ha 007 ‘3 Q We 99 0‘0 0 ”a . 2 / q ‘V Firebaugh RIVF’R gqu’ Q girl 1 AQ FRESNO n |_‘ i, l_ 150 r 150 \ f}? Kerman 0 T \g 41 0.9; '\ \ d> \. 6%? 36°30’ — \ _ 9L 0 ~\ EXPLANATION o 6‘ ; ’ \ 77777777777] ’9 <0 \ Boundary of deformed 7¢ ' Five Points rocks _ _ 0.02 Generalized line of equal ratio; interval , 0.01 Lower-zone compaction, 1943-59 _ (fig.2’7 ) Ratio of : . . . Increase in applied stress on lower zone, 1943-60 (fig. 26) . Strat- ford TULARE LAKE 5 1 0 15 MILES 0 / Kettleman BED 36°00, o 5 1o 15 KlLOMETRES / e I City Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 28.—Specific compaction of the lower zone, 194$60. much of the northern third of the area is twice that of ——hydrologic and geologic—affect compaction and sub- the southern two-thirds of the area. The variations in sidence within the Los Banos—Kettleman City area. The specific compaction demonstrate that other factors geologic and hydrologic factors affecting specific com- G34 paction and specific unit compaction are discussed in detail in Part 2 (Bull, 1974). A map showing estimated specific unit compaction of the lower water-bearing zone, 1943—60, was introduced in Part 2 (Bull, 1974, fig.54 ). That map was obtained by dividing the specific compaction of figure 28 by the thickness of the lower zone to derive values of compac- tion per foot of applied stress increase per foot of aquifer-system thickness. The resulting specific unit compaction was about four times as great in the north- ern part of the area as in the south. The geologic factors evaluated in part 2 are prior total applied stress, mean lithology, and the source and mode of deposition of the different genetic types of deposits. Based on the detailed analysis of the specific unit compaction map in Part 2 (Bull, 1974), it is concluded that the higher specific compaction in the northern area (fig. 28) is due principally to the following factors: 1. The prior total applied stress as of 1943 was less in the northern part of the area than in the southern part, and thus the compressibility of deposits of a given lithology is higher. In general, values of compressibility decrease as effective stress in- creases. 2. Genetic differences of the deposits are conducive to more rapid expulsion of water from the deposits in the northern area. The aquitards of the flood-plain deposits in the northern subarea are thinner than the aquitards of the alluvial-fan and lacustrine deposits in the southern subarea. Also the flood-plain aquitards may be twice as permeable as the alluvial-fan and lacustrine aquitards (Pt. 2, ' Bull, 1974, table 6). More rapid expulsion from the thinner more permeable beds should produce val- ues of specific compaction for the 1943—60 period that are closer to ultimate values than those to the south. These geologic factors contribute toward the higher specific compaction in the northern part of figure 28. Another hydrologic parameter that shows the con— centric, or enclosed, pattern of isopleths that is similar to the pattern of specific compaction within the study area is the overall pattern of seasonal head decline. The seasonal head decline shown in Part 1 (Bull and Miller, 1974, fig. 43) is for the period between December 1965 and August 1966. However, the pattern probably is representative of the latter part of the 1943—60 period because the area irrigated with ground water was about the same as in 1966. Seasonal variations in head during the early part of 1943—60 period probably were less along the west and south sides of the study area and probably were greater in the northern part. The small amount of seasonal head decline in the northern part of the area in 1966 (Pt. 1, Bull and Miller, 1974, fig. 43) is STUDIES OF LAND SUBSIDENCE due chiefly to the small number of wells taking water from the lower zone. Formerly, large amounts of water were pumped from the lower zone in the north end of the area, prior to delivery of water from the Delta-Mendota Canal in 1954. Geologic factors likewise affect the pattern of sea- sonal head decline. The seasonal head decline in 1966 was extreme near Kettleman City because of the bar- riers to recharge provided by the Kettleman Hills and the clay plug beneath Tulare Lake bed. Opposite the Big Blue Hills, seasonal head decline is largely influenced by wells tapping the Pliocene marine and estuarine sequence of the Etchegoin Formation (Miller and others, 1971, p. E16—E17) that receives negligible re- charge. The seasonal variations in head in the study area do not consist of a simple winter high and a summer low. The most common pattern, reflecting the irrigation schedule, is for the winter recovery high to be followed by a water-level decline in February and March that approaches the depth to water during the summer. Dur- ing April and May, water levels recover almost to the winter high before declining to the summer lows. Thus it is common in areas of large specific compaction for the lower-zone head to undergo two fluctuations each year that exceed 60 feet. Examples of hydrographs with large seasonal fluctuations in areas of large specific compac- tion are shown in figures 13 and 15—17. One possible explanation for the relation between the magnitudes of seasonal fluctuations in head and specific compaction is that hysteresis may be important in areas of large seasonal fluctuations in head. On the basis of laboratory tests, Terzaghi and Peck (1948, p. 107) stated, “If the load is removed at the same rate at which it was previously applied, the elastic recovery is smaller than the preceding compression. If the load is again applied, the recompression curve joins the main branch without any break, and the decompression and recom- pression curves enclose a hysteresis loop.” The rejoining of the recompression curve with the main branch of the curve of a stress-strain plot indicates that in situations of recurrent application of stress on either sands or clays. in laboratory consolidation tests (1) short-term de- creases in applied stress do not appreciably change the amount of ultimate consolidation from what it would have been if periodic decreases in stress had not oc- curred and (2) the maximum applied stress is the do- minant control in consolidation tests where stress is periodically decreased and reapplied gradually. The results of laboratory testing as just described suggest that the dominant controlling stress in areas of recurrent application of stress to unconsolidated de- posits as a result of artesian-head decline may be the summer pumping lows. Little is known about the effect LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 of periodic loading on the compaction characteristics of different types of naturally occurring materials, but the preceding discussion suggests that detailed studies of the relation between seasonal fluctuation in artesian head and specific compaction might be productive. CRITERIA FOR THE PREDICTION OF FUTURE SUBSIDENCE Estimates of the amounts, rates, and distribution of future subsidence are important in the planning, con- struction, and maintenance of large engineering struc- tures. The economic aspects of subsidence are particu- larly important for large water-distribution systems. The cost of the San Luis Canal section of the California Aqueduct was increased substantially because of the additional freeboard that had to be included for the estimated subsidence that would occur between the time the canal was constructed and the time when de- livery of imported water would raise ground-water levels sufficiently so that subsidence would cease. The canal passes through the areas of most intense subsid- ence caused by change in water levels. A master drain will be built low on the west slope near the valley trough to alleviate the problems associated with locally high water tables and to remove waste irrigation waters. This drain will be within the subsidence area. Another major expense caused by land subsidence is damage to well casings. Damage to the casings of wells pumped to supplement the surface-water imports will continue as long as compaction of the deposits adjacent to the casings continues. The prediction of subsidence is largely empirical. Al- though data about many of the factors affecting compac- tion have been obtained, the interrelations of these fac- tors are so complex that it is difficult to predict future amounts of subsidence with confidence. Prior attempts to predict subsidence by the use of laboratory data will be discussed, but the main purpose of this section will be to describe empirical techniques and criteria for es- timating future subsidence—criteria that are based on the past history of relations between change in applied stress and compaction within the study area. Compaction of the deposits in the Los Banos —Kettleman City area has occurred because large in- creases in effective stress have occurred, highly com- pressible deposits are present, and the compressible deposits are thick. These are the fundamental factors that determine the magnitude of ultimate compaction and subsidence. In those parts of the area where the deposits are generally of low compressibility or highly compressible deposits are thin, the magnitude of future subsidence would be small, even if future increases in effective stress were large. For example, 600 feet of applied-stress increase has resulted in only 1 foot of subsidence in the area adjacent to the Big Blue Hills G35 where wells tap the thick Etchegoin Formation. Con- versely, in those parts of the area where thick compres- sible deposits occur (southwest of Mendota and near Huron), large amounts of ultimate compaction and sub- sidence would occur even if future increases in effective stress should be moderate. However, the rate of future subsidence in some areas of thick compressible deposits may not be large because of the time required for the applied stresses to become effective in thick beds of low permeability. The factor subject to future variation is the change in applied stresses resulting from water-level changes. Because future rates of water-level change cannot be predicted with precision, the following discussion will be limited mainly to criteria for prediction, rather than the actual prediction of land-surface altitudes at specific future times. Sufficient information is available to es- timate the subsidence rates that will prevail after 60 feet of water-level recovery in the study area. TIMELAG OF COMPACTION Compaction of fine-grained beds (aquitards) and re- sulting land subsidence are time-dependent processes because water cannot be expelled rapidly from beds of low permeability when applied stress is increased. For this reason and because the compressibility of water is much less than the structural compressibility of fine-grained beds, the additional load applied to aquitards and aquicludes is initially borne almost en- tirely by the pore water. If stress is applied to the aquifer system by loading at the land surface, the im- mediate result is an absolute increase in pore pressure within the fine-grained beds. If the stress is applied by lowering head in confined aquifers, the immediate re- sult in the adjacent aquitards is an unchanged absolute pore pressure, which represents an increased pore pres- sure relative to the newly reduced head in adjacent aquifers. The increased pore pressures in the aquitards, whether absolute or relative, induce flow of water from these aquitards to adjacent aquifers and concurrent re- duction in pore volume of the aquitards. The rate of flow, and hence the rate of compaction, is, at any time, a function of the magnitude of the pore-pressure differ- ences between the aquitards and the aquifers. During a specified interval, the volume of water expelled, de- crease in pore volume, and volume of compaction are equivalent. Flow from aquitards to aquifers continues until the compaction of the aquitards produces a structure strong enough to withstand the increased applied stress. When the required compressive strength is attained, the pore water in the aquitards no longer bears a portion of the applied stress, and pore pressures thereafter are con- G36 trolled by the heads in the adjacent aquifers. Within the aquitards, as long as effective stresses do not exceed preconsolidation stresses, changes in pore pressures are characterized by steady—state vertical flow and negligi- ble changes in storage. During the period of nonsteady-state outward flow from the aquitards and gradual progression toward steady-state flow conditions, the difference between the pore pressure at a point in a fine-grained bed and the pore pressure that would exist at that point if steady- state flow conditions prevailed is termed “excess pore pressure.” At any time during the compaction of a clay bed, the average excess pore pressure within the bed is a measure of additional compaction that will occur ulti- mately if the increase in applied stress is maintained until all excess pore pressures have decayed. The time required to dissipate excess pore pressures in a clay stratum is determined by the volume of water (per unit area) that must be expelled to attain the re- quired reduction in pore volume and by the average rate (per unit area) of outward flow. The volume of water to be expelled varies directly with the magnitude of the increase in applied stress,Apa, the compressibility of clay, my, and the thickness, b’, of the bed. The average flow rate varies directly with the increased stress and the vertical permeability of the clay, K’, and inversely with the bed thickness. Thus, the time required for the decay of excess pore pressures in a clay bed is a non- linear function of a time constant for the bed defined by (mvvwb’Apa)/(ApaK’/b’), in which 7w is the unit weight of water. Multiplying mu by 'Yw converts the stress term in compressibility from units of force per unit area to units of equivalent head. In the latter form, it is dimen- sionally compatible with the conventional units for permeability (vertical hydraulic conductivity, K’) in which the hydraulic gradient is defined in units of head. Thus, the time constant, mvywb’2/K’, is seen to be the ratio of the square of the bed thickness to the hydraulic diffusivity, K ’/S 3', and to have the dimension of time. In the case of a clay losing water to both upper and lower sands, the half thickness, b’/2, rather than b' deter- mines the time constant. For a given sustained increase in applied stress on an individual clay bed, an interval of one time constant is required to permit dissipation of 93 percent of the resulting excess pore pressures in that bed. An interval corresponding to half the value of the time constant will permit 76 percent of the ultimate compaction to occur, but twice the time constant is re- quired to achieve 99 percent of ultimate compaction. In the study area, the diffusivities (equivalent to CD, the coefficient of consolidation) of the aquitards in the lower zone are low, typically 1—100 square feet per year (Johnson and others, 1968, table 9), and the aquitard thicknesses, though widely variable, may be substan— STUDIES OF LAND SUBSIDENCE tial. At the Cantua site, for example, 22 of the 138 aquitards in the lower zone range in thickness from 15 to 50 feet (Pt. 2, Bull, 1974, table 8). Thus, even if heads in the aquifer system are stabilized, many years may be required to approach steady-state pore pressures in ad- jacent aquifers and aquitards. The time-dependent nature of the pore-pressure decay in the aquitards and aquicludes is an important factor that complicates the problem of developing criteria for estimating or predicting compaction of heterogeneous aquifer systems, even when a substan- tial history of change in applied stress and correlative land subsidence is known, as in the Los Banos —Kettleman City area. If applied stress has increased during some time period and then has stabilized and the subsidence rate is observed for a number of years thereafter, methods are available for estimating the future subsidence by use of exponential decay curves (Prokopovich and Hebert, 1968). If, following a period of known applied-stress increase and observed subsidence, applied stress decreases sufficiently to stop subsidence, approximate values for the average compressibility of the compacting deposits can be computed. These computed compressibilities can be utilized to estimate the magnitude of ultimate com- paction (or subsidence) that would occur as a result of any future increase in applied stress beyond the precon- solidation stress (Poland, 1969b). The applied stress has continued to increase with time and in an irregular pattern in much of the study area, making it difficult to establish criteria for estimat- ing future subsidence under an assumed future change in applied stress. One of the principal reasons for this difficulty is that there is no economically practical way to measure vertical distribution of excess pore pressures in numerous aquitards at several sites. Some appreciation of the difficulty of developing criteria for estimating future subsidence under an as- sumed hydrologic change in the study area can be ob- tained at sites where long-term information about sub- sidence and applied-stress increase is available. The variation in the ratios of subsidence to increase in lower-zone applied stress and head decline to subsid- ence is instructive in illustrating the problem. If it were not for the time lag inherent in the compaction of the fine-grained sediments, the ratio of subsidence to increase in applied stress would represent the product of the compressibility and thickness of the aquifer system. At a given site, this product would be a constant that could be used to calculate the subsidence that would result from any specified future stress increase. It will be seen, however, that this ratio is far from constant and is, in fact, a complex function of stress history. LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 CONDITIONS BEFORE DELIVERY OF CANAL WATER Maximum canal deliveries are not scheduled until the mid-1970’s, and widespread compaction and subsid- ence will continue until the distribution systems to de- liver the canal water are completed. Additional compac- tion is anticipated in some of the thicker clays after maximum deliveries of imported water are attained because the rise in potentiometric levels in the aquifers probably will not be sufficient to eliminate all excess pore pressures in these clays. Wells will still supply nearly one-third of the irrigation water used in the Los Banos—Kettleman City area. The economics of pumping ground water will deter- mine, in part, the rates and amounts of subsidence be- fore canal water is available. Because the amounts of water pumped exceed recharge in the area, water levels have declined as much as 500 feet in the last 20 years. By 1966, the cost of pumping ground water had in- creased to more than $15 per acre-foot in large parts of the area. Equipment needed to pump the water has become progressively more expensive as pump bowls have been lowered to maintain submergence. Larger pump motors and additional electricity have been needed to raise the water to the land surface. The result has been one of the greatest concentrations of electric power use for agriculture in the world. The depths from which lower-zone water had to be pumped in the summer of 1965 are shown in figure 29. The depth to pumping level ranged from less than 200 feet to more than 1,000 feet, and in most of the area, water had to be pumped from depths of more than 400 feet. The increased costs of pumping water have reduced profit margins. In those areas where the depth to pump- ing level was 700—1,000 feet in 1965, the land is not farmed as intensively as it was when water levels were as much as 300 feet higher. The past rate of subsidence can be used to predict future subsidence if it is appropriate to assume that the past trend in Subsidence rate will be maintained into the future. Two types of subsidence plots at a given bench mark are shown in figure 30. The plot of cumula- tive subsidence provides information about the total amount of subsidence that has occurred at any particu- lar time, and changes in the slope of the cumulative subsidence plot are indicative of the general changes in rate of subsidence that have occurred. A plot of subsidence rate is much more instructive than a cumulative plot for predicting future amounts of settlement. The plot of subsidence rate in figure 30 is a generalized curve derived from a graphical integration of a rate bar graph. For examples of rate bar graphs and curves, see Part 2 (Bull, 1974, fig. 22). G37 Unforeseeable changes in rate make extrapolations of either cumulative subsidence or subsidence rate curves of limited value. For example, the changes in subsidence rate at bench mark 8661 in 1954, 1957, and 1962 shown in figure 30 would have been most difficult to predict in advance and actually were not noticed until several years after they occurred. In those parts of the study area where surface water has been available in some years but not in others, the trend in subsidence rates has changed more frequently and abruptly than in the example shown in figure 30. (See fig. 42.) Another approach is to estimate the amount of applied-stress increase per foot of subsidence. The amount of potentiometric level decline per foot of subsidence during a 10—20-year period can form the basis for predicting minimum amounts of future subsidence, should the rate of increase in applied stress, as indicated by water levels, continue to be the same. The number of feet of lower-zone head decline as- sociated with each foot of subsidence during the 1943—60 period is shown in figure 31. The change in the lower—zone potentiometric surface was chosen because three-fourths of the water pumped to cause the increase in applied stress and subsidence has been withdrawn from the lower zone, and at least three-quarters of the compaction has occurred there (Pt. 2, Bull, 197 4, fig. 45). The near-surface subsidence component has been re- moved from the total subsidence measured by bench- mark surveys for this period. The change in head is based on the maximum head decline during the period; therefore, in the northern part of the area where water levels were recovering in 1960, water levels of the mid-1950’s were used. The number of feet of lower-zone head decline as- sociated with each foot of subsidence during the 1943—60 period generally ranged from 15 feet to 400 feet. For large parts of the area, less than 25 feet of head decline were associated with each foot of subsidence for the 1943—60 period. The use of this map to make empirical predictions of the minimum amounts of subsidence that would occur in the future as a result of an assumed head decline would be dependent on the following assumptions. 1. It is recognized that substantial draft is from the upper zone in parts of the area where wells are perforated in both the upper and lower zones. It is assumed that the proportion of perforated interval in the upper and lower zones and the lateral re— charge characteristics of the two zones will not change. If this assumption is true, then a given amount of head decline in the lower zone will be associated with a proportionately similar head de- cline in confined aquifers in the upper zone. In effect, the technique described here would utilize G38 STUDIES OF LAND SUBSIDENCE 120°30' 120°00' 33 l 152 Los Banos 152 / / 37°OO’— Dos / Palos ./-\§r§§'_w/—---q,__x x’\_8iver _ 33 f ‘V Madera / 09% / £1 00 ‘2‘ O M 9}“,th 99 5 0 Ca” 0 ‘20 / \ °’ Firebaugh RIVER évgfi’ <99 °‘o ‘3' O / 0 eQ'co/eo “‘ e e 0‘ $09 I» 1°” 0/ 477’ Mendota l 76) O O Kerman (O a 2 ( (m 36°30’ — EXPLANATION ’9‘7¢ . Five Point , 620 Boundary of deformed e rocks ’0 200 Generalized line of equal depth to pumping level, in feet Interval 100 feet. 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Awiilimm mfigwm i541 WM mama fit yr‘ll WWW 1W8 mmmmmmwmmwmmm Wampum m‘hflwfimflmmm. h_mm,,QmemWWm WWmemmmwMM M We: WW SSW. m WWI Wam®wmamhMm mmifimwm mmmmwmwmmmmmmm mnmmmm mm 11% with“ 9% film 119% mmemmmmmmmmmm hwmwwamflmmwmmmm mwmmemMammwmw ma Wm WM mm m m WW. memmmmwmmw mmmnwm,mmmwmmm WMfiQfimmmfiwwmt hwmmm. "m WWMW/fimm—EIMQWM%WE%- Wmmmmm@mmmmm. mm W 11% W @m, and m w Wmhflemmmmmmmmma .meMMWsmeme mam {at film mm @381 WWW W in; G40 ‘ y : w .‘ STUDIES OF LAND SUBSIDENCE __ _ 120°3O’, 1207°ooh 33 , g, _ ‘ l. : ’ 152 LosBano's‘r“‘ "' ’ ’ " ' ‘, , . /_, . :;*,K 7. y. f D053]; ,. Palos / , ‘ ~’r\_8jver _ ' Madera ‘3 I. GO ; i., i" O ‘3 'f ‘\' w r. i 99 , k) 0 , ,Ch7,.; H 5‘ t C » Y Q? 2' ~ .7 ~ _, A .-_Y lFirebaugh , “RIVER é’ [59 , ‘ ,5 ._- . ~ u QQ' FRESNO n 77 1— iso\ Kerman J— 41 36°30” — _ ' 7, EXPLANATION ' V :.:::’r:::{:::r:l . Boundary of deformed " rocks- _‘ 100—"— rLin'e" ofgequal lower-zone head ,decline' _ associated with 1 foot of subsidence, ‘ ,. 1943-6o,'in feet; interval variable. Dashed ’ ' ' "9&0 ( 1‘ where approximate , '4‘ 1,, ”Eb 33 Based on: 1. Subsidence due to artesian-head de- ‘ , « ‘55 ‘ , cline, 1943-59;estimated near—sur- , : 750\ face subsidence component sub— "/ v5 tracted from total subsidence in / / ‘ ,9 near-surface subsidence areas ~/. ' a 9,0 2. Maximum artesian-head decline for V ’06, 'the lower water-bearing- zone, '° - " «94’ 1943-60 'PL ASANT , ‘ i , ; ,Coalinga; Q A _ V VALLEY.» V 19 . .,We_sthaven i z, Huronvo P;_«/ TULARE LAKE 0 5 10 15MILES - , X , ‘ . 1’ . s : h » “Hf/715' Ket-tleman BED .(5‘ I , City I——-1—L——r——-T—‘-—”—_‘ O 5 1O 15 KILOMETRES , ., , , Base from US. Geological Survey Central Valley map,'1:2§0,000, 195’8 ' ’ 36°OO’ . 3 FIGURE 31.—-Number of feet of lowerrzdnehead decline associatedrwith’each footaof subsidence,n1943—V60.V_ , i , é , excess poieiprESSUre'ih the aquitards during'the'con: grafihi‘bf figure 133Brr'ivv’0u1d' ”havea- uniform height that secutive time periods; If the time delay associated-With would be a function of the compressibility and thickness much of the compaction were not present, the bars of the of the deposits at the site. The changes in the ratios 37°00’ 36°30' — 36°OO’ LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 G41, 120°30’ 120°00' 33 I Los Banos 152 ’ / Dos / a 05 d\o ’,~‘\".’F_):e’§'_|0/\___ '99 / 33 :0 e14, Q27 E v /a.aa Mandala , a, ‘ ”9 Firieb‘augh Q x. 90“” ’o ———>— San Luis Canal - California Aqueduct 0.02 Generalized line of equal ratio; interval 0.01 and 0.02 Subsidence due to artesian-head de- cline, 1943-59 Lower-zone artesian-head decline 1943-60 Ratio of: Based on: 1. Subsidence due to artesian-head de- cline, 1943-59; estimated near-sur- face subsidence component sub- tracted from total subsidence in near-surface subsidence areas 2. Maximum artesian-head decline for the lower water-bearing zone, 1943-60 0 5 10 15 MILES O 5 1O 15 KILOMETRES 0'00 ‘\ ‘ o ”-04 Five Points -0 0.0;: \\ — _ _ _ _ o, \7 ,, Q 33 l / G ‘ —' < l r ’9/ (( fi- ~S‘ ‘ ‘3?“ . l \ Jim ‘ / w th\ n " 7 / es ave v22. ’9, ’0 Huron o I S: 0094/ , Strat a 6‘ 00 ford PL ASANT so ”0° Coalinga [go/0‘5 VALLEY {9% 0" p6. / TULARE‘ s, , >994, LAKE q Ill/Y I - Kettleman / / 33 (‘5‘ 1 City BED o Cantua Creek Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 32.—Specific subsidence, 1943—59 between 1940 and 1956 indicate that average excess become even more important since 19562because- the pore pressures doubled during this period of accelerat- ing increase of applied stress. Delayed compaction has rate of applied-stress increase has declined progres- sively. Nearly all the 2 feet of subsidence that occurred “ 9,99 was . flan #m i: . . 9., ~ I, r". ., ,. , ‘4 L ‘ n figmmmwlmmwmi n ‘- .J ‘ "v n; 7‘ ‘ v *7 ‘ ‘1 'P’. .v' F: 1“] >, . l ' u' 4 I“, ‘ ‘ I 1’ y ,. , . , V H , w l w, t, u ( . #993 C ‘/ A 1d,: ;‘ W “ 1am 13% , 7 fiwmmmmmmmmmmmfima 1m . ‘«rimwwwwwmlmwmamlmwmfi j tamiwmmmmw ”193.9% lWfiifiWfiWWMWQ? ammmmywmm 193%. . _ . , ‘mmfiwmmfimmwvma mammfimmmmmmflm WWfimMWWWMmWwaWt Q mm mm 9mm twin @m‘tm @m‘k. Alum mmwmamm fifiuMmfikfi M 129$th 9% haw-mm W. m gamma mtmmmmmmwwmmfi aMWQMaszmMQE‘WMm. figwmmwmmdeW%m swam m LANE sqhimm 9.1% ‘ am; M" I ’f? g / 7 . ’ ""‘n'f? """ V . . ”’ r"; - :W wmmmmmmfimm 12mg. ~25; wmwmmmmmmmmemamammm ‘ 22%" MWfiWmWW. "U WW! KW €1th 991mm gift-m diam in am \mthel'owma ,, 129%, 99W in Wind amenthghw mlhaimmblyhighMmmtfimemhhf Wu Between 1943 and 193% We chm in mm mm the, 1m fluctuating mmamaammaf amtnfimflmmmmmmmmma Mfifipi‘amM-sm WWW 9% WWW RWWWMMWMSWW mm . tammmefiw‘kwmmme 1m Mammmmmmmwmfl ,, k @413 m“ that m gamma; RWWWMW Hath m m mark H.237 WMWWWWmflIWlWQfi Em amaaummemmmwmamm mm. AM ma themm W may. Between y. 4. is. w, 1.; L98 BANMETTEEKKN @ITY AREA. @ALIFQRNIA; PART 3 1969 and 1933 the ratio was 0948. and borrow and 1936 the ratio increased to one The eoui head decline/subsidence ratio decreased from 69d the 194943 period to about 9 during the 1 99 period Comparison offigures 34A ands shows that Ween 1949 and 1993, when the rate ofappliedsstress so rangedirom 11 4to martyr=11 theratiooi‘su I to stress increase more than doubled homo to 9049 This change in the ratio is interpreted as seating a substantial increase in the magnitude cess pore pressures during a 29-year period of steady head decline with no intervening periods ofsta bead ‘ to provide sufficient time for the aquifer sys preach a steady-state porepressure distributionrll‘he 1933263 period was characterised by slightly tower compaction rates and a decrease in the rate of applied; stmss increase to only 6 it yr=1 Most ofthe compaction that occurred during the 196346 period is interpreted as being delayed virgin compaction resulting from prior periods of head decline. The variations of increase in applied stress in the vicinity ofbench mark PTS21$ are shown in figure 35. The bench mark is in the southern part ofthe study area about 2 miles north of Westhavent About 60 percent of the subsidence ofthis bench mark has been the molt of lame compaction Change in applied smss that can be attributed to change in the position ofthe water table is minor in the vicinity of the bench mark. The .s 34 0° 1980 “IT 7‘ i |' ' 7 ’7 ‘T'Y' 7 "7 '7 :f 7 i 7’ 33 , A as: r 7 5533*» 1 ‘n 3 fl ‘ / \ § 5 * / \ so 1 is: r ‘ :3 I ‘ gins ‘ ‘ a O i ‘ 33$“? ‘ "‘ u. < {a l , i V MW , 1320 coco taco 1950 moo 1an o - z" u; i i r' 7 1* 7 f i I? i ' :3 E: 12.3% B ~ooafi§o 13 not ‘ :35 '2- 3 ‘ x: Cumulatinwalun of ratios ‘ 39¢ III‘ \ 3'3 25m- «10‘335 33 soo- 3i: 3% soo‘ ‘ 9;. U unis: W/i / 1o/ t 32 D Q 3 .4“ homes—ammmwmmmmmmisn MinuteofmofappfiedmmthcmmB Minfikhfioof Wmmmhmappliedm 7'1. 9 , pp.) ‘1o‘ ' a estimated water-table rise has been only 16 festq compared with 422 feet oilower-rone head decal x II ‘ 19). Water-table rise accounts ibr less than 1‘ " ' the applied-stress increase at the site i i ‘ .. Because about 40 percent ofthe compaction of I. I W, mark H3218 has occurred in the upper soup; them ., '2' of subsidence to increase in lowercase : t. , :f are apttobemisleading. unless head changesth.I ' similar in the upper and lower cones. Sim V ' changes have occurred in the two zones dime haven» compactionqecorder site 5 miles to the : -, ' 1..“ bench mark PTS213 (Pt 1, Bull and Miller. 12143 I'; z" 14). It is tentatively assumed that the heads abs 2 M‘ , .‘ ap-below the Qarcoran also are similar in the area neér~ ' bench mark PTS218, but such an assumption isteiluoiih in an area of highly lensing alluvialdan deposits; Wu The history of applied-stress increase in‘ the vm ofbench mark PTS21S does not have a consistent trend . and is dominated by a period of35 ft yr= 1 applied-stress - increase between 1947 and 1954‘ ’ The ratio of subsidence to increase in lowensone ap plied stress at bench mark PTS218 decreased between 1923 and 1954, the ratio being only 0907 during'the 193747 period as compared with 0.019 during the 1923=33 period The overall trend since the mid-1940’s appears to have been one ofoverall increase ofthe ratio, which may be the result ofthe increasing importance of delayed compaction. The head declinel/subsidence ratio ram fiom about 140 that during the 1933-47 period to 14 feet during the 1954-57 period. The apparent lesser proportion of delayed compaction occurring at P’TS21S as compared with that at bench marks GWM59 and H237 (reset) may be because the post-1960 head de- clines have been roughly twice as large at PTSZIS or perhaps because relatively thick-bedded alluvial-fan deposits of low permeability at bench mark PTS21$ do not permit delayed compaction to occur as rapidly as at the other two bench-mark sites Figures 33 and 34 demonstrate the importance of time-delayed virgin compaction for those attempting to predict future subsidence, and figure 35 shows the ex- treme variations that can occur in cause-effect type ratios. The lack of consistent ratios at all three sites demonstrates the hazard of attempting to predict future subsidence by an extrapolation of such ratios when based on short time intervals. However, cumulative ratios derived for periods rang- ingfmm2tomorcthan4decadescanbeusedtofurnish minimum estimates of the subsidence that would occur ultimately from a given additional increase in applied stress—that is, subsidence in response to a given. in- crease in effective stress The cumulative ratios are computed from the total subsidence and applied-am G44 Such’minimval valuesWOuld serve as a floorfor esti- mates of subsidence obtained by other methods. The lcumulativevalues of the ratios for figures-3&35 are shown by the X’sers with other cumulatiVe graphical techniques, the effect-isto .smoothxout the short-term «variations. The cumulative values of these ratiosas «plottedfor, 1966 agree, with the ratios in-figure '32. «Another factor that L'should be Considered in areas of intenseland subsidence is the permeability decrease cauSed: by compaction.» Compaction of the aquitards has ‘reducedthein vertical permeability, thereby tending to increase the time required for excess pore pressures .in :the :aquitards-vto: reachiequilibrium with those in: adja- '=cent aquifers. Locally, the overall water-bearing section has been decreased» in thickness by 2‘percent or more. The actual decrease in thickness of some of thecompres- sible and rapidly compacting beds may be more than 4 ‘peroent-nUnder conditions of uniform increase in ap- plied stress, decreasing permeability of the compressi- ble beds that occurs as a consequence of compaction results 1n :1 decrease 1n the rate of pore- pressure decay and conipaotion of the aquitards. COMPUTATION 01 AQUIEER SYSTEM FORE PRESSURE ’ ” DECAY The compaction during a time period 1s a function of the rate of flow of water from the aquitards and aqui- cludes, which in turn isa- function ,of aquitard-aquifer pore-pressure differentials.sThus, prediction of therate ofporehpressure decayiand delayedzcompaction ata site provides estimatesof future subsidence, assuming that the appliedstress will. remain relatively constant. _ Two , ~ methods: ,«. of .. predicting aquifer-system pore- .pre‘ss‘l‘i-redecay can be illustratedby field data. from the Los; BanOseKettieman:Gity area» In- much of the north- ernz’part‘bfi the study area, an equilibrium hasbeen approached between ~ground:water inflow: and outflow. Although the applied stresshasbeen increased greatly rfromthe preagriacultural development conditions, little seasonal or longrterm changein applied :stresshasoc- curred during the 1960—67 periods Thus, bench-mark .sjurveysginthese areas provideinformation about de- crease in the rate of aquifer-system compaction under a constant stress- Future: compaction can then be . esti- mated by graphical projection or through the use of power- -function equations of the type described by Pro- kopovich and Hebert (:1968, p. 920:) - The preceding technique cannot be used 111 most of the study. area beeansex the arte’sian head has not been stabilized and hence applied stress has notébeeir con- stant during: 2—3 bench-marksurveys, as in the north— xernganea. However, atzso‘me sites the rate of- applied- stress increase has deereasedgreatly since 1960, and the total post-1960 applied-stress increase is only 2—6 STUDIES OF LAND SUBSIDENCE percent of the pre-1960 stress increase. Thus, when compared with the prior periods of stress increase, the load on the aquifer system; may be considered roughly iconstantrrasinoe about 1960. The lack of sufficient bench-mark surveys can be circumvented at somesites by. gusting. compaction-recorder . data." The . problem (if large seasonal variations in appliedstress - can ~be largely eliminated by using ‘9 recorded: - compaction amountsfor selected ranges of applied stress. Thistech- nique-worksbest at those sites Whererlarge amounts of compaction are being measured and where; seasonal and longer term applied—stress changes are minimal The minimum rate of decrease of delayed compaction after a given date at the four multiple compaction— recorder sites can be determined by computing the changes in:the.mean daily compaction rates :of lower- Zone deposits for selected applied stresses. The selected applied stresses for the four sets. of graphs :«in figure 36 are ranges - of _ applied stress. The minimum applied ~ stress was placed at a~lower~zone potentiometriclevel below which compaction was generally recorded-each month; The maximum. applied stress was the maximum depth to watersiforra given year- At all four-sites; the , maximumsummer depths to water (mmimumlower- . zone potentiometric levels) during- the11ast half of : the period .Of grecord'shown in figure 36 were deeper than the maximum Summer depths. to water during the first half of the periodof record; however, the change-was not large, and atthree of the sites the summerlow-water level increased 4—20 feet. The maximum depth to water had the following ranges: the Oro Loma site, 202—206 feet; the Mendota site, 496—516 feet; the Cantua site, 600—618 feet; and the Westhaven site, 419—458 feethhe component of change in applied stress that can , be attributed to water-table change at the four sites is negligible; hence, it is not portrayed in figure 36." Decrease in the mean compaction rate at the Oro Loma site for those days when the depth to water 111' well 16H6 exceeded 190 feet is shown in figure 36A. The compaction was measured 1n the depth interval extend- ing from 35 to 535 feet below the Corcoran. During the 1963—66 period, ,55 percent of the subsidencewas the result of compaction in the upper 1,000 feet cf deposits, and 45 percent of the subsidence was the result of com- paction occurring below 1,000 feet. For most of the period of record, the depth to water exceeded 190 feet for 365 days a year. The curve showing the trend of the ‘ , daily compaction rate shows a progressive de- creasé'in slope with time. In 1961 the mean daily com- paction rate was 0.0009 foot per day, but by 1967 the rate had decreased to 0 0003 foot per day Decrease 1n the mean compaction rate at the Mendota siteforthose days when the depth to water exceeded 470 feet is shown in figure 363. The compaction was meas- LOS BANos—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 G45 Meari compaction rate for those days when the depth to water exceeded 190 feet * 1 -’ V .;u_ ; .V g 1 g,» ,. ‘ . 1001 ~ 0‘ V .1 .1963 1965 xv". 0.001 \- , 460 , V ,. Maximum depth to water 0 \ 7 FEET PER DAY >. . a" 0.0010 0': Lu :1. 0 , ‘ - 7- . 1961 1963 1965 1967 E 00005 1961 1963 1965 1967 V . LI.| Meen‘ compaction rate for those days when the depthlto‘ _ L1. ‘ Mean compaction rate for those days when the depth to , ~ water exceeded 470 feet ' ‘ " water exceeded 410 feet FIGURE 36. —-Cha.r1ges in the mean daily compaction rate of deposits for selected applied stresses. A, Oro Loma site; depth interval 500—1 000 feet. B, Mendota site; depth interval 780—1 358 feet. C, Cantua site; depth interval 703—2 ,000 feet D, Westhaven site; depth interval 830—1, 930 feet. Aured in the depth interval extending from 80 feet to 658 ence occurred below the 1,358—foot depth, During the feet below the Corcoran. During the 1963—66 period, 31 period of record, the number of days that the depth to percent of the compactiOn that was causing the Sub‘sid- water exceeded 470 feet increased from 91 to 365 days. @439 The curve shows an overall decrease in the mean daily compaction rate with time in 1902 the mean daily ratewes00021oetperdaybutbyl90’ithe . compaction . ., ratehaddeoleaseutoooeotroctwdsy Decrease in the mean daily compaction rate at the statue. site ibr those days when the depth to water exceeded 690 fbet is shown in figure 9%.. The compare-4 . :tien-wasrneasured inthe depth interval extendingirem .128 ihet to 1,426 feet below the Gerceren. During the * . 11969200 W'led,. 12 percent of the compaction causing fits. Aimilegarithmic plot efthe decrease inthemean stibftidsnte at the site was the result of cornpactien' below 9,, 000 lbet The number efdays that the depth to ' “ .‘. wammacoreetnmseanomcseseodays during the period ofrecerd The curve showing the trend of decrease in daily compaction rate is close to all the points Data are not available ibr 1909 and 1994 be , cause of. a casing failure in the well used to observe changes in water level In 1961 the mean daily compac- tion rate was 000% fbet per day, but by 1967 the rate had decreased to 010016 ibot per day, Decrease in the mean daily compaction rate at the Westhaven site for these days when the depth to water exceeded 410 feat is shown in figure 980, The compac~ tion was measured in the depth interval extending from 100 icet to 1,185 feet below the Corcoran, About 95 percent of the compaction is estimated to occur above the 1,980-foot depth, During the period of record, the number of days that the depth to water exceeded 410 feet increased from 161 to 335 days. The curve at this site also is suggestive of a decrease in the rate of daily compaction, In 1968 the mean daily compaction rate was 0.0010 foot per day, but by 1967 the rate had de creased to 0000? foot per day. The rate at which applied strm becomes effective in the finegrained, poorly permeable parts of the aquifer system decreases progressively with time in an expe nential manner, All four mean-daily-compactien-rate plots in figure 36 are best fitted with exponential curves. mnmsermnnseesmei Themeandailycempactienratesinlmareenlyenea third is twethirds the rates at the mm of the 9—37- -year periods. The; mean-daily-compactien-rete plots may be rep resented by a general exponential equation eithe type ." t T. 29%” in whicite and m are demrmined by the date ier each daily tdihpactien rate of the Qantue site data (fig. 971)) shows that the points have virtually no scatter about the regression line. The daily compaction rate is de— creasing exponentially in the WWt-depth zone ibr these days in which the depth to water exceeds 690 first. The equation for the linear plot efmean daily compaction rate (y) and the time since mid-1991 in years it) is yaoloons 60%.. The intercept that controls the coefficient was selected arbitrarily as mid11991, but the exponent includes m=the rate efchange efy with respect to at (=01090) of the plot in figure 3'7, Comparison of values of m for similar plots in other depth zones, or areas, should pro vide some general useful information regarding the rate ofcompletien of pore-pressure decay in the aquifer systems, The curve in figure 87 may be extrapolated as an example efpredictive technique ifit is assumed that the maximum depth to water will continue to fluctuate be- tween 610 and 820 feet and that the water level will be deeper than 560 feet for 365 days each year, Despite the continued decrease in compaction rate, 04 foot ofcom~ paction would still be occurring in the 703-2,000‘foot-depth interval during the year 1971, During the period between the 1963—66 bench‘mark 0.003 n 9 § MEAN DAILY COMPACTION RATE FOR THOSE DAYS WHEN THE DEPTH TO WATER EXCEEDED 560 FEET, IN FEET PER DAY 0.001 n " U I I1 U 1962 1964 1966 Flam Ill—Decrease in the mean daily compaction rate in the manner-um). interval at the Camila site, , LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 G47 surveys, 18 percent of the compaction measured in the upper 2,000 feet of deposits occurred above 703 feet, and 12 percent of the subsidence was the result of compac- tion below 2,000 feet. If these proportions were the same in 1971, the amount of subsidenCe during the year would be about 0.56 foot (0.09 ft would be occurring in the 0—703-ft-depth interval, 0.40 ft would be occurring in the 703—2,000-ft-depth interval, and 0.07 ft would be occurring below a depth of 2,000 ft). Thus, the minimum amounts of future compaction and subsidence at the Cantua site would be large even if the water levels never exceed historic low levels. Importation of surface water in the next decade prob- ably will invalidate the assumption made for the pur— poses of the preceding discussion that the water level would be deeper than 560 feet at all times of the year. An estimate of the rate of subsidence after an assumed water-level rise will be presented in the next section. The time needed to approach steady-state pore pres- sures in the 703—2,000-f00t-depth interval at the Can- tua site can be estimated on the basis of figure 37. The total head decline at the site of roughly 400 feet is large compared with the 18-foot head decline of 1961—67. Therefore, for purposes of the projection shown in figure 38, it is assumed that mid-1961 is the time of an un- known mean aquitard-aquifer pore-pressure differen- tial and that the mean head in the aquifers remains constant thereafter. The rate at which the 1961 excess pore pressures would be dissipated can be expressed as a function of the change in mean daily compaction rate, using 1961 as the initial time. The curve in figure 38 describes the same equation as shown in figure 37 . The solid line represents the controlled time period shown in figure 37, and the dashed part of the curve, the post-1967 extrapolation of the curve, which after six decades, is essentially asymptotic to a zero-compaction rate line. Figure 38 shows a decreasing rate of comple- tion of post-1961 residual compaction. By mid-1962, 10 percent of the residual compaction had occurred, and by 1968, 45 percent had occurred. The estimate of the fu— ture percent completion of post-1967 compaction indi- cates that it would be 1975 and 1991 before 50 and 90 percent, respectively, of the residual compaction had occurred. By the year 2033, the yearly compaction would have decreased to only 0.001 foot. The decrease in the mean daily compaction rate of the lower zone at all four multiple compaction-recorder sites (derived from figure 36) is shown in figure 39. The plot for the Cantua site has little scatter, but the plots for the other sites have large amounts of scatter. The scatter is larger at those sites with low compaction rates, thus reflecting the problems in measuring small amounts of compaction with the equipment presently in use. The degree of scatter is so large for the Oro Loma site data that the points for 1962 and 1965 were rejected as being unreasonable. Computation of m values for the four lines shown in figure 39 gave the following results: Cantua site, —0.096; Mendota site, —O.21; Westhaven site, —0.091; and the Oro Loma site, —0.18 (a minimum value). The m values are indicative of only the general rates of decrease of compaction rates at the sites because the applied stresses were not constant during the periods of record. The implication in figure 39 is that the rate of de- crease in the mean daily compaction rate for the two southern sites is only about half that for the two north- ern sites. The mean daily compaction rate at the West- haven site has been decreasing less than at the Cantua site, but would have decreased more rapidly if there had not been an overall head decline of 39 feet from 1963 to 1966. The overall lithology of the lower zone (Pt. 2, Bull, 1974, fig. 61) is more clayey at the Oro Lorna and Westhaven sites than at the Mendota and Cantua sites. Therefore, the overall amounts of clay in the lower zone at the sites does not appear to explain the more rapid 1 0.0000024 , I I ffi;____4______,____ _,— 100 g 5.65 o /, “WC->2 /// _ ‘7‘ _ ‘- LU BI * // 8 "oi- _——>— O O BELOW LAND SURFACE, IN FEET b M U1 Annual discharge of Kings River E2; ~~"25.000 downstream from the Lemoore Weir (from Kings River Water 250,000 Association) _ — 375,000 500,000 ACRE-FEET P 01 P is Bench mark L157 p u I / 9 N o L I I SUBSIDENCE RATE, IN FEET PER YEAR V O 1950 1960 FIGURE 42~Interrelations of subsidence rates, artesian-head decline, and surface-water imports near Stratford and Lemoore. G54 STUDIES OF LAND SUBSIDENCE l rate, when compared with the mean subsidence rate in 2 years of abundant surface water. ‘ Measurements of the pumping level in well 21/19—2B1, although infrequent, show generall trends that agree with the records of subsidence rates and surface-water imports. This well is 1,990 feet deep and taps only the lower zone. The time of maximum re- corded depth to pumping level late in 1961 coincides with the year of minimum availability of surface water and occurs in the period of maximum subsidence rate. The time of minimum recorded depth to pumping level late in 1956 is associated with a year of large surface- water import and with a period when the subsidence rate was only 0.07 ft yr‘l. ‘ The interrelations shown in figure 42 indicate that little residual compaction would occur if water levels were raised more than 50 feet. ‘ Accurate prediction of subsidence rates for an entire region at a specified future date may not be possible because of the many highly variable factors that influence change in applied stress. However, it can be assumed that importation of canal water will decrease pumping and will cause artesian heads to rise, and thereby alleviate subsidence to varying degrees in all areas of decrease in applied stress and possibly elimi- nate subsidence in parts of the area. The following dis- cussion, although made in the form of a prediction, is intended as an example of the application of criteria for the prediction of future subsidence after a postulated decrease in applied stress. Estimated subsidence rates based upon a postulated increase in lower-zone artesian head are made in table 2 and in figure 43. The estimates were made On data available as of December 1967. The year 1970 is used as the time of the hypothetical head rise. It is necessary to specify a date for the estimated rates because of the continuing decay of excess pore pressures that have resulted from previous head declines. The year 1970 may or may not be the time of major recovery of lower- TABLE 2.—Estimated annual subsidence rates in the Los Banos- Kettleman City area if summer lower-zone water levels rose 60 feet and the seasonal fluctuation were reduced to 10—20 feet Estimated rate if water levels Estimated rate if water levels Subarea rose 60 feet in 19681 rose 60 feet in 19702 (ft/yr) (ft/yr) Hmwwaawmmwwww IIT\?VIITTTlIo 99999999999991 99 9 IT'lol'lkllol l i?” l Io 9999999999999 NNJBNUIBNNMCI‘WNN o999999999999 oopopcoopppoo 1Based on 196&66 subsidence rate map, compaction rate after 60 ft of water-level rise at compaction-recorder sites, lithofacies maps, and lower-zone seasonal fluctuat on map. 2Correction of estimated 1968 rates based on residual compaction graphs ( gs. 38, 39), zone artesian head. It can be stated with certainty, however, that increase in head as the result of canal— water imports will not be uniform, nor will it occur at the same time in all parts of the area. A 60-foot increase in head was selected for several reasons. It is a reasonable minimum amount of rise in the summer potentiometric level that will occur after large-scale deliveries are underway, but probably is less than the ultimate amount of head recovery that will occur in much of the area after the maximum delivery of surface water. It is possible that the lower-zone artesian head will rise more than 200 feet in parts of the study area, despite the estimate that total ground-water pumpage under full import conditions will still be about half a million acre-feet. About 60 feet of seasonal water-level recovery has occurred at many of the compaction-recorder sites. If a larger value of postulated head rise had been selected—100 feet, for example—then the compaction records would be of little use in determining the rate of compaction after given amounts of head recovery. The estimates of future subsidence rates after a pos- tulated head recovery represent an integrationof knowl— edge regarding many aspects of the hydrology and geology of the Los Banos—Kettleman City area. Because many different types of knowledge and experience are involved, the results should be considered in part to be subjective. However, the large amount of factual data that is available makes the estimates more objective than the reader might first suspect. The general pattern of subsidence rates is well established from the 1963—66 subsidence rate map (Pt. 2, Bull, 1974, fig. 19). The compaction rate after 60 feet of seasonal lower- zone head recovery is available from most of the compaction—recorder sites. In evaluating the compac— tion records, it is important to remember that the amounts of recorded compaction during a period of water-level rise are the net result of two components tending to change aquifer-system thickness: Delayed compaction of the aquicludes and many of the aquitards will tend to cause compaction to be recorded; elastic expansion of the aquifers and some of the aquitards also will tend to cause expansion to be recorded. The net result of these two components is dependent on the rates of delayed compaction and water-level rise. If the rates of water-level rise are sufficiently rapid, net expansion may be recorded, even though delayed compaction is continuing in parts of the aquifer system. In this case, recorded compaction may resume after a period of water-level rise, assuming that water levels are con- stant after the head recovery. Rates of delayed compac- tion that are recorded while water levels are rising are minimum rates. Two lithofacies maps (Pt. 2, Bull, 1974, figs. 63, 66) 9V LOS BAN OS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 G55 120°30’ 120°00’ 33 I Los Banos 37°OO’ Kermanc 41 EXPLANATION 36°3o' — 7777777772 9% _ Boundary of deformed Lo rocks 4 e Boundary and number of hydro|ogic 074/ geologic subarea Ii 5 50(43 9 o _. P N . o W 5 § 0<0.2 0.3-0.4 Estimated rate of subsidence in each sub- , / area in feet per year / 9/9 Based on the 1963-66 subsidence map, a, 00634, compaction rate after 60 feet of water- level rise at compaction-recorder sites, lithofacies maps, and lower-zone seasonal Coalinga fluctuation map; corrected on the basis of VALLEY graphs showing the decrease in the rate of delayed compaction at selected applied stresses / I Strat- ford PL ASANT TULARE LAKE O 5 10 15 MILES i—_r—1_T—T_;—J 0 5 1O 15 KILOMETHES / Base from US. Geological Survey Central Valley map, l:250,000, 1958 ;' Kettleman 1 City BED 3 6 ° 00' FIGURE 43r-Estimated annual subsidence rates in the Los Banos—Kettleman City area in 1970 if summer lower-zone water levels rose 60 feet and the seasonal fluctuation were reduced to 10—20 feet. were used in the evaluation. One map shows the general other map shows the distribution of genetic classes of patterns of the mean lithology of the lower zone, and the deposits with different types of bedding, which have an G56 STUDIES OF LAND SUBSIDENCE important influence on the rate at which water can be expelled from the compressible deposits and hence on the rate of compaction. Most of the subarea bou‘ndaries that trend generally east-west in figure 43 were selected on a hydrogeologic basis. Subarea boundar'es that parallel the length of the area also parallel the lines of equal subsidence rate, or boundaries of Sierra and Di- ablo deposits. , The lower-zone seasonal fluctuation had to bei consid- ered also. A 60-foot head rise for summer levels would raise the minimum seasonal water level 50 fe t above the 1967 winter high water levels in parts of the‘area. In other parts of the area, 60 feet is only half the seasonal fluctuation that was occurring in 1967. It is ssumed that seasonal fluctuation of artesian head will ecrease as the ground-water pumpage decreases. A range of 10—20 feet of seasonal fluctuation was selecte for the purposes of table 2 and figure 43. The amoun of sea- sonal fluctuation that is postulated is about the same as has been occurring in that part of the area that already has received large—scale surface-water imports—the service area of the Delta-Mendota Canal. In 1966 and 1967, seasonal fluctuations in most of thq‘ Delta- Mendota Canal service area were 5—20 feet. The factors just described were the principal sources of information used to estimate the subsidence‘ rates if summer water levels had risen 60 feet in 1968 (table 2). Maximum estimated subsidence rates after a pos- tulated water-level rise in 1968 exceed half a foot per year in subarea 9, but in most of the area would be 0.1—0.3 ft yr ’1. The estimates of 1968 subsidence rates if the pos- tulated water-level rise had occurred were made only to form a basis for predicting future rates within small areas, or at given points, after a summer head recovery has actually occurred. The potentiometric levels during the summer of 1968 actually reached historic lows in most of the area. To estimate subsidence for some future year, the de- crease in the rates of delayed compaction has to be estimated and applied as a correction to the 1968 esti- mates. The selected year of 1970 for a postulated 60 feet of summer head rise is 21/2 years after the December 1967 base date. The plots of decrease in the rate of delayed compaction in figures 38 and 39 indicate that after a 2V2-year period, residual compaction in the northern part of the area would be roughly 35 percent complete and would be roughly 15—20 percent complete in the southern part of the area. The larger correction factor was applied in subareas 1 through 4, land the smaller correction factor was applied in subareas 5 through 13. The end result of the foregoing computations and corrections is the set of estimated subsidence rates in 197 0 if the summer water levels in that year should be i 60 feet above the 1967 summer levels. These estimates do not take into account the elastic expansion, princi- pally of the aquifers, that will occur as a result of the postulated 60 feet of head rise. The only data available at the time of the writing of this paper are the amounts of net specific unit expansion at three sites. The net values are considered as minimum values of specific unit expansion, but at least 0.1 foot of expansion should occur in most of the area as a result of 60 feet of lower- zone head recovery. Change in altitude of bench marks surveyed before and after an actual 60-foot head recov— ery would include the effects of the elastic expansion of the more permeable beds within the aquifer system and thus may result in lower observed subsidence rates than shown in figure 43. The rates given in table 2 and figure 43 are based on the premise that summer water levels will not change significantly after the 60-foot water— level recovery. Over long time periods, elastic expansion of the lower zone in response to substantial recovery of artesian head may be offset by compaction resulting from in— crease in stress that will be applied to the lower zone as a result of water-table rise. The water table is rising at the present time in most of the study area. Importation - of additional supplies of water for agriculture probably will result in an acceleration of water-table rise. Every 5 feet of water-table rise will tend to offset 1 foot of lower-zone head recovery. For example, 50 feet of water-table rise in an area where the lower zone is confined and the lower-zone head remains constant will result in an increase in applied stress on the lower zone of 10 feet of water. Surface-water deliveries have been made in subarea 1A for a long time, and the head decline that has caused subsidence began in this area before 1920 (Pt. 1, Bull and Miller, 1974, fig. 21). Sixty feet of head rise should cauSe compaction to cease, except in the Corcoran, and probably will result in minor net expansion in much of the subarea. Subarea 1B is that part of the Delta-Mendota Canal service area adjacent to the area of excessive ground- water pumping to the south. Much of the delayed com- paction may have already occurred in the Diablo flood-plain deposits that underlie this subarea, and so it is anticipated that subsidence rates would be low should water levels rise. Most of subarea 2 bordering the foothills of the Diablo Range has never been irrigated, but the proportion of irrigated land increases to the, northeast. Much of the head decline and associated subsidence that has oc- curred in the past has been the result of ground-water movement to the areas of intense pumping to the northeast of subarea 2. The lower-zone deposits underlying subarea 3 consist chiefly of Diablo flood-plain deposits. The thin aquitards LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 ' typical of this class of deposits have contributed to rapid expulsion of water during past periods of applied stress. Subarea 4 also is underlain principally by Diablo flood-plain deposits. Although this has been the area of maximum subsidence rate in the past (Pt. 2, Bull, 1974, fig. 18), the potential for future delayed compaction is considered to be about the same as subarea 11, where lower subsidence‘rates have occurred in the past. Subarea 5 is underlain chiefly by Sierra flood-plain deposits, but these deposits are finer grained than the Sierra flood-plain deposits to the east in subarea 6. Future subsidence is expected to occur within this sub- area, but the amounts should be small. Nearly all the head decline that has occurred in sub- area 6 has been the result of excessive lower-zone over- draft to the west. Thus, 60 feet of head rise would consist mainly of a decrease in the gradient of the potentiomet- ric surface to the west. Subsidence rates may decrease to nearly 0 in parts of the area where the lower-zone de- posits consist mainly of sand that has few interbeds of fine-grained material. However, expansion of agricul- tural development and additional pumping of lower- zone water in those parts of the subarea outside of the San Luis Canal service area may result in subsidence rates of as much as 0.2 ft yr-1. Most of the wells in subarea 7 tap sands and thick clays of the Etchegoin Formation. Subsidence rates were low during the 1963—66 period, but probably will not decrease markedly because of the large excess pore pressures that probably exist in very thick clay beds. Also, 60 feet of head rise is minor when compared with the 400—500 feet of head decline that has occurred in the subarea. Subareas 8 and 9 have lower-zone deposits that are similar to those of subarea 4, except that the Diablo deposits consist of alluvial-fan instead of flood-plain deposits. Sierra and lacustrine deposits make up a large portion of the section. Records from the Cantua recorder site indicate that maximum delayed compaction may occur within sub- area 9. At least 100 feet and possibly more than 200 feet of head recovery may be necessary to eliminate excess pore pressures at this site. The area is underlain by several types of deposits. The water-table rise that should occur in the coarse- grained deposits of subarea 10 southwest of the confining influence of the Corcoran should cause a steady and rapid decline in applied stress on the aquifer system which approaches a water-table type of aquifer next to the foothills. The lensing clay beds in the fan deposits of the subarea generally are not thick, and periods of rapid water-level rise at one site (19/16—23P2) are accompanied by recorded net aquifer expansion. The amount of subsidence after delivery of canal water may be greater in subarea 11 than elsewhere in G57 the study area because of the thick section of interbed- ded fine-grained deposits from both Diablo and Sierra sources that constitute the lower zone in this subarea. Head declines have been large, but the rates of compac- tion have not been as rapid as in subarea 4, where much less head decline has occurred. These facts are inter— preted to mean that excess pore pressures are large in subarea 11, thus favoring large amounts of delayed compaction. Net expansion is recorded in the subarea, but only because of the rapid rate of head recovery that occurs after extremely large seasonal water-level de- clines (Pt. 1, Bull and Miller, 1974, fig. 43). Subarea 12 is much the same as subarea 6, except that heavy pumping has occurred in the upper as well as in the lower zone. The estimates of future subsidence are based on the premise of 60 feet of head rise in the upper as well as in the lower zone in subarea 12 and in the southeastern part of subarea 11. In many respects, the situation in subarea 13 is simi- lar to that in subarea 7, except that the deposits from which the water is being pumped are the lower part of the continental Tulare Formation. SUMMARY Water-level changes resulting from pumping of ground water and irrigation have changed the stresses tending to compress the alluvium of the Los Banos —Kettleman City area. Change in stress applied on the confined lower zone, in which three-fourths of the com- paction is occurring, is the algebraic sum of the follow- ing components of stress change: 1. A seepage stress equal to the lower-zone artesian- head change. 2. A seepage stress equal to the head differential caused by change in water-table position. 3. A stress caused by change in buoyancy of the de- posits within the depth interval that is being de- watered, 0r saturated, as a result of water-table change. 4. A stress caused by part of the pore water being changed from a condition of neutral to applied stress, or Vice versa, that occurs within the depth interval being affected by water-table change. The magnitudes of the various stresses on the confined zones (expressed in feet of water) is as follows, assuming a porosity of 0.4, a specific gravity of 2.7, and a moisture content (specific retention) of the dewatered deposits of 0.2 the volume: Seepage stresses resulting from either artesian-head change or change in water- table position cause 1 foot of change in applied stress per foot of change in head differential. Each foot of water- table change also causes a 06-foot stress change be- cause of removal or addition of buoyant support of the deposits within the interval of water-table change and a 0.2-foot stress change because of part of the pore water G58 being changed from a neutral-stress condition to an effective-stress condition, or vice versa. The effect of water-table change is to change the effective stress in the unconfined aquifer by 10.8 foot of water per foot of water-table change. The effect of water-table cha ge on stress changes in the deeper confined zones is to c ange the stress by only 10.2 foot of water because the seepage-stress change more than offsets the sum ‘of the two other stress changes. Applied-stress increase on the lower-zone de‘posits has been as much as 500 feet of water as a result of artesian-head decline, and water-table change has caused as much as 25 feet of stress increase n the northern part of the area and as much as 75 feet of‘ stress decrease in the southern part. ‘ Over long time spans, the rates of compaction (and subsidence) per unit applied-stress increase accelerate with additional applied-stress increase, but vary widely because of geologic and hydrologic factors. For example, in some areas applied-stress increases of less than 200 feet have resulted in 20 feet of compaction, but locally along the west margin of the area, increase in pplied stress of 400 feet has caused only 1 foot of compaction. Changes in aquifer-system thickness are elastEic (are reversible and occur with minor time delay) and nelas- tic (are irreversible and occur with large time delay). Under the pore-pressure conditions of the sixties, in much of the area net aquifer-system expansion odcurred briefly or not at all, but elastic changes affected the monthly amounts of measured compaction. Ma imum compaction rates occur during times of head decline because elastic compaction is additive with virgin com- paction; minimum compaction rates occur durin times of head rise because expansion is subtracted from virgin compaction. Removal of the estimated component of elastic change of aquifer-system thickness sho s that virgin compaction is distributed more uniformly throughout the year than is the observed net nilonthly compaction and decreases during times of applied- stress decrease. The elastic component of seasonal compaction varies from less than 5 to about 90 percent, dependin on the lithology and permeability of the deposits and on the magnitude and rate of applied-stress increase s com- pared with previous effective stress maximums and du- rations. Good records of net aquifer-system expansidn have been obtained at three sites. Amounts of net expansion of almost 0.1 foot have been recorded during imes of decrease in applied stress indicated by rise in rtesian head. Under the conditions of excess pore pressures existing in aquitards in the sixties, three co current processes were tending to change aquifer-syste thick- ness during times of applied-stress decrease+elastic STUDIESOF LAND SUBSIDENCE expansion with no measurable time delay (presumably chiefly of the aquifers), delayed elastic expansion (pre- sumably chiefly of the thin aquitards and the outer parts of the thick aquitards), and virgin compaction (presumably of the aquicludes and thick aquitards). Delayed compaction due to continuing decay of excess pore pressures may still occur in thick clay beds after 60 feet or more of head recovery in contiguous aquifers. The net change in aquifer-system thickness that re- sults from these three concurrent processes is chiefly a function of the rate of change of applied stress and the hydraulic conductivities of the different materials con- stituting the aquifer system. During rapid applied— stress decrease, net expansion may be recorded while some aquitards are still undergoing virgin compaction. Delayed expansion rates increase with decreasing ap- plied stress and may exceed the decreasing virgin com- paction rates for short time periods of rapid applied- stress decrease. During periods of slow applied-stress decrease, virgin compaction rates may continue to ex- ceed delayed expansion rates and net compaction re- sults. The approximate modulus of expansion (net specific unit expansion) of the upper-zone aquifer system at the Lemoore and Yearout sites is about 3.5 X 10‘6ft‘ 1. Dur- ing a period of seasonal head recovery at the Lemoore site, the net specific unit expansion varied from 0.6 to 3.6x 10—6ft_1, as the rates of virgin compaction and of nondelayed and delayed elastic expansion varied con- currently with changes in the magnitude and rate of applied-stress decrease. Little time is needed to raise pore pressures in many of the aquitards. Compaction ceases when aquifer pore pressures rise to equilibrium with the maximum pore pressure in contiguous aquitards, thus preventing further expulsion of water. Additional pore-pressure increases in the aquifers are transmitted fairly rapidly into the aquitards because their specific storage in the elastic range is small. The time lag between the start of head recovery and the start of recorded expansion depends on the mechanics of the aquifer and recorder systems. Net aquifer-system expansion will not occur until the ex- pansion rate exceeds the compaction rate. Net expan- sion will not be recorded until cable tension below the uppermost friction point between the casing and the cable is increased to the point where it overcomes the friction, reverses the sense of movement in the recorder system, and raises the counterweights. The minimum amounts of head recovery that occurred before net ex- pansion was first recorded were 6 feet at well 19/16—23P2 and 1 foot at well 18/19—20P2. Prediction of the amounts, rates, and distribution of subsidence during future time periods in the Los LOS BANOS—KETTLEMAN CITY AREA, CALIFORNIA, PART 3 Banos—Kettleman City area is not meaningful unless the magnitude and time distribution of change in ap- plied stress can be predicted with reasonable accuracy. The time-dependent nature of the pore-pressure decay in the aquitards and aquicludes also complicates esti- mates of compaction of heterogeneous aquifer systems. Therefore, the most practical approach is to provide criteria for the prediction of subsidence rate, assess the critical factors affecting compaction rates, and make predictions of future subsidence rates on the basis of postulated hydrologic changes. Prediction of trends of future subsidence based on historic subsidence graphs is most likely to be useful when based on subsidence-rate plots, rather than cumulative subsidence plots. Head decline/subsidence or subsidence/head decline ratios determined for long time periods on an areal basis are a useful tool for predicting minimum ultimate sub- sidence from a postulated additional head decline. These ratios also are useful for predicting the rate of future subsidence if the future rate of applied-stress increase is the same as the rate of applied-stress in- crease during the period for which the head decline/ subsidence ratios were determined. If the rate of applied-stress increase accelerates in the future, esti- mates of subsidence based on past ratios will most likely be less than the amounts of subsidence occurring in the future. If the rate of applied-stress increase decelerates in the future, estimates of subsidence based on past head decline/subsidence ratios will probably also be low compared with actual amounts of subsidence, because of the large amounts of residual c0mpaction that will con- tinue even during times of little or no increase in ap- plied stress. Most of the subsidence since 1960 has been the result of increase in applied stress prior to 1960 that did not have sufficient time to become fully effective in many of the thicker aquitards because of their low vertical per- meabilities. The occurrence of residual compaction is particularly apparent in areas of large head decline and subsidence that continue to have seasonal fluctuations in artesian head of more than 40 feet. In much of the area, the rate of increase in applied stress has been decreasing since the mid-1950’s .because the rate of lower-zone head decline has decreased from more than 10—15 ft yr“1 to only 1—5 ft yr‘l. The rates of compaction and subsidence have not undergone a proportionate de- crease. Instead, the rate of compaction has continued to be 1/3—% of the earlier rates as a result of a large compo- nent of residual virgin compaction that is occurring in thick beds with low permeabilities. The increase in the delayed compaction component occurring during the past few decades is readily apparent in plots of the ratio of subsidence to lower-zone increase in applied stress. G59 The rate of decrease of aquitard-aquifer pore- pressure differentials can be evaluated at some sites through study of change of mean daily compaction rates for selected applied stress levels. In the 703—2,000-foot-depth interval at the Cantua site, the relation between mean daily compaction rate (y) and time (x) for the 1961—67 period is y=0.0028e_0'096x. A 10-percent decrease in residual compaction rate had occurred as of mid-1962 and 45 percent by 1968, and a 90-percent decrease is predicted to have occurred by about 1986, assuming a hydrologic environment simi- lar to that of the 1961—67 period. Exponents of similar equations for other compaction-recorder sites indicate that the rate of pore-pressure decay is twice as rapid in the northern as in the southern part of the study area. Weighted mean aquitard thickness factors (aquitard thickness/2)2 derived from micrologs of core holes show that the sites of most rapid decrease of mean daily compaction rates have thinner aquitards than does the Cantua site in the southern part of the area. Laboratory consolidation test results are useful in predicting the rates and amounts of compaction of the clay beds from which the samples were cored, but esti- mates of future amounts of compaction of entire aquifer systems may be of doubtful value if based on only a few consolidation tests. Prior attempts to estimate future subsidence on the basis of consolidation-test results from the study area have resulted in underestimation of future subsidence because of an insufficient number of consolidation tests to define variations in compressibil- ity due to different types of aquitard materials. Importation of surface water in the past has resulted in marked reductions in subsidence rate. In the service area of the Delta-Mendota Canal, the subsidence rate during the 1959—63 period was less than that during the 1943—53 period, but in the area south of the service area, the rate of subsidence had doubled between the same time periods. Intermittent delivery of water from the Kings River in the Vicinity of Stratford and Lemoore, after construction of the Pine Flat Dam, has caused temporary rise in artesian head and decrease in subsid- ence to rates that were as low as 0.03 ft yr‘1 during years of abundant surface water. During years when surface water was not available, the artesian head de- clined, and subsidence rates increased to more than 0.44 ft yr—J. Delivery of water from the San Luis Canal section of the California Aqueduct should result in widespread alleviation of subsidence, even before max- imum deliveries are obtained. Assuming that as of 1970 lower-zone summer water levels throughout the study area will be raised 60 feet G60 and seasonal fluctuation will be reduced to 10—20 feet, the rate of subsidence should be reduced substantially for two reasons. First, the rate of subsidence wo Id be less even if water were not imported, because the r te of applied-stress increase has been decreasing and the de- layed compaction rate has been decreasing exppnen- tially. Secondly, a 60-foot water—level rise would limi- nate excess pore pressures in some beds and wou‘ d de- crease the applied stress on those beds still having ex- cess pore pressures. On the basis of many types of in- formation available in December 1967, a postulated 60-foot water-level rise by 1970 would result in max- imum subsidence rates of only 0.3—0.4 ft yr‘l, and large areas that were subsiding 0.2—0.4 ft yr‘1 between 1963 and 1966 would be subsiding less than 0.2 ft yr‘l. Water-level rises of 100—200 feet should eliminate or reduce subsidence rates to negligible amounts through- out the Los Banos—Kettleman City area. REFERENCES American Geological Institute, 1960, Glossary of geology and related sciences [2d ed.]: Washington, DC, Am. Geol. Inst, Natl. Acad. Sci.-Natl. 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Hydrology Pub. 88, p. 11—21. 1969b, Land subsidence and aquifer—system compaction, Santa Clara Valley, California, USA, in Land Subsidence, v. 1: Inter- nat. Assoc. Sci. Hydrology Pub. 88, p. 285-292. Poland, J. F., and Davis, G. H., 1969, Land subsidence due to with- drawal of fluids, in Varnes, D. J., and Kiersch, George, eds., Reviews in Engineering Geology, v. 2: Boulder, Colo., Geol. Soc. America, p. 187—269. Poland, J. F., and Ireland, R. L., 1965, Shortening and protrusion of a well casing due to compaction of sediments in a subsiding area in California, in Geological Survey research 1965: US. Geol. Survey Prof. Paper 525—B, p. B180—B183. Poland, J. F., Lofgren, B. E., and Riley, F. S., 1972, Glossary of selected terms useful in the studies of the mechanics of aquifer systems and land subsidence due-to fluid withdrawal: U.S. Geol. Survey Water-Supply Paper 2025, 9 p. Prokopovich, N. P., 1963, Hydrocompaction of soils along the San Luis Canal alignment, western Fresno County, California in Ab- stracts for 1962: Geol. Soc. America Spec. Paper 73, p. 60. Prokopovich, N. P., and Hebert, D. J ., 1968, Land subsidence along the Delta-Mendota Canal, California: Am. Water Works Assoc. Jour., v. 60, no. 8, p. 915—920. Riley, F. S., 1969, Analysis of borehole extensometer data from cen- tral California, in Land Subsidence, v. 2: Internat. Assoc. Sci. Hydrology Pub. 89, p. 423—431. Scott, R. F., 1963, Principles of soil mechanics: Palo Alto,_Calif., Addison-Wesley Pub. Co., Inc., 550 p. Taylor, D. W., 1948, Fundamentals of Soil Mechanics: New York, John Wiley & Sons, Inc., 700 p. Terzaghi, Karl, and Peck, R. B., 1948, Soil mechanics in engineering practice: New York, John Wiley & Sons, Inc., 566 p. A, B Page Alluvial-fan deposits ,,,,,,,,,,,,,,,,,,,, G6, 34, 57 Anticline Ridge ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 8, 29 Applied stress change ____________ 6, 13, 36, 37, 39, 44 relation to lower zone ,,,,,,,,,,,,,,, , 42, 58 relation to lower-zone compaction llllllllllll 27 relation to subsidence ____________________ 43, 59 relation to water-level changes _ 4, 27, 35 Yearout site ___ ___. .0 22 Applied stress computation“ __ 5, 7 Aquifer system, compaction ,,,,,,,,,,,,,,,,,, 23, 26 expansion AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA 23 porevpressure decay prediction _______________ 44 relation to lower zone compaction ____________ 6 thickness, changes ,,,,,,,,,,,,,, 8, 17, 18, 22, 58 relation to artesian-head changes ________ 11 unconfined ,,,,,,,,,,,,,,, Aquitard ,,,,,,,,,,, Aquitard permeability decrease ,,,,,,,,,,,,,,,,, 44 Aquitard pore pressure _________________________ 23 Artesian-head change ________ 8, 11, 17, 27, 29, 53, 56 Big Blue Hills ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 29, 34, 35 Buoyancy effect ,,,,,,,,,,,,,,,,,,,,,,,, 5, 8, 28, 57 C California Aqueduct ,,,,,,,,,,,,,,,, H, 35, 49, 59 Canal water," __ 37, 49, 59 Cantua site a" ,,,,,,,, 4, 16, 44, 46, 47, 48, 57, 59 Casing-cable friction ,,,,, "W 14, 18, 23, 25, 27 Clay deposits ____________________ 6, 18, 86, 37, 57, 59 Compaction ,,,,,,,,,,, 11, 26, 43, 46, 47, 48, 54, 58 cause _____________________________________ 4 Lemoore site ____________________________ 18, 21 mean daily rate ,___ _e. 44, 46, 47 measurement ,,,,,,,,,,,,,, 14, 17, 23, 24, 49, 59 Lemoore site ,,,,,,,,,,,,,,,,, Yearout site ,,,,,,,,,,,,,,,,,,,,,,,,,, 22 relation to aquitards ,,,,,,,,,,,,,,,,,,,, 35, 44 relation to artesian-head change ,,,,,,,,,,,,,, 17 relation to Corcoran Clay Member of the Tulare Formation ____________________ 29 relation to lower-zone aquifer system relation to water—level fluctuation ,, Compaction recorder, mechanical lag ______ Compression ___________________ Confined aquifer system ________ 4, 5, 6, 7, 18 Consolidation coefficient ______________________ 36 Consolidation tests ____________________________ 49 Corcoran Clay Member of the Tulare Formation __________ 8, 15, 18, 21, 29, 49 D, E, F Damage from subsidence ________________________ 35 Definition of terms _-_ 2 Delayed compaction ___________ 23, 41, 43, 44, 54, 58 Delayed expansion __________________________ 21, 58 Delivery of canal water ,,,,,,,,,,,,,,,,,,,,,,,,,, 5O Delta-Mendota Canal ,,,,,,,,,,,,,,,,,, 11, 34, 50, 59 Diablo flood-plain deposits, W _fi 57 Diablo Range ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 56 Effective stress ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 13, 35 INDEX [Italic page numbers indicate major references] Page Elastic change, relation to aquifer-system thickness ,,,,,,,,,,,,,,,,,,,,,,,,, G11 Elastic compaction ____________ 15, 17, 23, 26, 39, 58 Lemoore site ______________________ Yearout site _______________________________ 22 Elastic compression ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 13 Elastic expansions 13, 15, 16, 17, 23, 54, 56, 58 Yearout site ___________ _ 22 Elastic specific unit compaction “,1 15 Electric log __________________________________ 18, 27 Equipment ________________ 11, 14, 16, 17, 23, 25, 27 Etchegoin Formation ,,,,,,,,,,,,,,,,,,,,,, 34, 35, 57 Expansion ,,,,,,,,,,,,,,,,,,,, 1 7, 23 measurement 1-- 17, 23, 25, 27 Lemoore site __________________________ 21 Yearout site __ 22 Expansion of water ____________________________ 12 Five Points __________________________________ 10, 29 Flood-plain deposits ______________________________ 34 Fresno Slough ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 8, 29 G, H Gravitational stress ,,,,,,,,,, _ 7 Ground-water pumpage costs H 37 Head changes _________________________________ 7 Head decline ______________________ 8, 34, 37, 57, 59 Head decline/subsidence ratio ,,,,,,,,,,,, 9, 39, 43 Head increase ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 54, 58 Huron ___________ Hydraulic diffusivity ,,,,,,,,,,,,,,,,,,,,,,,,,, 36 Hydraulic head dissipation ,1 W 4 Hydrodynamic theory of soil consolidation ________ 18 Hydrographs ____________________________________ 9 I, K, L Inelastic change, relation to aquifer-system thickness __________________________ 11 Inelastic compaction . _ 13, 23, 39, 58 Lemoore site ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 21 Kettleman Hills _______ 34 Klausing, R. L., quoted ________________________ 5 Lacustrine deposits ________________________ 34, 49 Lemoore ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 53, 59 Lemoore site 1111111111 15, 18, 58 Lofgren, B. E., quoted ........ 5 Los Banos—Kettleman City area, compaction 4 location __________________________ 2 Lower zone, aquifer system ,,,,,,,,,,,,,,,,,,,, 5 aquitards __________________________________ 49 artesian head ,,,,,,,,,,,,,,,,,,,,,,,, 11, 54 compaction-related applied-stress change ______ 27 deposits 57 , 58 bedding _ ___- 48 head decline ___- 37, 38 potentiometric level __________________________ 44 water-level change __________________________ 16 Lower-zone app]ied-stress/subsidence ratio ,,,,,,,, 39 M, N, O, P Mendota ______________________________________ 8, 10 Mendota site ______________________ 14, 15, 44, 47, 48 Neutral pressure ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 7 Neutral stress ____________ Oro Loma site _ __ _ 11, 14,44,47, 48,49 Peck, R. B,, quoted _____________________________ 34 Pine Flat Darn _______________________________ 53, 59 Pore pressure ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 21 relation to aquifers and aquitards ______ 17, 35, 36, 40,44, 58, 59 Pore pressure decay, relation to effective stress “0 6 Potentiometric level __________________ ___ 7, 54, 56 lower zone _______________________________ 44 Preconsolidation stress __________________________ 36 Predicted compaction ________________________ 48, 54 Predicted subsidence 111111111111 35, 37, 50, 54, 59, 60 Previous work ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 2 Protrusion of casing ,,,,,,,,,,,,,,,,,,,,,,,,,,, 23 Pumpage costs of ground water _________________ 37 R, S Rate, applied-stress increase iiiiiiiiiiiiii 39, 42, 43 compaction“ 15, 16,17, 23, 44, 46, 47, 48, 49, 54, 58 elastic change ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 21 expansion ________________________ 15, 16, 17, 23 Lemoore site ____________________________ 21 pore-pressure change _____________ e 40, 47 subsidence ___. ___ 37, 50, 52, 53, 54, 56, 57, 59 Recharge ,,,,,,,,,,,,,, 34 Recorder mechanics ____________________________ 25 Residual compaction _________________________ 49, 59 Residual excess pore pressure _______________ 11, 23 San Joaquin Valley, "H W 2 San Luis Canal ,,,,,,,,,,,,,,,,,,,,,, 35, 49, 59 Santa Clara Valley ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 49 Saturated deposits ,, , 5, 27 Seasonal head decline,,,,,,,,,,,,,,,,,. ,,,,,,,,,, 34 Seepage force ____________________________ 4, 8, 27, 57 Sierra flood-plain deposits ________________________ 57 Sierra sands and silts ,,,,,,,,,,,,,,,,,,,,,,,,,,,, 21 Specific compaction ,,,,,,,,,,,,,,,,,,,, 27, 32, 33, 34 Specific gravity ___________ 5 Specific retention _. Specific subsidence _______ Specific unit compaction __________________ 27 , 29, 34 Specific unit expansion ________ 15, 19, 21, 27, 56, 58 Yearout site ,,,,,,,,, Specific yield ,,,,,,,,,,,,, Steady—state pore pressure ,,,,,,,,,,,,,,,,,,,,, 36, 47 Storage coefficient ,,,,,, 11, 13, 39 Stratford ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 59 Stress changes __________________________________ 4 Stress increase/subsidence ratio ________________ 44 Stress~strain plot ,,,,,,,,,,,,,,,,,,,,,,, 18, 19, 34 Study area ,,,,,,,,,,,,,,,,,,, 2 Subsidence ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 8, 29 after delivery of canal water H, 49 alleviation ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 52, 53 before delivery of canal water ,,,,,,,,,,,, 37, 50 future ,,,,,,,,,,,,,,,,,,,,,,,, 35, 50, 54, 59, 60 Subsidence/head-decline ratio ,,,,,,,,,,,,,, 9, 39, 43 Subsidence/lower-zone applied-stress ratio ,,,,,,,,, 39 Subsidence rate ,,,,,,,, 37, 50, 52, 53, 54, 56, 57, 59 Subsidence/stress increase ratio _____ 44 Surface-water deliveries _________________________ 56 Surface-water imports ,,,,,,,,,,,,,,,, 50, 53, 54, 59 G61 G62 T, U, V Page Terzaghi, Karl, quoted ,,,,,,,,,,,,,,,,,,,,,,,,, G34 Timelag of compaction ,,,,,,,,,,,,,,,,,,,,,,,, 35, 58 Total applied stress ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 29 Tulare Lake bed ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 34 Ultimate compaction ,,,,,,,,,,,,,,,,,,,,,,,, 36, 48 Unsaturated deposits ________________________ 6, 7, 27 Upper-zone head decline ,,,,,,, 37 Virgin compaction ,,,,,,,,,, 11, 15, 16, 21, 23, 43, 58 INDEX W, Y Page Water-table change ......... G6, 7, 27, 28, 29, 39, 56 relation to applied stress ______________ 4, 27, 35 relation to aquifer-system thickness ,,,,,,,, 8, 23 relation to compaction ,,,,,,,,,,,, 13, 23, 54, 57 relation to expansion ,,,,,,,,,,,,,,,,,,,,,,,, 27 relation to pumping W 17, 57 relation to subsidence ,,,,,,,,,,,,,,,,,,, 8, 60 Page Water-level fluctuations, Lemoore site .......... G18 Yearout site ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 22 Well casing rupture ,,,,,,,,,,,,,,,,,,,,,, Well construction ,,,,,,,,,,,,,,,,,,,,,,,, Westhaven __________________________________ 11, 43 Westhaven site ,,,,,,,,, 17, 44, 46, 47, 48 Yearout site ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 22, 58 U. S.GOVERNMENT PRINTING OFFICE: 1975-0-689-905/13 63:75. 7DAY V. 437' /“/ Land Subsidence in the San Joaquin Valley, California, és of 1_972_ GEOLOGICAL SURVEY PROFESSIONAL PAPER 437—H Prepared in cooperation with the California Department of Water Resources Land Subsidence? in the San Joaquin Valley, California, As of 1972 By J F. POLAND, B. E. LOFGREN, R. L. IRELAND, and R. G. PUGI—I STUDIES OF LAND SUBSIDENCE GEOLOGICAL SURVEY PROFESSIONAL PAPER 437—H Prepared in cooperation with the California Department of Water Resources A history of land subsidence caused by water-level decline in the San joaquin Valley, from the 1920’s to 1972 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON11975 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress Cataloging in Publication Data [and subsidence, San Joaquin Valley, California as of 1972. (Studies of land subsidence) (Geological Survey Professional Paper 437—H) Bibliography: p. 53-54. Supt. of Docs. No.2 I 19.162437—H l. Subsidences (Earth movements)—California—San Joaquin Valley. 2. Water, Underground—California—San Joaquin Valley. 1. Poland, Joseph Fairfield, 1908- 11. California. Dept. of Water Resources. 111. Series. IV. Series: United States. Geological Survey. Professional Paper 437—H. 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N _ fl OVI3 a a I. c! ._ Q o Answfiafi :03 um wmm< :38 5:3 He 85235 98 59% “:8 3 5303800 MN .fi mowing Ewuotoa .Hflom.u 3.550 .ooodmma $3.5m $3.31va .m.D Eofi omwm .595 «QSMSEémE/w 95 E nosommfiooohin ESSA «c mmwalwm 559m hwwu oop I_<>¢w._.z_ EDP—.200 056g. “vi—ova 33.3%? o. 26 88 _ :2: .5305 SEES—5 I5 w8< zeta—35893: =32:— uo 32¢. IIIJ‘IIII ZO—H>o I . . . . 26; 1 _ mm >23. >>NN¢ Emma _ h 0:32—20? _ c \ Vuu’. é were I 8.3 I__ .r.. I_III .III..IVI I low—w! Dam—mmmmv—(qi II .III_ _I m " _I,_I\.¢_ .\.. _ _ Faw. \JVNII 3013-58-5 P IV\ 7\l VII _ 9 \b.\A/|... \/ fl . _ 21 _ _ _ Em: .mvom: momc mmm: mmm m 8.2. Km m m 8: arm: .33. .33. ~85: LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA from 1975 to 1978 suggesting that the subsidence oc- curred from 1970 to 1975. AQUEDUCT SUBSIDENCE, MILE 238 TO MILE 287 Profiles of land subsidence from 1970 to 1978 along the California Aqueduct from mile 238 to mile 287, south- west of Wind Gap Pumping Plant are shown on plate 1 (see fig. 6 for location). The subsidence illustrated by these profiles represents change related to fluid with- drawal, hydrocompaction, and probably construction settlement. Areas of known hydrocompaction and the area of subsidence greater than 1 ft due to water-level decline in the Arvin-Maricopa area are shown on figure 38. Areas of known hydrocompaction along the aqueduct alinement were from mile 254 to mile 261, mile 274 to mile 280.5, and mile 282.5 to mile 286 (pl. 1 and fig. 38). As shown on plate 1, the State contracted for preconsolidation of hy- drocompactible deposits from aqueduct mile 255.7 to mile 288.7. The regional subsidence greater than 1 ft due to fluid withdrawal from 1926 to 197 0 extends from aque duct mile 259 to mile 280 (pl. 1). _ From aqueduct mile 238 to mile 254, the subsidence was generally less than 0.25 ft from 1970 to 1978. The profiles along this 17-mi reach show a maximum subsid- ence of 0.5—0.6 ft near mile 241. This sag, which is 1—2 mi long, is probably due to construction settlement and (or) hydrocompaction (prewetting for the hydrocompaction area to the northwest stopped at mile 238). The 1978 ele- vations show an apparent small land-surface recovery from aqueduct mile 238 to near mile 243. I Subsidence again reached one-half foot at mile 254, in the next known hydrocompaction area. From aqueduct mile 254—261 (known hydrocompaction area), subsidence ranges from near 0.25 ft to near 1 ft except at bench marks 255.77B and K1210. Bench mark 255.77B in the aqueduct lining subsided 1.31 ft from 1970 to 197 5 and 0.91 ft from 1975 to 1978. Bench mark K1210, set in an aqueduct structure (concrete overchute), shown at aque- duct mile 255.75, subsided 1.12 ft from 1970 to 1975 and 0.98 ft from 197 5 to 1978. Bench marks 255.00B and 255.36B, in the aqueduct lining to the west, subsided 0.40 and 0.35 ft from 1970 to 1978. Bench marks 256.12B and 256.56B, in the aqueduct lining to the east, subsided 0.55 and 1.01 ft from 1970 to 1978. The large change at mile 255.77 appears to be due partly to hydrocompaction and partly to structure settlement (note that the precon- solidated area started at mile 255.75). The undulating subsidence in this 7-mi reach from aqueduct mile 254 to mile 261 is attributed to hydrocompaction that has oc- curred since 1970 leveling. The reach from mile 261 to mile 274 is out of the known hydrocompaction area and in the area of regional I41 subsidence due to fluid withdrawal. Subsidence from mile 261 to mile 270 ranged from less than 0.2 ft to 0.4 ft, then reached 0.9 ft at mile 271.5 from 1970 to 197 8. Field extensometer 11N/21W-3B1 (fig. 66; see fig. 40 for location), approximately 1 mi north of the aqueduct at mile 272, recorded 1.84 ft of compaction versus 2.05 ft of subsidence (90 percent) from February 1965 to March 9, 1970, 0.57 ft of compaction versus 0.61 ft of subsidence (93 percent) from March 9, 1970, to May 3, 197 5, and 0.45 ft of compaction versus 0.61 ft of subsidence (73 percent) from May 3, 1975, to August 17, 1978. This extensometer well is 1,480 ft deep and measures most of the aquifer compaction due to ground-water pumping. The site was disturbed in early 1978 at about the time of the 1978 leveling. The concrete base that is the reference for all measurements had been undermined by water; however, repairs were made and the site restored. The aqueduct subsidence at bench marks 27 2.00B and 27 2.39A (not shown on pl. 1), approximately 1 mi south, was 0.31 ft from 1975 to 1978, suggesting a minor data problem at the extensometer site. Extensometer data (ta- bles 3 and 6) confirm that the measured compaction at well 3B1 from 1970 to 1978 was equal to 83 percent of the subsidence and that most of the subsidence from 1975 to 1978 occurred during the 1976—77 drought years. Erratic subsidence is demonstrated at bench mark 27 3.48A. This bench mark located in a concrete over- chute subsided 1.12 ft from 197 0 to 1975 and 10.63 ft from 1975 to 1978 (pl. 1). Bench mark 273.09A, not shown but in the aqueduct lining about 0.4 mi northwest of bench mark 273.48A, subsided 0.44 ft from 1970 to 197 5 and 0.24 ft from 1975 to 1978. Bench mark 273.758, in the aqueduct lining 0.27 mi southeast of bench mark 273.48A, subsided 0.38 ft from 1970 to 1975 and 0.20 ft from 1975 to 1978. Other bench marks in this area, not plotted on plate 1, also show erratic change, suggesting possible hydrocompaction, or structure settlement, or both. Another known hydrocompaction area, mile 274 to mile 280.5, is also in the area of subsidence due to fluid withdrawal. Maximum subsidence was 1.1 ft near mile 275 and 0.9 ft at mile 277. The settlement in this 6-mi reach is caused by both subsidence due to fluid with- drawal and subsidence due to hydrocompaction, chiefly the latter. Subsidence from mile 280.5 to 287 ranged from 0.2 ft at mile 280 to about 0.4 ft at mile 282, then de- creased to about 0.1 ft at mile 287. The southernmost known hydrocompaction area shows no continued hydrocompaction. ELK HILLS LEVELING The line of levels (Elk Hills loop) that runs through the Elk Hills from the California Aqueduct at mile 229.7 140 The reason for the subsidence in aqueduct miles 195-198 and 207—215 is not known. According to Wood and Davis (1959), the quality of the ground water beneath the Antelope Plain is generally poor, and for this reason, water wells are scarce. Ground-water pumpage data from some westside townships were published for years 1962—66 (Ogilbee and Rose, 1969a), 1967—68 (Mitten, 1972), 1969—71 (Mitten, 1976), and 197 5—7 7 (Mitten, 1980). The Geological Survey, as part Of the Central Valley Aquifer Project, has pre- pared estimates Of ground-water pumpage for additional townships in this area. A review Of these data for town- ships crossed by the aqueduct from 15 mi north Of Lost Hills (from aqueduct mile 190) to 10 mi south of Lost Hills (to aqueduct mile 215) shows that the only township in which ground-water pumping is appreciable is T. 27 S., R. 21 E. The north boundary Of this township extends from 2 mi east of Lost Hills (town) to 4 mi west. The estimated annual average ground-water pumpage from this town- ship was 23,400 acre-ft per year for 1961—66 and 18,600 acre-ft per year for 1967—77. These quantities are equiva- lent to 1 ft and 0.8 ft Of water, respectively, if applied to the full township acreage (23,040 acres). This amount of water is only one-half to one-quarter of the crop irrigation 3.0 STUDIES OF LAND SUBSIDENCE requirements in the San Joaquin Valley. Water-level measurements made in the 1970’s are available for three wells in the township. In the three wells, water levels are less than 80 ft below land surface and have been rising. The evidence just summarized, although fragmentary, suggests that ground-water withdrawal and decline of water levels has not contributed appreciably to subsid- ence Of the aqueduct in the reach from aqueduct mile 190 to aqueduct mile 215. Limited or local deposits susceptible to hydrocom- paction may be present and may have been wetted and compacted by water leaking from the aqueduct or used for irrigation. The State made contracts for preconsolidation Of hy- drocompactible deposits at aqueduct mile 177.4 to 177.7 (Arroyo Pino Creek), and also from aqueduct mile 215.6 to aqueduct mile 239 (pl. 1). Profiles of aqueduct subsidence were not drawn for the 20-mi reach from aqueduct mile 218 to 238 because maximum subsidence in the reach did not exceed 0.5 ft. Subsidence from 1969—70 to 1978 was 0.25 to 0.50 ft from aqueduct mile 218 to mile 230 near Elk Hills and 0.20 to 0.30 ft from aqueduct mile 230 to mile 239. Bench marks along this 9-mi length, mile 230 to mile 239, show an apparent minor recovery of 0.01-0.03 ft ‘ \ . 3.2:. \ m Lost Hills \ \ 0“ “ (1953-66 oil field \\ STA 1957-66) “- ; \ s3 3 APPROXIMATE‘ mar m z \ c o 8 PRODUCTION \ 0_45f[ / O = '1: o 3 a LIMIT /\ Q} (1953-66) 2-0 — / 3‘2” g *5 LOST HILLs \\ —( / 5 § 5 OIL FIELD \\ \ o 1KILOMETER I.’ L / s . g .\ / ,_Li / g g S ~1 0 1MILE ._ z ,9 IAL PLA 3 “5/ f: E 5 PART N VIEw i g .. «27 a .9 .. «a: .2. 7 o '7; a 2 1935 u: E 0 E E <2) 1.0 — / / \ <"’ a _ w / \ $< 0 9 65/51/ \ n ".2 " n 2 2/ ®“%* a: / / //’(9‘-"3 \\\\\ u 88 > E 53 ‘9 m /// \\\ _ 19353 __ 1953 _____1953l1_957 ,£::: / / J’s/3 \\ — .9??? _ 1959 — ‘— 1957:1959 é///Jfl\\\\\\ ,,_n_________"____ _E&_——— o " 1966 \‘ ”’"71 E BASE 1966 1955 #1910 mr““‘___ 1974 >912; >9/ 0 1 2 9 KILOMETERS I . .' H o 1 2 MILEs 1.0 FIGURE 37.—Profiles of land subsidence along State Highway 46 near Lost Hills. Location shown on figure 6. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA compaction below the bottom of the 2,000-ft extensome— ter, inasmuch as nearby wells extend to 2,750 ft. The data show that most of the subsidence at this site is caused by compaction of the aquifer system due to the pumping of ground water. This extensometer site and bench mark are 1A mile south of the aqueduct at mile 130, southeast of the hydrocompaction area shown on figure 36. Bench mark 100.55L, an example of differential bench-mark settlement (pl. 1) is located on the left side of Shields Avenue Bridge. This bench mark subsided 1.50 ft from 1967 to 1978, whereas bench mark 100.55R (not shown), located on the right side of the same bridge, sub- sided only 0.88 ft for the same period. Bench mark 81072, a mark in the aqueduct lining one-half mile north of Shields Avenue Bridge, and bench mark Z1072, a bench mark adjacent to the aqueduct 0.6 mi south of Shields Avenue Bridge, show 0.99 ft and 1.05 ft for the same pe- riod. This is a hydrocompaction area and was prewetted before construction. AQUEDUCT SUBSIDENCE, MILE 174 T0 MILE 218 Profiles of land subsidence along the California Aq- ueduct south of Kettleman City from mile 174 to mile 218 are shown on plate 1 (see fig. 6 for location). The base for these profiles is October 1967—January 1968. In the 10- year period 1967—77, these profiles show little or no change from mile 174 to mile 192. From aqueduct mile 192, the subsidence gradually increases to 1.2 ft between mile 197 and mile 198. Subsidence then decreases to less than 0.5 ft at mile 204, increases to a maximum of 1.45 ft at mile 208, and then gradually decreases to 0.45 ft at mile 218. The bench-mark numbers (aqueduct miles) originally assigned by the California Department of Water Re- sources and used by the National Geodetic Survey through 1975 for bench marks from aqueduct mile 172 near Kettleman City to aqueduct mile 220 were about 2.3 mi in error. Corrected mileage and bench-mark numbers of the Department of Water Resources are used in this report. Bench mark X1097, at aqueduct mile 196.75 on a turnout structure shown on this profile, is an example of structure settlement that is probably not related to the areal subsidence. The data show that this structure has subsided a maximum of 1.6 ft since construction, whereas bench mark 196.57 B, 0.2 mi north, and located in the aqueduct lining, has subsided 0.9 ft and bench mark 197.05B, 0.3 mi south and located in the aqueduct lining, has subsided 1.1 ft. The axis of the Lost Hills oilfield is approximately parallel to the aqueduct, and is 1—1.5 mi southwest. The productive limit of the field extends from aqueduct mile 198 to mile 207 (pl. 1). The discovery well, drilled in 1910, was completed at a depth of 530 ft. The shallower oil- producing horizons are 200—1,300 ft in depth; the deeper horizons are below a depth of 4,900 ft. Leveling surveys of bench marks along State High- way 46 at and near Lost Hills indicate that substantial subsidence has occurred both before and since the aque- duct was completed in 1967. Profiles of land subsidence along State Highway 46, from 3 mi west of Lost Hills (town) to 31/2 mi east are shown on figure 37 (see fig. 6 for location). Subsidence values for surveys prior to 1966 (pre-aqueduct) are plotted above the base, and values for subsequent surveys are plotted below the base. The most remarkable feature of this figure is the uniform subsid- ence of 0.4—0.5 ft that occurred from 1953 to 1966 by all the bench marks in the 41/2-mi reach from bench mark 0873 to G873 at the east end of the section. The reason for this uniform subsidence is not known. Lofgren (1975, p. D13—D15) stated that all bench marks in this area have a component of apparent subsidence which is not real. All or part of this apparent change (subsidence) from 1953 to 1966 may be related to tectonic uplift at supposedly sta- ble bench marks in the Tehachapi Mountains to the south, the Sierra Nevada to the east, and the Coast Ranges to the west. Note that bench mark G873, at the west end of the subsidence profile from Wasco to near Lost Hills (fig. 27), is common to both sets of profiles. The subsidence of the area 2 mi east of bench mark G873 (fig. 27) from 1957 to 1974 is double that of G873 and was caused by increased ground-water development in the 1960’s. Bench mark Y544 (fig. 37) at Lost Hills and east of the aqueduct subsided 0.41 ft from 1957 to 1966 and 0.59 ft from 1967 to 1978. Also bench marks E873 and 153A, about 0.5 mi west from Y544 and west of the aqueduct, subsided 0.41 ft from 1953 to 1967 and 0.73 ft from 1967 to 1978. Two miles west of Lost Hills at the axis of the oil- field, bench mark 383.7 subsided 1.22 ft from 1935 to 1953 and 1.02 ft from 1953 to 1966. These figures indicate that the crest of the oilfield due west of the town subsided 2.24 ft from 1935 to 1966 and probably has subsided consider- ably more since oil production began in 1910. No surveys were made between 1910 and 1935, and this bench mark ‘ has not been resurveyed since 1966. 'From 1967 to 1978, subsidence of the aqueduct paral- lel with the axis of the Lost Hills oilfield (aqueduct mile 198—207, pl. 1) ranged from 0.4 to 1.3 ft. At Lost Hills (town), the aqueduct has subsided 0.6—0.7 ft since 1967. This subsidence probably is due in part to continued re- moval of oilfield fluids and compaction of the shallow oil zones of the Lost Hills field. From aqueduct mile 198 to Lost Hills (mile 205), the oilfield subsidence is not known and, hence, no comparison can be made with the aque- duct subsidence. I39 I38 Between aqueduct miles 142 and 155, the 1975 profile shows as much as 0.2 ft of apparent rebound from the November 1971—February 1972 profile (pl. 1). The word “apparent” is used advisedly because there was some problem in the adjustment of bench-mark elevations for the 1975 releveling, although the same procedure was fol- lowed as during the earlier surveys by the National Geo- detic Survey. Extensometers in the Los Banos- Kettleman City area indicate a net compaction in the 3 years 197 2 to 197 5. Although the artesian head of the lower zone was recovering rapidly in that period and mi- nor rebound may well have occurred locally, the 197 5 pro- file should be viewed with caution. The 1972 and 1978 profiles would not be affected because the values were derived from independent adjustments. With the exception of the two areas susceptible to hydrocompaction and apparent minor subsidence of the Coalinga oilfield in the foothills (Bull, 1975, p. F8), all the subsidence that has been mapped in the Los Banos—Ket- tleman City area since the 1920’s is attributed to the great decline in artesian head, the consequent increase in effective stress, the compaction of the confined aquifer systems, and the resulting subsidence of the land sur- face. Within the two areas susceptible to hydrocompac- tion, two types of subsidence have occurred, namely: (1) regional subsidence due to aquifer-system compaction, and (2) hydrocompaction of moisture-deficient deposits between land surface and the water table when first wet- ted by downward percolating irrigation water. Because of the severe differential subsidence pro- duced by the hydrocompaction during many years of irri- gation, and as a result of field tests producing more than 10 ft of hydrocompaction (Bull, 1964a), the aqueduct builders, both Federal and State, concluded that the aq- ueduct alinement within the areas subject to hydrocom- paction should be prewetted from land surface to the water table to preconsolidate the deposits prior to con- struction of the aqueduct. This prewetting between aque- duct miles 98—103 and aqueduct miles 114-129 (fig. 36 and pl. 1) was done in 1964 and 1965. If the prewetting had achieved complete success, all deposits underlying the aqueduct alinement in these two reaches would be pre- consolidated from the land surface to the water table, no additional hydrocompaction would occur, and none of the subsidence shown on plate 1 would be caused by hydro- compaction. The two hydrocompaction areas, aqueduct miles 98—103 and 114—129, were preconsolidated in the follow- ing ways (Hall and Carlson 1965; US. Bureau of Recla- mation 1974). Preconsolidation ponds, 400—425 ft wide and of various lengths, were constructed to saturate both the aqueduct prism and the soil upon which the aqueduct embankments would be placed. Ponds were flooded 1 1/2-2 ft deep for 12—18 months. Gravel-packed infiltration wells STUDIES OF LAND SUBSIDENCE 75, 100, and 125 ft deep on a 100-ft grid were installed in the central two-thirds of the ponds to speed water deliv- ery to dry deposits. In the preliminary investigation, test holes, 200 ft deep, were drilled on 1-mi centers to the ap- proximate water table to obtain moisture and density de- terminations and again, after preconsolidation of the aqueduct alinement, to determine whether moisture from preconsolidation ponding had reached the mois- ture-deficient deposits. Maximum subsidence in the northern hydrocompac- tion area was 2 1/2 ft and in the southern hydrocompaction area was more than 5 ft in 1 1/2 years. Hall and Carlson (1965) predicted a certain amount of residual hydrocompaction would occur even after 1 1/2 years of saturation. The subsidence profiles define two features within the extent of the larger hydrocompaction area that dis- play recurring “sags” in the profiles, repeated in each re- leveling. These sags, centered at aqueduct miles 120 and 128, look like major features at the greatly distorting scale ratio. Actually, the overall sag at mile 120 is about 1 mi wide and has undergone 2.7 ft of subsidence at bench mark A1093 since November—December 1967, about 0.9 ft more than the regional subsidence at nearby bench marks Z1092 and B1093. The sag at mile 128 is about 3 mi wide and has undergone 3.9 ft of subsidence at bench mark R1093 since November—December 1967, whereas the regional subsidence at nearby bench marks N1093 and T1093 was 2.4 and 3.0 ft, respectively. In 1972 the California Department of Water Re- sources requested that the Geological Survey examine differential changes in elevation of the aqueduct, particu- larly near these two prominent sag areas, to see if any geologic anomalies of possible tectonic origin appeared to be developing. The physical dimensions of the two sags and their systematic growth does not suggest that these are geologic anomalies of tectonic origin. It is more likely that these two recurrent sags are caused by contin- uing hydrocompaction (consolidation) of two “islands” of deposits (of low vertical permeability) that have not yet been completely wetted. Test holes drilled to the water table and carefully sampled for moisture content could determine if these are “islands” of continuing hydrocompaction. Measured compaction to a depth of 2,000 ft at exten- someter site 16/15-34N1 (fig. 49) (see fig. 40 for location) was 90 percent of the subsidence measured at bench mark G1046 between November—December 1967 and No- vember 1971—February 1972. The data from the multiple extensometers at this site show that 0.46 ft of compacL tion (table 6) occurred above 503 ft and 1.57 ft occurred from 503 to 2,000 ft, that is, within the confined aquifer system. The 10 percent of total subsidence not accounted for by measured compaction presumably represents LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA subsidence. Areas of known hydrocompaction, shown on figure 1, were prewetted along the aqueduct alinement prior to construction. AQUEDUCT SUBSIDENCE, MILE 92 TO MILE 174 Profiles of subsidence along the California Aqueduct from mile 92 to mile 174 in the Los Banos—Kettleman City area from 1967 to 1977—7 8 are shown on plate 1. The leveling of November—December 1967 was used as the base instead of the February 1967 leveling because the coverage was more complete in December and also to al- low for settlement and stabilization after construction of the aqueduct was completed in 1967—68. Before examining these profiles, it is helpful to re- view major changes taking place in this 10-year period— changes in importation of surface water and in regional pumping of ground water, and the rapid change in the potentiometric surface (artesian head) of the confined aq- uifer system (lower water-bearing zone). Total surface- water deliveries to the San Luis service area (includes about 90 percent of the Los Banos—Kettleman City area) increased from 19,000 acre-ft in 1967 to 1,337,000 acre-ft in 1976 and then decreased to 308,000 acre-ft in the drought year 1977 (table 2). As a result of the increase in surface water supplied through the aqueduct, pumpage of ground water decreased from 1,040,000 acre-ft in 1967 to about 195,000 acre-ft in 197 6, but increased to 542,000 acre-ft in 1977, the second drought year (table 2)". In re- sponse to the reduction in ground-water withdrawal after 1967, the potentiometric surface (artesian head) of the confined system,-which had been drawn down steadfly for 20—30 years, recovered rapidly from 1967 to 1976. This recovery is demonstrated by the water-level profiles along the aqueduct (fig. 5), by the regional water-level re covery in the lower zone from 1967 to 1974 (fig. 15), and by the subsidence and extensometer graphs that show the rapid recovery of artesian head and the corresponding reduction in subsidence rates in the 1970’s (figs. 16, 17, 21—24). The leveling of J anuary—March'1975 to the leveling of November 197 7 -April 1978 show that subsidence rates increased as a result of the 1976—7 7 drought. Field exten- someters and water-level data confirm that most of the subsidence during 1975—77 occurred in 1977, the year of the greatest pumping drawdown (table 3 and figs. 41—56). The reach of the California Aqueduct from mile 92 to mile 174 has subsided more than any other aqueduct reach. This reach passes through two areas of hydrocom- paction (fig. 36) and through the three major subsidence depressions due to water-level decline—(1) southwest of 2Ground-water pumpage data for 1935—36 to 1965—66 are in Bull and Miller (1975, table 3). I37 TABLE 2.—Surface-water deliveries through the joint-use reach of the California Aqueduct and estimated ground-waterpumpage in the Los Banos—Kettleman City area, 1967— 77 [Surface-water deliveries for calendar year; data from U. S. Bureau of Reclamation. Deliveries are to San Luis service area and include water pumped from Mendota Pool by Westlands Water District. Ground-water pumpage for agricultural year beginning April 1 and ending March 31 for years 1967 through 1971 and for calendar years 1974 through 1977] Surface-water Ground-water Year deliveries pumpage ('1'L “ of acre-feet) 1967 _______________ 19 1 ,040 1968 _______________ 209 750 1969 _______________ 306 685 1970 _______________ 478 605 1971 _______________ 650 515 1972 _______________ 865 No data 1973 _______________ 856 No data 1974 ________________ 1,129 1194 1975 _______________ 1,368 1188 1976 _______________ 1,337 1195 1977 _______________ 308 1542 'For years 1974-77, estimates of pumpage in Westlands Water District (Mitten, 1980) were increased by 100,000 acre-ft per year to obtain estimated pumpage in the Los Banos-Kettleman City area. Mendota, (2) near the town of Cantua Creek, and (3) near the town of Huron (fig. 4). Because of the rapid rates of subsidence in the late 1960’s, more freeboard was added to the aqueduct in 1971 from mile 129 to mile 137, south and east of the town of Cantua Creek. More freeboard will be added to other subsiding areas along this reach in the near future. Subsidence rates were greatest from the leveling of November—December 1967 to that of December 1968-January 1969. During this 13-month period, subsid- ence ranged from less than a hundredth of a foot at bench mark J 107 2 at aqueduct mile 92 near the Fresno-Merced County line to a maximum of 1.4 ft at bench mark R1093 at aqueduct mile 128 west of the town of Cantua Creek (pl. 1). Note that the subsidence profiles along the aqueduct are drawn with a vertical scale of 1 in. = 1 ft, whereas the horizontal scale is 1 in. = 2 mi (10,560 ft). Thus, the verti- cal scale is 10,560 times as great as the horizontal scale. This scale difference serves to magnify greatly even very small lateral differentials in the magnitude of subsidence. In 1967 the artesian head in the permeable coarse- grained aquifers was at its historical low. The recovery of head began in 1968, and during the 1970’s pore pressures in the aquifers gradually increased toward equilibrium with residual excess pore pressures in the fine-grained compressible aquitards. The average effective stress and the rate of subsidence decreased at a fairly uniform rate from 1968 to 197 6. Compared with the November-December 1967 base, all the successive profiles show continuing subsidence with the exception of the January-March 1975 profile. I36 STUDIES OF LAND SUBSIDENCE 120°30’ 120°00’ I 37°00' "'\ we, 0 36°30' — . \{4 _ EXPLANATION '\ -' o WA I - “g“ 135 Five Points \ Boundary of deformed o _. rocks 0 ,I, $37 3.7 ................... ’9 ’6‘ // 14o Boundary of area historically affected ‘V ‘20 145 by or susceptible to hydrocompaction 4/ ‘9 3?? (data from US. Bureau of o '9/(( / / 4° Reclamation, July 1980) ‘9 4 (’60 150 6‘ 00) A B / @4 / / . _ Line of subsidence profile / / _/ ' 155 / //1 / a 0 Huron . F Fl r/ - / Line of water—level profile 4 PLEASANT / P fll h fl Coalinga ro es s own on sure 5 and plate 1, A—B Ab. VALLEY o 5 1o 1 20 25 o KIL ME ERS "L / } | I l 15' I 1 1 j 0 T \/g)> o 5 1o 15 MILES '4 (54’ @x 4 / 4'94 36°00’ L ,1 / 49 MILE 174 FIGURE 36.—Location of California Aqueduct subsidence and water-level profiles and areas of hydrocompaction in the Los Banos—Kettleman City area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. I35 LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA y n . n 1 m u e a _ 9 .r W 9 1| . 9 1 u 1 — w I. / JI b . J r u _ l. . . L\Q . n w . u m H... \ Sr a ” N...N W n M u. h x y 3 9 .r x 9 _ w . .J 9 1 . o 1 1 "- . . 1 . . . I. _ l . 2 .1: u a -\ a II; .v: v :3. .J, , . _ ~ \. x. .5 us u . VK¥ T» T” \. 1926-27 1958 1961—62 \_1 x, which was by the California Department of Water Resources.) 1 970 FIGURE 35.—Extent and times of leveling in the Arvin-Marieopa area. (All leveling by the National Geodetic Survey except 1978 134 STUDIES OF LAND SUBSIDENCE Tulare Tulare 1940 Tulare 1942—43 1935 1% August-October December—March .— 1931—1935 5 January—March ‘3 ‘0 '5 .9 Woody ° Woody ° Woody o 1935 Wasco was“, ° 1 Tulere 1947 Tulare’ 1948 were 1953-54 . November 1953- A I—J _ pn une ‘ February June March 1954 _. \ by” \ Woody ° ‘ Woody ° Woody ' Wagco Wasco Wesco Tulare 1957 Tulare \ 1953-59 Tulare 1962 Jam"‘"Y‘M‘W November 1958—- January-March . F . _ March 1959 _ J [l ‘V / 1- 1 I Woody Woody Woody Wesco ' Wasco Wesco , I I T l j Ware. 1964—66 Tulare 1959-70 Tulare’ 1974—75 January—March November 1969- ' February 1970 g | 3 g; o Woody Woody Woody Wasco Wesco ° 1 v 1 Wesco FIGURE 34,—Extent and times of leveling in the Tulare-Wasco area. (All leveling by the National Geodetic Survey except 1974—75 which was by the Los Angeles City Department of Water and Power) LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA I33 Los Banos 1933 on 1935 Los Banos 1943 Los Banos 1947 Los Banos 1953 L05 35005 1954 March—May 1933 December 1942- February-May December 1952— FebruarY—JUIV January—May 1935 April 1943 February 1953 Kettleman City Kettleman Cityo Kettleman City Kettieman City Kettleman City Los Banos 1955 Los Banos 1957 1505 Banos 1958 Los Banos 1959 Los Banos 1963 September-November January-May December 1958- October 1959— February—March January 1959 January 1960 l, —1 fl: 1 ii Kettleman City-\l Kettleman City Kettleman Cityk Kettleman City ° Kettleman City Los Banos 1954 Los Banos 1966 gas Banos 1967 %os Banos 1967 L05 33"“ 1969 October 1964- January-March January—March November—December November 1968- January 1965 April 1969 "L Kettleman City Kettleman City Kettleman City° Kettleman City Kettieman City '3“ 39"“ 1969 '3” “an“ 1970 Los Banos 1972 $05 Banos 1975 I508 Banos 1978 October—November November 1970— November 1971— January—March 0 November 1977— 0 9% January 1971 March 1972 Q April 1978 ‘0 ’4}, er, 1v _ 6' % Kettleman City Kettleman City Kettleman City % Kettlemen City 66 0 A Kettleman City FIGURE 33.—Extent and times of leveling in the Los Banos—Kettleman City area. (All leveling by the National Geodetic Survey except 1977—78 which was by the California Department of Water Resources.) I32 STUDIES OF LAND SUBSIDENCE 120' 119° 118° 1 36° — EXPLANATION Outline of valley Drawn chiefly on boundary of consolidated rocks Wf/W Area of detailed study of land subsidence . Las Banos—Kenleman City . Tulare—Wasco . Arvin—Maricopa Bakersfiel OW}- 1 35° — Line of leveling HACHAPI MTS Line of l—fool subsidence, from figure 2 TE 0 10 20 30 40 50 60 KILOMETERS }_1_r_l___.l1_J_r.|—L_l 0 10 20 30 40 MILES l l I FIGURE 32.—Network of leveling by the National Geodetic Survey and three areas of detailed studies of land subsidence. Base from US. Geologi- cal Survey. 11,000,000, State of California map, 1940. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA 35° I I I I Welldepth 1,480ft E 400 I— _ Lu LL E ui U , :5 450 — — a: 3 m o z S 500 H _ 3 o _J LU a: .‘f, 550 — — 1.0 5 '- in < IL 3 z e __ Compaction depth _ . O E 1,480f! 05 I: m o a E E O . . —- 0 U l I I I 1965 1970 1975 1980 FIGURE 31.—Seasonal fluctuations of water level and measured compaction in well 11N/21W-SBl. Location shown on figure 30. bench mark at Woody in the Sierra Nevada. Woody (shown on fig. 32) is about 10 mi due east of State High- way 65 along the easterly projection of the south bound- ary of T. 25 S. (Lofgren and Klausing, 1969, fig. 37). The Los Angeles Department of Water and Power ran levels in 1974 and 1975 from Woody westward through Delano and Wasco (fig. 34) to near Lost Hills (shown on fig. 6). In the Arvin-Maricopa area, the first precise leveling by the National Geodetic Survey was done in 1926—27. Four subsequent partial surveys were run by 1953. In 1957, as a result of ecordinated efforts of an Inter-Agency Committee, an extensive network of bench marks was established throughout the area of suspected subsidence (fig. 35). Thus, by 1957, detailed bench-mark networks had been established in all three of the principal subsidence areas. Level nets in the subsiding areas were surveyed every few years, because of the accelerated subsidence rates during the late 1950’s and 1960’s. Table 1 shows, for each of the three subsidence areas, the date the network was first established and the years of relevelings of the network. The National Geodetic Survey leveled the California Aqueduct in February 1967; November—December 1967; December 1968—J anuary 1969; October—November 1969; November 1970—January 1971; November 1971—March I31 TABLE 1.— Years of leveling control of the network of bench marks in three subsidence areas by the National Geodetic Survey Los Bones—Kettleman City Tulare~Wasco Arvin-Maricopa ______________________ 11948 ‘1955 __________________ 1953 1957—58 ________________ 1957 11957 1959—60 _______________ 1958—59 1958—59 1963 __________________ 1962 1962 1966 __________________ 21964 1965 1969 __________________ 1969—70 1970 197 1 —72 Wear network established. 2Partial releveling of net. 1972; and J anuary—May 1975. These relevelings were sometimes partial lengths of the aqueduct, such as the part in the Los Banos—Kettleman City area. The California Aqueduct was leveled by the Califor- nia Department of Water Resources in November 1977—April 1978. MONITORING ALONG THE CALIFORNIA AQUEDUCT Profiles of land-surface change (subsidence) along three segments of the California Aqueduct are included in this report (fig. 6, segments A—B, B-C, and D-E). The northern segment is in the Los Banos—Kettleman City area and extends from aqueduct mile 92 at the Fresno- Merced County line to aqueduct mile 174 near Kettleman City (pl. 1; see fig. 36 for location). The middle segment extends from mile 174 near Kettleman City southward past Lost Hills to aqueduct mile 218 (pl. 1; see fig. 6 for location). The southern segment is in the Arvin-Maricopa area and extends from aqueduct mile 238 to aqueduct mile 287 southwest of Wind Gap Pumping Plant (pl. 1; see fig. 6 for location). Three types of bench marks are used in preparing these aqueduct profiles: bench marks set in the aqueduct lining, bench marks on aqueduct structures, and bench marks adjacent to the aqueduct. Bench marks on aque- duct structures (such as bridges, pumping plants, turn- out structures, and checks) show more settlement, especially differential settlement (structure settlement is greater on one side than the other), than bench marks in the aqueduct lining or bench marks adjacent to the aque duct. Examples of differential structure settlement are shown on each segment. Bench marks in the aqueduct lining are used on these profiles, where possible, because they are more representative of the aqueduct subsidence. The aqueduct traverses areas of subsidence due to water-level decline, hydrocompaction, and oilfield sub- sidence, and these areas may also be affected by tectonic STUDIES OF LAND SUBSIDENCE I30 .Aom .mw .mp9 .338 98 «Ea—end 8.8235 c N159 5 EB vwom «Q8132 mac? 98 mm ~33:me 33m use? ugh—w 0535me 152% Z 2: ma 32.. mam—95g Bob 53 8 mama 89¢ 85335 Eugen?" 3 “we 85 9: mm hfioflo gmmfioo dean «Q0032.§ on... E .2339 .88333 vSfiIdm 3565 Pump. oop 4<>¢whz_ EDP—.200 Mud: a v o _ _ L + _ a . mzwhwEde NF w v o .>>mfim .>>ON.I ,>>_.Nvm A>>NN.m ,>>mN.m 5:82 x38 5:3 2; :95 553530 8% 82 _ BEBE 85233 :38 we 9:5 N (km; (29.5 m.=_>_ _ _ _ m: “ 29:59.0 imlmwflonfllm‘. _ mini .mvomF—Zw mi .me.m .me.m .ocem: .mhw‘: .w0N.m .mpom: .mmm‘m .mei .699.— LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA 129 \\l l I I I l I I \ \ \ .\ ( \009\ter 1— 5° _ {war Confined water level ‘— 3 \°’\/ LL 6" \ elf], Z \8170 u: \ o \. < 100 _ \ Seasonal highs __ E \ Well 16N3 D m / a 2 <2 _I g 150 — O _l m m n: u] p— ; 200 — 0 Seasonal lows 1- W ” 16N3 E e \ :1. Lu 0 250 — Conflnlng clay\_. _ _ _ _ _ _ _ _ _ _ 300 1 I 1 1 1 _—— 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 FIGURE 28.—Long—term trend of water levels near Pixley, and seasonal high and low artesian head in observation well 23/ 25-16N3. Location shown on figure 25. 100 I l I ‘I I Water level well depth 430 ft, perforated 360—430 ft p. LU LU LL 2 1 150 — — ul 0 < LL 1: 3 200 — _ 1:: z 5 g 250 1— ~ 1.0 5 d E 2 z w . z E 300 — — 0.5 9 3 Compaction depth 5 O 760fl < p— o. 1:5 E e H o 8 o l 1 960 I 1965 l 1970 l 1975 FIGURE 29.—Seasonal fluctuations of water level in observation well 23/ 25-16N 3 and measured compaction in well 23/25-16N1 near Pixley. Location shown on figure 25. network of leveling control in the three subsidence areas was periodically resurveyed by the National Geodetic Survey (fig. 32). Control is concentrated in the three sub- sidence areas and ties are run to about a dozen “stable bedrock” reference bench marks around the perimeter of the valley. . The extent and times of leveling in the Los Banos-Kettleman City, 'I‘ulare-Wasco, and Arvin-Mari- copa areas are shown in figures 33-35. In the Los Banos—Kettleman City area, the first lev- eling was done in 1933 and 1935 by the National Geodetic Survey. The first extensive leveling, done in 1943, was fol- lowed by partial levelings in 1947, 1953, and 1954. In 1955 a detailed network of bench marks was laid out and lev- eled in connection with a topographic map revision pro- gram (fig. 33). In the Tulare—Wasco area, the first precise leveling was done by the Geological Survey along the Southern Pacific railroad in 1901—02. In 1931, a line of first-order levels was run along the Southern Pacific railroad by the National Geodetic Survey. In 1948 a detailed network of lines was laid out and leveled throughout the subsidence area (fig. 34). Beginning in 1957, a tie was made to a stable 128 area. West of bench mark T457, subsidence from 1970 to 1974 was more than twice as much as from 1966 to 1970. The generalized trend of water levels in the confined system near Pixley from 1905 to 1958, and seasonal high and low artesian head fom 1958 to 1980 in observation- well 23/25-16N3 at the same location are shown in figure 28. This site is in one of the maximum subsidence centers in the Tulare-Wasco area (fig. 25). The artesian head de- clined approximately 130 ft from 1905 to 1959 and reached a historic low in the 1977 drought year. The seasonal fluctuations of water level in observa- tion well 23/25-16N 3 and measured compaction in well 23/25-16N1 near Pixley from 1958 to 1980 are shown in figure 29. Water-level data are from the same site as on figure 28. The compaction rates were greatest in the late 1950’s and early 1960’s owing to large withdrawals of ground water. Compaction rates are related inversely to the amount of surface water available and related di- rectly to the amount of ground water pumped. Deeper seasonal lows produced greater amounts of compaction (see fig. 29). ARVIN-MARICOPA AREA Land subsidence in the Arvin-Maricopa area was re- ported in Lofgren (1975), and Poland and others (1975) updated and summarized the subsidence in this area. Lo- cation of the area, C, is shown on figure 32. The last areawide leveling in the Arvin-Maricopa area was in 1970. The historical land subsidence in the STUDIES OF LAND SUBSIDENCE Arvin-Maricopa area as of 1970 is shown on figure 30. Maximum subsidence exceeded 9 ft. Leveling in this area since 197 0 was along the California Aqueduct. Bench marks along the California Aqueduct were surveyed by the National Geodetic Survey in 1970 and 1975, and the Elk Hills line was surveyed in 1975 (see figs. 30 and 32 for location). The California Department of Water Resources releveled the California Aqueduct and the Elk Hills line in 1978. The seasonal water-level fluctuation and measured compaction in well 11N/21W-3B1, 17 mi east of Maricopa is shown on figure 31. (See fig. 30 for location.) Measured compaction was greatest from 1963 through 1970, rang- ing from 0.30 to 0.45 ft per year as water levels declined at a steady rate. As surface water from the California Aqueduct replaced ground water for irrigation, water lev- els recovered more than 150 ft from 1970 to 1976. Com- paction rates decreased from 197 0 to 1976, averaging about 0.09 ft per year. During the 1976—77 drought, the artesian head declined 90 ft at this site, causing 0.15 ft of compaction in 1976 and 0.23 ft of compaction in 197 7. In 1978 water levels recovered and subsidence stopped. In fact, approximately 0.02 ft of expansion was measured in 197 8 followed by 0.02 ft of compaction in 1979. ESTABLISHMENT AND RELEVELING OF BENCH-MARK NETWORK The bench-mark network in the San Joaquin Valley has grown irregularly since the early part of 1900. The K K' m .J :‘ : mg m g cage) to m mh§m$h é angg mé 7‘ m m (n l~ Q m .— IO B Q U) N ” 9 szeoazaeeahfisargels 9; 0 I _ 1957 base State Hwy46 \ 1957 base \~ 1959 1959 1°62 1962 l-\_ )- _ ~19£7\/ 1966 _ w 0.5 \/ N u. 10 z «‘5 w / ‘91.. __ ‘ _ 1970 o z 1.0 - " “OJ '\4 / (7: \ g 1974 ”1.5— Nt III I' tht' I - \4 08:8 evelng yte alona N Geodetic Survey except 1974; 1974 leveling by Los Angeles City Department of Water and Power 2.0 0 2 4 6 8 KILOMETERS }___L__r_;l_r__l 0 4 MILES FIGURE 27.——Profiles of land subsidence, 1957—74, from Wasco to near Lost Hills. Location shown on figure 25. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA I27 J1 EAST —I I I I I 369 689? 65:9): 509 6891 sesw seam o sssa 3 \\ 6890 f ‘ ‘\ sssu 5 \ \ 99 4941qu 9:918 — “99 \ Geodefic Survey excep‘ 1974; 1974 leveling by Los Angeles City Department of Water and Power LSLE I 9995 LSLD \&/§. 0?; ‘91“ Note: all leveling by the National O: LSLB In ssuu 2 QSLA M $/// 99m- vao wax-auvud— 95mi- // 99m S 10 KILOMETERS 99H] SELL 9st A 55 Aemqlim aims —— 99LS v QSLH \ \ 9§LlN V T ” 9§LN 6 MILES 8 6 FIGURE 26.—Profiles of land subsidence, 1957—74, from bench mark 598, west of Woody, to 19 mi west of Delano. Location shown in figure 25. N 99nd 'mv \ 9SLW f \ o o 9511 \ \ er AUMIIBIH ems — area I WSW 99m / / ssuo '9svd { ' ssua / / / 7 aezu ssu em: I I I I saw {I / 99m I I I I Ch 5I 37 EI é: o I I I l E I / I ‘ 5 I / I ‘ 2’ I / I I / I I DHUOAV M180 _ L978 I I I I a E L I 1 I I L 3 T o ‘- N n v It) Had NI 'BONBOISEHS I26 ‘ west of Delano through 1974. Maximum subsidence east of Delano near State Highway 65 was 3.5 ft at bench mark E757 from 1957 to 1974. Lofgren and Klausing (1969, fig. 50) showed 1—2 ft of subsidence from 1926 to 1962. Many acres of land were opened up to agriculture in this area in the 1960’s and 1970’s (Williamson, 1982). Many wells were drilled because surface water was not available; ground-water pumping increased, and ground- STUDIES OF LAND SUBSIDENCE water levels declined, causing subsidence rates to in— crease. Subsidence at bench mark E757 was 1.4 ft from 1964 to 1970 and 1.7 ft from 1970 to 1974. Maximum sub- sidence west of Delano at bench mark M541, 1 mi west of State Highway 43, was 4.3 ft from 1957 to 1974. Profiles of land subsidence along State Highway 46 from Wasco westward to near Lost Hills from 1957 to 1974 (fig. 27) show that subsidence is continuing in this 119° 30' 119'15 .\ l I g . \\ I lo I Tulare T. \ 8 U : / ' \ 20 \ ml: . \ \ S. O < I I '5': : I l I >£ u I— L 7 ----------- H-———I——— H— - / I : \ l; ‘ Cor or I .. T. . ‘ 21 ° I ...4-- " \ S. "l I / ’ —‘ ‘ \ \ | _____ {_______i_____‘_\__\_'_ Tipt;\ I | T, PI | 22 if \ \ 390309 1 s -— 1— ‘ \ I .— \ "\ EXPIANATION --3." {0 -_\._'_____ _ _I v \ ’*’ ”I l m T. l I : Basement as I ' 1 complex . | / . . ‘ {EC _ _ _ ,_ : gamma“ _ i - _______ _ -' —_—F_— — ____ ___'| Consolidated II : sedimentary rocks I I I of Tertiary age 24 I .. , l S- : <3 : 2—— l ) . . A Line of equal |_ _ __ - __‘ ..'_ ‘3 & ‘ subsidence I I - Dashed where approxi— ‘ J ' .A 5 .. - mate, interval2ft, 350' 3457i ' :\ J’ except for l-lt contour- 45’ I I f; T- I I \ 59 J—JI 25 : i S Line of subsid— S. :__=____ ___i_ _________ L _____________________ ence profile T. : : : Observation well 236 I I e and number ‘ | I l K i i \ x 6873 T. FEE—\— — _.'_ f“ _________ 7 _ — _ ‘ Bench mark loca— 2S7 : : l was“) V285 ( tion and number ‘ ' l l ' | . R. 22 E. R. 23 E. R. 24 E. R. 25 E. R. 26 E. R. 27 E. 0 2 4 6 8 10 12 KILOMETERS |_I_'_;LT_;II_.J.I 0 2 4 6 8 MILES ‘ FIGURE 25.—Land subsidence, 1926—70, and location of subsidence profiles, 'I‘ulare-Wasco area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. Compiled from (1) 1948-70 subsidence (Poland and others, 1975, fig. 27), (2) 1926—62 subsidence (Lofgren and Klausing, 1969, fig. 50), and (3) 1962-70 subsidence (Poland and others, 1975, fig. 24). DEPTH T0 WATER BELOW LAND SURFACE, IN FEET DEPTH TO WATER BELOW LAND SURFACE, IN FEET LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA 300 I I I l 35° — Well depth — 1,358 ft 400 — _. 450 — — 500 ~— 550 —~ Compaction depth 1,358 ft Li— I I I I 0 1 960 1 965 FIGURE 22.—Seasonal fluctuations of water level and measured 1 970 1975 1 980 1985 compaction in well 14/13-11D6 southwest of Mendota. 350 I 400 450 500 550 600 — 650 Well depth 2,315 ft Compaction depth 2,315 ft I '—LI_' ..__..._______ 1965 1970 1975 1980 1985 .5 COMPACTION, IN FEET FIGURE 23.—Seasonal fluctuations of water level and meas- ured compaction in well 17/15-14Q1 south of the town of Cantua Creek. COMPACTION, IN FEET I25 3°° l I I T 350 Well depth 1,007 ft 400 450 DEPTH T0 WATER BELOW LAND SURFACE, IN FEET 500 — —‘ 550 ‘—' —‘ 1.0 p— I“ I“ IL 3 i 600 — -< 0.5 9 p— o < Compaction depth g H ° J I I I 1965 1970 1975 1980 FIGURE 24.—Seasonal fluctuations of water level and meas- ured compaction in well 20/18-6D1 northeast of Huron. The last areawide leveling in the ’I‘ulare-Wasco area was done in 1969—70. Land subsidence from 1926 to 1970 in this area and location of profiles are shown on figure 25. The only known leveling in this area since 1969—70 was-done by the Los Angeles Department of Water and Power in 1974 and 1975. That agency ran a line of levels from bench mark B11 (assumed stable mark in the Sierra Nevada) at Woody (not shown in fig. 25) westward through Delano and Wasco to a proposed nuclear power plant site (which has since been abandoned) west of Wasco. Profiles of land subsidence from 1957 to 1974 from bench mark 598, west of Woody, westward through De- lano are shown in figure 26. The leveling from 1957 to 1970 is by the National Geodetic Survey. The 1974 level- ing is by Los Angeles Department of Water and Power. These profiles show subsidence to be active both east and 124 STUDIES OF LAND SUBSIDENCE 10° I I I I I I I E k E ~\‘erg\t~errn Z 200 — \‘x ”I \\\‘t9 7 5:) \f@,\ ‘L \ / I: \ 91, D \9/ U, 300 — \\ _ a ‘ Canal E \\ ca imports \ o be un 3 \99 9 9 400 — \ _ if \\ WELL 34m 5 \ Seasonal ’- \ h' h g 500 — \ II: S _ 0 Base of confining clay\ \\ I— ‘__. E \xxmmmxum w 500 — Seasonal Iows\ —I ° WELL 34N4 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 FIGURE 20.—Long-term trend of water levels near the town of Cantua Creek, and seasonal high- and low- levels in observation well 16/15—34N4 since 1960. 350 I ’— Lu W ‘L 400 — _ E Iu‘ Water Ievel well E depth 1,130 ft x ._ _. D 450 (I) o E 500 — -1 3 O .1 W m E 550 I— — < 3 .9 I— _ E 600 nu ._ —- 1.5 o ’— W 650 ~— . — E _ Compachon depth _ 1.0 E 2,000 ft . z 9 .— o — — 0.5 g l E I O I o I I 1_1 0 I I I I I 1955 1960 1965 1970 1975 1980 1985 FIGURE 21.—Seasonal fluctuations of water level in well 16/15-34N 4 and measured compaction in observation well 16/15-34N1 near Cantua Creek. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA artesian head in the lower water-bearing zone. Extensom— eter well 14/13-11D6 (fig. 22) measured a net compaction of 0.18 ft in the drought year 197 7, 0.07 ft expansion in 1978, and 0.01 ft expansion in 1979. Extensometer well 17/15- 14Q1 (fig. 23) measured a net compaction of 0.54 ft in the drought year 1977, 0.20 ft expansion in 1978, and no com- paction or expansion in 1979. This site is subject to win- ter flooding and was flooded in 1978, therefore, the record in 1977 and 1978 is questionable. Extensometer well 20/ 18-6D1 (fig. 24) measured a net compaction of 0.19 ft in the drought year 1977, 0.09 ft expansion in 197 8, and 0.02 ft of compaction in 1979. This extensometer supplies only a partial measurement of the total compaction of the aq- uifer system; the extensometer depth is 867 ft and irriga- 123 tion wells are much deeper in this area. This well is located within 100 ft of the California Aqueduct and is strongly influenced by pumping of an irrigation well 150 ft to the north, which explains why the seasonal draw- down in well 6D1 was an astonishing 250 ft in the drought year 1977. TULARE-WASCO AREA Land subsidence in the Tulare-Wasco area was re- ported by Lofgren and Klausing (1969). Poland and oth- ers (1975) updated and summarized the subsidence in this area. Location of the area, B, is shown on figure 32. H a H' - Q ANTICLINE S i Fresno RIDGE % S- Slough V692 U|< M692 FEBRUARY 1943 26782 0 I I | I I | March 1947 // 4 — / _ '33?“ ed (9 \ 13’ a — 5° 0° .9 _ 06 e .4 r a? e a " 4“ A E 5 5" Lu c u. o z * 3‘” 2 € § _ Lu N g .6 .. 3 s” 33° A” In 3 .9 K e 6 e g 16 — «5° _ Enld °f|_1978 Note: The 1975 leveling shows an eve "'9 apparent land surface rebound of 0.20 ft one mile west and 0.05 ft two miles west of bench mark M692. (Bench 20 — marks not shown on profile.) — 24 I l l I I 0 4 8 12 16 20 24 DISTANCE, IN MILES FIGURE 19.—Profiles of subsidence, 1943—78, Anticline Ridge to Hesno Slough. 122 same location in observation well 16/15-34N4 for 1961—80 are shown in figure 20 (see fig. 6 for location). Irrigation wells in this area pump principally from the confined aq- uifer system, and observation well 16/15-34N4 is perfo- rated in the 1,052- to 1,132-ft depth range in the confined system. This site is in the trough of maximum subsid- ence about 20 mi south of Mendota (fig. 4). The rate of decline accelerated from 1905 to 1960; water levels de- clined nearly 500 ft. In the early 1960’s. the seasonal low levels in the confined aquifer system started dipping be- low the base of the clay confining layer. These seasonal lows had a marked effect on the storage characteristics of the aquifer system. With little or no change in pumping pattern, water levels declined very little from 1960 to 1968 when canal imports caused an abrupt decrease of ground-water pumpage and water-level recovery began. From 1968 to 1976 water levels recovered rapidly about 250 ft, mostly because of reduced pumping rates. This overall trend is rather typical of the heavily pumped ar- eas of the western and southern parts of the valley, but the drawdown below the base of confinement is typical of only a few of the most heavily pumped areas. The unwa- tering below the base of the confining layer indicates a condition that could prevail in much of the valley if over- draft continued (Bull and Miller, 1975, fig. 34). STUDIES OF LAND SUBSIDENCE At the extensometer site 16/15-34N1 near Cantua Creek, there was an abrupt water-level recovery in well 16/15-34N4 following the importation of canal water to the area in 1968, and a corresponding gradual cessation of compaction (fig. 21; see fig. 6 for location). Water-level data are from the same site as in figure 20. Water levels recovered until the drought years of 1976—77, then when the surface-water deliveries stopped, the water levels were drawn down by intensive pumping of ground water and the compaction rate for 1977 increased to about that of 1970. The extensometer measured a net compaction of 0.42 ft in the drought year 1977. In 1978 when surface water was again available, water levels recovered to pre- drought levels, and the extensometer measured a net ex- pansion of 0.06 ft. The extensometer measured 0.01 ft of compaction in 1979. At three other extensometer sites in the Los Banos—Kettleman City area— southwest of Mendota (fig. 22), south of the town of Cantua Creek (fig. 23), and northeast of Huron (fig. 24) (see fig. 6 for location)—a sim- ilar trend of water-level recovery and decrease in meas- ured compaction was recorded, followed by an abrupt wa- ter-level decline and renewed compaction during the 1977 drought. All four figures (figs. 21—24) show comparable records of measured compaction in response to change in TUMEY :33; HILLS 5 5 Mendota P661 5661 APRIL 1943 175 (USGS) 0 l l l ' l 1 February 1947 a — _ '— W W LL .2. “J z 18 — U.) E (D m D (I) 24 — — \1975 I I I I 32o 4 a 12 1s 20 DISTANCE, IN MILES FIGURE 18.—Profiles of subsidence, 1943—77, Tumey Hills to Mendota. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA 121 of maximum subsidence on this profile, 21.2 ft, from 1943 files show decreasing subsidence in the 1970’s as more to 1972. This bench mark was not leveled in 1975 or water was imported into the Los Banos—Kettleman City 1977—78. Both profiles show subsidence during nine peri- area. ods since 1943 and two partial relevelings in 1975 and The long-term trend of water levels in the confined 197 7—78 (California Aqueduct leveling, 1977 ~78), using aquifer system near the town of Cantua Creek from 1905 the 1943 control as a horizontal reference base. The pro— to 1964 and the seasonal high- and low-water levels at the 400 I I Subsidence bench mark Y883, 1954~72 and Q L885, 1972—78 500 -— _ o 01 l ,_ l “” ‘1 Lu LL E u; \ ° \ E 00 6 '— —4 5 a b E 3 Q ‘2‘ S Pumping / —_ Lu ; '°V°' (k Static level, N1 <2) O 14.1 a \q 9 a: 8.? 0: E1 5 700 — \\ — 1o 3 \ 3 o “x '— \o I l: \ Lu Water level, wells 0 ‘3 17/15—21N1,o1 and 2251 Q 800 — } pp -— 15 N1 ‘0’ 900 l I I 20 | l l 2 u; E E n: w u] > U a: l—— — 1 fig 9 E / 8 “.1 7/??? 3 E //;?// / / /‘fl / I / / / // 0 1940 1950 1960 1970 1980 FIGURE l7.—Subsidence and artesian-head change near Cantua Creek. I20 6 for location). Measured change of 27.13 ft at this bench mark since 1943, plus 2.5 ft of topographic change from the 1920’s through 1943, make this the locus of maximum known subsidence in the San Joaquin Valley. The arte- sian-head decline through 1967-68 illustrates the increas- ing stress causing the subsidence. As the artesian head recovered, subsidence rates became progressively lower. The bar graph of the subsidence rate clearly shows the effect of the importation of surface water in the late 1960’s and 1970’s. The yearly subsidence rate in 1969—72 was only about one-third that of 1966—69. During the drought years of 1976—77, subsidence rates averaged 0.12 ft per year; at this site the water-level drawdown of 120 ft in 1977 was not sufficient to increase the rate of subsidence. The magnitude of subsidence at this site, 9 m, from 1925 to 197 7 is shown in figure 16. The photograph, taken in 1979 by the US. Geological Survey, shows the approxi- mate position of land surface in 1925, 1955, and 1977. The artesian head and the rates of subsidence (fig. 17) l I l )— — 0 E Subsidence, u. bench mark g 3661 g 300 — _ 5 < E 3 2551}? a) \ d1 9 o o 2 b 0/) 1.10 i; S \ p’ '. l E 3 N1\ d l v z 0 Static level, E2 I if _. d O I, 0 3 an 9 5 5 50° F P ping o ,i‘ 915 o > um A Winter ‘71 5 '°"e‘ N2\ high if g 5 ~ . w 2 \ ¢ \ I g — Water level, wells Summer ‘ 20 14/13-26. N1, N2, ; £2, and 2551 QR K g £2}3 . 700 — fi 25 l l l l l 2 w a: p— < 5 n: >- 3 E _ I — 1 E o. // e E g E / a z WW % 0 1940 1950 1960 1970 1980 STUDIES OF LAND SUBSIDENCE near the town of Cantua Creek (see fig. 6 for location) changed remarkably during the years from the 1950’s to the 1960’s. When surface water was imported to replace pumpage from wells, water levels rose and the rate of sub- sidence decreased markedly in the early 1970’s. The rate of subsidence in 1976—77 was nearly double that of 1973—75. Evidently, drawdown was substantial in 1977, but, unfortunately, the water level in well N1 was not mea- sured in 1977. The historical subsidence southwest of Mendota and along Five Points Road from 1943 to 197 7—7 8 is shown in the two transverse subsidence profiles (figs. 18 and 19; see fig. 4 for locations). Water-level decline along both pro- files was the sole cause of the subsidence (Poland and oth- ers, 1975). Profile G-G’ (fig. 18), which extends from the foothills of the Diablo Range through Mendota, passes close to the site of maximum subsidence (bench mark S661). Profile H—H’ (fig. 19), which extends northeast— ward along the Five Points Road from Anticline Ridge to Fresno Slough, passes close to bench mark M692, the site FIGURE 16.—Subsidence and artesian-head change, 10 miles southwest of Mendota, and photograph illustrating magnitude of subsidence at this site. Joseph Poland of the U. S. Geological Survey is pictured standing by the powerpole. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA 120°30’ 33 152 Los Banos 37°oo' “R r .. \r—u. \g‘lfif - 120°00' 4 ‘5» O 9 m 0 x 7 <9 ( O o 0/5 Vol/4,5 x 3930' — 0 ’9 6’00 ’00 antua Cree l(( 6 X)* 1135‘ \9 x9 4) N o 00 om EXPLANATION 1? 0/9 ‘7 Q WA 4, (’6‘ Boundary of deformed rocks 0 ’9/(‘6‘ -25-- e \\ Water—level contour Line 0] equal water—level change, 1967— / 198 I 1974; dashed when: approximately // % / 4, \ '3, located. Contour Internal 25 feet / 0’90 \\ xo I (/ \ Clio” X; \ PLEASANT \f, Coalinga @" VALLEY 5 10 15 20 25 30 KILOMETERS 1 I l 5 10 15 MILES 36°00’ I / 119 FIGURE 15.—Generalized water-level change for the lower water-bearing zone, December 1967 to February 1974, in the Los Banos—Kettleman City area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. 118 STUDIES OF LAND SUBSIDENCE 120°30’ 120°00’ I/__{1gz\___\ Los Banos 152 33 ’ 37°00' (3% 2:; ,/ l . o -. F ., 9/9 °., --.r\...f.~-—’£‘-’f?1,...\n/lvsrr . .43 D Kerman \< 41 ,9 \ V906 35°3°'— O / [006‘ \ antua Creek \‘\-‘{”’_ _ ( '. (6‘ +25 \ \ I \ Five Points \ EXPLANATION \ ‘ l .\C._‘, - .;,7 WA ’9 9/0 J \l 7 ..' Boundary of deformed rocks 4 Q T\\ \ ,./— (I . : ¢ 6‘ x) g . -25—— O '94 °\\ Water—level contour (5‘ \z; Generalized contour on the potentl- 6 ii, ometrlc surface of the lower water— ' bearing zone; dashed where approx- / 193 3 imately located. Contour Internal 25 // // / 4," 41 and 50 feet. Datum in sea level. 9,? A3 Subuldence area: land surface al- (big, 45(11th tituden used in computations are from the U.S.Geologlcal Survey top- PLEAgAaTiT // \ ographlc map Ierles of 1919—32 0 n9& / VALLEY TULARE LAKE 0 5 10 15 20 25 30 KILOMETERS BED : l I I .1 I II I 0 5 ‘ 10 15 MILES Kettleman City 36°00’ 1 FIGURE 14.—Generalized water-level contours for the lower water-bearing zone, December 1976, in the Los Banos—Kettleman City area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA Il7 120°30’ 120°00 ' l A.__/152\____§ Los Banos 152 33 ’ o , Dos / 37 00 004:: alos / Fm. . n ~. 96% ...,-\.__/‘_..—~_._?xr_m\gqgf/— \w '-.‘<': 00 K, (9 0° w ., 0/ o a \, ”*6?“ +6 “\Mfi'fdala / \ \ . "'\ O Firebaugh .9, Y’ a “NE / '7 O FRESNO / / 9‘09. 400,4, "u— 4 4°..- Mendota ': \ .71“ 7 180 L 1E) \ A #180: g ‘ *6ch I Kerman *“ x9 \ .._\\ a \,\ o 2 / K \0 "\ r \ \-\ / (m \ \6‘ *3? ,g f 2 \) 0 so\ 7 \ ‘2 00 6 ‘6 V) 203?» 33 \ \ § 6‘ o \ .. \ )0 -\ ( ’57 4’s \ \ 0 (<9 F \ \\ MO \ \ c 4/ L‘d‘ o , 439 ~69 . \ \ 3’0?» 35 30 “ ’9, [00¢ Cantua Creek \ \ \4 _‘ (( \ '. vS‘ EXPLANATION \ \., W \ u “”8 P°"“\‘ \ p G _ _. Boundary of deformed rocks 00 o 'r’J -25__ ,9 0/0 Water—level contour Q Generallzed contour on the poten- 4/ 06‘ tiometrlc audace o] the lower 67 water-bearing zone: dashed where G ((.9 approximately located. Contour ln- 6‘ terual 25 It. Datum la lea level. Sub- 1 L . _ ‘ ‘ ‘ ‘ ‘ sldence area: land-cudace altitudes / 198 7 “\ uoed ln computations are from the // y / 4’ \Westhaven. I US. Geological Survey lopograph- / 0))0 Huron . lc map eerlu of 1919—32 mlnul qgfi, the 1928—72 subsidence making thlc , the approxlmate true elevatlon of PLEASANT / \ : the water ourface as of 1974 Coalinga \ VALLEY l TULARE 0 5 10 15 20 25 30 KILOMETERS / I 1 I I l 1 I 4'6 I l l I )> o 5 10 15 MILES ‘61,, 33 4 Kettleman City 36°00’ l / FIGURE 13.—Generah'zed water-level contours for the lower water-bearing zone, February 1974, in the Los Banos—Kettleman City area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. 116 37°00' 36°30' STUDIES OF LAND SUBSIDENCE 36°OO’ '5 120°30’ 7 120°00' 33 'A——f15%——-—\ Los Banos 152 \ 33 ’ Dos / 09>._ alos ’ ‘5 '\6 .A 6'6 yrs 0 ._ O k. «9/9 w . 0/ o a \.y@9 M / 9* "‘5'ldfla ¥ ""\ O Fltebaugh \’ I / / "2 72 4 % endota 71’ g, o 180 O O \ g e \ \ O 3"; ‘l‘ ‘75 ( I (m 7 \ 33 <9 )0 ’00 ( @fi‘k "35 ‘5‘ M ‘75 o 0 ~00 ‘775 l/ \ 0/58 4’5 200 l’ \ 0 ’0 '39 '9/ 06‘ ‘90 ((J‘ 00 \ EXPLANATION W4 ’9 0’0 Boundary of deformed rocks ‘7 4’ Q06 '25__ O Isl/Q ~75 Water—level contour ‘9 , 0° Generallzed contour on the potentl- 6 1 \\ | ornetrlc surface of the lower water— \ - ‘ bear-lug zone; dashed where approx- / / 198 725; “Kama. lrnately located. Contour Interval 25 // 4% Hur’on \ ‘\ \) and 50 feel. Datum ls sea level. fiQ’ \_1 0 /I \ gag Subsidence area: land surface al- $0,» ,175 I I O titudes used in computations are PLEASANT / / 0/ Iron: the U.S.Geologlcal Survey top- Coalin . / / $0 C; 9 // <99 6" ographlc map series of 1919—32 VALLEY \ 6;¢ 0 5 1o 15 20 25 30 KILOMETERS ’ I l 1 n I l 4: l7 l | T O 5 10 15 MILES FIGURE 12.—Genera]ized water-level contours for the lower water-bearing zone, January 1972, in the Los Banos-Kettleman City area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. 36°30’ 36° 00’ LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA 115 120°30' 120°00' I 9 [[4 fi 152 ._ L‘\ Los Banos ® Kerman l \ \\~<>4.,\ EXPLANATION me Points " WM Boundary of deformed rocks -25__. Water—level contour Generalized contour on the potentio ometric surface of the lower water- bearing zone; dashed where approx- imately located; queried where doubtful. Contour interval 25 feet. Datum in yea level. Subsidence area: land—audace altitudes need in computations are from the US. Geological Survey topographic map series of 191942 0 5 10 15 20 25 30 KILOMETERS I; I I l 1 I l x l l 0 5 10 15 MILES Kettleman City J FIGURE 11.—Generalized water-level contours for the lower water-beating zone, December 1967, in the Los Banos—Kettleman City area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. 114 37°00’ 36°30’ STUDIES OF LAND SUBSIDENCE 120°30’ 120°00’ 33 152 Los Banos EXPLANATION We 6» Boundary of deformed rocks _25———. Water—level contour Generalized contours on the potenti- ometrlc surface of the lower water— bearing zone: dashed where approx- imate. Measurements represent ap- proximate high level for the 1965— 66 winter season. Contour interval 25 feet. Datum is sea level. Subsid- ence area: land—surface altitudes used in computations are from the US. Geological Survey topographic map series of 1919432 5 10 15 20 25 1 1 I 15 MILES O——o 30 KILOMETERS 1 WP— 152 f -. 1,. Wyaf - \ ... ENE“ 1180- FRESNO r m l Kerman PLEASANT Coallnga VALLEY / 36°00’ FIGURE 10.—Genera1ized water-level contours for the lower water-bearing zone, December 1965, in the Los Banos—Kettleman City area. Base from US. Geological Survey, 1:250.000, Central Valley map, 1958. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA Il3 120l°30' 120°00' 33 W3 Los Banos 152 \ 33 ’ o ,_ Dos 37 00 \._ alos / F . re . \E o --.n...,..-—J29y_...yaerr --\ ._ 0 K. «9/9 0‘ ._ 0/ o Ia \Kyéé QQ. .. endure / /_—‘ . /-—- "'\ O Firebaugh / / "°°o / / \’... / / / ’0 Mendota ': XL 180L ‘3; '- m \“3 0 I» o 2 \\ ° ‘5 r 9 / (m ‘9 7 v0” 33 ’93 0 ). \ o \ {so ( ’9/(476 f’6‘ \ < P b o \S‘ 6‘ 01v 0C“ 0’6); [4’5 ‘300 . 0 36°30’ — "o 9/0 "335 él’Q 0‘ \a 2' 6‘ v3. \ \f, Five Points \ EXPLANATION \ ‘ €39 \C- " Q7 o 03’ | “7“" W/W/x/Q ’9 ’6‘ Boundary of deformed rocks ‘7 0Q, l \ \ f"— 6‘ " " 4’ «y 7 \' —150—— o /(( \ c \ \ "5 Water—level contour 6‘ : ‘5 Generallzed contour on the potentl- l .3 ometrlc curface o! the lower / 193 \ : water—bearing zone; dashed where / / Westhaven \ ‘ approximately located. Contour ln- // / 4'); \ uron \\ $3 41 term! 25 feet. Datum la sea level. "I Q, \\\~\ .' Subaldence area: land-eurface al— %¢4’ \ \ 0 Stratfor\ tltuda used In computatlonc are PLEASANT \,]75 00/0 :' from the U.S.Geologlcal Survey top- Codinga \ ‘2‘36‘0 —9%0 /\ ographlc map series of 1919—32 ) °1Q$fi C9 VALLEY \%~% Q $ /TULARE :90 K‘_ / LAKE 0 5 10 15 20 25 30 KILOMETERS BED l l I l I I I 43‘ \ / I I I l )>, \ \_/ / o 5 10 15 MILES ($4, \\ 33 4, “((8 Kettleman City 36°00’ 1 FIGURE 9.—Genera1ized water-level contours for the lower water-bearing zone, December 1962, in the Los Banos—Kettleman City area. Base from US. Geological Survey, l:250,000, Central Valley map, 1958. 112 36°30 ' 36°00’ EXPLANATION W/// /W// Boundary of deformed rocks 50 — — Water—level contour Generalized contour on the potentl- ometric ludace of the lower water— bearing zone; dashed where approx. imately located. Contour interval 50 ft. Datum is sea level. Subsidence area: land—surface altitudes used in computations are from the US. Geological Survey topographic map series of1919—32 STUDIES OF LAND SUBSIDENCE 120°30’ 120°00’ 1+». ? ..(, we, \. lve Points \ / 7 / /. // /'¢ 0 Huron ’ - A PLEASANT ,/ Coallnga @ o AVALLEY so 01—0 20 L 25 30 KILOMETERS l J r 15 MILES VX/ . kx" l FIGURE 8.—Generalized water-level contours for the lower water-bearing zone for April—May 1955, in the Los Banos—Kettleman City area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA 111 120°30’ 120°00' 33 l 152 Los Banos 152 33 ’ 37ooor Dos / \M. Palos / F . TCIIIO I' -. a, --.n...,~...~--Ww/ x... 36°30’ — EXPLANATION W/W,W,ZA ’9 0’0 Boundary of deformed rocks 0 —25—— 4, (06‘ Water—level contour 0 '9’Q Generallzed contour on the potentl- 6 '5‘ {a ometrlc audace of the lower water— ‘5‘\ bearlng zone; dashed where approx- 98 \“ > lmately located. Contour Interval 25 y/ / 1 feet. Datum ls sea level. Subsldence // ’1’) area: land—audace altitude. used In (/ computations are from the U.S. Q? 4’ Geological Survey topographic PLEASANT map series of 1919—32 Coalinga @ Y VALLE 5 10 15 20 25 30 KILOMETERS I 41 I 1 I I l 5 10 15 MILES O-—o 36°00’ I / FIGURE Z—Generalized water-level contours for the lower water-bearing zone, spring and summer 1943, in the Los Banos—Kettleman City area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. 110 STUDIES OF LAND SUBSIDENCE to construct an accurate water-level map for the lower water levels recovered as much as 200 ft in the 6 years water-bearing zone. During the 197 6—77 drought, how- from 1967 to 1974. ever, many new wells were drilled and many of the old The measured subsidence at bench mark S661 and wells were repaired and reactivated. artesian—head change in nearby wells, 10 mi southwest of A map (fig. 15) of the water-level changes shows that Mendota, from 1943 to 1977 is shown in figure 16 (see fig. 121° 120° 119° 118° I I I j: ‘ l f _ :1 MW ..... — , \ ‘ 8" l ./ . 1 °\ fl , Area of‘erepon 37° — \‘\ 0 .1 K ’7 c \ Cantua >1 oCreek 14011 _ Y883 L885 .. 1N1,01 " _ 2E1 Han J‘ < , x . 1- \ 601 L I l '3 \ l l I Kettleman 36° k ;._ a r i 'a MILE 174 EXPLANATION Outline of valley Drawn chlefly on boundary of consolidated rocks ————— . l Approximate boundaries of \(C . I I principal confining beds MILE leI I where known ' 4? n._ . QQILE 238 033‘ 9 \ / ’2 Observation well and number , .C l R.20 E. ‘3 5661 MT DIABLO BASE ‘l H.215 E. 1381; A/ l X SAN BERNARDINO T.12 N.‘ . 11E i 35" *— Bench mark and number BASE T.1 1 N] 1 MILE 28 s _ l R. 25 wj ,ITEHACHAPI A B MTS l———-I Line of subsidence profile 0 10 20 30 40 50 60 KILOMETERS l___l_[_.L_H_l_rl_L‘ 0 10 20 30 40 MILES l I I l FIGURE 6.—Location of California Aqueduct, subsidence profiles, selected observation wells, nearby bench marks, and boundaries of principal confining beds. 19 LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA omm 8m 8w 8N oo— .85 $0 aaofiwméfim 2: .35 22 05 89¢ mum—=30 Mike—E 65H 8 $3 .uonvwsd< «anemic 93 £853 88 wgwnaflms .533 2: 8m 859E qu>£t3u3 guwnmwld auburn 33.35 53:8 >3 .32: 53:8 557.325 mam: E9: 23 ”302 332%“: :2 I.I tonEoooe $9 I 138089 «o9 III 68:32.88.an I..I a8. runawafifl I ::::: $958338. II A>u2u__a$mm2 II 3:05. mozm= 523 29.525me mugs. 5:839‘ 8. 8m 8a SN 8m 9.: 2: cm o 3%. 92 @2300— >538 OZmfllm . 085: l _ k 133i NI 'BSVS mt 3H1 WOHd 13A3'I USLVM NI BDNVHO I8 STUDIES OF LAND SUBSIDENCE 120 ’30’ ,- § ‘ \ @X. 05 Banos 2 l 9 o\ 37'00', 36°30’ >— EXPLANATION Boundary of deformed rocks g___ Line of equal subsidence in feet. Dashed where approximate. Interval variable _)—)._ California Aqueduct G — 6’ Line of subsidence profile xM692 Bench mark and number 0 5 10 0 5 FRESNO '\ 15 20 25 KILOMETERS 10 l 15 MILES m\ o - ‘ Ktfileman City 36'00’ FIGURE 4.—Land subsidence, 1926-72, Los Banos—Kettleman City area. Base from US. Geological Survey, 1:250,000, Central Valley map, 1958. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA STATUS OF SUBSIDENCE AND WATER-LEVEL CHANGE LOS BANOS-KETTLEMAN CITY AREA Land subsidence due to water-level decline in the Los Banos—Kettleman City area was reported in Geological Survey publications by Bull and Miller (1975), Bull (197 5), and Bull and Poland (197 5); a report by Poland and others (1975) updated and summarized subsidence in this area. Location of the area, A, is shown in figure 32. Land subsidence due to hydrocompaction in the Los Banos—Kettleman City area was reported by Bull (1964a). The hydrogeology of the ground-water reservoir in the Los Banos—Kettleman City area was described by Miller and others (1971). Land subsidence in the Los Banos—Kettleman City area reached a maximum of 29 ft in 1972 and 29.6 ft in 1977. Figure 4 shows the historic subsidence in the Los Banos—Kettleman City area from 1926 to 1972, the last areawide leveling in the Los Banos—Kettleman City area. The maximum subsidence of 29 ft occurred southwest of Mendota (within the 28-ft subsidence contour). Three ma- jor subsidence depressions, a large area south and west of Mendota, an area south and west of the town of Cantua Creek, and a large area in the vicinity of Huron, all show more than 20 ft of subsidence. The California Aqueduct traverses all three of these major subsidence depressions. Additional leveling data are available in the area along the California Aqueduct and will be discussed later (pl. 1). The aqueduct profiles show substantial subsidence along the aqueduct during construction, and decreased subsid- ence after 1968 because of increasing importation of sur- face water, then increased subsidence during the drought years 197 6—77. As stated earlier, the unconfined to semiconfined wa- ter-bearing deposits above the principal confining bed are referred to as the upper water-bearing zone, and the confined system beneath the confining bed as the lower water-bearing zone. The upper water-bearing zone has a water table, and locally the water is unconfined. The most permeable aquifers in the Los Banos—Kettleman City area are in the upper water-bearing zone but are of limited extent. Ground water of the upper water-bearing zone generally contains high concentrations of calcium, magnesium, and sulfate, except near Fresno Slough (Bull and Miller, 1975). The lower water-bearing zone is confined by the Cor- coran Clay Member of the 'I‘ulare Formation except in the southwestern part of the Los Banos—Kettleman City area where the Corcoran Clay Member is absent and con- finement is poor or lacking. Deposits forming the lower water-bearing zone aquifer system in the Los I7 Banos—Kettleman City area are locally less permeable than the deposits forming the semiconfined aquifer sys- tem of the upper zone. Before surface water was imported into the Los Banos—Kettleman City area via the Califor- nia Aqueduct, at least 75—80 percent of the irrigation wa- ter pumped in the area was from the lower zone (Bull and Miller, 1975) because of the greater thickness of the lower- zone deposits and the generally poorer quality of the wa- ter in the upper zone. . Seven generalized water-level profiles for the lower water-bearing zone beneath the California Aqueduct from 1943 to 1976 in the Los Banos—Kettleman City area show the changes from the 1943 level (fig. 5; see fig. 36 for location). These profiles show the water levels declining from 1943 through 1967, then recovering to 197 6 (using 1943 as a base). The water-level data on these profiles, when compared with the subsidence data on plate 1, show the changing stresses that produce subsidence or re- bound. These profiles were prepared using maps of the potentiometric surface of the lower water-bearing zone (figs. 7—14), constructed by the Geological Survey. The water-level contour maps were overlaid on the California Aqueduct alinement and elevations of the potentiometric surface were plotted at selected distances along the aque- duct alinement. Water-level changes at the selected dis- tances were determined by subtracting the 1943 water-level elevation from the plotted elevation for the potentiometric surface for each of 7 years. Figure 6 shows the location of subsidence profiles along and near the California Aqueduct, selected obser- vation wells, nearby bench marks, and boundaries of the principal confining beds in the valley. The generalized water-level contours on the potentio- metric surface of the lower water-bearing zone at seven times from 1943—76 in the Los Banos—Kettleman City area are shown in figures 7 -14. The water-level maps were constructed using the topographic elevations mapped in the 1920’s; the continuing land subsidence was not sub- tracted from the water-surface elevation except on the 1974 map (fig. 13) where the 1926—72 subsidence (fig. 4) has been subtracted. Thus, the 1974 map shows the ap- proximate true elevation of the water surface in wells tap- ping the lower zone. After the California Aqueduct was completed and surface water became available in 1968, many wells were abandoned, destroyed, or taken out of service for eco- nomic reasons. Representative water-level measure- ments became more difficult to obtain. Many of the casings of the older wells were broken due to compaction and compressive failure; some were cut off, capped or buried. The large recovery in artesian head in the lower water-bearing zone from 1967 to 1976 almost equalized water levels in the upper and lower water-bearing zones » in some parts of the area, making it increasingly difficult STUDIES OF LAND SUBSIDENCE 16 bbreviations N and W in the township-and-range her. all range numbers east. Therefore, as in the example the a the base and meridian and are identified by inclusion of above, the abbreviations S and E are omitted from the part of the well num well number for brevity. Wells referenced to the San Bernardino base and meridian are all north and west of f the base and meridian, making all township numbers south and ort wells referenced to the Mount Diablo In this rep base and meridian are all located south and east 0 u a, ”a 93. w... ......b. 3... ’3”... ...: . .. Go a eoooo c cowOWOOQO &%. 6.... .. 4 «o 3.... o. o o .... .. .. ... a. o o %& ... o o o o o o o 06 .. o o o o o o o o 9%”. x.” o ” .. o o v t‘.‘ o o o A% o 9, o o o . ... .”.”””””..”.. .... o o o o q o o o . .. o o o o A% o o .. . o o o o / .. ... 9.5%. gs. >« o o o o gw . ..”.. .. ....... .... ”.. .. 0 FIGURE 3,—Well-numbering system. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA 15 Gas and Electric Co.] (1977) and the Geological Survey indicated a steady increase in ground-water pumpage for the entire San Joaquin Valley from 91/2 million acre-ft in 1974 to 13 million acre-ft in the drought year 1977. In the Los Banos—Kettleman City area pumpage increased to 470,000 acre-ft, and surface-water deliveries were 308,000 acre-ft in 1977 compared to 1,337,100 acre-ft in 1976 (US. Bureau of Reclamation, 1978). During 24 years that subsidence and water-level data were collected, water levels were drawn down to his- torical lows in the late 1960’s causing subsidence rates that locally exceeded 1 ft per year. After the delivery of surface water, heads recovered in the middle 1970’s to lev- els of the 1940’s, and subsidence nearly ceased. During the drought of 1976-77 renewed demand was imposed on the aquifer systems. The resulting second cycle of head decline proceeded much more rapidly than the first cycle because the water of compaction produced by each foot of head decline was only a small fraction of that produced during the first cycle. Associated with the rapid head de- cline were subsidence rates typical of those observed dur- ing the late 1960’s. In 1980, when seasonal rainfall was above normal and surface water was available, ground-water levels re- covered above their pre-drought levels and subsidence rates again were low. This report is an update of an earlier work. It con- tains data on fluctuation of water levels, associated com- paction and expansion of the aquifer systems as measured in extensometer wells, and subsidence of the land surface since 197 0. Basic-data graphs and computer- plotted stress-strain relationships constitute a major part of this report. They are based on 8—24 years of de- tailed field measurements of both water-level change and compaction collected by the US. Geological Survey at 24 selected locations in the San Joaquin Valley. PURPOSE OF REPORT This report is part of a study of land subsidence in California in cooperation with the California Department of Water Resources; the study has been closely interre- lated with a Federal research investigation of the me- chanics of aquifer systems. Subsidence in the San Joaquin Valley has been studied in this cooperative pro- gram since 1956. The Geological Survey published a re- port by Poland and others (1975) that summarized land subsidence in the San Joaquin Valley through 1972. The report also contained an annotated bibliography of the principal published reports resulting from the two re- search studies. The reader interested in learning more about the scope and findings of those reports is referred to Poland’s annotated bibliography. The purposes of this report are (1) to review the sta- tus of water-level trends and of subsidence in the San Joaquin Valley through 1979; (2) to present updated wa- ter-level, compaction, and subsidence data; (3) to present profiles of land subsidence along the California Aqueduct based on relevelings since the 1967 or 1970 base leveling, in order to define the extent and magnitude of subsidence that has occurred along the aqueduct and to identify probable causes where practicable; and (4) to propose a continuing surveillance program for monitoring areas of continuing or potential subsidence, with special atten- tion to conditions along and near the California Aque- duct in the San Joaquin Valley. The report incorporates field data through December 1979. ACKNOWLEDGMENTS The writers acknowledge the cooperation of Federal, State, and local agencies, irrigation districts, private companies, and individuals. Leveling data used in the preparation of the various subsidence maps and graphs and in calculating magnitude and rates of subsidence were almost all by the National Geodetic Survey, a com- ponent of the National Ocean Survey (formerly the US. Coast and Geodetic Survey); the 1977—78 leveling along the California Aqueduct was by the California Depart- ment of Water Resources. Water-level data used in this report were chiefly from field measurements made by the Geological Survey, but some records were from the US. Bureau of Reclamation, the California Department of Water Resources, Pacific Gas and Electric Co., and irrigation districts. Many Sur- vey workers have contributed to this continuing program. WELL-NUMBERING SYSTEM The well-numbering system (fig. 3) used in California by the Geological Survey and the State of California shows the locations of wells according to the rectangular system for the subdivision of public lands. For example, in the number 12/12-16H2, the part of the number preced- ing the slash indicates the township (T. 12 S.), the part between the slash and the hyphen shows the range (R. 12 E.), the number between the hyphen and the letter indi- cates the section (sec. 16), and the letter following the sec- tion number indicates the 40-acre subdivision of the section. Within each 40-acre tract, wells are numbered serially as indicated by the final digit of the well number. Thus, well 12/12-16H2 is the second well listed in the SE 1A of the NE% of sec. 16, T. 12 S., R. 12 E. Except for the extreme south end of the valley, which is referenced to the San Bemardino base and meridian, all wells are refer- enced to the Mount Diablo base and meridian. I4 STUDIES OF LAND SUBSIDENCE the west side and to the south end of the valley, extrac- tions of ground water decreased. Ground-water pumpage in the San Joaquin Valley as a whole decreased 1 to 2 million acre-ft a year from 1969 through the early 1970’s (Mitten, 1976). From 1974 through 1976, pumpage in the Los Banos—Kettleman City area averaged less than 121' 120° 100,000 acre-ft annually. Ground-water levels began to re- cover in those areas during 1969-71 and subsidence rates decreased. During the drought years, 1976-7 7, surface water was in short supply, and many new wells were drilled and old wells were reactivated. Estimates by Harris [Pacific 119° 118° Reservoir 37° ~ 36° — 9 a . EXPLANATION , Q ‘2‘» Outline of valley Drawn chiefly on boundary of consolidated rock: 4 Line'of equal subsidence, in feet Interval voriable. Compiled from comparison of U .5. Geological Survey topographic maps prior to about 1955 and subsequent leveling of National Geodetic funfy. South of Bakersfield, compiled wholly from eve mg ‘ 35° — 0510 Han—11% 0 5 1O 15 I l 15 20 25 30KILOMETERS 20 MILES l l I l FIGURE 2.—Land subsidence in the San Joaquin Valley, California, 1926—70. Base from US. Geological Survey, 11,000,000, State of California map, 1940. LAND SUBSIDENCE IN SAN JOAQUIN VALLEY, CALIFORNIA I3 importation of surface water and the decrease of ground-water pumping in the late 1960’s and 1970’s. Then, during the drought of 1976—77, heavy ground- water pumping caused renewed subsidence, and water levels declined at a much faster rate than during the first period of decline because of the reduced storage capacity due to compaction of the compressible mate- rials in the aquifer system. CAUSES, HISTORY, AND EXTENT OF SUBSIDENCE Four types of subsidence occur in the San Joaquin Valley. In order of decreasing magnitude, they are (1) sub- sidence caused by water-level decline (ground-water over- draft) and consequent compaction of aquifer systems, (2) subsidence related to the hydrocompaction1 of moisture- deficient deposits above the water table, (3) subsidence related to fluid withdrawal from oil and gas fields, and (4) subsidence caused by deep-seated tectonic movements. A fifth type, subsidence caused by the oxidation and compaction of peat soils, occurs in the Sacramento—San Joaquin Delta area. The primary causes of subsidence in the San Joaquin Valley are aquifer-system compaction due to water-level decline and near-surface hydrocompaction. The data pre- sented in this report are mostly related to these two types of subsidence. The areas (fig. 1) affected by subsid- ence caused by water-level decline and hydrocompaction are principally in the western and southern parts of the valley where runoff from surface streams is minimal. Most of the subsiding area in the San Joaquin Valley is underlain by a continuous and extensive confining bed; and most of the pumping overdraft and compaction due to head decline occurs in the confined aquifer system be- neath this bed. The approximate boundary of the confin- ing bed, where known, is shown in figure 1 (Lofgren and Klausing, 1969; Miller and others, 1971; Croft, 1972). North of Wasco, the confining bed is the Pleistocene Cor- coran Clay Member of the Tulare Formation, which also has been called the E-clay by Croft (1972). The boundary of the confining bed (fig. 1) conforms fairly closely with the area affected by subsidence, except in the semicon- fined system east of Delano (Lofgren and Klausing, 1969). For convenience, the unconfined to semiconfined water-bearing deposits above the confining bed are re- ferred to as the upper water-bearing zone and the con- fined system beneath the confining bed as the lower water-bearing zone. )Hydrocompaction is the process of volume decrease and density increase that occurs when moisture-deficient deposits become compacted as they are wetted for the first time since burial (Prokopovich, 1963; Lofgren, 1969, p. 273). The vertical downward movement of the land surface that results from this process has been called “shallow subsidence” (Inter- Agency Committee on Land Subsidence in the San Joaquin Valley, 1958, p. 22) and “near- surface subsidence" (Lofgren, 1960; Bull, 1964a). Subsidence due to hydrocompaction has occurred in two areas west and southwest of Mendota (Bull, 1964a), a small area just south of Kettleman City (not shown in fig. 1), and in five areas south and southwest of Bakersfield (California Department of Water Resources, 1964, pl. 2; Lofgren, 1975, pl. 30). The total area known to be suscep- tible to hydrocompaction is about 225 mil, of which about 145 mi2 is north of Kettleman City (Prokopovich, 1970). The magnitude and extent of land subsidence in the San Joaquin Valley (fig. 2) from 1926 to 1970 has been compiled from topographic maps and leveling data. Agricultural development in the San Joaquin Valley has been intensive, especially since World War II. In the eastern part of the valley, from Kings River to the north, surface streams from the Sierra Nevada supply most of the water for irrigation but the surface streams are sup- plemented by ground water, especially after midsummer when streamflow is deficient. From Kaweah River to the south—except for the Kern River and its alluvial fan— and in the west-central area from Mendota to Kettleman City, local surface-water supplies have been small to neg- ligible. Prior to the construction of major canals or aque- ducts, irrigation was almost wholly from thousands of large and deep irrigation wells; conditions of ground-wa- ter overdraft had prevailed since the 1930’s. Extractions of ground water in the San Joaquin Valley for irrigation increased from 3 million acre-ft in 1942 to at least 10 mil- lion acre-ft in 1966 (Ogilbee and Rose, 1969a, 1969b; Mit- ten and Ogilbee, 1971). Importation of surface water to areas of serious over- draft on the east side of the valley began in 1950 when water from the San Joaquin River was brought south through the Friant-Kern Canal, which extends to the Kern River (fig. 1). The average annual delivery from this canal is about 1 million acre-ft. Of this total, an average of 750,000 acre-ft per year was delivered to irrigation dis- tricts in the Tulare-Wasco area from 1956 through 1972 (Poland and others, 1975, table 4). Surface-water imports to the northwestern part of the area from the Sacramento-San Joaquin Delta via the Delta-Mendota Canal began in the early 1950’s. About two-thirds of the water in the Delta-Mendota Canal that is transported southward to the San Joaquin River at the Mendota Pool is used by west-side irrigation companies in exchange for water formerly taken from the San Joaquin River, thus releasing rights to water behind Friant Dam for east-side deliveries through the F‘riant- Kern Canal. The remaining one-third of the water from the Delta-Mendota Canal is delivered to irrigation con- tractors along the canal (William R. Cooke, U.S. Bureau of Reclamation, oral commun., 1981). From 1968 to 1971, when surface water from the Cali- fornia Aqueduct became available to deficient areas on 12 managed for cyclic storage without appreciable future subsidence; (3) the basin has provided a field labora- tory for testing compression characteristics of complex aquifer systems on site and for measuring mechanical STUDIES OF LAND SUBSIDENCE and storage characteristics of aquifer systems under a wide range of loading stresses. After many years of continued water-level decline and subsidence, water levels recovered because of the 118° 37° Hydrocompaction .. areas EXPLANATION 36 ° Outline of valley Drawn chiefly on boundary of consolidated rocks // Area where subsidence due to water—level decline is more than 1 foot Area of subsidence due to hydrocompaction S 35° Area of little or no subsidence Approximate boundary of principal confining bed where known rea of‘ Q report ford ;, / Ijl/9//// ettleman lty \E “be, EMIGDIO MTS O 10 20 30 4O 50 60 KILOMETERS }__|_[_;11_L__'J_l_l 0 10 20 30 40 MILES Figure 1.—Geographic features of centr al and southern San Joaquin Valley and areas affected by subsidence. Base from US. Geological Sur- vey, 1:1,000,000, State of California map, 1940. STUDIES OF LAND SUBSIDENCE LAND SUBSIDENCE IN THE SAN JOAQUIN VALLEY, CALIFORNIA, AS OF 1980 By’R. L. IRELAND, J. F. POLAND, and F. s. RILEY ABSTRACT Land subsidence due to ground-water overdraft in the San Joaquin Valley began in the mid-1920’s and continued at increasing rates until surface water was imported through major canals and aqueducts in the 1950’s and late 1960’s. In areas where surface water replaced withdrawal of ground water, water levels in the confined system rose sharply and subsidence slowed or essentially eased. The three major subsiding areas in the San Joaquin Valley in this report are the Los Banos—Kettleman City area, largely in western Fresno County; the 'I‘ulare—Wasco area, mostly in Tulare County; and the Arvin-Maricopa area, in Kern County. The latest areawide leveling was in 1972 in the Los Banos—Kettle— man City area and in 1969—70 in the TulareWasco and Arvin-Maricopa areas. The 1972 leveling in the Los Banos—Kettleman City area showed that subsidence rates had decreased sharply with the importation of surface water through the California Aqueduct in the late 1960’s and early 1970's. The California Aqueduct leveling showed a continued de- crease in the rate of subsidence along the aqueduct through 1975, fol- lowed by increased subsidence during the drought years of 197 6—77. Leveling by the Los Angeles Department of Water and Power in the Tulare-Wasco area showed that east and west of Delano, subsidence continued into 1974. In the late 1960’s and early 1970‘s, water levels in wells recovered to levels of the 1940’s and 1950’s throughout most of the western and southern parts of the valley, in response to decreased ground-water withdrawals because of the importation of surface water through the California Aqueduct. Concurrently, the borehole extensom- eters recorded decreasing compaction rates. By the mid-1970's, compac- tion had diminished to near zero at some sites. Data collected at water-level and extensometer sites during the 197 6—77 drought showed the effect of the heavy demand on the ground- water reservoir. With the water of compaction gone, anesian head de- clined 10 to 20 times as fast as during the first cycle of long-term drawdown that ended in the late 1960’s. Extensometers measured com- paction ranging from 0.1 to 0.5 foot in 1977. In 1978-79 water levels re- covered to or above the 1976 predrought levels. Extensometer response ranged from compaction of a few hundredths of a foot to expansion of nearly 0.20 foot. The report suggests continued monitoring of land subsidence in the San Joaquin Valley, utilizing extensometers, water-level recorders or measurements, and periodic releveling. INTRODUCTION GENERAL STATEMENT The San Joaquin Valley (fig. 1) is a broad alluvi- ated structural trough constituting the southern two- thirds of the Central Valley of California. It is 250 mi long, averages 40 mi in width, and encompasses 10,000 mi2 excluding the rolling foothills that skirt the valley on three sides. The pertinent geographic features of the area discussed in this report are those in the southern four-fifths of the valley (fig. 1). Land subsidence due to ground-water withdrawal began in the San Joaquin Valley in the mid-1920’s and locally exceeded 28 ft by 1970 (Poland and others, 1975); in December 1977, subsidence reached a maxi- mum of 29.6 ft in western Hesno County. More than 5,200 mi2 of irrigable land, one-half the entire valley, has been affected by subsidence. Subsidence in the San Joaquin Valley probably represents one of the greatest single manmade altera- tions in the configuration of the Earth’s surface in the history of man. It has caused serious and costly prob- lems in construction and maintenance of water-trans- port structures, highways, and highway structures; also many millions of dollars have been spent on the repair or replacement of deep water wells. Subsidence, besides changing the gradient and course of valley creeks and streams, has caused unexpected flooding, costing farmers many hundreds of thousands of dol- lars in recurrent land leveling. Not all the effects of subsidence due to ground-wa- ter withdrawal have been negative. Benefits attribut- able to or associated with subsidence include: (1) The tremendous volume of water of compaction released to wells as subsidence progressed; thus, water levels de- clined more slowly, and pumping lifts were less than would have occurred if comparable volumes had been withdrawn from a less compressible aquifer system; (2) the compressible deposits of the ground-water reser- voir have been “preconsolidated” by earlier pumping stresses—rapidly draining beds to the maximum stresses of the mid-1960’s, slowly draining beds to some lesser stress; within the range of stresses in which preconsolidation has actually been accom- plished—which can only be determined by precise field measurements—the ground-water reservoir can be 11 % ‘\ _ a, u; z. E CONTENTS CONVERSION FACTORS The inch-pound system of units is used in this report. For readers who prefer metric (SI) units, the conversion factors for the terms used are listed below: Multiply By To obtain acre 4047 m2 (square meter) acre-ft (acre-foot) 1233 m3 (cubic meter) ft (foot) 0.3048 In (meter) inch (in) 2.54 cm (centimeter) mi (mile) 1.609 km (kilometer) mi2 (square mile) 2.590 km2 (square kilometer) National Geodetic Vertical Datum of 1929 (NG VD of 1929): A geodetic datum derived from a gen- eral adjustment of the first-order level nets of both the United States and Canada, formerly called mean sea level. NGVD of 1929 is referred to as sea level in this report. 28. 29. 30. 31. 32. 33-35. 41.—66. 67. TABLE 1. 2. OIUIvbQD CONTENTS Page Graph showing long-term trend of water levels near Pixley, and seasonal high and low artesian head in observation well 23/25-16N3 .......................................................................................... 129 Graph showing seasonal fluctuations of water level in observation well 23/25-16N3 and measured compaction in well 23/25-16N1 near Pixley ................................................................................. 29 Map showing land subsidence, 1926—70, in the Arvin-Maricopa area. .............................................. 30 Graph showing seasonal fluctuations of water level and measured compaction in well 11N/21W—3B1 ...................... 31 Map showing network of leveling by the National Geodetic Survey and three areas of detailed studies of land subsidence... 32 Maps showing extent and times of leveling: 33. Los Banos—Kettleman City area. .................................................................... 33 34. 'I‘ulare—Wasco area. ................................................................................ 34 35. Arvin-Man'copa area. .............................................................................. 35 . Map showing location of California Aqueduct subsidence and water-level profiles and areas of hydrocompaction in the Los Banos—Kettleman City area. ........................................................................... 36 . Profiles of land subsidence along State Highway 46 near Lost Hills ............................................... 40 . Map showing areas of known hydrocompaction in the Arvin-Maricopa area. ........................................ 42 . Diagram of recording extensometer installations ............................................................... 44 . Map showing location of water-level and compaction measuring sites .............................................. 45 Computer plots showing: 41. Hydrographs, compaction, and subsidence, 12/12-16H ..................................................... 62 42. Hydrograph, compaction, and subsidence, 13/12-20D1 ..................................................... 63 43. Hydrograph, compaction, and subsidence, 13/15-35D5 .................................................... 63 44. Hydrograph, compaction, and subsidence, 14/12-12H1 ..................................................... 64 45. Hydrographs, change in applied stress, compaction, subsidence, and stress-strain relationship, 14/13-11D ........... 65 46. Hydrograph, compaction, and subsidence, 15/13-11D2 ..................................................... 67 47. Hydrograph of well 15/14-14J1, depth 1,010 ft ............................................................ 67 48. Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship 15/16-31N 3 ....... 68 49. Hydrographs, change in applied stress, compaction, subsidence, casing separation, and stress-strain relationship, 16/15- 34N .................................................................................... 69 50. Hydrograph, compaction, and subsidence, 17/15-14Q1 ..................................................... 73 51. Hydrograph, compaction, and subsidence, 18/16-33A1 ..................................................... 73 52. Hydrographs, change in applied stress, compaction, subsidence, and stress-strain relationship, 18/19-20P ........... 74 53. Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship, 19/16-23P2 ______ 76 54. Hydrograph, compaction, and subsidence, 20/18—6D1 ..................................................... 77 55. Hydrograph, compaction, stress-compaction relationship, 20/18-11Q1 ......................................... 78 56. Hydrograph, change in applied stress, compaction, subsidence, and stress-strain relationship, 20/18-11Q3 ........... 79 57. Hydrograph, change in applied stress, compaction, and stress-compaction relationship, 22/27-30D2 ............... 81 58. Hydrographs, change in applied stress, compaction, subsidence, and stress-strain relationship, 23/25-16N __________ 82 59. Hydrographs, change in applied stress, compaction, and stress-strain relationship, 23/25-16N 3 and 4 .............. 84 60. Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship, 24/26-34F1 ...... 86 61. Hydrograph and change in applied stress at 25/26-1A2, compaction, subsidence, and stress-compaction relationship at well 24/26-36A2 ............................................................................. 87 62. Hydrograph, change in applied stress, compaction, and stress-compaction relationship, 25/26-1A2 ................ 89 63. Hydrographs, change in applied stress, compaction, and stress-compaction relationship, 26/23-16H ................ 90 64. Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship, 32/28-20Q1 ...... 91 65. Hydrograph, compaction, and subsidence, 12N/21W-34Q1 .................................................. 92 66. Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship, 11N/21W-3B1. . _ . 93 Graph showing relation of compaction/subsidence ratios to depth at extensometer wells in the San Joaquin Valley ......... 58 TABLES Page Years of leveling control of the network of bench marks in three subsidence areas by the National Geodetic Survey ......... I31 Surface-water deliveries through the joint-use reach of the California Aqueduct and estimated ground-water pumpage in the Los Banos—Kettleman City area, 1967—77 ................................................................. 37 . Annual compaction at compaction-measuring sites, San Joaquin Valley ............................................. 46 . Computer simulation of aquifer-system compaction. ............................................................ 48 . Information on wells or sites for which records are included in figures 41—67 ........................................ 51 . Ratio of compaction to subsidence for periods of leveling in the Los Banos—Kettleman City, T‘ulare-Wasco, and Arvin-Mari- copa areas ........................................................................................... 54 CON TE N TS Page Page Abstract _____________________________________________ I 1 Monitoring along the California Aqueduct .................. 131 Introduction. ......................................... 1 Aqueduct subsidence, mile 92 to mile 174 ............... 37 General statement __________________________________ 1 Aqueduct subsidence, mile 174 to mile 218 .............. 39 Causes, history, and extent of subsidence ............... 3 Aqueduct subsidence, mile 238 to mile 287 .............. 41 Purpose of report .................................. 5 Elk Hills leveling ................................... 41 Acknowledgments .................................. 5 Monitoring of compaction and change in head. .............. 43 Well-numbering system. ............................. 5 Computer simulation of aquifer-system compaction. ......... 46 Status of subsidence and water-level change ................ 7 Computer plots of field records ........................... 50 Los Banos—Kettleman City area. ..................... 7 Compaction-subsidence ratios ............................ 53 Tulare—Wasco area ................................. 23 Suggestions for continued monitoring ..................... 57 Arvin-Maricopa area. ............................... 28 Selected references ..................................... 58 Establishment and releveling of bench-mark network. ........ 28 ILLUSTRATIONS Page PLATE 1. Profiles of land subsidence along the California Aqueduct in the Los Banos—Kettleman City area, south of Kettleman City, and in the Arvin—Maricopa area, California. .......................................................... In pocket FIGURE 1. Map showing geographic features of central and southern San Joaquin Valley and areas affected by subsidence ............ I 2 2. Map showing land subsidence in the San Joaquin Valley, California, 1926—70 ........................................ 4 3. Diagram of well-numbering system. ......................................................................... 6 4. Map showing land subsidence, 1926—72, Los Banos—Kettleman City area. .......................................... 8 5. Graph showing generalized water-level profiles for the lower water-bearing zone beneath the California Aqueduct, 1943 to 1976, showing change from the 1943 level, Los Banos—Kettleman City area. ..................................... 9 6. Map showing location of California Aqueduct, subsidence profiles, selected observation wells, nearby bench marks, and boundaries of principal confining beds .................................................................... 10 7—14. Maps of the Los Banos—Kettleman City area, showing generalized water-level contours for the lower water-bearing zone: 7. Spring and summer 1943 ........................................................................... 11 8. April—May 1955 ................................................................................... 12 9. December 1962 ................................................................................... 13 10. December 1965 ................................................................................... 14 11. December 1967 ................................................................................... 15 12. January 1972 ..................................................................................... 16 13. February 1974 .................................................................................... 17 14. December 1976 ................................................................................... 18 15. Generalized water-level change for the lower water-bearing zone, December 1967 to February 1974, in the Los Banos—Kettle— man City area. ....................................................................................... 19 16. Graph showing subsidence and artesian-head change, 10 miles southwest of Mendota, and photograph illustrating magni- tude of subsidence at this site ........................................................................... 20 17. Graph showing subsidence and artesian—head change near Cantua Creek. ........................................... 21 18. Profiles of subsidence, 1943—77, 'I‘umey Hills to Mendota. ....................................................... 22 19. Profiles of subsidence, 1943—78, Anticline Ridge to Fresno Slough. ................................................ 23 20—24. Graphs showing: 20. Long-term trend of water levels near the town of Cantua Creek, and seasonal high- and low-levels in observation well 16/15-34N 4 since 1960 ....................................................................... 24 21. Seasonal fluctuations of water level in well 16/15-34N4 and measured compaction in observation well 16/15-34N1 near Cantua Creek. ............................................................................ 24 22. Seasonal fluctuations of water level and measured compaction in well 14/13-11D6 southwest of Mendota. .......... 25 23. Seasonal fluctuations of water level and measured compaction in well 17/15-14Q1 south of the town of Cantua Creek. 25 24. Seasonal fluctuations of water level and measured compaction in well 20/18-6D1 northeast of Huron. ............. 25 25. Map showing land subsidence, 1926—70, and location of subsidence profiles, 'I‘ulare-Wasco area. ........................ 26 26. Profiles of land subsidence, 1957-74, from bench mark 598, west of Woody, to 19 miles west of Delano ................... 27 27. Profiles of land subsidence, 1957—74, from Wasco to near Lost Hills ................................................ 28 Land Subsidence in the San Joaquin Valléy, California, as of 1980 By R. L. IRELAND, J. F. POLAND, and F. S. RILEY STUDIES OF LAND SUBSIDENCE U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 437—1 Prepared in cooperation with the Calzfomia Department of Mter Resources UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1984 DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Ireland, R. L. Land subsidence in the San Joaquin Valley, California, as of 1980 (Studies of land subsidence) (Geological Survey professional paper; 437—1) "Prepared in cooperation with the California Department of Water Resources." Bibliography: p. 158-160 Supt. of Docs. no.: I 19.16z437—I 1. Subsidences (Earth movements)——California—-San Joaquin Valley. 2. Water, Underground--California--San Joaquin Valley. I. Poland, J. F. (Joseph Fairfield), 1908- . II. Riley, Francis S. (Francis Stevenson), 1928— . III. California. Dept. of Water Resources. IV. Title. V. Series. V1. Series: Geological Survey professional paper ; 437-1. GB485.C2174 1984 551.3'5 84-600081 For sale by the Distribution Branch, Text Products Section, US. Geological Survey, 604 South Pickett St, Alexandria, VA 22304 Magnitude of subsidence at a site 10 mi southwest of Mendota in the San Joaquin Valley, Calif. Joseph E Poland, principal subsidence researcher and coauthom of report, stands alongside a power pole which shows the approximate position of land surface in 1925, 1955, and 1977. Land surface was lowered about 9 m during that period. LAND SUBSIDENCE IN THE SAN JOAQUIN VALLEY, CALIFORNIA, AS OF 1980 29x 09%?!“50’1 my H78 STUDIES OF LAND SUBSIDENCE TABLE 8.—Notes on wells or sites for which records are included in figures 53—78—Continued . . N be f St - t; Fig. WellNo; Slte collngzggign 1113;325:512 oiegggggggrgign Remarks Arvin-Maricopa area 76 12N/21W—34Q1 ________ 1 1 ________________ Well 810 ft deep. 77 32/28—20Q1 ________ __ 1 1 Stress-compaction Well 970 ft deep. 78 11N/21W-3B1 __________ 2 1 Stress-strain Well 1,480 ft deep, but strain computed for 670-5; thickness. EARTH SCIENCES LIBRARY r...” . knees 911919472997, SAN JOAQUIN VALLEY, CALIFORNIA H77 TABLE 8.—Notes on wells or sites for which records are included in figures 53—78 [For location of well or site, see fig. 50] Fig. No. Well or site 0. Number of compaction plots Number of hydrographs Stress-compaction or stress-strain plot made Remarks Los Banos—Kettleman City area 53 54 55 57 58 59 60 61 62 63 64 65 66 67 68 69 12/ 12—16H _____________ 13/12—20D1 ____________ 13/15—35D5 ____________ 14/13—11D ______________ 14/12—12H1 ____________ 15/13—11D2 ____________ 15/14-14J1 ____________ 15/16—31N3 ____________ 16/15—34N ______________ 17/15—14Q1 ____________ 18/16—33A1 ____________ 18/19—20P ______________ 19/ 16-23P2 ____________ 20/18—6D1 ______________ 20/18—11Q2 ____________ 20/18—11Q1 ____________ 20/18—11Q3 ____________ 2 1 Stress-compaction ________ do________ Stress-strain Stress-compaction Stress-strain Stress-strain Complex head relations, lower zone. Primarily observation well, lower zone; compaction measurement includes only part of lower zone. Com action, upper zone; by rograph not represen- tative for all stress-change interval. Well is east of Fresno Slou h. Compaction or interval 578 ft thick in lower zone. Primarily observation well, lower zone; compaction measurement includes only part of lower zone. Primarily observation well, lower zone; compaction measurement includes only part of lower zone. Representative for the lower zone. Compaction and hydro- graph, upper zone. Compaction for interval 1,297 ft thick in lower zone. Deepest compaction anchor, 2,315 ft below land sur- face. Primarily observation well, lower zone; compaction measurement includes only part of lower zone. Compaction and water level, upper zone. Compaction to depth of 2,200 ft. Primarily observation well, lower zone; compaction measurement includes only part of lower zone. Casing-separation plot; hydrograph for top of lower zone. Compaction and hydro- graph, upper zone. For most of lower zone; hydrograph for lower part of lower zone. Tulare-Wasco area 70 71 72 73 73 74 75 23/25—16N ______________ 24/26—34F1 ____________ 24/26—36A2 ____________ 25/26—1A2 ______________ Do __________________ 25/26—1K2 ______________ 2 Stress-strain > ________ do-___---- Stress-compaction _ ________ do- _ _ _ _ _ _ _ Confined system, com- paction in 430—760-ft- depth interval. Confined system, assumed all compaction in 250—430- ft-depth interval occurred in 330—430-115 depth. Compaction to 1,510 ft. Assumed that hydrograph for 1A2 represents stress change in compacting zone of 36A2. Compaction measured to depth of 892 it. Perforated 1,000—2,200 ft. Perforated LOGO—2,200 ft. H76 STUDIES OF LAND SUBSIDENCE 3 5 360 3 1— 400 g z 440 m _ U-I m” 480 L; o 3 If 520 O [I 1- 8 560 E n. 600 W D E: ti o 11' Lu I n. '-L 40 < z E Z .‘3‘ so Lu 8 u. Change in stress (5 l“ O 120 e E I (I) o 160 B 0—810feet u'i o_14ao feet LIJ u. E 5‘ E : u. 0 z < . “- 11.1 3 Bench M991 g o E a In D (I) —1.5 E —1.0 “- —o.5 E 5' 0.0 g 0.5 E 1.0 o o 1.5 2.0 1 960 1961 1962 1963 1964 1965 1966 1 967 1 968 1969 1970 D 160 u; 3 140 E E 120 Stress-strain +- 3; 100 -‘ 1.1. E o 80 35 6° u. {5‘ Z 40 E 20 I o o —12 —10 as —6 «4 —2 o 2 4 6 8 10 12 13x10“ STRAIN E FIGURE 78.—Hydrograph, change in applied stress, compaction, subsidence, and stress-strain relationship, 11N/21W—3B1. A, Hydrograph of well 11N/21W—3B1, perforated 1,037-1,237 feet. B, Change in applied stress, water table assumed constant. C, Compaction to BIO-foot depth at well 12N/21W—34Q1 and to 1,480-foot depth at well 11N/21W—3B1 and subsidence of bench mark M991 at well 11N/21W—331. D, Compaction in 810—1,480-foot.depth interval. E, Stress change versus strain (670-f‘t thickness). DEPTH TO WATER BELOW LAND SURFACE, IN FEET CHANGE IN APPLIED STRESS, IN FEET OF WATER COMPACTION. IN FEET 1 60 200 240 280 320 360 40 80 120 160 200 CHANGE IN APPLIED STRESS, IN FEET OF WATER SAN JOAQUIN VALLEY, CALIFORNIA Change In applied stress E 0—970 feet u. E ui o z m 9 a) co :3 w 1963 1964 1965 1966 1967 1968 1969 1970 C 160 140 120 100 i Stress-compaction 80 60 40 20 0 0 0.5 1 .0 1 ,5 2.0 COMPACTION, IN FEET D FIGURE 77.——Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship, 32/28—20Q1. A, Hydrograph of well 32/28—20Q1. B, Change in applied stress, water table assumed constant. C, Compaction to 970-foot depth at well 32/28—20Q1 and subsidence at bench mark L365, 1 mile north on State Highway 99. D, Stress change versus com- paction of deposits above 970-foot depth. H75 H74 STUDIES OF LAND SUBSIDENCE g 280 g E 320 g! E 360 E Z_ 400 w '- o 440 g E Hydrograph, 1K2 o g 480 " m E 520 1% 560 O 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 FIGURE 75.——Hydrog'raph of well 25/26—1K2, perforated LOGO—2,200 feet. a z j 160 3 200 9 E 5.3 L; 240 E T :1 8 280 3 E 320 O r- 8 360 I E 400 o A E Lu u. E o- . Lu 5 E 8 W1 156 Z < u; o- 0 5 z 0 “9‘ m ‘3 a) 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 B FIGURE 76.—Hydmgraph, compaction, and subsidence, 12N/21W—34Q1. A, Hydrograph of well 12N/21W—34Q1, perforated 400—800 feet.B, Compaction to 810-foot depth and subsidence of bench mark W1156 at well 12N/21W—34Q1. SAN JOAQUIN VALLEY, CALIFORNIA H73 280 320 360 400 440 480 520 560 DEPTH TO WATER BELOW LAND SURFACE, IN FEET US E 0 .5 E 40 o '2 80 E E —J u. 120 5% o < {4—1 160 z E E 200 ‘25 Z 240 E 280 o B 5 0—692 feet cm M 2m 0 o. u. z '— Lu Lu 3 3 e E 0 Bench mark T945 3 E 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 03‘) C 280 St ress- 260 compaction 240 $— 220 g 200 n: ,_ 2 El 180 g g 160 -’ u. & O 140 < l— 120 z E Lu “- 100 <5 Z 5 so I O 60 40 20 o 0,0 0.2 0.4 COMPACTION, IN FEET D FIGURE 74.—Hydrograph, change in applied stress, compaction, and stress-compaction relationship, 25/26—1A2. A, Hydrograph of well 25/26—1A2, perforated 200—600 feet. B, Change in applied stress, water table assumed constant. C, Compaction to 892-foot depth and subsidence of bench mark T945 at well 25/26—1A2. D, Stress change versus compaction of deposits above 892—foot depth. H72 STUDIES OF LAND SUBSIDENCE 280 320 360 400 440 480 520 560 DEPTH T0 WATER BELOW LAND SURFACE. IN FEET 40 80 1 20 1 60 200 240 280 Change in applied stress CHANGE IN APPLIED STRESS. IN FEET OF WATER ~0.5 E E 0.0 2 0.5 . E — Compacmn, 0—2200 feet Lu 2' 1.0 u. 9 1 5 z I— . - 0 Lu ff 2.0 2 5 Bench mark S1156 Lu 0 2.5 Q o 3 1957 1958 1959 1960- 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 a C 280 - 260 240 g; 220 8 200 E 5 2 I; 180 L3 g 160 .1 g L5 140 < 1— 120 $ Z 100 3 so 5 60 Stress-compaction 40 20 0 0.0 0.5 1.0 1.5 1.8 COMPACTION, IN FEET D FIGURE 73.—Hydmgraph and change in applied stress at well 25/26—1A2 and compaction, subsidence, and stress-compaction relationship at well 24/26—36A2. A, Hydrograph of well 25/26—1A2, perforated 200—600 feet. B, Change in applied stress, water table assumed constant. C, Compaction to 2,200-foot depth at well 24/26—36A2 and subsidence of bench mark 51156, 265 feet east-southeast. D, Stress change versus compaction of deposits above 2,200-t‘oot depth. H71 SAN JOAQUIN VALLEY, CALIFORNIA L335 NI 'EONSCIISEII'IS o.— md 90 .Hmwméflva swims £99983?” .VAEvmémEm dim—852w.— nomuuafi$mma5m can 605335 EQSoaAEco amok—m 355m E manage .sawnmguzmlflh ESUE .53". 83.954 025a 353% he 5:33:59 wag“; mum—«:0 mmwhm “Q Ahvmémxvm :95 «a 3mm ”15: 5:3 Mo 85233 ES 59% 88.3w; 3 sign—Eco .0 .3333 vofidmmm 033 :35» .mmoflm 3:an E mung—5 .méowm mmmafilocfi Easing Q Emu“— Z_ .ZO_._.O D mmoaw umiam E 09550 ./ >(\.\> \ MIC/II . x. \ / \A \ /2 £2 /\ /2..\/\ \ \ r\ (K r E V \I I > 7 D _/> / \>,/\\> \\/ \ 1/I a \> 7 \/ f r (I ,\ . uUOu \//I\\/\ (\f? KI Fig.3. com oo— our on ov oov omwm own 0mm own com 09 BBLVM :IO 133d NI ‘SSEIBlS 03|1ddV NI 39NVHO 133d NI ‘aovauns GNV'I MO'IBEI HELVM OJ. HLdEICI H70 CHANGE IN APPLIED STUDIES OF LAND SUBSIDENCE D 2 j 40 5’11"; 60 duu.‘ 120 a: E; 160 W Egg 200 0%: 240 1—3 :1: 290 E 320 I.” D ._ 5 LL“: EE 3;; LL E0 ._ (I) p— E u- 0—250 feet Z 2' g p— O < D. 2 o o '— Lu Lu LL 3 25043011291 2' Q '6 < CL (23 2.0 o 1958 1959 1960 1 961 1962 1963 1 964 1965 1966 1 967 1968 1969 1970 D 160 140 120 Stress-strain a: 100 E so 3 60 LL 0 40 E 20 “' 0 Z_ 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 3 [LI E U) B E 160 a. 140 < z 120 W 100 0 . E 80 Stress-strain I 0 so 40 20 o 37 39 41 43 45 47 49 51 59 55 57 59 61 63 65 67 69 71 73x10" STRAIN E FIGURE 7l.—Hydrog‘raphs, change in applied stress, compaction, and stress-strain relationship,23/25—16N3 and N4.A,Hydrographs of wells 23/25—16N4, perforated 200—240 feet, and 23/25—16N3, perforated 360—420 feet. B , Change in applied 9 trees. C, Compaction to 250-foot depth in 23/25—16N4 and to 430-foot depth in 23/25—16N3.D, Compaction in 250-430-foot-depth interval.E, Stress change versus strain (100-11. thickness). SAN JOAQUIN VALLEY, CALIFORNIA H69 3 1— 93 4o LLI LL :0 Z 80 E Lu- 120 :9 160 3 E 200 95; 240 E3 230 320 35 8.— :w 0 gEE w 581.1. 120 stress EE" $33 (I) 5 B 1— DJ LIJ U. E 2‘ 1— 9 E 5 u. :5 Z. 2 3 0 Z 0 Lu 9 U) to D U) ._ uJ LIJ LL Z 2” 430-760 tee! Q [— o < D. 2 8 4‘0 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 D 160 E 140 2 120 100 3 _ . 3 80 Stress straln E 60 w 40 “- 20 3 o v; 22242628303234363840424446485052 8 a: 1— (0 E1 160 - E 140 < 120 g 100 g 80 z 60 Stress-strain E 40 - ° 20 - 0 54565860626466687072747676 606264 8688 90x10“ STRAIN E FIGURE 70,—Hydrographs, change in applied stress, compaction, subsidence, and stress-strain relationship, 23/25—16N. A, Hydrog‘raphs of wells 23/25—16N4, perforated 200—240 feet, and 23/25—16N3, perforated 360—420 feet. B, Change in applied stress C, Compaction to 430- foot depth in well 23/25—16N3 and to 760-foot depth in well ‘23/25—16N1 and subsidence of bench mark Q945 at well 23/25—16N1. D, Compaction in 430—760-foot—depth interval. E, Stress change versus strain (330-3 thickness). H68 STUDIES OF LAND SUBSIDENCE o z 5 280 E 5 :11 E 320 m z 360 1.: __ Hydrograph, 1103 {-3 Lu 400 < 0 g E 440 ,9 a 480 E 520 B A B ._ 0 5.1 w 40 g u- E, Change in stress 2 Z l; 80 L: $ E 120 (9 LIJ o E E 160 5 w 200 B Casing protrusion (compaction 0—845 feet) ,— LIJ LIJ LL Z 5 P 0.1990 feet 'u'.» 0 Lu 5 u. g E 0 0 Bench mark C999 a Q (n a: D m E Compaction, 845—1930 feel u. E z' 9 5 < o. 2 O O 1958 1959 1 960 1961 1 962 1 963 1964 1965 1965 1967 1 968 1969 1970 D (/5 160 m 140 E [I a) E 120 o < y E 100 -‘ u. g o 50 Stress-strain < E Z a] 60 g E 40 E 20 0 0 1 3 5 7 9 1 1 13 15 17 19 X 10 " STRAIN E FIGURE 69,—Hydrograph, change in applied stress, compaction, subsidence, and stress- strain relationship, 20/18-11Q3. A, Hydrograph of well 20/18—11Q3, perforated 1,885— 1,925 feet. B, Change in applied stress, water table assumed constant. C, Casing protrusion (compaction to 845—11 depth), compaction to 1,930-foot depth, and subsidence of bench mark C999 at well 20/18—11Q3. D, Compaction in 845—1,930-fi; depth interval. E, Stress change versus strain (1,085-t’c thickness). SAN JOAQUIN VALLEY, CALIFORNIA H67 320 360 400 440 480 SURFACE, IN FEET 520 560 DEPTH TO WATER BELOW LAND 4o 80 S'reSS 1 20 1 so 200 CHANGE IN APPLIED STRESS, IN FEET OF WATER —0.5 'u'.» E 0.0 0—71 E 0.5 i g 1.0 ,_ 2 1‘5 "2‘ O 2.0 0 25 I 1955 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1959 1970 C 160 8” Lu 140 It! 55 ‘20 Stress-strain a; 100 _l &5 80 4: E5 60 w“- _ (52 40 E— I 20 o 0' 012 3 4 5 6 7 8 91011121314151617181920 2122x104 STRAIN D FIGURE 68.—Hydragraph, change in applied stress, compaction, and stress-strain relation ship, 20/18—11Q1. A, Hydrograph of well 20/18—11Q1, perforated 650—710 feet. B, Change in applied stress, water table assumed constant. C , Compaction to 710-foot depth at we 11 20/18—11Q1. D, Stress change versus strain (650-ft thickness). H66 STUDIES OF LAND SUBSIDENCE D Z S 440 3 480 «oz 520 5-. :8 560 SE 600 0% "m 640 I E 680 LL! 0 A E E g E 2- 0—867 feet ”- 2 Q _ 5 8' < 2 EL Lu 2 o 0 :73 0 co 3 1964 1965 1966 1967 1968 1969 1970 m B FIGURE 66.—Hydrograph, compaction, and subsidence, 20/18—6D1. A, Hydmg'raph of well 20/ 18—6D1, perforated 716—736, 760—835, and 851-872 feet. B, Compaction to 867-foot depth and subsidence of bench mark P999 at well 20/18—6D1i o z j 230 3 320 360 I: Z Hydrograph, 1102 W u.i 400 '2 0 a E 440 O t: 1- 5’, 480 E 1% 520 0 A G LIJ LL E g Casing separation, 1102 and 03 (’3 < n. 2 O O 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 B FIGURE 67.—Hydrograph, casing protrusion, and casing separation, 20/ 18—11Q2 and 20/18—11Q3.A, Hydrograph of well 20/18—11Q2, perforated 755—805 feet. B, Casing protrusion (protrusion of the 11%-in. casing, 11Q2, above the land surface) and casing separation (vertical separation between the 113/4-in. casing, 11Q2, and the 4-ini casing, 11Q3). SAN JOAQUIN VALLEY, CALIFORNIA 3|— 9% 440 $2 480 gm- 520 <9 560 Eu. 0g 600 "w E0 640 Z 680 LU OS 8»- :iu-l 0 &E5 40 <31- a; so m8 (259(18 120 E5 160 0 if: 0—22001eet Ll.l U. Z 5' E \ g Bench 2833 o O 1959 1960 Change applied Bench 1966 1967 2998 1 968 1969 1 970 SUBSIDENCE, IN FEET 1961 1962 1963 1964 1965 C a 160 n: I 140 5 L” 120 o '2 . L! B 100 Stress-compaction -’ u. 3- 0 80 LL] ”- 40 o z E 20 5 o 0.0 0.5 1.0 1.5 2.0 2.5 COMPACTION, IN FEET D 3.0 3.5 4.0 4.5 H65 FIGURE 65,—Hydrograph, change in applied stress, compaction, subsidence, and stress— compaction relationship, 19/16—23P2. A, Hydrograph of well 19/16—23P2. B, Change in applied stress, water table assumed constant.C, Compactionto 2,200-foot depth atwell 19/16~23P2 and subsidence of bench marks Z888, 575 feet south-southwest, and 2998 at well 19/16-23P2. D, Stress change versus compaction of deposits above 2,20 0-foot depth. H64 STUDIES OF LAND SUBSIDENCE 120 160 240 280 320 360 DEPTH T0 WATER BELOW LAND SURFACE, IN FEET 80 120 160 200 240 280 320 DEPTH TO WATER BELOW LAND SURFACE, IN FEET 40 80 1 20 1 60 200 CHANGE IN APPLIED STRESS, IN FEET OF WATER ,_ g a Z M7Sfeet E 1 z Z _ 9 markA51 (U3 ’— 2 E a. D 2 <7; 8 1967 1968 1969 1970 g (I) D (/5 U) Em 100 BE 80 Stress-strain D< W3 31:. 60 D. :10 <1- 40 ZLIJ ;E 20 (52 z— o ‘ -. g —10123456789x10 o STRAIN E FIGURE 64,—Hydrographs, change in applied stress, compaction, subsid- ence, and stress-strain relationship, 18/19—20P. A, Hydrograph of well 18/19—20P1 (lower zone), perforated 647—687 feet.B, Hydrograph of well 18/19—20P2 (upper zone), perforated 497—537 feeti C, Change in applied stress (upper zone), water table assumed constant. D, Compaction to 578-foot depth at well 18/19—20P2 and subsidence of bench mark A516, one~half mile west. E, Stress change versus strain (347-fl: thickness)‘ SAN JOAQUIN VALLEY, CALIFORNIA H63 480 520 Hydrograph, 1401 640 680 720 DEPTH T0 WATER BELOW LAND SURFACE, IN FEET | 9 01 0,0 015 1.0 1.5 2.0 0—2315 feet COMPACTION, IN FEET 1969 1970 B FIGURE 62.—-Hydmgraph and com- paction, 17/15—14Q1. A, Hydrograph of well 17/15—14Q1, perforated 1,064—1,094 feet. B, Compaction to 2,315-foot depth in well 17/15—14Q1. 360 400 440 480 520 560 600 DEPTH T0 WATER BELOW LAND SURFACE, IN FEET ,_ m E z Compaction, 0—1029 feet 2 _ g 00 g ,_ 2 o 5 B E E Bench mark Y998 g ; O 1 O D - O U) 1964 1965 1966 1967 1968 1969 1970 B FXGURE 63.—Hydrograph, compaction, and subsidence, 18/16—33A1. A, Hydrog'raph of well 18/16—33A1, perforated SSS—1,070 feet. B, Compaction to 1,029-foot depth and subsidence of bench mark Y998 at well 18/16—33A1. H62 COMPACTION, IN FEET CHANGE IN APPLIED STRESSJN FEET OF WATER 1 958 100 80 40 20 140 STUDIES OF LAND SUBSIDENCE 1 959 F —-0.5 . 0 0 Casmg . 0—900 0.5 1.0 1.5 2.0 2.5 3.0 3.5 COMPACTION. IN FEET 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 G {WWW ..... Skew-compaction 2.0 2.5 3.0 3.5 4.0 ________ N “$0.an Stress-compaction 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 COMPACTION. IN FEEI' H FIGURE 61.——Continued. SAN JOAQUIN VALLEY, CALIFORNIA 3 1»- 1 o “1 6° 1 d E 200 Hydrograph 34N5 2 g 240 ' L13 3 440 E E 480 o g 520 E <0 560 o E z 600 g 5 640 o E E .1 E E 5 E Z L: (“3 E E z E O E m o '— LLI L|J LL Z i Q ’6 < n. 2 o o i— E LL Z ' Compaction, Z 9 l— o < a 2 o o [- ILI LIJ LL 2 . z- 6.0 IE 2 6.5 E E 7.0 “e: E 7.5 (L3 8 so a 8.5 g 9.0 ‘3 9.5 m 10.0 10.5 11.0 11.5 12.0 12.5 1958 1959 1 960 1961 1962 1963 1964 1 965 1 966 1967 1 968 1969 1970 E FIGURE 61.—Hydrographs, change in applied stress, compaction, subsidence, casing separation, and stress-compaction relationship, 16/15—34N. A, Hydrographs of wells 16/15—34N5 (water table), perforated 240-300 feet and 16/15—34N4 (lower zone), perforated 1,052—1,112 feet. BY Change in applied stress. C, Compaction to SOS-foot depth in well 16/15—34N3 and to 703-foot depth in well 16/15—34N2. D, Compaction in 503—703- foot-depth interval. E, Compaction to 703-f00t depth in well 16/ 15—34N2, to 2,000~foot depth in well 16/ 15—34N1, and subsidence of bench mark G1046 at well 16/ 15—34N3. F , Compaction in 703—2,000-foot-depth interval. G , Compaction to 1,096-foot depth and casing separation (compaction to 900-foot depth) in well 16/15—34N4. H, Stress change versus compaction of deposits in the 703—2,000-foot-depth interval. Figure continued on following page. H61 H6O STUDIES OF LAND SUBSIDENCE 240 280 320 360 400 440 480 SURFACE, IN FEET 1959 1960 1961 1962 1963 1964 1 965 1 966 1 967 1 968 1969 1970 DEPTH TO WATER BELOW LAND FIGURE 59,—Hydrograph of well 15/14—14J1, depth 1,010 feet. A O 80 120 160 200 240 280 Hydrograph, 31 N3 DEPTH TO WATER BELOW LAND SURFACE, IN FEET stress CHANGE IN APPLIED STRESS, IN FEET OF WATER I— I— w “d “L 05961661 “- z z z' 111’ g o 5 Bench vso9 E z 9, 5 9 8 1967 1968 1969 1970 u, C D E It. 7" Lu 1:: 60 Stress-compaction a. “- m < z I- a 9 Lu (0 U) LL (5 Lu 0 E n: 0 5 :7, o 0.1 0.2 0.3 0.4 COMPACTION. IN FEET D FIGURE 60i—Hydrograph, change in applied stress, compaction, subsid- ence, and stress-compaction relationship, 15/16—31N3. A, Hydrograph of well 15/16—31N3, perforated 497—537 feet, upper zone. B, Change in applied stress, water table assumed constant. C, Compaction to 596-foot depth at well 15/16—31N3 and subsidence of bench mark Y509, 220 feet north of 15/16—31N3. D, Stress change versus compaction of deposits above 596-foot depth. SAN JOAQUIN VALLEY, CALIFORNIA H59 g 360 3 L? 400 9 m g u. 440 E Z_ 480 LIJ L? g 520 g u. Hydrograph, 12H1 o ‘5 560 l' w I 600 E D 640 ._ LU u: LL 3 0.913 feet 5‘ 8' g E '1: < D m — LL (1. (I) 2 mark 12H1 a: Z O D O U) 1964 1965 1966 1967 1968 1969 1970 B FIGURE 57.— Hydrograph, compaction, and subsidence, 14/12—12H1. A, Hydrograph of well 14/12—121-11, perforated 740—936 feet. B, Compaction to 913-foot depth and subsidence of bench mark 12H1 at well 14/12—12H1. D Z S 480 3 520 m z 560 E —_ '5: (15: 600 g E 640 o E l- a) 680 E $ 720 0 A E {E 0—958 feet ,_ g H 2, LL 9 Z ,_ . 0 8 < z “- w 2 o o _ 0 g 8 1 964 1965 1 966 1 967 1968 1969 1970 B FIGURE 58.—Hydrograph, compaction, and bench-mark subsidence, 15/13—11D2.A, Hydrograph of well 15/13—11D2, perforated 900—960 feet. B, Compaction to 958-foot depth and subsidence of bench mark 15/13-11D2 at well 15/13—11D2. H58 STUDIES OF LAND SUBSIDENCE so g 120 S 160 EL: 200 .1“! u.I|-L 240 ”z (:1 280 mm :32 320 3E 360 93 400 (I) Hdror h,11D6 E 440 y gap 0. Lu 0 480 520 40 80 120 160 200 siress OF WATER CHANGE IN APPLIED STRESS. IN FEET —0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4,5 5.0 5.5 0—780 feet COMPACTION, IN FEET SUBSIDENCE. IN FEET 780—1358 feel COMPACTION, IN FEET 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 D 1 60 1 40 1 20 10° Stress-strain 60 40 20 CHANGE IN APPLIED STRESS, IN FEET OF WATER 8 —2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 43x10" STRAIN E FIGURE 56.— Hydrographs, change in applied stress, compaction, subsidence, and stress- strain relationship, 1M13—11D. A, Hydrographs of wells 14/13—11D3 (water table), perforated 180—240 feet, and 14/13—11D6 (lower zone), perforated 1,133—1,196 feet. 3‘, Change in applied stress. C, Compaction b0 780$oot depth in well 14/13—11D4, compaction to 1,358-foot depth in well 14/13—11D6, and subsidence of bench mark GW6 at well 1 4/13—11D6. D, Compaction in 780—1,358-font-depth interval. E, Stress change versus strain (578-11 thickness). SAN JOAQUIN VALLEY, CALIFORNIA H57 D Z 5 360 g m 400 .1 Lu 3 g 440 fi uj 480 O E ff 520 Hydrograph,2001 CE 9 8 560 I E 600 DJ D '— Lu LLI LL g 0—681 feet 2' 9 u] 5 \ 0.0 g [I E o 5 3 w 2 Bench mark A998 (7) u' o m z 0 1.0 3 w 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 B FIGURE 54i—Hydrograph, compaction, and subsidence, 13/12—20D1. A, Hydrograph of well 13/12—20D1, perforated 425665 feet. B, Compaction to 681~foot depth and subsidence of bench mark A998 at well 13/12—20D1. D Z 5 -40 3i— 0 2E“ .32 4o 5-. P8 so << 3E 120 o 1—3 160 E n. 200 Lu 0 A .. LLI LU LL E z' I.“ g 0-0 2.— 5 Bench mark 13/1543505 g E < 05 (7)“ E g; 8 1965 1966 1967 1968 1969 1970 w B FIGURE 55.—Hydrograph, compaction, and subsidence, 13/15—35D5. A, Hydrograph of well 13/15-35D5, perforated 3734333 feet. B , Compaction to 440-th depth and subsidence of bench mark 13/ 15—35D5 at well 13/15—35D5i STUDIES OF LAND SUBSIDENCE {I} an as a: O 120 160 200 240 280 320 DEPTH T0 WATER BELOW LAND SURFACE. IN FEET ,_ in E 0.350 feet E z" 9 l- o < D. 2 O O _ ~05 2 g E 0.0 350—500 (g) E 0.5 2 5 _ 8 1 .0 1 .5 C '_ o— m m E E _z_ E 2‘ Compaction, 0—1000 8 9 z '5 Bench mark 97.68 ‘ \ g < «7: a. a: g D o w ,_ Lu LIJ LL Z 2- 500—1000 feet 9 )— o < m 5 O O 1958 1959 1960 1961 1 962 1963 1964 1965 1966 1 967 1968 1969 1 970 E FIGURE 53.—Hydrographs, compaction, and subsidence, 12/12—16Hi A, Hydrographs of wells 12/12—16H5, perforated 670—712 feet, and 12/12—16H6, perforated 770—909 feet. B, Com- paction to 350-foot depth in well 12/12'16H3 and compaction to SOD-foot depth in well 12/12—16H4. C, Compaction in 350—500-foot-depth interval. D, Compaction to 500-foot depth in well 12/12—16H4, compaction to 1,000-foot depth in well 12/12—16H2, and subsidence of bench mark 97‘68(USBR), 330 feet south-southeast of well 12/12—16H2. E, Com» paction in 500—1,000-foot-depth interval. FIGURES 53—78 AND TABLE 8 H54 areas in central California: U.S. Geol. Survey Prof. Paper 497—A, 71 p. Lofgren, B. E., 1961, Measurement of compaction of aquifer systems in areas of land subsidence, in Geological Survey research 1961: U.S. Geol. Survey Prof. Paper 424—B, p. B49—B52. 1968, Analysis of stresses causing land subsidence, in Geological Survey research 1968: U.S. Geol. Survey Prof. Paper GOO—B, p. B219—B225. 1969, Land subsidence due to the application of water, in Varnes, D. J ., and Kiersch, George, eds., Reviews in Engineering Geology, v. 2: Boulder, Colo., Geol. Soc. America, p. 271—303. 1975, Land subsidence due to ground-water withdrawal, Arvin—Maricopa area, California: U.S. Geol. Survey Prof. Paper 437—D, 55 p. Lofgren, B. E., and Klausing, R. L., 1969, Land subsidence due to ground-water withdrawal, Tulare-Wasco area, California: US. Geol. Survey Prof. Paper 437—3, 103 p. Meade, R. H., 1964, Removal of water and rearrangement of particles during the compaction of clayey sediments— review: U.S. Geol. Survey Prof. Paper 497—B, 23 p. . 1967, Petrology of sediments underlying areas of land subsid- ence in central California: U.S. Geol. Survey Prof. Paper 497—C. 83 p. 1968, Compaction of sediments underlying areas of land subsidence in central California: U.S. Geol. Survey Prof. Paper 497—D, 39 p. Miller, R. E., Green, J. H., and Davis, G. H., 1971, Geology of the compacting deposits in the Los Banos—Kettleman City subsidence area, California: U.S. Geol. Survey Prof. Paper 497—E, 46 p. Mitten, H. T., 1972, Ground-water pumpage, San Joaquin Valley, California, 1967—68: U.S. Geol. Survey open-file report, 6 p. Mitten, H. T., and Ogilbee, William, 1971, Ground-water pumpage in parts of Merced, Madera, Fresno, Kings, and Tulare Counties, California, 1962—66: U.S. Geol. Survey open-file report, 8 p. Ogilbee, William, and Rose, M. A., 1969a, Ground-water pumpage in STUDIES OF LAND SUBSIDENCE Kern County, San Joaquin Valley, California, 1962—66: U.S. Geol. Survey basic-data compilation, 5 p. 1969b, Ground-water pumpage on the west side of the San Joaquin Valley, California, 1962—66: U.S. Geol. Survey basic- data compilation, 7 p. Page, R. W., and LeBlanc, R. A., 1969, Geology, hydrology, and water quality in the Fresno area, California: U.S. Geol. Survey open-file report, 193 p. Poland, J. F., and Davis, G. H., 1969, Land subsidence due to with- drawal of fluids, in Varnes, D. J ., and Kiersch, George, eds., Reviews in Engineering Geology, v. 2: Boulder, Colo., Geol. Soc. America, p. 187—269. Poland, J. F., and Evenson, R. E., 1966, Hydrogeology and land subsidence, Great Central Valley, Calif, in Bailey, E. H., ed., Geology of northern California: California Div. Mines and Geology Bull. 190, p. 239—247. ' Poland, J. F., Lofgren, B. E., and Riley, F. S., 1972, Glossary ofselected terms useful in the studies of the mechanics of aquifer systems and land subsidence due to fluid withdrawal: U.S. Geol. Survey Water-Supply Paper 2025, 9 p. Riley, F. S., 1969, Analysis of borehole extensometer data from cen- tral California, in Tison, L. J ., ed., Land subsidence, v. 2: Internat. Assoc. Sci. Hydrology Pub. 89, p. 423—431. 1970, Land-surface tilting near Wheeler Ridge, southern San Joaquin Valley, California: U.S. Geol. Survey Prof. Paper 497—G, 29 p. Riley, F. S., and McClelland, E. J ., 1972, Application of the modified theory of leaky aquifers to a compressible multiple-aquifer sys- tem: U.S. Geol. Survey open-file report, 96 p. Wood, P. R., and Dale, R. H., 1964, Geology and ground-water features of the Edison-Maricopa area, Kern County, California: U.S. Geol. Survey Water-Supply Paper 1656, 108 p. Wood, P. R., and Davis, G. H., 1959, Ground-water conditions in the Avenal—McKittrick area, Kings and Kern Counties, California: U.S. Geol. Survey Water—Supply Paper 1457, 141 p. SAN JOAQUIN VALLEY, CALIFORNIA H53 TABLE 7 .—Tent'ative elastic storage parameters [Numbers in parentheses are provisional] Fig. Well or site Storage coefficient Thickness of Average No. No. component, S ke compacting specific storage (dimensionless) interval component, S, ske Remarks (in (ft‘ 1v 60 15/16—3N3 ________________ 1.06 X 10'“ (276) (3.8x 10's) Upper zone. 64 18/19—20P2 ________________ 1.2><10'8 347 3.4><10‘6 Do. 70 23/25—16N ________________ 0.64 X 10‘8 330 1.9 X 10"3 Interval 430—760 ft. 71 __________ d0 ______________ 0.7 X 10'3 100 7.0 x 10'“ Interval 330—430 ft. Sum for site 16N ________ 1.3x 10'3 430 Interval 330—760 ft. 72 24/26—34F1 ________________ 2.5><10'3 (1,310) (1.9X10'“) 74 25/26-1A2 ________________ (0.6x 10'3) __________________ May still be transient value. 1When stress is expressed in feet of water and unit weight of water=1, the numerical value on the average compressibility (it"y of the compacting interval equals the average specific storage component. Riley (1969, p. 427) used the stress-compaction plot for a 405-foot thickness at Pixley (the 355—760 ft-depth zone) to obtain Ske which he found to be 1.15 X 10‘3. The com- ponent of the storage coefficient for the depth interval 330—355, which Riley did not include in his estimate, is 7X10—5ft—1 x25 feet or 0.18x10*3. Adding this ele- ment to Riley’s 1.15X10—3 gives 1.3: x10—3, which is the sum of the two components of the storage coefficient given for 23/25—16N in table 7. In short, the elastic stor- age parameters in table 8 are consistent with Riley’s (1969). The rising artesian head in the aquifers of the lower zone in the Los Banos—Kettleman City area is rapidly reducing the pore-pressure differential between aqui- fers and aquitards, and hence the graphs showing a large rise in head from 1968 through 1970 also show a very marked decrease in rate of compaction. As the artesian head continues to recover, the pore pressures in the aquifers at some sites are (1973) approaching values equal to the pore pressures in the central parts of the thicker aquitards. When the aquifer pressures ex- ceed the aquitard central pore pressures, the response of the system will be wholly in the elastic range. At that time, elastic parameters can be derived from stress compaction plots for the lower zone—the main confined aquifer system. The required head recovery will be greatest where the aquitards are thickest, all other factors being equal. REFERENCES CITED Bull, W. B., 1964a, Alluvial fans and near-surface subsidence in western Fresno County, California: US. Geol. Survey Prof. Paper 437-A, 71 p. 1964b, Geomorphology of segmented alluvial fans in western Fresno County, California: US. Geol. Survey Prof. Paper 352—E, p. 89—129. 1972, Prehistoric near-surface subsidence cracks in western Fresno County, California: US. Geol. Survey Prof. Paper 437—0, 85 p. 1975, Land subsidence due to ground-water withdraWal in the Los Banos—Kettleman City area, California. Part 2, Subsidence and compaction of deposits: U.S. Geol. Survey Prof. Paper 437—F, 90 p. Bull, W. B., and Miller, R. E., 1975, Land subsidence due to ground- water withdrawal in the Los Banos—Kettleman City area, California. Part 1, Changes in the hydrologic environment con— ducive to subsidence: U.S. Geol. Survey Prof. Paper 437-E, 71 p. Bull, W. B., and Poland, J. F., 1975, Land subsidence due to ground- water withdrawal in the Los Banos—Kettleman City area, California. Part 3, Interrelations of water-level change, change in aquifer-system thickness, and subsidence: U.S. Geol. Survey Prof. Paper 437—G, 62 p. California Department of Water Resources, 1963, Ground-water con- ditions in central and northern California, 1959—60: California Dept. Water Resources Bull. 7 7—60. 1964a, Design and construction studies of shallow land subsid- ence for the California Aqueduct in the San Joaquin Valley— Interim report, California Dept. Water Resources, 130 p. 1964b, Ground-water conditions in central and northern California, 1960—61: California Dept. Water Resources Bull. 77—61. California Division of Water Resources, 1931, San Joaquin River Basin: California Div. Water Resources Bull. 29, 651 p. Croft, M. G., 1972, Subsurface geology of the Late Tertiary and Quaternary water-bearing deposits of the southern part of the San Joaquin Valley, California: US. Geol. Survey Water-Supply Paper 1999—H, 29 p. Davis, G. H., and Green, J. H., 1962, Structural control of interior drainage, southern San Joaquin Valley, California, in Geological Survey research 1962: US. Geol. Survey Prof. Paper 450—D, p. D89—D91. Hotchkiss, W. R., and Balding, G. 0., 1971, Geology, hydrology, and water quality of the Tracy-Dos Palos area, San Joaquin Valley, California: US. Geol. Survey open-file report, 107 p. Ingerson, I. M., 1941, The hydrology of the southern San Joaquin Valley, California, and its relation to imported water supplies: Am. Geophys. Union Trans, pt. 1, p. 20—45. Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1955, Proposed program for investigating land subsid- ence in the San Joaquin Valley: Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, Sacramento, Calif, 60 p. 1958, Progress report on land-subsidence investigations in the San Joaquin Valley, California, through 1957: Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, Sac- ramento, Calif, 160 p. Johnson, A. I., Moston, R. P., and Morris, D. A., 1968, Physical and hydrologic properties of water-bearing deposits in subsiding H52 surface bench mark located at the measuring site, de- termined by periodic instrumental surveys to a stable bench mark, are also included for all or part of the period of compaction measurement. Table 8, also at the end of this report, supplies pertinent notes on the indi- vidual graphs. Site locations are shown in figure 50. With respect to the objectives of the cooperative study of land subsidence, the primary purpose of including these records is to show graphically the measured com- paction and the subsidence at specific sites, and, so far as possible, the change in effective stress in the perti- nent aquifers at these sites, as indicated by the hydro- graphs. Because of confining beds and multiple- aquifer-aquitard systems, it is difficult to obtain water- level measurements that one can be confident represent the mean stress and stress change for the interval in which compaction is being measured. At each of several sites, one to three additional observation wells would be needed to define the magnitude of head change, if any, in aquifers 100—200 feet below the water table. Howeve- r, funds for exploring the variation in head with depth have been limited. Change in applied stress and stress-compaction or stress-strain relationships are plotted for 14.of the 26 figures. In these figures, compaction equals the change in thickness of the compacting interval, and strain re- fers to the unit change in thickness or the compaction divided by the thickness of the compacting interval. Of the 14 relationships included, 7 are in the Los Banos— Kettleman City area, 5 are in the Tulare-Wasco area, and 2 are in the Arvin-Maricopa area. Change in applied stress was plotted for each site where the meas- urements of depth to water were considered to define, at least approximately, the change in applied stress on the aquifer-system thickness interval being measured by the extensometer. .At sites where both the water table and the artesian head were measured, as at 16/15—34N (fig. 61) and 23/ 25—16N (figs. 70, 71), the computer program made use of the equation cited on page 44 to determine the change in applied stress. At sites where changes in the water table were not known or were assumed to be 0, the plot of _ change in applied stress is identical in direction and magnitude to the change in artesian head (plotted as depth to water) because (1) both are expressed in feet of water and (2) the change in stress in the confined system is solely a change in seepage stress, with magnitude equal to the change in vertical distance between the water table and the artesian head. (See p. 43; fig. 45.) _ Stress-compaction plots are included for six wells in which the measured water-level change is considered to be representative for the compacting zone being meas- ured but where the thickness of the compacting zone is not known. For example in well 15/16-31N3 (fig. 60), STUDIES OF LAND SUBSIDENCE the extensometer measures change in thickness be- tween the land surface and the anchor at a depth of 596 feet. Inspection of the electric log (not shown) suggests that the deposits to a depth of 320 feet below land sur- face probably are not experiencing as much change in stress as is indicated by the hydrograph and may not be experiencing any change in stress. The hydrograph does represent change in applied stress in the depth interval 320—596 feet, and the compacting interval is at least 276 feet thick. At least one additional observation well would be required, however, to resolve the question of whether any compaction is occurring above the 320-foot depth. If it is, at least two additional wells would be required to define magnitudes of change in stress. The stress-compaction plot for 16/ 15—34N (fig. 61H) is an exception because the thickness of the compacting zone is known (1,297 ft), and hence a stress-strain plot could have been made. Stress-strain plots are included for seven wells in which the measured water-level change is considered to represent change in applied stress throughout the com- pacting zone being measured and where the thickness of the compacting zone is known. For example, at site 23/25—16N (fig. 70), the extensometers in wells N3 and N1 measure change in thickness between the land sur- face and the anchors at depths of 430 and 760 feet, respectively. The deposits between depths of 430 and 760 feet are 330 feet thick and are affected by the stress change defined by the hydrographs for wells N3 and N4. Therefore, on the stress-strain plot for this site and depth interval (fig. 70E ), the strain has been computed as measured compaction divided by 330 feet of thick- ness. Elastic storage parameters are given in table 7 for five sites, based on the stress-compaction or stress- strain plots for the respective sites. All these plots have hysteresis loops developed during the elastic response range of stress change. The storage parameters are computed following the example given on page 50 for site 18/ 19—20P2. In table 7, the first two sets of parame- ters are for principal parts of the upper zone in the Los Banos—Kettleman City area; the other three are for sites in the Tulare-Wasco area. At well 15/16—31N3, 596 feet deep, the thickness of the compacting interval is at least 276 feet. If any compaction is occurring at a shal- lower depth than 320 feet, the average specific storage component, Sske, would be reduced accordingly. At site 23/25—16N, the storage coefficient component of the aquifer system skeleton, Ske, for the bottom inter- val 330 feet thick about equals that for the overlying interval 100 feet thick, and for the two intervals to- gether, Ske =1.3 X 10—3. Thus, the average specific stor- age component for the 100-foot interval, 7 X 10’6 ft—l, if four times as large as that for the 330-foot interval. SAN JOAQUIN VALLEY, CALIFORNIA H51 14° _1960 1961 1962 1963 F— 120 — — E’ 100 — ~ it 80 — No record (L5 60 — ——————— ,_ 4o — . J 11$: 20 g Stress-compaction a Z 0 l l I | I I J | | | l | | l | l l l 4 | | l | l w- 2.0 2.5 3.0 3.5 4 o g} COMPACTION, IN FEET CE (’7) 0 E .1 k 140 < 1964 1965 1966 1967 1968 1969 1970 Z 120 l— H “J _ o 100 E 80 _ I o 60 H 40 Stress-compaction _ 20 — o 4.5 5.0 5.5 6.0 6 5 7.0 7 5 a 0 COMPACTION, IN FEET FIGURE 51.—Stress change versus compaction at 16/15—34N (for the depth interval 703—2,000 ft, 240 l , lel to the dotted lines) represents the average slope of ,_ the straight-line segments in the elastic range of stress. LLI _ . . . ”LL” 7 The rec1procal of the slope of the hne is the component of .2. 200 _ the storage coefficient attributable to elastic deforma- 5 tion of the aquifer-system skeleton, Ske’ and equals g: — 1.2X10“3. The component of average specific storage 0 due to elastic deformation, Sske’ equals Slag/347 feet or 2 16° , _ 3.4X10_6ft_1. The average elastic compressibility of 1- .' - $ 367'], , M the skeleton, ,Bk, IS a , 1968 1969/ 1970 ' l l S k =3.4><10—6ft—1/0.433 1b in ‘2 ft‘1=8><10‘61b1n‘2 120 I l J . l l l I s e o 2 4 6 8 10x10" I STRAIN 1 0 0.1 0,2 03, where yw is the unit weight of water. In consistent units, COMPACTION, IN FEET FIGURE 52.—Stress change, compaction, and strain, well 18/19—20P2. by the irrigation withdrawals and remain constant. The yearly fluctuation of water level caused by the seasonal irrigation demand and the permanent compaction that occurs each summer when the depth to water is greatest produces a series of stress-strain loops. The lower parts of the descending segments of the irrigation-year loops for the three winters 1967—68 to 1969—70 are approxi- mately parallel straight lines (the four dotted lines are drawn parallel), indicating that when the depth to water is less than about 180 feet, the response (expan- sion or compaction) of the system is essentially elastic in both aquifers and aquitards. The heavy dashed line in the 1968 loop (drawn paral- however, when stresses are expressed in feet of water and 'ywzl, Bk=Sske=3.4x10—6 ft-l. Thus, at this site, the value of the elastic storage parameters can be close— ly approximated through use of the stress-strain plot after only 2—3 years of record. Because maximum sea- sonal stresses increased only slightly during this period of record, the inelastic response characteristics of the aquifer system to significant increased stresses cannot be calculated from this record. COMPUTER PLOTS OF FIELD RECORDS The records of compaction and of depth to water in the extensometer wells or in nearby observation wells have been computerized on a daily basis, and computer plots of these records through 1970 are included as figures 53—78 at the end of this report. Graphs of subsidence of a H50 STUDIES OF LAND SUBSIDENCE TABLE 6.—Annual compaction rates at compaction-measuring sites, San Joaquin Valley [In order to arrive at consistent sums, the amount of annual compaction is shown to a thousandth of a foot; however,many of the measured yearly rates are not accurate to less than a few hundredths of a foot] W Anchor depth Depth mg)“; d ell when installed interval Start Of 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 su . number (it) (it) recordl compggztion Los Banos—Kettleman City area 12/12—16H3' ______ 350 0— 350 5/19/58 0,053 —0.004 0.013 0.036 0.005 0.008 0.007 0.002 0.004 0.002 0 0.002 0.180 16H4 . . 500 350— 500 5/19/58 .087 .019 .002 .008 .003 .011 .013 .011 .013 .015 .008 .007 .229 16112 _ . 1,000 50(L1,000 5/19/58 .302 .293 .325 .158 .187 .173 .066 .125 .105 .075 .060 .060 2.140 16112 . . 1,000 0—1,000 5/19/58 .442 308 .340 .202 .195 .192 .086 .138 .122 .092 .068 .069 2.549 13/12—20D1 . , 681 0— 681 10/10/61 , ___ 077 .340 .215 .119 .182 .120 .094 .074 .056 .032 1.309 13/15—35D5 W , 440 0— 44 5/13/66 . _ . W. . W .......................... v.022 .014 .022 .006 .034 .054 14/12—12H1 W _ , 913 0— 913 1/10/65 . - - ........................ .414 .336 .239 .139 .097 .164 1.389 14/13—11D4 , . 780 0— 780 1/1/61 ,,,,, .310 .196 .222 .199 .108 .194 .160 .071 .001 .013 1.474 11D6 .W 1,358 780—1,358 5/25/61 ,,,,, .354 .462 .259 .400 .322 .279 .326 .157 .073 .078 2.710 11D6 .._ 1,358 0—1,358 5/25/61 ,,,,,, .480 .658 .481 .599 .430 .473 .486 .228 .074 .091 4.000 15/13—11D2 W _ 958 0— 958 1/11/65 ............................... .204 .154 .126 .099 .060 .047 .690 15/16—31N3 W _ 596 0— 596 3/23/67 .................................... .088 .120 .092 .032 .332 16/15—34N3 . _ 503 0— 503 9/25/58 .093 .087 .138 .082 .082 .085 .090 .101 .130 .112 1.224 34N2 . . W 703 503— 703 9/25/58 .123 .191 .167 .172 .104 .104 .122 .118 .046 .077 1.724 34N1 W , 2,000 703—2,000 9/25/58 .717 .867 .697 .710 .634 .614 .604 .573 .812 .202 7.902 34N1 _ 2,000 0—2,000 9/25/58 .933 1,145 1.002 .964 .820 .803 .816 .792 .488 .391 10.850 34N4 W 1,096 0—1,096 8/16/60 .232 .661 .648 2 .416 .................................... 1.957 16/15~34N43 900 0— 900 9/15/64 ,,,,,,,,,,,,,,,,,,,,,,,,,, .358 .320 .340 .334 .233 .210 1.795 17/15—14Q1 _ 2,315 0—2,315 11/4/69 ..... , ........................................... .079 .478 .557 18/16—33A1 .. 1,029 0—1,029 3/10/65 ,,,,,,,,,,,,,,,,,,,,,,,,, .128 .210 .186 .124 .034 .094 .776 18/19—201’2 _ 578 0— 578 3/24/67 .................................... .026 .070 .036 .065 .197 19/16—23P2 . 2,200 0—2,200 1/2/60 .508 .660 .553 .378 .259 .552 .355 .328 .201 .192 4.410 20/18—6D1 867 0— 867 1/11/65 ............ , _ ._ ............ .273 .267 .280 .179 .090 .121 1.210 11Q1 710 0— 710 7/24/64 A. _ _ .................. .115 .259 .240 .225 .224 .149 .145 1.357 11Q2“ 845 0— 845 2/27/63 W _ _ ,,,,,, ,4 _ _ .230 .330 .300 .330 .290 .280 .220 .190 2.170 11Q2 845 710— 845 7/24/64 u _ _ ................... .025 .041 .090 .065 .056 .071 .045 .393 11Q3 1,930 845—1,930 2/27/63 ,,,,,,,,,,,,,,, 261 .212 .357 .240 .199 .259 .207 .160 1.895 11Q3 , 1,930 0—1,930 1/1/63 ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, .611 .542 .657 .570 .489 .539 .427 .350 4.185 TulareoWasco area 23/25—16N4 .. . 250 O— 250 6/24/59 ,,,,,, 0.005 0.024 0.024 0.008 0.007 0.022 0.009 0.001 0 0.003 —0.002 0 0.101 16N3 . _ 430 250— 430 6/24/59 ,,,,,, .055 .100 .062 .120 .042 .080 .048 .085 .003 .057 .005 .033 .690 16N1 . 760 43(L 760 6/24/59 ,,,,,,, .184 .433 .473 .051 .056 .253 .131 .225 .063 .160 .036 .100 2.165 16N1 , . 760 [L 760 4/18/58 04454 482 .557 .559 .179 .105 .355 .188 .311 .066 .220 .039 .133 3.648 24/26—34F1 , 1,510 0—1,510 1/21/59 ,,,,,, .242 .100 .111 —.051 .018 .063 -.025 .068 —.031 .038 —.057 .038 .514 36A2 , 2,200 0—2,200 5/12/59 _ .059 .342 .333 .059 .096 .329 .062 .145 —.045 .168 —.060 .143 1.631 25/26—1A2 892 0» 892 4/6/59 ...... .058 .061 .059 —.013 - 004 .050 -.003 .096 —.012 .018 — 001 .014 .323 Arvm-Maricopa area 32/28—20Q1 W... .. 970 0— 970 4/11/63 ________________________ .192 0.365 0.178 0.255 0.219 0.124 0.124 0.095 1.552 12N/21W—34Q1 .. 810 0— 810 6/2/60 ______ 0.207 0.326 0.271 .209 .186 .266 .197 .130 .014 .186 .153 2.145 11N/21W—3Bl. .. . WW . .. 810—1,480 4/12/63 ,,,,,,,,,,,,,,,,,,,,,,,, .188 .261 .135 .229 .184 .344 .152 .149 1.642 3131 ,,,,,, 1,480 04,480 4/12/63 ,,,,,,,,,,,,,,,,,,,,,,,, .326 .447 .401 .426 .314 .358 .338 .302 2.912 ‘Date when stabilized installation began giving acceptable record. 2Compaction to June 11, 1963. 3Compaction based on protrusion of 4-inch casing. the end of each calendar year indicates the yearly mag- nitude of compaction. The decrease in applied stress beginning late in 1968, reflecting the recovery in arte- sian head due to surface-water imports and reduction in ground-water withdrawal, has had a notable effect on the rate of compaction: 0.2 foot in 1970 compared with 0.87 foot in 1961. (Also see table 6.) The stress-compaction plot has moved consistently to the right throughout the period graphed, indicating that the compaction recorder has not registered net expansion at any time. Even during times of rapid de- crease in applied stress (rapid increase in head), such as late in 1961 and 1962 and even during the 80-foot de— crease in stress since August 1968, the rate of elastic expansion of the aquifers and of the outer parts of the aquitards has not been sufficient at any time to exceed the rate of continuing compaction of the central parts of the aquitards. However, at least three times in 1969—70 during periods of decrease in applied stress, the stress- compaction curve has been essentially vertical, indica- ting that the elastic expansion was about equal to the continuing compaction during those intervals of head increase. This suggests that pore pressures in the aqui- fers are approaching pore pressures in the central parts of the thicker aquitards. Under these transient condi- tions, one cannot derive either the elastic or the virgin parameters of storage and compressibility. In contrast to figure 51, the stress-strain relations shown in figure 52 have been largely in the elastic range of stress application since the start of the record in 1967. Well 18/19—20P2, 17 miles west of Hanford (fig. 50), is 578 feet deep. Depth to water is plotted increasing up- ward, representing increasing stress. Change in depth to water represents change in effective stress in the aquifers in this confined aquifer system, which is 347 feet thick, from 231 to 578 feet below the land surface. It is assumed that the water table and pore pressures in thin aquifers above the 231-foot depth are not affected SAN JOAQUIN VALLEY, CALIFORNIA H49 1 20 ' 1 1 9 ° 1 1 8 ° T | 1 5 S 37° — ._ River ©20 1' oHan”ord (91 1 Q?! _ 3 "ll'ulai e 360 _ ’ 33:-. J Keltlefm City g! _ .. v ¢ EXPLANATION R 15 E Delanools 1 A; 1K2 Outline of valley ’9 _ E: Drawn chiefly on boundary % ' Wasco 3% of consolidated rocks C%\ Type of observation well 0 Water level .. O I ‘. Extensometer T . ©16H2'6 R 20 E W 11 d( ) t t MT DIABLO BASE e an or ex ensome er SAN BERNARDINO T 1‘ N 35. _ ““mber BASE T11 N — 0 10 20 30 40 MILES t_'_l_f_rlfl_l__—J 0 10 20 30 40 KILOMETRES J | l Base from US. Geological‘Survey 1:1,000,000, State base map, 1940 The record from the multiple-depth installation indi- cates the magnitude and rate of compaction, not only within the well depths but also within the depth inter- vals between well bottoms. Figure 51 is a plot of com- paction for the depth interval 7 03—2,000 feet below land FIGURE 50.—Water-level and compaction measuring sites. surface versus the change in applied stress in this inter- val, as represented by change in water level in well 16/15—34N4 (fig. 61A, B). The interval compacted 7.9 feet from 1958 through 1970 (table 6; fig. 61F). The horizontal distance between the vertical lines drawn at H48 were in the Los Banos—Kettleman City area, 6 in the Tulare-Wasco area, and 3 in the Arvin-Maricopa area. Water levels were being measured in 21 of these wells and in 4 supplementary wells. Bull (1975, table 1) gave supplementary information for the 22 wells in the Los Banos—Kettleman City area. Several improvements in measuring equipment have been made since the first installation in 1955. Figure 49 is a diagram of the re- cording compaction gage and illustrates the general type of equipment used in the later installations. Figure 50 shows the location of the 31 sites where water-level changes and compaction of the water- bearing deposits are currently being measured. Table 6 summarizes the net annual compaction rate (in feet per year) at each of the 31 sites through 1970 and also gives compaction in 8 additional depth intervals defined by multiple-depth installations. For example, at 12/ 12- 16H, wells H2, 3, and 4 are respectively 1,000, 350, and 500 feet deep. The extensometer in well H2 records total compaction from land surface to the 1,000-foot depth, and the extensometer in H4 measures the compaction from land surface to the 500—foot depth. By subtracting the compaction in H4 from that in H2, the compaction of the 500—1,000-foot-depth interval is calculated. Water- /Recorder Sheaves mounted in teeter bar ‘ 1.,Compaction tape /Stee| table Cou nterweights VCIamp Concrete slab Bench mark: Cable, 1/8-inch stainless/f steel, 1 x 19 stranded ' . reverse lay Well casing .3”, 4-13 inches Anchor weight, _'\"‘ zoo-300 pounds\fl 3: FIGURE 49.—Recording compaction gage. STUDIES OF LAND SUBSIDENCE level and compaction data from these sites are plotted and interpreted by computer and are monitoring the characteristics and changes of the aquifer system at these selected locations. The maximum recorded compaction of 10.85 feet from September 1958 through 1970 occurred at well 16/15— 34N1, which is 2,000 feet deep and is adjacent to the California Aqueduct in the joint-use reach in western Fresno County. Four wells in the Tulare-Wasco area showed negative compaction in certain years. For example, the record for well 24/26—34F1 shows negative compaction in the 4 years 1962, 1965, 1967, and 1969. In other words, the extensometer registered net expansion of the measured interval (0—1, 510 ft) during each of those 4 years. Fig- ure 72 shows depth to water (A), change in applied stress (B), measured compaction (C), and a stress- compaction plot (D) for this well. Inspection of graphB indicates that in each of these 4 years the applied stress at yearend was less than at the beginning. Evidently the elastic expansion due to the net decrease in stress was larger than any continuing compaction of the cen- tral parts of the thicker aquitards. Hence the aquifer system showed net expansion for each of these years. By 1967, the stress change being applied was wholly in the elastic range. In the 4 years 1967—70, the net expansion of the aquifer system was 0.012 foot. INTERRELATIONS OF WATER-LEVEL CHANGE, COMPACTION, AND SUBSIDENCE EXAMPLES OF STRESS-STRAIN GRAPHS Field measurements of compaction and correlative change in water level serve as continuous monitors of subsidence and indicators of the response of the system to change in applied stress. They also can be utilized to construct stress-strain curves from which, under cer- tain favorable conditions, one can derive storage and compressibility parameters of the aquifer system, as demonstrated by Riley (1969). Two examples will serve to illustrate the stress-strain relations obtained from the measuring sites in the San Joaquin Valley and the significance of these curves. Figure 51 depicts the stress-strain relations at a site where compaction of the aquifer system has continued uninterrupted since 1958 and there has been no net expansion of the measured interval at any time. The other, figure 52, shows stress-strain relations since 1967 at a site where aquifer-system response has been in the elastic range of stressing (expanding when the stress is decreased) when the depth to water has been less than about 180 feet. At site 16/15—34N, on the west side of the valley 18 miles south of Mendota (fig. 50), compaction is recorded in three adjacent wells, 503, 703, and 2,000 feet deep. SAN JOAQUIN VALLEY, CALIFORNIA TABLE 5.—Surface-water imports from the F riant-Kern Canal and the California Aqueduct to the Arvin-Maricopa area, 1962—72 [Deliveries, in thousand acre-feet] Year Friant-Kern Canal California Aqueduct1 Combined 1962 ____________ 9.8 ______ 9.8 1963 ____________ 15.9 ______ 15.9 1964 ______________________________ 1965 ____________ 8 8 ______ 8.8 1966 ............ 43.7 ______ 43.7 1967 ____________ 85.5 ______ 85.5 1968 ____________ 54.6 ______ 54.6 1969 ____________ 176.8 ______ 176.8 1970 ____________ 143.0 ______ 143.0 1971 ____________ 149.5 100.9 250.4 1972 ____________ 62.5 185.0 247.5 Total ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, 1,036.0 ‘South of Buena Vista Pumping Plant. be beneficial in decreasing effective stress on the con- fined system. Also, if recharge can be accomplished by injection through wells directly in the confined system, the pressure buildup will be directly beneficial. If, however, the recharge from the imported water percolates down to a water table in unconfined or semiconfined deposits overlying a compacting confined aquifer system, as occurs in most of the principal subsid- ing areas in the San Joaquin Valley, any buildup of the overlying water table will be nonbeneficial with respect to the confined system. The water-table rise will have the net effect of increasing stress applied to the confined system by 0.2 foot per foot of rise. (See page 44.) Thus, in much of the area now being supplied with imported water, the net change in effective stress on the confined aquifers is the result of two opposing compo— nents, a recovery of artesian head in the confined sys- tem due to the decrease in pumping and a rise of an overlying but hydraulically separate water table due to recharge by imported water moving down through the unsaturated zone. Because the recovery of artesian head decreases the effective stress 1 foot per foot of head rise, whereas the water-table rise increases the effective stress only 0.2 foot per foot of water—table rise (for the parameters assumed earlier), each 1 foot of artesian head rise offsets 5 feet of water-table rise. Furthermore, the recovery of artesian head is very substantial as shown by several of the graphs (figs. 8—11, 23, and sev- eral of the computer plots), but the rise in water table (not shown) is small. In the Los Banos—Kettleman City area, for example, the hydrograph for well 16/15—34N4 (fig. 61A; for loca- tion, see fig. 50) shows artesian-head recovery of about 80 feet from mid-1968 to the end of 1970, whereas the water table in well 16/15—34N5 (fig. 61A) rose only 2 feet in the 21/2 years. Hence, at this site, the effective stress on the confined aquifer system decreased by about 80 feet during the 21/2-year period. The general recovery of . artesian head in 1969 through 1971 produced a drama- H47 tic decrease in the rate of subsidence. (See figures 12, 16.) In the Tulare-Wasco area, recovery of artesian head northeast of Delano has been as much as 230 feet since 1950 (fig. 23). At the same site, the rise in the water table has been about 90 feet. Thus, the effective stress on the confined aquifers decreased about 210 feet in the 20 years. Even though 12 feet of subsidence occurred in this general area from 1926—54 (Lofgren and Klausing, 1969, fig. 43) and shows as a 12-foot subsidence “hole” on the long-term subsidence map of 1926-70 (fig. 27), subsidence from 1962 to 1970 was negligible (figs. 23, 24). ' MEASUREMENT OF COMPACTION Two principal objectives of the cooperative program with the California Department of Water Resources on land-subsidence studies, and essential elements of the Federal program on mechanics of aquifer systems, are to determine the depth interval(s) in which compaction is occurring and to measure the magnitude and the time distribution of the compaction where possible. Such in- formation, together with periodic measurement of land subsidence as determined by spirit-level surveys to sur- face bench marks, is essential to determining the cause of subsidence and for monitoring the magnitude and the change in rate of subsidence. Also, when coupled with measurement of water-level or head change in the stressed aquifer systems, these data supply the param- eters required for stress-compaction or stress-strain analysis. As an initial step in developing techniques for measuring compaction, the Geological Survey installed the first equipment to record compaction in well 19/17— 35N1, 16 miles northwest of Kettleman City in 1955. The equipment constituted a heavy weight lowered to the bottom of the well (2,030 ft below land surface) on an attached cable that was counterweighted at the land surface to maintain constant tension. Compaction was measured continuously by a recorder mounted over the casing and attached to the downhole cable. Both the equipment and the record of compaction to the autumn of 1960, when the cable failed because of corrosion, have been described by Lofgren (1961, p. B49—B51 and figs. 24.1, 24.2; also see Bull and Poland, 1975, fig. 11). In 4.8 years, measured compaction within the 2,030-foot- depth interval was 3.8 feet, or 82 percent of land-surface subsidence of 4.6 feet in the same period. Because of the success of the first installation, in 1958 the Survey began installing a large number of compac- tion recorders (extensometers) in selected wells in the valley. Companion water-level recorders also were in- stalled wherever possible to measure the change in applied stress. By the end of 1961, 18 extensometers were operating, and by 1969 there were 31. Of these, 22 H46 into the Kern River channel from the Friant-Kern Ca- nal, began in 1962 and undoubtedly have affected sub- sequent water levels on the north margin of the subsid- ence area. Deliveries from the Friant-Kern Canal to the Arvin-Edison Water Storage District on the eastern and southern part of the area south of the Kern River began in 1966 and have since been a major source of water supply. Then in 1971, deliveries from the Califor- nia Aqueduct replaced much of the ground-water pump- ing around the south and west margins of the area. In 1971 the combined importation from the Friant-Kern Canal and California Aqueduct was 250,000 acre-feet (table 5), or about 40 percent of the annual pumpage of ground water from the subsiding area from 1962 through 1964 (Lofgren, 1975, table 6). In 1972, a year of low precipitation and runoff in California, the combined importation decreased to 247,500 acre-feet, but import- 125°lllllllllllllllllllllllll ._ _ LU _ Emoo— - ”a 1 II 0 < D ‘2’ 0:750 _ 3 O I I- E @500 — I uJ Z _l Lu 0 2' 2250 — < 0 0 23 a 8 a .2 z 22 2 2 2 2 2 FIGURE 47.—Surface-water deliveries from the Friant-Kern Canal to irrigation districts in the Tulare-Wasco area, 1949—72. (Data in thousand acre-feet per calendar year, from US. Bureau of Reclamation.) TABLE 4,—Summary of surface-water deliveries from the Friant—Kern Canal to irrigation districts in the Tulare-Wasco area, 1949—72 [In thousand acre-feet per calendar year; data from US. Bureau of Reclamation. Imports through 1964 given by district in Lofgren and Klausing, 1969, table 3] Year Delivery Year Delivery Year Delivery 1949 ______ 31 1957 ______ 788 1965 ______ 1,137 1950 ______ 163 1958 ______ 800 1966 ______ 660 1951 ______ 304 1959 ______ 724 1967 ______ 870 1952 ______ 412 1960 ______ 441 1968 ______ 519 1953 ______ 573 1961 ______ 374 1969 ______ 809 1954 ______ 627 1962 ______ 1,096 1970 ______ 722 1955 ______ 724 1963 ______ 1,042 1971 ______ 693 1956 ______ 868 1964 ______ 638 1972 ______ 533 Total" 15,548 STUDIES OF LAND SUBSIDENCE ation through the California Aqueduct increased 85' percent from 1971. Total imports from 1962 through 1972 equaled 1,036,000 acre-feet (table 5). The importation of surface water to replace mining of ground water has two effects, not necessarily entirely beneficial, with respect to subsidence alleviation. The immediate effect is to reduce or eliminate pumping of ground water in the area of surface-water delivery, causing the artesian head to rise in the zones experien- cing reduced pumping. This effect is wholly beneficial because it reduces seepage stresses and hence effective stresses. The second effect of importation is to increase recharge because any imported water that seeps through the soil zone and reaches the water table, whether from stream channels, canals, ditches, or field irrigation is a net increase to the ground-water supply. This increase tends to raise the water table. If the re- charge is accomplished in deposits in hydraulic con- tinuity with a compacting confined system, such as the recharge (intake) area for that system, then buildup of the water table will be transmitted to the confined sys- tem as a pressure increase. This pressure increase will 3°°|||||1|1ll|llll|ll| 250 — —_ _ California Aqueduct (southwestern pan of area)\ B E u; 200 — — I: 0 < O z < a) 8 Friant—Kern Canal 13-: 15° _ (southeastern part of area)\ § — E. s s E \ 2 \ —- \ g 100 — § — 21 s z 5 s \s 50 “‘ §§ — Friant-Kern Canal \§ (northern part of area) §§ \ o 1 l I l l I Wg / I l B 8 3 E 2 2 2 2 FIGURE 48.—Surface-water imports to the Arvin-Maricopa area, 1962-72. SAN JOAQUIN VALLEY, CALIFORNIA down to the prior maximum effective-stress level with- out inducing appreciable compaction and subsidence. Effects of secondary consolidation, due to internal pro- cesses that continue after pore pressures reach steady state, are not considered in this discussion. Remedial action to raise water levels can be ac- complished by reducing ground-water pumpage or in- creasing recharge, or both. In an area that has been intensively developed agriculturally by overdraft of the ground-water supply, reduction of pumping does not occur until pumping lifts or well yields become un- economic, water quality becomes unusable, an adjudi- cation of water rlghts is reached through legal proce- dures, or until water is imported. As of 1972, surface water was being imported into all three principal subsiding areas in the San Joaquin Val- ley (fig. 3). These imports now constitute a large part of the applied irrigation water in each area and have re- placed much of the ground-water withdrawal of prior years. Therefore, a brief summary of the quantity of imports to each of the subsiding areas follows. Imports to the northern part of the Los Banos— Kettleman City area began in 1951 when the Bureau of Reclamation completed the Delta-Mendota Canal. Sup- plemental water from that canal has been used only in the northern part of the area (north of the midline of T. 14 S. (fig. 4). Surface-water deliveries from the Sacramento—San Joaquin Delta through the joint-use reach of the California Aqueduct to the San Luis service area of the Bureau of Reclamation (for location, see Bull and Poland, 1975, fig. 40) began in 1967 (table 3). This service area occupies most of the Los Banos—Kettleman city area west of Fresno Slough and, as of 1967, utilized 930,000 acre-feet of ground-water pumpage—about 90 percent of the total ground-water pumpage in the area (Mitten, 1972). Imports to the service area through the 104-mile Federal-State joint-use reach of the California Aqueduct (fig. 46) increased from 19,000 acre-feet in 1967 to 650,000 acre-feet in 1971. Of this 1971 total, 450,000 acre-feet was used on cropland downslope from the aqueduct, and 200,000 acre-feet was used upslope. Deliveries through 1971 were most extensive north of T. 17 S., but by December 1971 water was being deliv- ered throughout the aqueduct joint-use reach to Ket- tleman City, although no distribution laterals had been completed south of T. 19 S. These importations have had a very significant effect on water levels because several hundred irrigation wells have been shut down. The artesian head for the lower zone rose about 60 feet from December 1967 to December 1971 and slowed subsid- ence rates substantially during that period. (See figs. 12, 16.) Deliveries in 1972 rose to 865,000 acre-feet, 93 percent of the estimated ground-water pumpage from the San Luis service area in 1967. Surface-water imports into the Tulare-Wasco area H45 from the Friant-Kern Canal of the Bureau of Reclama- tion began in 1949 and since the early 1950’s have served as a supplemental irrigation supply to irrigation districts throughout the area (fig. 47). Cumulative im- ports to yearend 1972 were 15.5 million acre-feet. (See table 4.) As noted earlier (Lofgren and Klausing, 1969, fig. 14, table 3), Friant-Kern Canal deliveries, on the average, represent roughly 80 percent of the total surface-water inflow to the Tulare-Wasco area and have had a marked effect on both the ground-water pumpage and subsidence rates through the years. Imports into the Arvin-Maricopa area since 1962, from the Friant-Kern Canal and the California Aqueduct, are shown in figure 48. Deliveries to the Rosedale—Rio Bravo Water Storage District, released TABLE 3.—Surface-water deliveries through the joint-use reach of the California Aqueduct to the Los Balms—Kettleman City area, 1967—72 [In thousand acre-feet per calendar year; data from US Bureau ofReclamatiun. Deliveries are to San Luis serv1ce area and include water pumped from Mendota Pool by Westlands Water District] Total Part from Mendota Pool Year deliveries included in total 1967 ______________________ 19 18 1968 ______________________ 209 26 1969 ______________________ 306 15 1970 ______________________ 478 15 1971 ______________________ 650 23 1972 ______________________ 865 23 1ooo Illllllll '— LLI LLI LL E750— — O < 0 Z < U) I) o I r-soo— — E (D E CE LIJ 2 _l LU 02550— — _J < Z < 0 ol ID 0 N (D N l\ O) O) 0) FIGURE 46,—Surfacevwater imports from the joint-use reach of the California Aqueduct to the Los Banos—Kettleman City area, 1967—72. (Imports include water from Mendota Pool but exclude deliveries from Delta-Mendota Canal; data from US. Bureau of Reclamation.) H44 STUDIES OF LAND SUBSIDENCE 0 s = Stress due to unsatu- rated deposits ' ' 5‘ Water table Potgflgggigtnc b 17 b = Stress due b 200 “HO-O ”HO-OH”- l0 SUD- merged Potentiometric ii Unconfined deposits surface u.| aquifer s. 0000 ooooobooooo 3 LL Z A " 400 I' W E Confimn bed LIJ o A 600 — J Confined aquifer Aquitardt M W 800 l system | \L l 1 \G \LD 0 200 400 600 0 200 400 600 STRESS, IN FEET OF WATER A. WATER TABLE AND POTENTIOMETRIC SURFACE COMMON STRESS, IN FEET OF WATER B. WATER TABLE CONSTANT. POTEN- TIOMETRIC SURFACE LOWERED FIGURE 45.—Effective stress for a confined aquifer system overlain by an unconfined aquifer. change in seepage stress (differential between water table and potentiometric surface of confined system) is — 1.0 foot, and so the net unit change in applied stress in the confined system is —O.2 foot of water. Conversely, if the water table is raised, the net change in applied stress is +0.2 foot per foot of rise. In summary, water-level fluctuations change effec- tive stresses in the following two ways: 1. A rise of the water table provides buoyant support for the grains in the zone of the change, and a decline removes the buoyant support; these changes in gravitational stress are transmitted downward to all underlying deposits. 2. A change in position of either the water table or the artesian head, or both, may induce vertical hy- draulic gradients across confining or semiconfin- ing beds and thereby produce a seepage stress. This stress is algebraically additive to the gravita- tional stress that is transmitted downward to all underlying deposits. A change in effective stress results if preexisting seepage stresses are altered in direction or magnitude. The change in applied stress within a confined aquifer system, due to changes in both the water table and the artesian head, may be summarized concisely (Poland and others, 1972, p. 6) as Apa = _(Ahc _AhuYs), where pa is the applied stress expressed in feet of water, he is the head (assumed uniform in the confined aquifer system, hu is the head in the overlying unconfined aquifer, and Y8 is the average specific yield (expressed as a decimal fraction) in the interval of water-table, fluctuation. In the San Joaquin Valley, the areas in which subsi- ence has been appreciable coincide generally with the areas in which ground water is withdrawn chiefly from confined aquifer systems (figs. 1, 4; also Poland and Davis, 1969, fig. 32). Furthermore, the great increases in stress applied to the sediments in the ground-water reservoir by the intensive mining of ground water have developed chiefly as increased seepage stresses on the confined aquifer systems. METHODS FOR STOPPING OR ALLEVIATING SUBSIDENCE Studies of land subsidence in California and in other parts of the world furnish conclusive evidence that de- crease in artesian head increases effective stress, caus- ing compaction of sediments and correlative land sub- sidence (Poland and Davis, 1969). Conversely, increase in artesian head decreases effective stress and slows or stops land subsidence. In a compacting confined system, if fluid pressures in the aquifers are increased, the rate of subsidence will decrease; if fluid pressures in the aquifers are increased sufficiently to eliminate all ex- cess pore pressures in the aquitards, subsidence will stop. If artesian head declines for several years, causing compaction, and subsequently the head fluctuates sea- sonally with about the same maximum stress applica- tion (depth to water) each year, compaction will con- tinue, but the annual rate of net compaction will gradu- ally decrease until hydraulic equilibrium is reached— until pore pressures in the fine-grained beds attain steady state with pressures in adjacent aquifers. Com- paction (and subsidence) will then stop. (Parameters determining the time required to reach equilibrium are on page 40.) If the artesian head in the system then recovers to a higher level, it can subsequently be drawn SAN JOAQUIN VALLEY, CALIFORNIA H43 21 Assumptions table 6‘ n =0.4O . Head 2 00% reduction, 3 a I)", g =2.7 confined 9: (o 200 H aquifer % / system ’9}; p’=p—uw O Unconfined 4'“ aquifer 400 —— . —__ —_*._._~.~_______ l— ,1 w Confining .‘ l u. bed // Z '74 2 # _ _ _ .i _ E \ D. Z 2 \ 5‘ 600 .4 Confined \ aquifer Fluid \ system ( le \ Effective \ (p l \ 800 ~~———————— Aquitard 1000 ‘ ' ' | SECTION 200 400 600 PRESSURE, IN POUNDS PER SQUARE INCH 800 FIGURE 44.—Pressure for unconfined aquifer and confined aquifer system; head reduction, confined aquifer system only. deposits increases directly with depth below the water table, as indicated by the increasing vector lengths, b, at the base of the confining bed and the top of the aquitard. If the potentiometric surface of the confined aquifer system is drawn down 100 feet as in diagramB, gravita- tional stresses remain as inA because the water table is unchanged. However, a downward hydraulic gradient is developed across the confining bed, which induces downward movement of water through the pores and exerts a viscous drag on the grains. The force trans- ferred to the grains at any depth is measured by the head loss to that depth. The stress so exerted on the grains in the direction of flow is called a seepage stress. This third effective stress component, represented by vector J, is algebraically additive to the gravitational stresses and is transmitted downward through the confined aquifer system. The solid vectors to the right of diagramB indicate the net change in effective stress at the base of the confining bed and below, from the hydro- static condition of diagram A. Because the water table is unchanged, the net change is the change in seepage stress, which is equal to the decrease in fluid (neutral) pressure represented by line C—F (base of aquiclude). The increase in effective stress in the permeable aquifers occurs simultaneously with decrease in head, but decrease of pore pressure in aquitards and confining beds is delayed because of their high compressibility and low permeability. During this period of transient pressures, the effective stress can increase only as rapidly as the excess pore-pressure decreases. The gen- eral pattern of decay is illustrated in diagramB—in the confining bed by dashed line B—E—F and in the aquitard by dashed line H—I—J. Full dissipation of excess pore pressures to equilibrium (dashed lines B—F and H—J) may require months or years. Note that water drains through both boundaries of the aquitard, but only through the lower boundary of the confining bed under the specified conditions. If the potentiometric surface of the confined aquifer system remains constant and the water table is lowered or raised, both gravitational and seepage stresses change, but with opposite sign (not illustrated in fig. 45, but see Lofgren and Klausing, 1969, fig. 52). For exam- ple, if the water table is lowered and the parameters are as assumed earlier, the change in gravitational stress is + 0.8 foot of water per foot of lowering; however, the unit H42 STUDIES OF LAND SUBSIDENCE 119°30’ 119°15’ 119°00’ 118°45’ R. 23 E. R. 24 E. R. 25 E. R. 26 E. R. 27 E. R. 28 E. \ €00- \ T~ Butt nwillow \ \ 29 \- S. a T. 30 S. 35 ° 1 5’ T. 31 S. EXPLANATION T. 32 E S. . Unconsohdated deposits T. 12 V N. m T Semiconsolidated rocks 1 1 N. 35°00’ Consolidated rocks -— —- 0.2 — —- T. Line of 0.2 foot of sub- 10 sidence 1962— 65 N 0.30 . . ., Line'ofequal subsidence/ R. 24 w. R. 23 w. R- 22 W R‘ 2‘ W' R. 20 w. R. 19 w. R' 18 w. Pumpage ram . 0 5 10 MILES 0.19 Base from U.S. Geological Survey Central 0 5 1O KILOMETRES Computed subsidence/ Valley. California, South Area, 1:250,000 1958 CONTOUR INTERVAL 100 FEET pumpage ratio for quarter township DATUM IS MEAN SEA LEVEL FIGURE 43.—Proportion of pumpage derived from water of compaction, 1962—65, in the Arvin-MariCOpa area. gren (1968) on the analysis of stresses causing land subsidence and also in part from Bull and Poland (1975). Diagram A of figure 45 illustrates part of a confined aquifer system containing an aquitard, overlain by a confining bed and an unconfined aquifer. The water table and the potentiometric surface of the confined system are initially at the same depth; hence, fluid pressure at all depths is hydrostatic. If we assume an average porosity, n, of 40 percent, an average specific gravity, G, of 2.70 for the grains, an average specific retention, rs, of 0.20, and let the unit weight of water be unity, then the effective unit weight of moist deposits above the water table, 7,”, equals 1.8 feet of water per foot of thickness: ym=[G(1—n)+rs]'yw or [2.7(1—O.4)+0.20]1=1.8 Also, the effective submerged, or buoyant, weight of saturated deposits, 7b: equals 1 foot of water per foot of thickness: 7b =(1 —n)(G — 1)‘yw or (1 —0.4)(2.7—1)1 = 1.0 If these gravitational stresses are expressed in feet of water (1 ft of water = 0.433 lb in ‘2, they can be added directly to hydraulic 'stresses. Vectors to the right of diagram A (fig. 45) represent the two components of effective gravitational stress at three depths. At the 400-foot depth, for example, the stress due to the unsaturated deposits, 3, equals 200 feet of thickness times 1.8, or 360 feet of water; the stress due to the buoyant weight of submerged deposits, b, equals 200 X 1.0, or 200 feet of water. The sum of s +b, or ' 560 feet of water, is the grain-to-grain stress at this plane of reference. The effective stress of the saturated H41 SAN JOAQUIN VALLEY, CALIFORNIA 120°00' 120° 30' tratford FRESNO X1 131] RIVER Madera .-_/"‘\RI:V3r_..r ., m» T m m s.“ N m rm.“ M C Eirgbaug h / 0.4 to 0.6 >0.6 EXPLANATION Boundary of deformed rocks 0 2 Line of equal subsidence/ pumpage ratio 15 MILES 15 KILOMETFlES Kettleman City l 10 36°30’ 36°00’ Base from US. Geological Survey Central Valley map, l:250.000, 1958 FIGURE 42.—Proportion of pumpage derived from water of compaction, 196&66, in the Los Banos—Kettleman City area‘ changes in terms of gravitational and seepage stresses, in the direction of flow is a seepage stress. We have found it quantitatively convenient in treating complex which are algebraically additive. The following brief aquifer systems to compute effective stresses and stress discussion is largely summarized from a paper by Lof- H40 F Maricopa R326 STUDIES OF LAND SUBSIDENCE F; Mettler Y826 0 1935-39 base ‘ 19412 ‘ SUBSIDENCE, IN FEET VERTICAL SCALE GREATLY EXAGGERATED 7/? 9 I l | l l l | o 4 8 12 1e 20 24 28 DISTANCE, lN MILES FIGURE 41.—Profiles of land subsidence F-F' along the Maricopa Road, Maricopa to Mettler, 1935—39 to 1970. where becomes effective only as rapidly as pore pressures decay toward equilibrium with those in adjacent aqui- p' = effective stress (effective overburden pres- fers. (See dashed pore-pressure lines of fig. 44, where mt sure or grain-to-grain load), represents the excess pore pressure at time t.) Attain- . In nt r - r ' i r' m ' p 2 total stress ( geost at1c pressure), and e of po 9 p essure equil b m (dotted lines) may uw = pore pressure (fluid pressure or neutral stress). The lowering of artesian head in a confined aquifer system, for example, from depth zlto 23 in figure 44, does not change the geostatic pressure appreciably. There- fore, the increase in effective stress in the confined aquifers is equal to the decrease in fluid pressure. The compaction in these is immediate and is chiefly recover- able if fluid pressure is restored, but usually it is small. On the other hand, in the aquitards (fine-grained interbeds) and confining beds, which have low vertical permeability and high specific storage under virgin stressing, the vertical escape of water and the adjust- ment of pore pressures is slow and time dependent. Hence, in these fine-grained beds the stress increase applied by the head decline in the confined aquifers take months or years; the time varies directly as the specific storage and the square of the draining thickness and inversely as the vertical hydraulic conductivity of the aquitard or the confining bed. Although not illustrated in figure 44, it is readily apparent that increase of fluid pressure from a steady- state condition decreases effective stress and causes expansion of the pressurized sediments (as in subsid- ence control and underground waste disposal). Fluid pressure cannot exceed geostatic pressures without causing uplift of the overburden. The stress relations of figure 44 serve to illustrate the principle of effective stress, but do not emphasize the hydrodynamic cause of compaction. Actually, the down- ward hydraulic gradient developed across the confining bed by the head decline induces downward movement of water through the pores that exerts a Viscous drag on the clay particles. The stress so exerted on the particles SAN JOAQUIN VALLEY, CALIFORNIA E Bakersfield 1926 base H39 E' Grapevine K54 1935—39 SUBSIDENCE, IN FEET VERTICAL SCALE GREATLY EXAGGERATED Data adjusted for 1952 I fault uplift fl | I i I ,0 I I I 0 4 8 16 20 24 32 DISTANCE, IN MILES FIGURE 40,—Profiles of land subsidence E—E’ along U.S. Highway 99, Bakersfield to Grapevine, 1926—70. The subsidence/pumpage ratio was computed for all unit areas enclosed within or crossed by the 02-foot line of equal subsidence for the 1962—64 period (shown in figure 43). The method of computation was the same as has been described for the Los Banos-Kettleman City area. The ratio map so obtained (fig. 43) is remarkably similar in shape to the longer term subsidence maps for the area. The ratio, which is the proportion of water pumped in the 3 years that was derived from compaction of the ground—water reservoir, ranges from 0.01 (1 per- cent) at several points around the perimeter of the sub- siding area to more than 40 percent in the area of maximum subsidence. The subsidence/pumpage ratios of figure 43 are a rough indication of the recharge characteristics of the ground-water reservoir. Where recharge is adequate, little or no long-term water-level decline or associated subsidence occur and subsidence/pumpage ratios are small, even though pumping may have been substan- tial. In the central part of the subsiding area, however, water levels have declined rapidly in response to pump- ing, and as much as 40 percent of the water is mined from the compressible beds. ANALYSIS OF STRESSES CAUSING SUBSIDENCE Increase in effective stress (grain-to-grain load) is the cause of compaction of sediments. Change in stress can be examined in terms of total, fluid, and effective stresses, the classical method, or solely in terms of effec- tive stresses. There are advantages to each approach. The idealized pressure diagram of figure 44 utilizes the classical method to illustrate the stresses that cause subsidence (Poland and Davis, 1969, p. 194). The with- drawal of water from wells reduces the head in the aquifers tapped and increases the effective stress borne by the aquifer matrix. In 1925, Terzaghi introduced the theory of effective stress, p=p'+uw STUDIES OF LAND SUBSIDENCE I I 8 I Probable rate \ (estimated) I Average for period \ (computed) r m o | \ \ I SUBSIDENCE RATE, IN THOUSANDS OF ACRE FEET PER YEAR 8 I I / I—I’——/7‘—I I 1930 1940 1950 1960 1920 1970 FIGURE ill—Rate of subsidence in the Arvin-Marlowe area. 1926-70. ‘2 I | I I | 0.8 - 0.6 — 0.4 — VOLUME OF SUBSIDENCE, IN MILLIONS OF ACRE-FEET 4L.”-+/ I I I 1930 1940 1950 1960 1970 0 1920 FIGURE 38.—Cumulative volume of subsidence in the Arvin-Maricopa area, 1926—70. Points indicate times of leveling control. subsidence, is increased by the barrier effect of the fine-grained deposits beneath Tulare Lake bed which inhibit recharge from the east. In the remainder of the mapped area of figure 42, the ratio is irregular, without any specific pattern. Nearly all the recharge moves southwest across the trough (Fresno Slough) as underflow. Subsidence decreases rapidly to the east of Fresno Slough, as historic head- decline decreases. Therefore, as would be expected, the ratio is less than 0.2 along much of the valley trough. The two central areas along Fresno Slough where the ratio is greater than 0.4 are irrigated chiefly with sur- 10 I I 8 _\.\ _ In \ E 6 — - — Z \ uf o . z .. \ Q 4 __ /Planimetered acreage with- _ 8 in the lines of equal sub- : \ sidence for fig. 36 In 2 -— \.\ — Volume, 1.06 million '\ \ acre-feet \ \ l I I l \ 0 0 1 2 3 4 5 AREA, IN HUNDRED THOUSAND ACRES FIGURE 39.—Relation of magnitude to area of subsidence, 1926—70, Arvin-Marieopa area. face water. For this reason the ground-water pumpage is low, which explains the high ratio. In several areas bordering the foothills, the ratio is less than 0.2. These low ratios are related chiefly to small values of subsidence in an area where the subsidence/head-decline ratio has been very low (Bull and Poland, 1975, fig. 32), even though the historic head decline has been many hundreds of feet. In general, water wells adjacent to the foothills tap older deposits than wells to the east at equal depths. These older deposits have substantially lower average compres- sibilities than the younger deposits to the east, and therefore the subsidence/pumpage ratios also tend to be low. The total pumpage from the area for which the subsidence/pumpage ratio is mapped in figure 42 was about 3.7 million acre-feet in the 3 years. The subsid- ence in the same area was about 1.1 million acre-feet. Thus, the average “water of compaction” for the 3 years was approximately 30 percent of the pumpage. ARVIN-MARICOPA AREA 'In the Arvin-Maricopa area, the pumpage and subsidence were compared for the 3-year period March 1962 to March 1965. Pumpage estimates (Ogilbee and Rose, 1969a) are available for this exact period, and a subsidence map is available from leveling of the bench-mark net by the National Geodetic Survey in January 1962 and March 1965 (Lofgren, 1975, pl. 4C). SAN JOAQUIN VALLEY, CALIFORNIA H37 119°30' 119°15' 119°00' 118°45’ a. 23 E. R. 24 E. R. 25 E. R. 26 E. R. 27 E. R. 23 E. R. 29 E R. 30 E. R. 31 E. Soarfing' T- Buttanillow ", 21% 29 . / I" ”2 S- ; @QSQKER Ens x ~3- _ y“ ‘- \\\;\\.\ . gi!“L~" .. "- g E: i" i”??? 30 . / : r- {V Greenfield 35‘15’ T. 31 a Buena Vista gfi 99 EXPLANATION E Unconsolidated deposits i . » Mari opa 500 N 700—\ 35°OO’ .. Semiconsolidated rocks \Whee er Ridge" 900 Consolidated rocks ’o // °o\ 2 T /4°oo° Line of equal subsidence 10 "ogooo\_ Interval I-foot N E E’ . . .. .. . .. Alinement of subsidence R. 24 w. R. 23 w. n. 22 w. R. 21 w. R. 20 w. R 19 w. R- ‘8 W~ profiles 0 5 10 MILES Profiles shown in figures Base from US. Geological Survey Central 0 5 10 KILOMETRES 40 and 41 Valley, California, South Area, 1:250,000 1958 K367 CONTOUR INTERVAL 100 FEET X DATUM IS MEAN SEA LEVEL Bench mark and number FIGURE 36.—Land subsidence, 1926—70, and location of subsidence profiles, Arvin-Maricopa area. Compiled chiefly as the sum of (1) approximated subsidence from 1926 to 1957 from level- ing data of the National Geodetic Survey along US. Highway 99 and along Maricopa Road and (2) 1957—70 subsidence from figure 35. numbers. The ratio values, entered in the center of each unit area, were then contoured to construct the lines of equal subsidence/pumpage ratio shown in figure 42. The ratio in figure 42 ranges from less than 0.2 to more than 0.6, indicating that the percentage of pump- age derived from "water of compaction” ranged from a few percent to more than 60 percent. This ratio is re- lated to the recharge characteristics of the compacting aquifer systems in the subsiding area and to the mag- nitude of delayed compaction occurring in response to prior water-level decline. In figure 42, the ratio exceeds 0.6 both near the north end and at the south end of the map. In the northern area between Los Banos and Mendota where the ratio exceeds 0.6, the subsidence was small, ranging from 0.3 to 1.0 foot in the 3 years, and was largely in response to earlier head decline. But the pumpage also was small because much of this area is irrigated with surface water. Therefore the ratio far exceeded unity in some unit areas where pumpage was very small. In the southern area between Kettleman City and Stratford, the subsidence ranged from 0.4 to 2.0 feet in the 3 years. In several of the unit areas, pumpage was very small, in part because of surface-water irrigation from the Kings River. In years of abundant surface-water supply, the ratio would be higher than in years of deficient supply because the quantity of ground water pumped varies more significantly than the subsidence on a year-to- year basis. Also, the rate of water-level decline in re- sponse to pumping in this area, and hence the rate of H36 STUDIES OF LAND SUBSIDENCE 119°30’ 119“15’ 119°00’ 118°45’ R. 23 E. R. 24 E. R. 25 E. R. 26 E. R. 28 E R. 29 E. R. 30 E. . R. 31 E. T- Butt nwillow S. ‘ k % :mx KER} 35°15’ T. 31 EXPLANATION E Unconsolidated deposits a. 24 w. R. 23 w. R- 22 W- R- 2‘ W' 0 Base from US. Geological Survey Central 0 5 Valley, California, South Area, l:250,000 1958 N Semiconsolidated rocks 7 00/ Goo \Whee er Ridge” 900 Consolidated rocks 2.0— — Line of equal subsidence Dashed where approx- imat'e. Interval 1.0 for foot except 0.5-foot line .1 . R. 20W. R. 19W. R 8W 5 10 MILES 10 KILOMETRES CONTOUR INTERVAL 100 FEET DATUM IS MEAN SEA LEVEL FIGURE 35.-—Land subsidence, 1957—70, Arvin-Maricopa area. Compiled from leveling of the National Geodetic Survey, January—February 1957 and January to May 1970. 1935—39 base and was most rapid from 1959 to 1965, averaging about 0.5 foot per year. From 1965 to 1970 the rate of subsidence averaged 0.38 foot per year. RELATION OF SUBSIDENCE TO PUMPAGE Recently, quantitative estimates of ground-water pumpage for agricultural use, based chiefly on metered electric power consumption and computed average power per acre-foot, have become available for the years 1962—66 (Ogilbee and Rose,1969a; Mitten and Ogilbee, 1971). These estimates provide the data to compare areally the volumes of subsidence and pumpage for a common 3-year period in both the Los Banos— Kettleman City and the Arvin-Maricopa areas. From these data, subsidence/pumpage ratio maps have been derived, this ratio being an approximation of the proportion of pumpage derived from water of compac- tion (assumed equal to the subsidence volume). LOS BANOS—KE'ITLEMAN CITY AREA In the Los Banos—Kettleman City area, the pump- age and subsidence were compared on an areal basis for the 3-year periodlMarch 1963 to March 1966. In this appraisal, pumpage (Ogilbee and Rose, 1969b) was summed by unit area for the 3 years 1963—65 (agricul- tural power year Aprill—March 31),expressed in feet of water. The average subsidence for the same period (Bull, 1975, fig. 13), derived from leveling of the bench-mark net by the National Geodetic Survey in March 1963 and March 1966, was visually assigned to each unit area. A ratio of subsidence to pumpage was then derived for each unit area from the two sets of SAN JOAQUIN VALLEY, CALIFORNIA H35 119°30' 119°15' 119°00' 118°45' R. 23 E. R. 24 E. R. 25 E. R. 26 E. R. 28 E. R. 29 E R. 30 E. R. 31 E. ~/\\l>\3r\l ; Butt nwillow < _ /-,\A{-\’\ s. W QEQEQKERSFIE \ \- .- 'I 2% ' . \‘V 30 \\ so .‘ / 5 i s. 35°15’ T. 31 Buena Vista 300‘ Lake Bed ( EXPLANATION E Unconsolidated deposits 10‘ N. R24 w. R. 23 w. R- 22 W. R- 2‘ W‘ 0 Base from US. Geological Survey Central 0 5 Valley, California. South Area, l:250,000 1958 m Semiconsolidated rocks F.— 60° 700/ 000 \Whee er Ridg\e’ X900 Consolidated rocks ’0 co 00‘ —o.3 / {Goooxa Line of equal fgooo _ subsidence rate Interval 0.1 foot . ~. . . per year R. 1 W. R. 20 W. R. 19 W. 8 5 10 MILES 10 KILOMETRES CONTOUR INTERVAL 100 FEET DATUM lS MEAN SEA LEVEL FIGURE 34.—Average annual rate of subsidence, 1965—70, Arvin-Maricopa area. Based on control data of figure 33. As of 1970 the cumulative volume of subsidence since 1926 was 1.06 million acre-feet (fig. 38). About 80 per- cent of the subsidence has occurred since 1950, and 44 percent since 1960. Figure 39 illustrates that the area affected by subsid- ence as of 1970 is about 700 square miles (450,000 acres). About 500 square miles (320,000 acres) has sunk more than 1 foot, and 100 square miles (64,000 acres) has sunk 5 feet or more. The rate, magnitude, and distribution of subsidence are well displayed in subsidence profiles. Two profile alinements are shown for the Arvin-Maricopa area (for location, see fig. 36): one extends from Bakersfield south to Grapevine (fig. 40); the second, about perpendicular to the first, extends from Maricopa east along the Maricopa Road (fig. 41). In figure 40, the 1926 leveling used as a base was followed by partial releveling in 1935—39, 1942, and 1947 and then by six relevelings from 1953 to 1970 extending across the full 32-mile reach. The 1957 level- ing marked the establishment of the bench-mark net over the full subsiding area. The profiles demonstrate that the axis of maximum subsidence has shifted northward slightly through the years and in 1970 was close to bench mark L365. Maximum subsidence was insignificant until 1942, increased to an average rate of 0.35 foot per year in 1947—53, and 0.45 foot per year in 1959—62. The profiles of figure 41 extend 28 miles east from Maricopa to 3 miles east of US. Highway 99 and define an axis of subsidence at bench mark K367. Subsidence at this bench mark has been about 8.5 feet since the H34 STUDIES OF LAND SUBSIDENCE 119°30’ 119°00’ 118°45' R. 23 E. Fl. 24 E. R. 28 E. A» T- Butt nwillow . ‘ 29 . / 1.: S. \ §§g\\_ . _ Q "- T. . L: g 30 i E S. i "‘5 Gr® / / L 35 °15’ T. 31 ,3 S. W 6’ «9’ 0‘ / 303 .4K W EXPLANATION . rn - T. , /4/L§Re_ 32 "Mi/Bed S. 1,8’—\ . -400 o Unconsolidated T. 0 lq, ZZN deposrts 12 \\\\M/ / //7//\,—/-=V// “ N. X/r/Goo Mét’tler / (600 k T. 7 0° 7/ Semiconsolidated rocks 11 800 “700/ N 9 . \ 500 o I \Whee er Ridg\é‘ 35 00 \900 Consolidated rocks ¢o°°o\ 0.2 T. / @ooox. Line of equal subsidence 1"? goo \— lmerval 0.2 four R. 24 w. R. 23 W. R- 22 W- R' 21 w. .R. 20 w. ‘R. 19 w. H“ 18 w. B f U ‘ o 5 10 MILES ase rom .8. Geological Survey Central 0 5 10 KIL OMETRE S Valley, Calitomia, South Area, l:250,000 1958 CONTOUR INTERVAL 100 FEET DATUM IS MEAN SEA LEVEL FIGURE 33,—Land subsidence, 1965—70, in the Arvin-Maricopa area. Compiled from leveling of the National Geodetic Survey, March 1965 and January—May 1970. was about 700 square miles. Using the leveling data for pre-1957 subsidence and figure 35 for post-1957 subsid- ence, figure 36 is an approximation of the total man- made subsidence in the Arvin-Maricopa area. The total volume of subsidence is estimated to be 1.06 million acre-feet, based on planimetry of figure 36. The average rate of subsidence for the seven periods of leveling control beginning in 1926 is illustrated by the bar diagram of figure 37. . As already noted, bench marks along US. Highway 99 from Bakersfield to Grapevine were first leveled in 1926 and releveled periodically thereafter. The areal network was first leveled in 1957. To approximate the rate of subsidence for time intervals prior to 1957, the assumption was made that the volume of subsidence for the Arvin-Maricopa area increased proportionately to the respective areas under the 1926—57 subsidence profiles along US. Highway 99 (fig. 40). Thus, the three approximate rate bars of figure 37 prior to 1957 were derived from the respective estimated volumes. The four since 1957 were by planimetry of the subsidence maps. The probable rate (dashed line) increased about sixfold from 1942 to 1948, was fairly constant to 1959, and increased to the maximum rate of 60,000 acre-feet per year in 1960 (owing to very deficient rainfall and runoff in 1959—61). From 1962 to 1970 the yearly rate has been about 48,000 acre-feet. Up to the time of the 1970 leveling, no irrigation water had been delivered to the subsiding area through the California Aqueduct. Deliveries started in 1971 and water levels started to recover as a result of decreased pumping of ground water. As a result of decreasing stress, the subsidence rate began decreasing in 1971 as shown by the compac- tion record at well 11N/21W—3B1. SAN JOAQUIN VALLEY, CALIFORNIA H33 50 \/\/\ \ \Vf ’\ \ /N°" \ V k“ l y , 150 V V I_._. I I 3. I I NF I I or I I m or? vmm TI 9 I «m. dmxwm l o 9 8, mm? new nmmw ( I 0% I v I N _ _ _ o mmmo mm... $3 59 \I | I '1 I I l \\ mmmz «IS? Bx Sofia". cum—on. 9.3::me >25; :29; PEEP .Q Q .LEI':I:| NI 'BONBCIISGnS SAN JOAQUIN VALLEY, CALIFORNIA 200 l l l l Probable rate (estimated)\ ’7 A I" \\ 100 — — 150 — Average for period 50 — ted (oompu )\ / _ I /-—_ : l l 1930 1940 1950 1960 SUBSIDENCE RATE, IN THOUSANDS OF ACRE FEET PER YEAR O 1920 1 970 FIGURE 28.—Rate of subsidence in the Tulare—Wasco area, 1926—70. 3~5 I I | I I 3.0 — _ 2.5 — — 2.0 fl — VOLUME OF SUBSIDENCE, IN MILLIONS OF ACRE-FEET Estimated 1.0 ~ — o 5 — / — o /I I I I 1920 1 930 1940 1950 1960 1 970 FIGURE 29.—Cumulative volume of subsidence in the Tulare-Wasco area, 1926—70. Points indicate times of leveling control. Lofgren (1975) described the geologic and hydrologic setting, the history of water-level decline, the available records of subsidence, and the compaction that has been measured in several wells to 1970. The development of ground water south and east of the Kern River alluvial fan was described in some detail by Wood and Dale (1964). Although there was substan- tial development of ground water in the Arvin-Edison area by 1930, development in the area south of T. 31 S. was small until 1945. By 1950, most of the productive H31 ‘5 I I * '\ u.I E 10 _. — . \ U; o o \ 2 g ‘ Planimetered acreage within (7) 5 - \ / the lines of equal sub- " g - sidence for fig. 27 u: Volume. 3.32 miliior\. acre-feet . 0 2 4 6 8 10 AREA, IN HUNDRED THOUSAND ACRES FIGURE 30.—Relation of magnitude to area of subsidence, 1926—70, Tulare-Wasco area. land was under cultivation, and many wells had been drilled to depths of LOGO-1,500 feet. Figure 32 shows the water-level trend for three piezometers at 32S/28E—30D1 and the plot of subsidence at bench mark L365 near the center of the subsid- ing area (fig. 36). These piezometers, completed with well points at the depths indicated, were installed by the Bureau of Reclamation in 1952. The water levels in the three piezometers declined rapidly into 1957. The level in the shallow zone (No. 1) was about constant from 1957 to the end of record in 1961. The winter high water level for the intermediate zone (No. 2) at 611 feet declined 75 feet from 1957 to 1967 at a nearly uniform rate and then was about uniform into 1970. The level for the deep zone (No. 4) 1,220 feet below the land surface declined at roughly the same rate as No. 2 until 1962, although its peak water level was 2—3 months later than that in No. 2. In 1962, the level fell rapidly about 94 feet to 47 feet below the level in No. 2 piezometer, and the seasonal fluctuation nearly tripled, suggesting the onset of pumping draft from new and nearby irrigation wells. Since 1967, however, the winter high has been about constant. At bench mark L365, the average rate of subsidence (lower graph, fig. 32) for the period 1962- 65 was equal to that of 1953—57, but from 1965 to 1970 the average rate decreased noticeably in response to the lack of water-level decline in 1967—70. The latest leveling of the bench-mark net in the Arvin-Maricopa area was in 197 0. Figure 33 shows the magnitude and areal extent of subsidence for 1965—70. The maximum subsidence in the 5 years, centered 6 miles northwest of Mettler, was 2.2 feet (fig. 33). A small secondary center of 0.4 foot enclosed the town of Arvin. About 530 square miles of land subsided more than 0.2 foot in the period. The volume of subsidence in the 5 years was 230,000 acre-feet. The average annual rate of subsidence in this 5 years was 0.44 foot at the center (fig. 34). H30 STUDIES OF LAND SUBSIDENCE 119° 30' 119°15’ 119°00’ \ . | ' x37 e \ | I In \ lo I rum :\ \ : ”saw/(Q: 7:,” Jo \ 8i: : / “l I \\ \\ ‘ ‘ 3’“ \U’o: I I | I V I S' #2.: : ’ : I I I I a ,V’ "5H2 J h A I I I I — —————————————————— — -— ——— —|—————--——-I————— -———‘r ——— 7/ — ————— X] I E \ ' l/ “LIE/1’ I ‘22) [/0 T. Cor or I >9 I \>\I\_j_~" ”let I 23‘. ° I J" / \ :\,\ \ : “r- \ | T. 22 S. 36 00 \ ‘é‘. J «s17. ‘ EXPLANATION I I l .. . I D 23 \ : ’ I S- I : Unconsolidaled I I deposits ' I _____ _ _ _I V I k\\ .. ‘ I T. K399, IConsolidated sedimentary 24 \ I I rocks of Teniary age S. ~ I " . A V// _ N ' [I j Basement complex \ 35°45' ‘1 2 —-— T. \ Line of equal subsidence 25 Dashed where approxi- 5- mate. Interval 2feer, —————————————— F? _23 E” ‘ except for 1 foot con- ' ‘ tour T. ~ D D’ 286 Alinement of subsidence ' \ pmfile Profile shown in figure , _ 31 T. _ _ _ I 287 \ a w I \ IgmosoI xC825 . asco ‘ I . I CBPS \ Bench mark and number R. 22 E. Fl. 23 E. R. 24 E. R. 25 E. R. 26 E. Base from US. Geological Survey Central 0 2 4 6 8 MILES Valley map, 1:250,000. 1958 l—I—LH—I—JT; 0 2 4 6 8 10 KILOMETRES FIGURE 27.—Land subsidence, 1926—70, and location of subsidence profile, Tulare-Wasco area. Compiled from (1) 1948—70 subsidence (fig. 26 this report), (2) 1926—62 subsidence (Lofg‘ren and Klausing, 1969, fig. 50), and (3) 1962—70 subsidence (fig. 24 this report). based on planimetry of figure 27. Of this area, about 200,000 acres had subsided more than 5 feet, and 20,000 acres had subsided 10 feet or more. Land-subsidence profiles from Tulare to Famoso (fig. 31) illustrate subsidence along a 44-mile reach of the Southern Pacific railroad for 10 periods since 1931. Leveling for these profiles was by the National Geodetic Survey, and the 1931 control has been used as the refer- ence datum. Changes since the 1901—2 leveling of the Geological Survey are shown above the 1931 datum for the eight bench marks recovered in 1931. Maximum subsidence since 1901—2 is 14.2 feet at bench mark N88 between Pixley and Earlimart. This site has been the center of maximum subsidence continuously since 1953—54. ARVIN-MARICOPA AREA As of 1970, about 700 square miles in the Arvin- Maricopa area (fig. 3) had been affected by subsidence, and 100 square miles had subsided more than 5 feet. SAN JOAQUIN VALLEY, CALIFORNIA 119° 30’ 119°15’ H29 119°OO’ l | I | | I I l l INGS CO TULARE CO -—1_IE T. 22 S. 36° 00’ 35°45' T. 25 S. / Unconsolidated deposits ..__ IConsolidated sedimentary l rocks of Tertiary age Basement complex 2.0—— Line of equal subsidence Dashed where approxi- mate. Interval [.0 foot except for 0.5-foo! line T. 26 S. T. 27 S. Fl. 22 E R. 23 E. R. 24 E. R. 25 E. Base from U.S. Geological Survey Central 0 2 Valley map, l:250,000. 1958 0 2 4 Fl. 27 E. 6 8 MILES 6 8 10 KILOMETRES FIGURE 26.—-Land subsidence 1948—70, Tulare-Wasco area. Compiled from leveling of the National Geodetic Survey, February—May 1948 and November 1969—February 1970, Ingerson demonstrated (1941, fig. 7) that this “hole” was about half developed by 1940. (See also Lofgren and Klausing, 1969, p. B49, fig. 36.) A comparison of topo- graphic maps of the Geological Survey made in 1926 and 1953—54 (Lofgren and Klausing, 1969, fig. 43) indi- cates that the land surface in this subsidence “hole” north of Delano had subsided more than 12 feet by 1954. The average yearly rates of subsidence during the seven periods of control between 1926 and 1970 are shown by the bars in figure 28. The dashed line repre- sents the estimated probable rate of subsidence at any particular time. During 1948—54, the subsidence rate increased to 1950, owing to expanding ground-water use and then decreased rapidly as surface water from the Friant-Kern Canal replaced ground water. The highest yearly rate of subsidence—that from 1959 into 1962—occurred during a drought period. The cumula- tive volume of subsidence from 1926 to 1970 was 3.32 million acre-feet (fig. 29). Almost half of this subsidence occurred since 1960. The area affected by subsidence from 1926 to 1970 was about 1,420 square miles or 9.1 X 105 acres (fig. 30), H28 STUDIES OF LAND SUBSIDENCE 119° 30’ 119°15’ 119°00’ | ' ' I . o I Tulare T. 8'0 I 20 a, l“ l m s. o M < | E I._I I D I M I— _J ________ T. 21 S. T. 22 S. I 36° 00’ ' ‘ —— ————————————— /I EXPLANATION l I = E 23 I S' : Unconsolidated I deposits I ““““ "I m I k am. I T. | 39» IConsoIidated sedimentary 24 : '\_ r : rocks of Tertiary age S. ‘ .. ~ . | 3 | " ; ..—I V// _ TULABE CO _ chgrove I _ & l [A KERN CO | B | : asement complex I k 35 °4 5’ i ‘5 0.3 __ _ T. I Line of equal subsidence 25 I \ rat S- : Dashed where approxi- ——————————————————————————————— mate. Interval 0.1fool i R. 28E peryear I T. I . 26 I S. I i x I T. __________________________________ ’1 27 I S. I I I R. 22 E. R. 23 E. Fl. 24 E. Base from U.S. Geological Survey Central 0 2 Valley map, 1:250,000. 1958 R. 27 E. 8 MILES 4 6 l—|'_|_l'—‘TL_l—‘Ll—_J o 2 4 6 a 10 KILOMETRES FIGURE 25,—Average yearly rate of subsidence, 1962—70, Tulare-Wasco area. Based on control data of figure 24. Kern Canal began in 1950 and 1951. In the 22 years from 1948 to 1970, a major subsidence “hole,” centered 3 miles south of Pixley (fig. 26), developed in an area irrigated chiefly by ground water. This major sink ex- tended 9 miles north to Tipton and 12 miles west to Alpaugh and was a maximum at bench mark N88R (for location, see fig. 27), which subsided 11.7 feet. Subsid- ence at a second much smaller depression, centered 1 mile west of Richgrove, was more than 6 feet in the 22 years. More than half of this subsidence in Richgrove developed between 1948 and 1954 because of increased pumping from new deep wells (Lofgren and Klausing, 1969, fig. 44 and p. B58). The long-term subsidence from 1926 to 1970 (fig. 27) is characterized by two major subsidence “holes” along U.S. Highway 99; the 6-foot subsidence line encloses both. The “hole” south of Pixley is slightly larger and deeper than that in figure 26. Bench mark N88R had subsided 12.8 feet since its establishment in 1940, and total subsidence at this site was over 14 feet. By 1970, the land surface in the southern “hole,” centering 3 miles north of Delano, had subsided more than 12 feet. SAN JOAQUIN VALLEY, CALIFORNIA H27 119° 30' 119°15' 119°00' l I ' ‘ l . i Tulare 8'8 I 20 ml: : E! S. O < | ,. ,, El; . .3 | _:\_¥|_il: ________ .1 ______ '_ ____ T. 22 S. 36° 00’ 35°45’ T. 25 S. iConsolidaIed sedimentary I rocks of Tertiary age Basement complex 2.0—— Line of equal subsidence Dashed where approxi - mate. InlervaIOJfoot . 1A2 Water-level and com ac— tion recorders. an numbers 036A2 Compaction recorder and number R. 22 E. R. 23 E. R. 24 E. Base from U.S. Geological Survey Central 0 2 Valley map, 1:250,000. 1958 Fl. 27 E. 8 MILES 4 6 HajfiJ—ra—J 0 2 4 6 8 10 KILOMETRES FXGURE 24.—Land subsidence, 1962—70, Tulare-Wasco area. Compiled from leveling of the National Geodetic Survey, January—April 1962 and November 1969—February 1970. ence in the Tulare-Wasco area during the latest period of control, from 1962 to 1970. Two features are notewor- thy. First, the map is pockmarked with subsidence “holes,” indicating areas of continued intensive pump- ing. The biggest “hole,” exceeding 3 feet during the 8-year period, is southwest of Pixley, an area irrigated mostly from wells. Second, the beneficial effects of sub- stituting surface water from the Friant-Kern Canal for well water are demonstrated by the area of nearly 200 square miles in the south-central part of the map, be- tween Earlimart and Famoso, that subsided less than 0.5 foot in the 8 years. About half of that area subsided less than 0.3 foot. The average yearly rate of subsidence from 1962 to 1970 exceeded 0.1 foot in about half (800 sq mi) of the Tulare-Wasco area (fig. 25), mostly in the west half within lands not served by the Friant-Kern Canal. Only in two areas, southwest of Pixley and southwest of Al- paugh, did the average yearly rate of subsidence exceed 0.3 foot. The leveling network was established in 1948, short— ly before surface-water imports through the Friant- H26 generalized trend of water-level decline), and parame- ters for estimating subsidence under assumed hy- drologic change. Historically, water levels in wells in the area have responded differently depending on whether the wells tapped the confined system west of Delano (fig. 4) or tapped the semiconfined to confined system to the east (Lofgren and Klausing, 1969, figs. 13, 45, table 3). Water levels in wells tapping the confined system west of Delano have declined throughout the period of record (Lofgren and Klausing, 1969, figs. 34, 35). Water levels in wells to the east, in much of the service area of the Friant-Kern Canal, declined from 1920 to 1951, but have recovered substantially in the past two decades as STUDIES OF LAND SUBSIDENCE surface-water imports through the Friant-Kern Canal permitted reduction of pumping and increased re- charge. The decline and recovery pattern is well dem- onstrated by the multiple hydrograph of figure 23 for three wells northeast of Delano (fig. 4). The water level of 1970 (well 34F1) was equal to that of 1930 (33H1), following a recovery of 230 feet from the low level of 1950. This recovery has stopped the subsidence of bench mark G758 since 1962. The most rapid average rate of subsidence at bench mark T88 was 0.54 foot per year during 1948—54, when water levels reached their his- toric low. From 1962 to 1970, however, the average rate at that bench mark was only 0.04 foot per year (fig. 23). Figure 24 shows the magnitude and extent of subsid- I I I I I I I I I | I I I I I I I | I I | I | I | I I I | I I | [- 200 “r \+\ o E mm Benfigrflitsli? ég‘fi1Tlles \+\/ / ‘7 F / /I I I I 1930 1940 1950 1960 1970 SUBSIDENCE FIATE, IN HUNDRED THOUSANDS OF ACRE FEET PER YEAR 0 1 920 FIGURE 18.—Rate of subsidence in the Los Banos—Kettleman City area, 1926—72. H23 ally in figure 19 to show the relation between subsid- ence volume and pumpage. At a scale ratio of 1 to 3, the correlation is remarkably consistent, indicating that throughout the 43 years since subsidence began (1926 into 1969) about one-third of the water pumped has been water of compaction derived from the compaction of the aquifer systems. As of 1969, about 1.3 million acres (2,030 sq mi had subsided more than 1 foot (fig. 20), and the total area affected by subsidence was 1.53 million acres (2,400 sq mi). About 400,000 acres had subsided more than 10 feet, and 80,000 acres more than 20 feet. 10 CUMULATIVE PUMPAGE. IN MILLIONS OF ACRE-FEET VOLUME OF SUBSIDENCE, IN MILLIONS OF ACRE—FEET 0 1970 FIGURE l9.—Cumulative volumes of subsidence and pumpage, 1926—69, Los Banos— 0 1920 1930 1940 1950 1960 Kettleman City area. Points on subsidence curve indicate times of leveling control. 3° I I I 25 L — 20—- — 10— SUBSIDENCE IN FEET a I I \ Planimetered acreage with- _ -/ in the lines of equal sub- \idence for fig. 15 5 T Volume, 9.92 million . _ acre-feet \ 0 I I I I I\I-\I\. O 2 4 6 8 10 12 14 16 AREA, IN HUNDRED THOUSAND ACRES FIGURE 20.-Relation of magnitude to area of subsidence, 1926—69, Los Banos—Kettleman City area. H22 STUDIES OF LAND SUBSIDENCE 37°00’ 36°30' 'Madera CO MADF’RA CO R VER FY3340 E NO \\ FIRSQV‘ \\ 1m Kei‘manC \ \\ \ \ ’17 \\ / l . ((06) / Kl}??? \ \ L \»\ A .Cantua Creek 120°30’ 120°00’ 1’; / \ \ / 2 \ El Nidoo \\ /”“~ 0 \\\ \\ ('4’ ‘9 . os Banos 2 \\ / w / /—\ . \Iliyer EXPLANATION Boundary of deformed rocks ——8_ _ Line of equal subsidence, in feet Dashed where approximately located, interval variable California Aqueduct 0 5 10 15 MILES '—'_l_'—_l_l—I 0 5 1O 1 5 KILOMEI'RES 36'00’ Base from U.S. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 17.—Land subsidence, 1926—72, Los Banos—Kettleman City area. Compiled as sum of subsidence for 1926—69 (fig. 15) and for 1969—72 (fig. 16). SAN JOAQUIN VALLEY, CALIFORNIA H21 120°3o' 120.00. I , :3 Los Banos 152 152 / 33 / 37°OO’ / 99 F . Dos Palos "~/\-‘_J.»——EM9\,_H\’,_/ \R(|:gr__.. 09/ m Madera ’9 / ’> we ' o 1 I2 . 05,0 / e / Canal / Firebaugh RIVER O O, o 0 «y 9.)" C0 0%0 . . "'4 90/ whoesgo Co @6205? / .m- $9.?! FRESNO 9' '1 ' Q ’97”, '.,, . Mendota R -.. 0 Q1 ' '- 180 "9| ”fl 1m ‘8‘ ":. :‘3 a4 gel c Kennan 047 1., 5: 0'6 o? g, \ o \ ll ' .63).. . /0.4 I 2.3?" __\9 \ )‘ I o - «a 9/044“), '- o 0.5‘ . ‘.ol 0 \fw)’ 5‘s . . " 5 -. 'V " °\ ' 4’04, < 0.. 33 'g "' \ . . C} We '... _ 06‘ figfio 36'30’ _ {991,0 9/0 3.. . 1523 Cantua Cree 5 . _ ’9/ O : '. l o ((0 (Q E . C03 7: .9 EXPLANATION ’9 F' P ' 0%; t , «74’ 17.2 we °“‘ S 019 FRESNO c_ _ Boundary of deformed 06‘ 9% YEINQS. 'QQ’; rocks I . 0,0 04 = x 1.0 9‘ av / 2, Line of equal subsidence (’6‘ 0 Interval 02 foot. Compiled from leveling of the Na- 6% 75 . V . . (5: 3 tlonal Geodetic Survey, December l968+lpnl [969 K33, and November l97l—March I972 a 06 65 - . | ' m Boundary of near-surface subsidence area as of 1961 / / 1,2«0 ”"9 o 5 // :49) Huron W sthaven I K73 o a 2' California Aqueduct a 006:4} 006:9 OO\ {3 J a}: PLEASANT 27"” 1' 2 / tratford Coalinga 9 {o VALLEY Q9 ’ TULARE 00 {:39 60 LAKE “Q'eo’i’ BED o 5 1o 15 MILES 33 ‘1- fps 36° 00, 5 10 15 KILOMETRES | x «(S 414,1, J ettleman City Base from US. Geological Survey Central Valley map, 1:250,000, 1958 FIGURE 16,—Land subsidence, 1969v72, Los Banos—Kettleman City area. Compiled from leveling of the National Geodetic Survey, December 1968—April 1969 and November 1971—March 1969—72 (fig. 16) exceeded 1 foot only in two small areas, 1972. the El Nido area, at the north edge of the map. Subsid- the configuration of the lines of equal subsidence in ence in the El Nido area is controlled by leveling of the figure 17 differs little from that in figure 15, except in National Geodetic Survey along Highway 152 at five STUDIES OF LAND SUBSIDENCE H20 120°30’ 120°00' \ 7 \ \ 152 33 Los Banos \ J 152 \ / l ‘\ l I / 33 37°00' / / Fr ‘ l o Dos Palos A- .J~-"'Te'wgr- i 6’9 / Us}; l ”014/ \ 0’0 \ ‘° \ Canal \\ Firebaugh \ RIVER \ O O, “o \ 0%00 a 700:, \ 596:0 ($8 (3; a?» '- _ ’72 993’s FRESNO ego , -. : 2o 6 \ \ - m ‘37,, - . Mendo "1175(USGS) \ X 00 . . m | 150 ‘6‘ ‘ .' 9g \ Kennan 047 g \" \. \ 6} pm \ 3661 \ \ O \ 8 \ .. \ . .4 P66 -_ e \ )0 \ z '. 2 \ 9/0/90}, “. .' . .- l \ 6‘ .. a ._ o ' \ 440 33 . I " \ 4/00 . e \ ‘42,}0 \ 0, 04,6 .. . \ $9 C \ 6:9 ‘ 3 Ca tua Creek 5 \ 36°30’ — [/0 g - . E \\ _ ,5, 00 . 267 \ /((6‘ (Q E \(z EXPLANATION -‘ -' 9° \ 0 16\F' . 77777777777, <14] we PM" K, FRESNO €9_ Boundary of deformed 06‘ K; KlfiQS QO/ rocks \ I 7" ' — — — 0’0 \ M692 5 ,/ Line of equal subsidence. in feet Q08 6’0 \/ Dashed wliere approximately located. interval I variable 67Q® C224 E ‘ V69 ‘33 Boundary of near-surface subsidence area as of I96] C 19 ‘ B —*——-——>—-— / \ ‘3 ..- 6\\ California Aqueduct 1/ / 74/) Hurfin W sthavc 0 K73 B———-— ' 906194; \ \..° 3; m u‘. Alinement of subsidence profile °" ‘6 6‘ \ {J "1&0 Profiles shown in figures 2] and 22 PLEASANT <9 u / Ldl x M692 coalmgaVALLEY 7: Bench mark and number \ TULARE \ Co ,- m0 0 // ‘56 %C\ / LAKE Q (9904' \ // /,_ __ \ o 5 10 15 MlLES 33 ‘1- $6 \ _,/// BED o 5 1o ‘5 KILOMETRES l ’ "(s 4’44/ 1 "Kettlema.n City 36°OO’ Base from US. Geological Survey Central Valley map, 12250.000, 1958 FIGURE l5.—Land subsidence, 1926—69, Los Banos—Kettleman City area Compiled chiefly as the sum of (1) a comparison of topographic mapping by the US. Geological Survey done be- tween 1920—28 and in 1955 and (2) levelingof the National Geodetic Survey in 1955 and 1969. Figure 17 shows the subsidence from 1926 to 1972. By 1972, maximum subsidence had reached 29 feet, 10 ing an irregular pattern of surface-water deliveries and miles southwest of Mendota. Because subsidence in hence of irrigation well shutdown and artesian-head recovery. SAN JOAQUIN VALLEY, CALIFORNIA H19 120°30’ 120°00' I r 152 33 Los Banos x52 / ‘ \ / \ l 3 7 ° 00' I \ ‘ 33 \/ 99 / \ F Dos Palos \ A .J— "EMQ,~-~\,r-/M\Rl‘i€’__n Os ' \ m Madera ”’9 ’ \ “-2 \ 419th [Q / \ \,\ Canal 2 \ \ A . Firebaug \ RIVER 0 \ 0 Jo \ Q ’0 «y EVJ‘ CO 0%0 . .. 90/4, \ w" Sgo c ' «3&2? , 4 “3’ FRESNO <6 : 6 \ N Q ’° 9 Mendota \ \ 'y’b '. .0 \ Q, . .0 70 Ian \ 0“ Q”: L "& “k .. \ Kerman . 12 E 04, g r \ \ 6% t» \ ’ \ l O \ \ l u " ' 1\ \\ \ n I 72 3- i. \ » o - \ 0 \ . it; $036), \ .. '. -. . . _ \‘390 6‘ \ \ '._ \ \ 410 . v 33 . \ 41°CZ ‘- 9 Z _ _ 0% \ 0’s [4’6 - . . "%‘4\ \ 36‘30’ ’— ‘0 9/0 . . _. o antua Creek \a \\ _ ”/< 62o = ‘ 7 _ __ (‘9 E ." >' \)V / / EXPLANATION i . ’ 944’ \ Five Pomts PM FRESNO CO 77777577777, 0 I k:_—Klf S, 0—- Boundary of deformed 6 I 7"'N\ Q14 rocks Q \ .4 A 6‘ 4 ‘ /' a— — _ °———>— / ,1 -. 7 t H ron California Aqueduct 6‘90"}, \ u 0 a, 064’ \ \ PLEASANT 0 "Mord Coalinga @/ a \ 7 VALLEY Q\ \2;\ TULAFlE O O LAKE QQ- o 5 10 15 MILES 33 BED o 5 10 15 KILOMETRES | ’ Kettleman City 36°OO' Base from US. Geological Survey Central Valley map, 1:250,ooo, 1958 FIGURE 14.—Land subsidence, 1955—69, Los Banos—Kettleman City area, Compiled from leveling of the National Geodetic Survey, September-November 1955 and December 1968—April 1969. 1/5 to as much as 4/5. The irregularity of the lines of pattern of figure 12, reflects the progressive completion equal subsidence in figure 16, in contrast to the smooth of the irrigation distribu tion system in the area, caus- H18 STUDIES OF LAND SUBSIDENCE 120° 30’ 120°00' I ’ 152 33 Los Banos 152 /‘ 33 / 37°OO’ 0 7 / 99 , F ' Dos Palos /\ .._/-- -‘—Le£”9\,V..N,.-./ \Rifle/L 694 I ‘9 Madera 9‘ Z 9 ”do"? Canal / . O Firebaugh RIVER 00/0 02 J04 EM CO 6, O 0.2 90 who 0 , Q- 0 .- .. ’4, sfi C emf , «5 FRESNO ‘1' '-. ‘ ’V Q ’97 ’.,_ 0'4 Mendota N ¢ . Q1 . .. no in ‘6‘ ":. V: ‘- Kennan 047 2 5: b \«.. 02 rm U N. 0 GD » '- ’ '1 (I g . (a 90:9; ' -' \foe e 41 as "- 04,00 . '. a; 0% ’4’6‘ . -. 0 3 ”0%, 3 6° 30, _ 9&0 ,9/ . . o Cantua Creek -. __ 6r 00 o ‘ Q ' 1 {(0 6 o. y \l 0' . 'o. '00 - 09¢ '9 F" P ‘ t 44’ we om s K _: FRESNO C9_ 52° i-KIFQS. QC.» 0 I ‘7‘, . EXPLANATION ’0 G I ’ (06‘ I 7/‘7777777;/ 6% ~73. Boundary of deformed rocks ‘9 ‘ [3° 0.3 I"‘ 0.2 | : Line of equal subsidence rate a 19! Interval 0.2 foot per year, except for the / / ’ M o 5 0.1-faot line I/ 2130 um“ sthaven R73 ’0on o 3‘ Boundary of near-surface subsidence area ‘5 6‘ o as of 1961 PLEASANT ‘> I 3! ‘ tratford ' \ _>___>_ Coalmga g 9. California Aqueduct VALLEY 0 \\ x ( .7 TULARE \ 0000 $39 90 LAKE 6? 04’ o 5 1o 15 MILES 33 ‘1- She BED 3900, o 5 1o 15 KILOMETRES | . ’ 449 4’44 | Kettleman City Base from US. Geological Survey Central Valley map, 12250.000, 1958 FIGURE 13.—Average yearly rate of subsidence, 1966—69, Los Banos-Kettleman City area. Based on control data of figure 12. aqueduct 2 miles west of Cantua Creek (town), com- subsidence shows a decrease in the magnitude com- pared with 2.7 feet in 1966—69. Everywhere the 1969—72 pared with 1966—69, but the ratio ranges widely from SAN JOAQUIN VALLEY, CALIFORNIA H1 7 120°30’ 120°00’ l 152 33 Los Banos 152 / 33 37 °OO’ / 99 F Dos Palos "'f\~..J~--’£e£n9\,._.x,n—/ \RiligL... 01° m Madera @ , 12 ‘4! 9%,q / / Canal / Firebaugh RIVER ./ O «7 CO 90 509 / w 0 C 4’ “35$ 0 FRESNO ‘ N endota " \ N we \ 130 36°30' — " . _ O : .: .0 . ,9 ‘74, FRESNO CO 6‘ r’q‘ Ta‘os, o“ EXPLANATION 6‘ . " N‘ Q‘H 0 , 7777/7777? ’0 ' , 9‘0 Boundary of deformed rocks 6‘ 6r / 2‘5— -— — ((«S‘ Line of equal subsidence Interval 0.5 foot. Compiledfrom leveling of the Na- tional Geodetic Survey, F ebruary—March I966 and q / K December 1968w4pn'l 1969 / ‘ ,7 30 05 / 4, . / ,> ............... ’9’qu Boundary of near-surface subsidence area as of 1961 a, 6204’ 9 9 PLEASANT “word California Aqueduct Coalinga Q VALLEY . TULAFlE Q: LAKE Q s, 0 5 10 15 MILES 33 ‘9 BED l——i—‘—i—r‘——' 36°00' o 5 1o 15 KILOMETRES I ’ Kettleman City Base from US. Geological Survey Central Valley map, l:250,000, 1958 FIGURE 12.—Land subsidence, 1966—69, Los Banos—Kettleman City area. Compiled from leveling of the National Geodetic Survey, February—March 1966 and December 1968—Apri11969‘ mark elevations, we have not attempted to update other 17.) The 1969—72 change in both magnitude and pattern subsidence graphs 0r maps beyond the 1969 data except of subsidence from 1966—69 (fig. 12) is striking. figures 8—10 and 18, but we have added figures 16 and Maximum subsidence of about 1.6 feet occurred on the H16 STUDIES OF LAND SUBSIDENCE T l v 0 Subsidence, bench mark Y286 ° ‘ 5 Lu u. Z [Ll m _ 1 5 g E 5 9 Z a: 8 - W O D 3 50 u. m E 3 Water level, n: {(3 well 19/22—19A2 8 (0 (upper zone) 1% ~— 10 3 3 O _l g 100 ~ 50 n; E < E O '— E - l (333 Water leg/el, well 19/ 2—19A1 150 #100 (lower zone) I . N 3‘, . 8 —150 u. Lu J < 0 a) 2 (I < LLl >— n «1 E n. Subsidence 5 rate uJ u. / / 0 1930 1940 1950 1960 1970 FIGURE 11.—Subsidence and head change in two zones near Hanford. Figure 16 shows the subsidence from 1969 to 1972. (Because of the late availability of the 1971—72 bench- this was in 1968) and net change in artesian head was small. SAN JOAQUIN VALLEY, CALIFORNIA 1 1 200 a — 0 Subsidence, bench mark 3807 300 — N1 _ 5 l— 1— w in Lu LLl LL Li. Z E E 400 r #10 8 Lu E —' o 2 a a :> E (D E 500 — — 15 O '— I r— n. E 600 — N3 a 20 Water level, wells 19/18—20N1, 20D1, 16N2, 18N3, M1 and mm 700 l 1 l 1 1 1 2 u: Subsidence ff. rate >- L ' H II / 77r7ZF 1 E // /// g / // u. / fl 4 //1 0 1940 1950 1960 1970 FIGURE 10.—Subsidence and artesian-head change near Huron. average rate of 0.2 foot per year in 1969-72 was only 11 percent of the 1953—55 maximum; near Huron the aver- age rate was only 22 percent of the 1960 average. Figure 11 shows the trends of subsidence and head decline in two zones near Hanford (for location, see fig. 4). The upper zone is above the principal confining bed—the Corcoran Clay Member of the Tulare Formation—and the lower zone is below. This location is outside the Los Banos—Kettleman City area (fig. 3), but in general the same effects of overpumping have occurred. About 8 feet of subsidence has been measured in this area (fig. 5), mostly since 1953. At bench mark Y286, the maximum subsidence rate of 0.6 foot per year (lower graph, fig. 11) was measured in 1959—62. The average rate in 1966—69 was less than half this amount. Of the two water levels, the hydrograph of shallow well 19/22—19A2 (110 ft deep) seems to more closely parallel the subsidence trend, although the deep summer low levels registered in observation well 19/22—19A1 (well point set at 559 ft) undoubtedly contributed to the sub- sidence. H15 Figure 12 shows the magnitude and areal extent of subsidence in the Los Banos—Kettleman City area dur- ing the 3 years 1966—69. The construction of the California Aqueduct south to Kettleman City was com- pleted early in 1968. About 230,000 acre-feet of surface water had been imported by the end of 1968 (see table 3), thereby causing about 20 percent reduction in pumpage and about a 20-foot average recovery of the artesian head of the lower zone. Hence, the rate of subsidence must have decreased substantially during 1968, but even so, the 3-year total exceeded 2.5 feet along a 4-mile stretch of the aqueduct west of Cantua Creek and ex- ceeded 2 feet for an aggregate length of 32 miles. The average yearly rate of subsidence during 1966— 69 (fig. 13) was derived by dividing the values of figure 12 by three. The average rates shown undoubtedly are lower than the actual rates of 1966 and higher than the actual rates of 1968. Nevertheless, the map indicates that for 60 miles from west of Mendota to 3 miles north of Kettleman City the average yearly rate of subsidence along the central subsidence trough exceeded 0.4 foot per year. Figure 14 shows the total subsidence in the 14 years since the bench-mark network was established in 1955. The maximum subsidence of 14 feet was 10 miles southwest of Mendota. More than 10 feet of subsidence occurred during the mapped period in a 50-mile reach extending from west of Mendota southeast past the Kings County line. The total subsidence due to man’s overall increase of subsurface stresses from 1926 to 1969 is shown in figure 15. By 1969, maximum subsidence exceeding 28 feet affected an area of about 1 square mile, 10 miles south- west of Mendota. Subsidence exceeded 10 feet in about 600 square miles and 4 feet in 1,200 square miles. Fig- ures 12 through 15 delineate by a dotted outline the areas west and northwest of Cantua Creek (town) and 16—19 miles west of Mendota where hydrocompaction has been a problem for many years. In December 1972, after the draft of this summary report was completed, the National Geodetic Survey supplied a tentative adjustment of bench-mark eleva- tions for the survey of November 1971—March 1972. Adjustments were made on the same basis as for the surveys of 1966 and 1969. During the 3-year period 1969—7 1, the increasing importation of surface water through the California Aqueduct (fig. 46) and the con- sequent decrease in ground-water pumpage greatly de- creased the stress applied to the fine-grained beds (aquitards). Imports during this period totaled 1,434,000 acre-feet (see table 3), and the artesian head of the lower water-bearing zone rose an average of 42 feet, in contrast to the previous 3-year period, 1966—68, when imports totaled 228,000 acre-feet (92 percent of H14 increased subsidence along the aqueduct alinement in this reach. However, it should be noted that two bench marks on US. Highway 466 at the axis of the Lost Hills oil field (SW. cor. sec. 33, T. 26 S., R. 21 E.) subsided 2.24 feet, 1935—66, and 1.04 feet, 1954—66. Evidently this local subsidence was caused by fluid production from the oil field, but it represents no hazard to the aqueduct which is about 2 miles to the east. LOS BANOS—KE'I'I‘LEMAN CITY AREA Roughly 2,400 square miles of the Los Banos— Kettleman City area (fig. 3) has been affected by subsid- ence, of which 1,500 square miles is west of the valley trough as defined by the San Joaquin River and Fresno Slough. For a detailed discussion of the geology, hydrol- ogy, and characteristics of the compacting aquifer sys- tems, reference is made to comprehensive reports listed in the section “Annotated Bibliography.” Figures 8, 9, and 10 are comparative records of sub- sidence and change in artesian head of the lower zone l 200 —‘ — O Subsidence, bench mark $661 300 — _ 5 E E E g 400 - — 10 [L cf m g. E m ‘3‘ Static level, 52 L2’ Lu 9 Q 500 — I g E m {‘5' N2 600 — Pumping level, wells 14/ 13—26 N1. N2, and E2 700 ~ ~ 25 | l | l l l 2 Subsidence o: / rate < u.l / >- — / — 1 E EL % n LIJ /% ”L 2% o 1940 1950 1960 1970 FIGURE 8.—Subsidence and artesian-head change 10 miles southwest of Mendota. STUDIES OF LAND SUBSIDENCE 400 I 500 — — 0 E w : Q1 d Subsidence 5 E _. , _ u_ E, 600 bench mark 2 —' Y883 l; 2 0 CL E 3 Q at 700 — E1 — 10 g 9 a I Water level, I— wells 17/15—21 ii] N1, 01. and 2251 0 800 — V — 15 N1 | l l 2 Subsidence a: rate 5 >. _ — 1 E o. E LIJ L I O 1940 1 950 1960 1970 FIGURE 9.—Subsidence and artesian-head change near Cantua Creek. (confined aquifer system) at three centers of rapid sub- sidence. (For location of these wells and bench marks, see fig. 4.) At each location, an extended period of water-level decline accompanied by rapid subsidence was followed by a few years of water-level rise. The Federal San Luis Project area includes most of the ag- ricultural land in Fresno County west of Fresno Slough (fig. 13); surface-water deliveries to this area from the joint-use reach of the California Aqueduct increased from an initial 200,000 acre-feet in 1968 to 865,000 in 1972. As shown by the bar diagrams in the three figures, the rate of subsidence in 1966—69 compared with the rate in the early 1960’s decreased markedly southwest of Mendota (fig. 8) and appreciably near Huron (fig. 10), but registered little change near Cantua Creek (fig. 9). Southwest of Mendota, by 1966—69 the yearly rate had decreased to 38 percent of the maximum rate in 1953— 55. The average rate of subsidence in 1969—72 decreased drastically at all three sites because of the rapid rise in artesian head caused by the increase in surface-water imports (table 3) and the resulting decrease in ground- water draft. For example, southwest of Mendota the SAN JOAQUIN VALLEY, CALIFORNIA I 325 300 — San Joaquin River 275 1921 autumn J \/’\\’/ M 929 autumn ELEVATION OF WATER TABLE, IN FEEI' ABOVE MEAN SEA LEVEL H13 Fowler 2‘. .11 W {I} o- I: n 0:) i ngs Rner 250 — // ................ \ 225 :fi - - - 1960 autumn A 200 VERTICAL SCALE GREATLY EXAGGERATED <7? a a 6'? (I? O (D O (D (D m (D (I) 0‘) co 3 a a a a N co m m B a 0 Q (D g g Ix Ix Ix ‘0 <0 <0 0 l\ 00 § as 1930 2% aBASEsé 5 8 as ’— u.I u.I LL ; 0.1 i L ui O 2 Lu 9 0.2 — L (I) no :> a) 0.3 0 5 10 MILES L I I I I I I 0 5 10 15 KILOMEI'RES FIGURE 7.—Apparent subsidence and water-table decline along the Southern Pacific Railroad between the San Joaquin and Kings Rivers. Delta-Mendota Canal was completed in 1951. During 1962-66, one-quarter of the irrigation water in this northern area (about 300,000 acre-ft/yr) was supplied from wells, and three-quarters (900,000 acre-ft/yr) from canals (Hotchkiss and Balding, 1971). In general, water levels in wells have been rising for the past two decades, and so subsidence would not be anticipated to be a current problem. On the other hand, the area traversed by the California Aqueduct between Kettleman City and T. 30 S. (fig. 4) never had been developed agricul— turally prior to canal deliveries in 1970 because inferior quality of the ground water had discouraged well de- velopment (Wood and Davis, 1959). Here also, subsid- ence from water-level decline would not be antici- pated. In 1966, the California Department of Water Re- sources made a brief analysis of bench-mark surveys by the National Geodetic Survey north of Los Banos and between Kettleman City and Tupman (in T. 30 S., R. 24 E., sec. 24; fig. 4). The purpose was to appraise historical land subsidence in these areas, with respect to State water facilities—the California Aqueduct then under construction and the proposed Master Drain. From Tracy to 50 miles southeast to within 5 miles of Los Banos, the maximum historical subsidence (1935—66) along the Southern Pacific Railroad was about 0.5 foot, and the rate of subsidence was lowest in the 1960’s (Marvin V. Damm, written commun., June 29, 1966). From Kettleman City south to Tupman (in T. 30 S., R. 24 E.; see fig. 4), subsidence along the general Califor- nia Aqueduct alinement did not exceed 0.2 foot in the period between the first leveling control of the National Geodetic Survey (in 1935 or 1942) and 1966 (Marvin V. Damm, written commun., July 12, 1966). Leveling by the National Geodetic Survey in 1969—70 southeast of Kettleman City shows only a few hundredths of a foot of H12 / 12 MILLION ACRE-FEET on 1930 1 940 0 1920 1950 1960 1970 FIGURE 6.—Cumulative volume of subsidence, 1926—70. TABLE 2.—Summary of extent and volume of subsidence, 1926—70, San Joaquin Valley Area where subsidence Total area affected1 Volume Area exceeds 1 foot Square Square Acres X 103 miles Acres X 103 miles Acre-feet X 10“ Los Banos— Kettleman City2 ______ 1,300 2,030 1,530 2,400 9.92 Hanford 350 550 435 680 1.31 Tulare-Wasco __________ 800 1,250 910 1,420 3.32 Arvin-Maricopa __________ 320 500 450 700 1 06 Total (rounded) ____ 2,750 4,300 3,300 5,200 1Extra 2Subsi lated graphically to zero subsidence. ence, 1926-69. Probably more than 900 square miles has been af- fected by subsidence, but falls outside the 1-foot line of figure 5. Certainly, elevation differences of 005—03 foot are indicated along many bench-mark lines which have been resurveyed 10—40 years after the first survey. However, most leveling surveys are not that precise. Complications that include distance to bedrock ties, stability of bedrock ties, instruments used, order of ac- STUDIES OF LAND SUBSIDENCE curacy required, adjustment procedures, and other problems lead to the conclusion that comparative eleva- tion changes at individual bench marks (from surveys tens of years apart) which do not exceed 0.2—O.3 foot are of questionable value as indicators of subsidence trends. For this reason, we have not attempted to map overall subsidence in the valley to limits of less than 1 foot, although we have mapped subsidence in active subsid- ence areas to 0.1 foot under favorable conditions. As shown later, generally there is a close correlation between subsidence and water-level trends. When this correlation does not exist, other causes or spurious data are suspected. Figure 7 is an example of small apparent subsidence that does not correlate with water-level de- cline and which may not be real. The water-level and subsidence profiles are along the Southern Pacific Rail- road, between the San Joaquin and the Kings Rivers (for alinement, see section A—A ’, fig. 5). The water-level profiles are from 1960 data of the California Depart- ment of Water Resources (California Department of Water Resources, 1963, 1964b) and from its predecessor (California Division of Water Resources, 1931, pl. 13; 1921 and 1929 autumn levels); the subsidence profiles are from bench-mark surveys by the National Geodetic Survey. This profile alinement is along the upper reaches of the alluvial fans of the San Joaquin and Kings Rivers. To the depths of 150—300 feet tapped by water wells, these deposits are primarily coarse sand and gravel, and the ground-water body at these depths is unconfined (Page and LeBlanc, 1969, pls. 8, 10). The indicated subsidence from the 1930 base as of 1952—53 averaged about 0.06 foot (max 0.10) and as of 1959—60 ranged from 0.02 to 0.20 foot. However, the maximum indicated subsidence from 1930 to 1960 was between Fowler and Selma, in the area of only 10—15 feet of water-table decline (autumn low level, 1929 and 1960), whereas the reach of maximum water-table de- cline of 40 feet in the city of Fresno subsided only half as much (0.08—0.09 ft) in the 30 years. Thus, the apparent subsidence does not correlate with water-table decline; except for three bench marks, the 30-year subsidence is less than 0.1 foot and thus may represent adjustment procedures from different bedrock ties. It is possible that vibrations caused by the passage of several thousand trains per year might cause differential com- paction of as much as 0.1 foot between bench marks 1—3 miles apart in a period of 30 years. Two long reaches of the California Aqueduct traverse the west side of the valley north and south of the Los Banos—Kettleman City subsidence area. The mag- nitude and extent of historical subsidence in these two areas is of interest. To the north, the area between Los Banos and Tracy (57 miles northwest; not shown) has been irrigated primarily with surface water since the SAN JOAQUIN VALLEY, CALIFORNIA 6) is derived by addition of the volumes for individual areas. Figure 5 shows the areal distribution of this 15.6 million acre-feet of subsidence. However, figure 5 only defines the extent of subsidence that exceeds 1 foot, an area of 4,300 square miles. Extrapolation of the magnitude-area graphs for the four areas given in table 121° 120° H11 2 (such as fig. 20 for the Los Banos—Kettleman City area) to zero subsidence suggests that the total area affected by subsidence is about 5,200 square miles (table 2) and hence that the area in which subsidence is less than 1 foot but greater than zero is 900 square miles. ' 118° o Merced El Nido EXPLANATION Outline of valley Drawn chiefly on boundary of consolidated rocks ‘97,, 626. 0" 4 Line of equal subsidence, in feet Interval variable. Compiled from comparison of U .S . Geological Survey topographic maps prior to about 1955, and subsequent leveling of National Geodetic Survey. South of Bakersfield, compiled wholly from leveling lib/1 ' Alinement of subsidence and water—table profiles Profile shown in figure 7 0 10 20 30 0 10 20 30 40 KILOMETRES lit-per EHACHAPI MTS EMIGDIO MTS 40 MILES Base frorn U.S. Geological Survey 1:1,000,000, State base map, 1940 FIGURE 5.—Land subsidence, 1926—70. Compiled from comparison of U.S. Geological Survey topographic maps prior to about 1955 and subsequent leveling of National Geodetic Survey. South of Bakersfield, compiled wholly from leveling. H10 STUDIES OF LAND SUBSIDENCE TABLE 1.—Years of leveling control of the network of bench marks in three subsidence areas by the National Geodetic Survey Los Banos—Kettleman City Tulare-Wasco Arvin-Maricopa Los Banos—Kettleman City Tulare-Wasco Arvin-Maricopa __________ ‘1948 _______-__ 1963 1962 1962 11955 1953 __________ 1966 21964 1965 1957—58 1957 11957 1969 1969—70 1970 1959—60 1958-59 1958—59 1971—72 ____________________ ‘Year network established. 2Partial releveling of net. 1 2 1 ° 1 1 8 a l \\ wt I 37° — # 36° — Keltlembn —‘ City R EX PLAN ATION Outline of valley Drawn chiefly on boundary of consolidated rocks T _____ 30 Approximate boundary of _ S principal confining T ' T bed where known . 9A MT DIABLO BASE R 20 E . g2 1 1 SAN BERNARDINO T 12 N ' . 32 E 35° — 0 A2 BASE T 11 N Mam?” - Observation well and R 25 W : T TEHACHAPI number 10 MTS N 8661 EMIGDIO >< MTS Bench mark and number 0 10 20 30 40 MILES r—r—H—fil—r—L—J 0 10 20 30 40 KILOMETRES l | Base from US. Geological Survey 1:1,000,000, State base map, 1940 FIGURE 4.-—Location of selected observation wells, nearby bench marks. and boundary of the principal confining beds. SAN JOAQUIN VALLEY, CALIFORNIA 120“ 119° H9 118‘? l Merced Reitleman '. - - City I " EXPLANATION Outline of valley 6.37 Drawn chiefly on boundary $ 62¢ d3 09 0’08“ 0‘. 4’43 ....o-.-., of consolidated rocks Wf/V/ Area of detailed study of land subsidence A. Los Banos—Kettleman City 3. Tulare—Wasco C. Arvin—Maricopa t... Line of leveling Bakersfiel : Line of l—foot subsidence, from figure 5 SAN EMIGDIO MTS O 10 2O 30 40 MILES | 0 10 20 30 40 KILOMETRES Base from U.S. Geological Survey l:l,000,000, State base map, 1940 FIGURE 3,—Network of leveling by the National Geodetic Survey and three areas of detailed studies of land subsidence. subsidence (fig. 6) remained small until after World the initial storage capacity of Lake Mead. The volume of War II. By 1970, the total volume of subsidence for the subsidence for any interval of leveling control is ob- 44-year period (table 2) was 15.6 million acre-feet, hav- tained by planimetry of the subsidence map for that ing doubled since 1957. This volume is equal to one-half period. The cumulative volume for the entire valley (fig. H8 (4) deep-seated tectonic settlement. A fifth type, subsi- dence caused by the oxidation and compaction of peat soils, occurs in the Sacramento—San Joaquin Delta area and is not considered in this report. Figure 1 shows the principal areas affected by subsid- ence caused by water-level decline and hydrocompac- tion. These areas are principally in the western and southern parts of the valley, where runoff from surface streams is minimal. Subsidence due to hydrocompac- tion (also called near-surface or shallow subsidence) has occurred in two areas southwest of Mendota (Bull, 1964b) and in five areas south and southwest of Bakersfield (California Department of Water Re- sources, 1964a, pl. 2; Lofgren, 1975, pl. 30). The total area susceptible to hydrocompaction is about 210 square miles, of which about 130 is north of Kettleman City. Oil-field subsidence is known to occur in a few small areas south and west of Bakersfield (Lofgren, 1975). For the most part, this type of subsidence has been less than 1 foot during the .period of leveling control and is re- stricted to local areas. Present subsidence rates are generally very low. During earlier periods of maximum production, however, subsidence rates in some oil fields undoubtedly were much greater than during the period of measurement. This type of subsidence has little effect on the long-term subsidence trends in the valley and is not considered further in this report. Little information is available on rates of tectonic downwarping occurring in the San Joaquin Valley. Davis and Green (1962, p. D—90) postulated that post- depositional downwarping was responsible for 300 feet of deformation of the Corcoran Clay Member of the Tulare Formation beneath Tulare Lake bed. Carbon-14 dates used to calculate average depositional rates south of Kettleman City (Lofgren, 1975) indicate that if struc- tural downwarping has been occurring uniformly since the Pleistocene, tectonic subsidence would have been so slow that it would not have affected bench marks ap- preciably during the historical span of leveling control. Of particular significance, however, are the evidences of tectonic movement of “stable bedrock” bench marks in the Coast Ranges to the west and the Tehachapi Moun- tains to the south. Apparent tectonic movements of as much as 0.8 foot in these bedrock tie points has affected the computed elevations of many of the bench marks in the valley. The magnitudes of these movements are not precisely measurable with present methods and in— struments, but probably represent several tenths of a foot for many bench marks during the period of record. SUBSIDENCE DUE TO WATER-LEVEL DECLINE SAN JOAQUIN VALLEY In 1956 when this cooperative investigation was in- STUDIES OF LAND SUBSIDENCE itiated, subsidence centered in three broad areas of known pumping overdraft. These were designated (fig. 3) (A) the Los Banos—Kettleman City area, (B) the Tulare-Wasco area, and (C) the Arvin-Maricopa area, and most of the subsequent studies and reports have considered these separately. As of 1956, a valleywide bench—mark network of leveling control, with some pre- cise leveling dating back to 1902, was available. A bench—mark network had been established in the Tulare-Wasco subsidence area in 1948 through the ef— forts of the Geological Survey, the National Geodetic Survey, the Bureau of Reclamation, and other in- terested agencies. Similar networks were established in the Los Banos—Kettleman City area in 1955 and in the Arvin-Maricopa area in 1957 (Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1958, pls. 4—6). Figure 3 shows the network of leveling control, periodically resurveyed by the National Geodetic Sur- vey. The control is concentrated in the three subsidence areas and ties to a dozen “stable bedrock” reference bench marks around the perimeter of the valley. Table 1 shows for each of the three subsidence areas the date the network was first established and the years of relevel- ing of the network. Significantly, most of the subsiding area in the San Joaquin Valley is underlain by a continuous and exten- sive confining bed (aquiclude). Most of the pumping overdraft and most of the compaction occurs in the ar- tesian aquifer system beneath this confining bed. The boundary of this bed, where known, is shown in figure 4 (Lofgren and Klausing, 1969; Miller and others, 1971; Croft, 1972). North of the vicinity of Wasco, the confining bed is the Corcoran Clay Member of the Tu- lure Formation which also has been called the E clay by Croft (1972). Figure 4 also shows the location of selected observation wells and nearby bench marks discussed in this report. Figure 5 shows the magnitude and extent of subsid- ence exceeding 1 foot in the San Joaquin Valley from 1926 to 1970 (1926—69 in the Los Banos—Kettleman City area). Three centers of subsidence stand out on the map. The most prominent is the long narrow trough west of Fresno that extends 90 miles from Los Banos to Kettleman City. Maximum subsidence in this area to 1969 was 28 feet, 10 miles southwest of Mendota. The second center, between Tulare and Wasco, is defined by two closed 12-foot lines, 20 and 30 miles south of Tulare, respectively. The depression near Delano had subsided 12 feet by 1954 (Lofgren and Klausing, 1969, fig. 43); subsidence of the northern depression has doubled since 1954. The third center, 20 miles south of Bakersfield, has subsided a maximum of about 9 feet, mostly since World War II. Manmade subsidence began in the San Joaquin Val- ley in the middle 1920’s, but the cumulative volume of SAN JOAQUIN VALLEY, CALIFORNIA clay-filled tension cracks were found in the alluvial fans of western Fresno County which raised the possibility of postconstruction tensional rupture of the canal. Many filled near—surface subsidence cracks occur in the small fans, and evidence is pre- sented to show that many of these are historic. They have a mean spacing of less than one per hundred feet of canal length. On the other hand, the thousands of filled near—surface subsidence cracks in the large fans have a mean spacing of two to six per 100 feet of canal. The study revealed that virtu- ally all the cracks in the large fans are prehistoric and that the possibility of future near-surface sub- sidence which would cause damage to the Califor- nia Aqueduct is slight. Professional Paper 497—B, “Removal of water and rear- rangement of particles during the compaction of clayey sediments—review,” by R. H. Meade (1964). Review of pertinent literature on the factors influencing the water content and clay-particle fabric of clayey sediments under increasing over- burden pressures. Professional Paper 497—G, “Land-surface tilting near Wheeler Ridge, southern San Joaquin Valley, California,” by F. S. Riley (1970). Two continuous- recording liquid-level tiltmeters and three as- sociated borehole extensometers recorded tilt at land surface and compaction of the upper 150 feet of alluvial-fan deposits at the site of a future pumping plant of the California Aqueduct. The site bordered a large bowl of land subsidence due to ground-water overdraft and overlay deposits susceptible to hy- drocompaction. Repeated releveling of an array of surface bench marks agreed with the tiltmeter data in defining two principal periods of northward tilt- ing per year. Professional Paper 497—H, “Application of the modified theory of leaky aquifers to a compressible multiple-aquifer system,” by F. S. Riley and E. J. McClelland (open file, 1972). Detailed description of practical procedures, based on the Hantush “modified theory of leaky aquifers,” for analyzing pumping-test data. Application of the Hantush function is illustrated by the analysis of one recov- ery and five drawdown tests made near Pixley in the San Joaquin Valley, in a heterogeneous allu- vial aquifer system. Water-Supply Paper 2025, “Glossary of selected terms useful in studies of the mechanics of aquifer sys- tems and land subsidence due to fluid withdrawal,” by J. F. Poland, B. E. Lofgren, and F. S. Riley (1972). The glossary defines 25 terms as they are used in Geological Survey research reports con— cerned with the mechanics of stressed aquifer sys- tems and of land subsidence. Most are terms that H7 have appeared in engineering or hydrologic litera- ture, but several have been introduced as a result of the Survey’s studies. Geological Society of America, Reviews in Engineering Geology 11, “Land subsidence due to the application of water,” by B. E. Lofgren (1969). Hydrocompac- tion has produced widespread subsidence in low density moisture-deficient deposits and is of serious concern in the design and construction of many engineering structures. Deposits susceptible to hydrocompaction worldwide are described. In western and southern San Joaquin Valley, proba- bly 200 square miles of irrigated farm land is sub- siding because of the application of water, and at least another 50 square miles of susceptible land has not yet been irrigated. Preconsolidation before construction begins usually minimizes damage. Geological Society of America, Reviews in Engineering Geology II, “Land subsidence due to withdrawal of fluids,” by J. F. Poland and G. H. Davis (1969). A review of the known (1963) examples of appreciable land subsidence due to fluid withdrawal through- out the world, with a brief examination of the prin- ciples involved in the compaction of sediments and of aquifer systems as a result of increased effective stress. Special emphasis is given to studies in the San Joaquin Valley. Other areas in California af- fected by subsidence due to withdrawal of fluids are Santa Clara Valley, Wilmington, Lancaster, and La Verne. Several ways to alleviate subsidence are mentioned. Professional Paper 352—E, “Geomorphology of seg- mented alluvial fans in western Fresno County, California,” by W. B. Bull (1964). A study of the interrelations of alluvial-fan morphology, drainage- basin characteristics, and tectonic and climatic events. This study presents data on the geomorphology of alluvial fans in the west-central part of the San Joaquin Valley. It provides informa- tion concerning deposition and erosion of the fans as well as the relations of fan size and slope to drainage-basin area and lithology. The overall shape of the fans was studied by means of radial and cross-fan profiles. Fan segmentation, revealed by the radial profiles, was used to decipher tectonic history. CAUSES OF SUBSIDENCE Four types of subsidence are known to occur in the San Joaquin Valley. In order of their magnitude, they are (1) subsidence caused by water-level decline and the consequent compaction of aquifer systems, (2) subsid- ence related to the hydrocompaction of moisture- deficient deposits above the water table, (3) subsidence related to fluid withdrawal from oil and gas fields, and H6 STUDIES OF LAND SUBSIDENCE water table for the first time since burial. Detailed description of surficial deposits on alluvial fans in west-central San Joaquin Valley, where about 124 square miles of deposits has subsided or probably would subside if irrigated. Tests on surface samples under hygroscopic conditions indicate that max- imum compaction occurs at a clay content of about 12 percent. Professional Paper 497—E, “Geology of the compacting deposits in the Los Banos—Kettleman City subsi- dence area, California,” by R. E. Miller, J. H. Green, and G. H. Davis (1971). This report de- scribes the geology of the deposits undergoing com- paction due to head decline, including source, type, physical character, and mode of deposition and the hydrologic framework so developed. In a series of subsurface maps and sections based on electric logs and core records, the Tulare Formation and overly- ing younger deposits are subdivided into alluvial- fan, flood-plain, deltaic, and lacustrine deposits and are identified as from the Sierra Nevada or the Diablo Range. Professional Paper 437—E, “Land subsidence due to groundwater withdrawal in the Los Banos— Kettleman City area, California. Part 1, Changes in the hydrologic environment conducive to subsid- ence,” by W. B. Bull and R. E. Miller (1975). With- drawing water for agriculture and thus increasing the stress tending to compact unconsolidated de- posits by as much as 50 percent has created in the west-central part of the San Joaquin Valley what is believed to be the world’s largest area of intense land subsidence. More than a million acre-feet has been pumped from the ground-water reservoir each year during the period 1951—65, lowering the potentiometric surface as much as 600 feet, revers- ing the eastward gradient of 2—5 feet per mile to a westward gradient of 30 feet per mile, and causing water levels to decline below the base of the Corcor- an Clay Member of the Tulare Formation adjacent to the Diablo Range. Professional Paper 437—F, "Land subsidence due to ground-water withdrawal in the Los Banos— Ket- tleman City area, California. Part 2, Subsidence and compaction of deposits,” by W. B. Bull (1975). In the west-central San Joaquin Valley, Calif, as of 1966, 2,000 square miles had subsided more than 1 foot, and the area that had subsided more than 10 feet was 70 miles long. Maximum subsidence was 26 feet. The rates, amounts, and distribution of subsidence within the area are described and are shown to be highly dependent on regional varia- tions of certain geologic factors influencing the compaction of unconsolidated deposits. The report describes the measurement of compaction, the rates and amounts occurring within specified depth in- tervals, and the proportions of subsidence being measured, and then assesses the geologic factors influencing compaction. Professional Paper 437—G, "Land subsidence due to ground-water withdrawal in the Los Banos— Kettleman City area, California. Part 3, Interrela- tions of water-level change, change in aquifer- system thickness, and subsidence,” by W. B. Bull and J. F. Poland (1975). This report relates changes in thickness of the aquifer-system skeleton to water-level changes. Reviews analysis of stresses and change in stress. Describes various parameters necessary for a better understanding of the mechanics of aquifer systems and the compaction of sediments and for the development of criteria for predicting future subsidence. TULARE-WASCO AREA Professional Paper 437~B, "Land subsidence due to ground-water withdrawal, Tulare-Wasco area, California,” by B. E. Lofgren and R. L. Klausing (1969). More than 800 square miles of irrigable land has subsided in the Tulare-Wasco area, owing to intensive pumping of ground water. The mag- nitude and rate of subsidence are directly related to the change in effective stress within the various beds that results from water-level changes and to the thickness and compressibility of the compact- ing deposits. In the southeastern part of the area, subsidence nearly stopped in the late 1950’s, when water levels recovered as much as 130 feet in re- sponse to reduced pumping and increased recharge resulting from importation of water through the Friant-Kern Canal. ARVIN-MARICOPA AREA Professional Paper 437—D, "Land subsidence due to ground-water withdrawal, Arvin-Maricopa area, California,” by B. E. Lofgren (1975). As of 1970, 700 square miles of irrigable land—roughly 60 percent of the area—had subsided owing to intensive pump- ing of ground water. Maximum subsidence ex- ceeded 9 feet, and the total volume (1926—70) is about 1 million acre-feet. The report describes four types of subsidence occurring in the Arvin- Maricopa area and develops criteria that may be applied to estimate the amount of subsidence that will occur under assumed hydrologic change. SPECIAL STUDIES Professional Paper 437—C, “Prehistoric near-surface subsidence cracks in western Fresno County, California,” by W. B. Bull (1972). During the exca- vation for the California Aqueduct, thousands of SAN JOAQUIN VALLEY, CALIFORNIA well 12/ 12—16H2 is the second well listed in the SE% of the NE% of sec. 16, T. 12 S., R. 12 E. Except for the extreme south end of the valley which is referenced to the San Bernardino base and meridian, all wells are referenced to the Mount Diablo base and meridian. REPORTS BY THE GEOLOGICAL SURVEY In December 1954, concerned Federal and State agencies formed an Inter-Agency Committee on Land Subsidence in the San Joaquin Valley to plan and coor- dinate subsidence studies. The first major activity of this Committee was the preparation of a proposed pro- gram of investigation (Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, 1955). As one product of the inter-agency planning, the Geologi- cal Survey began in 1956 an intensive study of the extent, rates, and causes of subsidence in the San Joa- quin Valley, in financial cooperation with the Califor- nia Department of Water Resources. At the same time, a companion federally financed study of the mechanics of aquifer systems was initiated to determine the prin- ciples controlling the compaction and expansion of aquifer systems under pumping stresses and to deter- mine hydrologic storage parameters from field meas- urements. These two projects, cooperative and Federal, have resulted in a number of published or open-filed research reports. An annotated bibliography of the more significant contributions resulting from this re- search follows under the following five topic headings: (1) valleywide investigations, (2) Los Banos—Kettleman City area, (3) Tulare-Wasco area, (4) Arvin-Maricopa area, and (5) special studies. Professional Papers in the 437 number series represent products of the cooperative program on land subsidence; those in the 497 number series are products of the Federal program on mechanics of aquifer systems. At the end of this report, complete bibliographic cita- tions are given. Many additional shorter papers have been published or open filed. Some of these are referred to in the text and cited under references. ANNOTATED BIBLIOGRAPHY VALLEYWIDE INVESTIGATIONS Inter-Agency Committee on Land Subsidence in the San Joaquin Valley, “Progress report on land- subsidence investigations in the San Joaquin Val- ley, California, through 1957.” Prepared chiefly by J. F. Poland, G. H. Davis, and B. E. Lofgren of the Geological Survey (1958). Reviews the program of the Inter-Agency Committee on Land Subsidence in the San Joaquin Valley and describes the work accomplished through 1957. Includes maps and graphs showing results of precise leveling in the H5 Los Banos—Kettleman City and Tulare—Wasco areas. Includes maps of areas of shallow subsidence (hydrocompaction) and reports on construction and operation of test plots. Summarizes geologic and hydrologic aspects of subsidence due to artesian- head decline. Professional Paper 497—A, "Physical and hydrologic properties of water-bearing deposits in subsiding areas in central California,” by A. I. Johnson, R. P. Moston, and D. A. Morris (1968). To provide infor- mation on the water-bearing deposits in the princi- pal subsiding areas, six core holes were drilled in the San Joaquin Valley as part of the program of the Inter-Agency Committee on Land Subsidence in the San Joaquin Valley. In all, 462 samples from these core holes were tested by the US. Geological Survey for physical and hydrologic properties, and 86 samples were tested by the US. Bureau of Rec- lamation for engineering properties, including one-dimensional consolidation tests. This report presents core-hole logs and laboratory data in tabu- lar and graphic form, describes methods of labora- tory analysis, and shows interrelationships of some of the physical and hydrologic properties. Professional Paper 497—C, “Petrology of sediments un- derlying areas of land subsidence in central California,” by R. H. Meade (1967). Describes pet- rologic characteristics that influence compaction of sediments in the San Joaquin and Santa Clara Val- leys, including particle size, clay minerals, and as- sociated ions. Tabular presentation of results of laboratory tests from four core holes in the Los Banos—Kettleman City area, two each in the \Tulare-Wasco area and Santa Clara Valley, and from one in the Arvin-Maricopa area. Montmoril- lonite is the principal clay mineral in each area. Professional Paper 497—D, “Compaction of sediments underlying areas of land subsidence in central California,” by R. H. Meade (1968). This report relates, partly by statistical analysis, the variation in overburden load and petrologic factors to varia- tions in the pore volume and fabric of the water— bearing sediments in subsiding areas in the San Joaquin and Santa Clara Valleys. These sediments have been compacted by effective overburden loads ranging from 3 to 70 kilograms per square cen- timetre (40—1,000 lbs. in *2). LOS BANOS—KETTLEMAN CITY AREA Professional Paper 437—A, “Alluvial fans and near- surface subsidence in western Fresno County, California,” by W. B. Bull (1964a). A study of com- paction caused by water percolating through moisture-deficient alluvial-fan deposits above the H4 STUDIES OF LAND SUBSIDENCE “ ‘z‘. 29. 06:9 <6 / 9909950 ‘33:? 6’ /’6’ do ‘ » ‘> ’ ’ 6606/ ozozozo‘o’QQWgW’oQ‘o’o‘v/Q 999900 o’ooooo’o’o’o 09999040999999 %:®:W»&:®&€l %:o£s§b’o’o’®%%’ o.:’¢’o’o’oo’o‘ ¢ « w 9’»: m W 99 Q FIGURE 2.—Well-numbering system. by the Geological Survey and the State of California the range (R. 12 E.), the number between the hyphen shows the locations of wells according to the rectangu- and the letter indicates the section (sec. 16), and the lar system for the subdivision of public lands. For ex- letter following the section number indicates the ample, in the number 12/12—16H2, the part of the 40-acre subdivision of the section as shown in figure 2. number preceding the slash indicates the township (T. Within each 40-acre tract, wells are numbered serially 12 S.), the part between the slash and the hyphen shows as indicated by the final digit of the well number. Thus, SAN JOAQUIN VALLEY, CALIFORNIA supplied to irrigation districts south of the Kaweah River. Importation from the Friant-Kern Canal to the east side area south of the Kern River did not begin until 1966. Surface-water imports to the northwestern part of the area Via the Delta-Mendota Canal began in the early 1950’s. Additional large surface-water imports from the Sacramento—San Joaquin Delta to deficient areas on the west side and to the south end of the valley are being provided by the California Aqueduct and its joint-use reach between Los Banos and Kettleman City. This joint-use facility serves the San Luis project area of the Bureau of Reclamation and transports State water south to Kettleman City. The joint-use reach was com— pleted in 1968, and water deliveries from the aqueduct to the San Luis project area increased from 200,000 acre-feet in 1968 to 865,000 in 1972. After completion of the distribution system in the middle 1970’s, a maximum of about 1.2 million acre-feet of water can be delivered annually to the San Luis project area. The California Aqueduct was completed south to the Tehachapi Mountains in 1970, delivered 570,000 acre- feet to the southern part of the San Joaquin Valley in 1971, and eventually will supply 1.35 million acre—feet per year to the San Joaquin Valley south of Kettleman City under long-term contracts. Surface-water imports to subsiding areas through the Friant-Kern Canal and the California Aqueduct through 1972 are given in tables 3—5. As a result of the importation of large surface-water supplies, pumping of ground water has been reduced, and the rapid decline of artesian head has been reversed in parts of the areas of overdraft. By the end of 1971, many hundreds of irrigation wells were idle, and sub- sidence trends were leveling out as stresses on the de- posits were reduced. Today (1973), after three decades of overdraft, much of the overdrawn area of the San J oa- quin ground-water basin is returning to a stable water budget, and artesian pressures are recovering toward their presubsidence levels. Although subsidence has caused serious and costly problems, not all its effects have been bad. The deposits of the ground-water basin are now largely “preconsoli- dated” to their historic low water levels, and thus the basin can be managed for cyclic storage nearly to the historic low levels without the threat of serious subsid- ence. Also, the basin has provided a field laboratory for testing compression characteristics of complex aquifer systems, in situ, and for measuring mechanical and storage parameters of aquifer systems under a wide range of loading stresses. An incidental minor economic benefit is that the depth to water and hence the pump- ing lift have increased more slowly than if comparable volumes of water had been withdrawn from a less com- pressible aquifer system. H3 PURPOSE OF REPORT This report is part of a study of land subsidence in California in financial cooperation with the California Department of Water Resources; the study is closely interrelated with a concurrent Federal research inves- tigation of the mechanics of aquifer systems. Subsid- ence in the San Joaquin Valley has been studied in this cooperative program since 1956. This report is intended to present an up—to-date factual summary of recorded land subsidence in the valley. More specifically, the purpose is to show the overall extent and magnitude of subsidence for the full period of available vertical con- trol, to describe the several causes of subsidence, to present the latest available information on magnitude and rates of subsidence in the principal subsiding areas, to report on the volume of subsidence and, where possi- ble, its relation to pumping draft, and to ShOW the rela- tionship between water-level change (stress change), measured compaction, and subsidence, chiefly by use of computer plots of Geological Survey field data. These computer graphs contain the essence of 13 years of field measurements by the Geological Survey. From these data, the stress-strain characteristics of complex aquifer systems can be obtained and their rela- tion to the magnitude, rate, and causes of subsidence studied. The report incorporates field data through De- cember 1970 and demonstrates that water levels at many of the observation sites are in the transition from a declining to a rising trend. ACKNOWLEDGMENTS The writers acknowledge the cooperation of Federal, State, and local. agencies, irrigation districts, private companies, and individuals. All leveling data used in the preparation of the various subsidence maps and graphs and in calculating magnitudes and rates of sub- sidence were by the National Geodetic Survey, a com- ponent of the National Ocean Survey1 (formerly the US. Coast and Geodetic Survey). Water-level data utilized in this report were chiefly from field measure- ments by the Geological Survey, but some records were from the Bureau of Reclamation, the California De- partment of Water Resources, the Pacific Gas and Elec- tric Co., and irrigation districts. Many Survey workers have contributed to this continuing research program; some of these are listed in the section “Annotated Bib- liography.” WELL-NUMBERING SYSTEM The well-numbering system (fig. 2) used in California 1The agency requests that all inquires for geodetic control data (including vertical-control data) be directed to the National Geodetic Survey, Rockville, Md. 20852 and advises that this name will replace Coast and Geodetic Survey on future publications. Accordingly, sub- sequent reference in this report is to the National Geodetic Survey. H2 120° 1 o Merced 37° — 36° -— EXPLANATION Outline of valley Drawn chiefly on boundary of consolidated rocks // ’///// Area where subsidence due to water-level decline is more than 1 foot Area of subsidence due to hydrocompaction E Area of little or no subsidence 0 10 i—l—L‘l—l'i—l_L——i 0 1o 20 30 4o KILOMETRES STUDIES OF LAND SUBSIDENCE 118°- \f K rt rea 0 ~ IS repo 0 Bakersfiel . EMIGDIO MTS 20 30 40 MILES Base from U.S. Geological Survey l:l,000,000, State base map, 1940 FIGURE 1.—Pertinent geographic features of central and southern San Joaquin Valley and areas affected by subsidence. caused numerous farming and engineering problems. Clearly, remedial action was urgently needed. Importation of surface water to areas of serious over- draft began in 1950 when water from the San Joaquin River was brought south through the Friant-Kern Can- al, which extends to the Kern River (fig. 1). Of the average annual deliveries of about 1 million acre-feet of water from this canal, about 80 percent has been STUDIES OF LAND SUBSIDENCE LAND SUBSIDENCE IN THE SAN JOAQUIN VALLEY, CALIFORNIA, AS OF 1972 By].F. POLAND, B. E. LOFGREN, R. L. IRELAND, and R. G. PUGH ABSTRACT Land subsidence which began in the mid-1920’s due to ground- water overdraft in the San Joaquin Valley has caused widespread concern for the past two decades. Withdrawals for irrigation increased from 3 million acre-feet in 1942 to 10 million acre—feet in 1966. Water levels declined at unprecedented rates during the 1950’s and early 1960’s. Pumping lifts became inordinately high, well casings failed at alarming rates, and differential settlement caused numerous farming and engineering problems. By 1970, 5,200 square miles of valley land had been affected, and maximum subsidence exceeded 28 feet. The valleywide volume of subsidence totaled 15.6 million acre-feet—one-half the initial storage capacity of Lake Mead. This subsidence represents one of the great environmental changes im- posed by man. Importation of surface water to the northwestern and eastern areas of overdraft in the valley began in the 1950’s and to the much larger western and southern areas in the late 1960’s. Canal imports have largely replaced ground-water pumpage in these areas. As of 1973, after three decades of continued declining water levels, many hun- dreds of irrigation wells are idle and water levels are rising. Through- out much of the valley, artesian pressures are recovering toward their presubsidence levels, and elevations of the subsiding land surface are stabilizing. Basic-data graphs and computer-plotted stress-strain relationships constitute a major part of this report. They are based on 10—13 years of detailed field measurements of both water-level change and compac- tion collected by the US. Geological Survey at 20 selected locations in the San Joaquin Valley. The recharge characteristics of a ground-water reservoir are indi- cated roughly by the volume ratio, which is subsidence/pumpage. In the Los Banos—Kettleman City area, the values of this ratio range from less than 0.2 near the perimeter to more than 0.6 in the central part of the area. In the corresponding parts of the Arvin-Maricopa area, the ratio ranges from near 0 to more than 0.4. INTRODUCTION THE SUBSIDENCE PROBLEM Land subsidence in the San Joaquin Valley, Calif, represents one of the great changes man has imposed on the environment. About 5,200 square miles of irrigable land, one-half the entire valley, has been affected by subsidence, and maximum subsidence exceeded 28 feet in 1970; by 1972 subsidence was about 29 feet. Throughout most of the area, subsidence has occurred so slowly and over such a broad area that its effects have gone largely unnoticed by most residents. It has created serious and costly problems, however, in construction and maintenance of water-transport structures; also, many millions of dollars have been spent on the repair or replacement of deep water wells because of ruptured casings. The San Joaquin Valley (fig. 1) is a broad alluviated structural trough constituting the southern two-thirds of the Central Valley of California. It is about 250 miles long, averages about 35 miles in width, and encompas- ses 10,000 square miles, excluding the rolling foothills that skirt the valley on three sides. Figure 1, showing the pertinent geographic features of the area discussed in this report, covers the southern four-fifths of the valley. Agricultural development in the San Joaquin Valley has been intensive, especially since World War I . In the eastern part of the valley from the Kings River north, surface streams from the Sierra Nevada supply most of the irrigation needs, but are supplemented by ground water, especially after midsummer when streamflow is deficient. From the Kaweah River south—except for the Kern River and its alluvial fan—and in the west-central area from Mendota to Kettleman City, local surface— water supplies have been small to negligible. Prior to the construction of major canals or aqueducts, irriga- tion was almost Wholly from thousands of large and deep irrigation wells; conditions of ground-water over- draft have prevailed since the 1930’s. Extractions of ground water in the San Joaquin Valley for irrigation increased from 3 million acre-feet in 1942 to at least 10 million acre-feet in 1964 (Poland and Evenson, 1966) and in 1966 (Ogilbee and Rose, 1969a, b; Mitten and Ogilbee, 1971). The trend of declining water levels was well estab- lished long before the problems or the causes of subsid- ence were recognized. Few areas had sufficient level- ing control to reveal the subtle land-surface changes; however, induced by greater and deeper pumping, the subsidence that began in several centers of overdraft in the 1920’s became of widespread concern in the late 1940’s and early 1950’s. Through the 1950’s and early 1960’s, water levels declined at an unprecedented rate throughout much of the area. Pumping lifts became inordinately high, well casings failed at an alarming rate, and differential settlement of the land surface H1 TABLE English unit Inch Foot Mile Acre Square mile N \IO'J CONTENTS V TABLES Page . Years of leveling control of the network of bench marks in three subsidence areas by the National Geodetic Survey_.H10 . Summary of extent and volume of subsidence, 1926—70, San Joaquin Valley ____________________________________ 12 . Surface-water deliveries through the joint-use reach of the California Aqueduct to the Los Banos—Kettleman City area, 1967—72 __________________________________________________________________________________________ 45 . Summary of surface-water deliveries from the Friant-Kern Canal to irrigation districts in the Tulare-Wasco area, 1949—72 _______________________________________________________________________________________________ 46 . Surface-water imports from the Friant-Kern Canal and the California Aqueduct to the Arvin-Maricopa area, 1962— 72 ______________________________________________________________________________________________________ 47 . Annual compaction rates at compaction-measuring sites, San Joaquin Valley ___________________________________ 50 . Tentative elastic storage parameters _________________________________________________________________________ 53 . Notes on wells or sites for which records are included in figures 53—78 ___‘ ______________________________________ 77 METRIC CONVERSION TABLE Equivalent Metric English Equivalent Metric Symbol ( multiply by) unit Symbol unit Symbol (multiply by—) unit Symbol (in.) 2.54 Centimetres (cm) U.S. gallon (gal) 3.785 Litres ______ (ft) 0.3048 Metre (m) Acre-foot (acre-ft) 1,233.5 Cubic metres (m3) (mi) 1.609 Kilometres (km) U.S. gallon per (g/m) 0.0631 Litres per (US) ______ 0.405 Hectare _ _ - _ _ _ minute second (miz) 2.590 Square (kmz) Cubic feet per (ft3/s) 1.699 Cubic metres (ma/min) kilometre second per minute IV FIGURE 29. 30. 31. 32. 33—36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 51—78. CONTENTS . Page Graph showing cumulative volume, 1926—70, Tulare-Wasco area ________________________________________________ 31 Graph Showing relation of magnitude of subsidence to area, 1926-70, Tulare-Wasco area _________________________ 31 Land-subsidence profiles along US. Highway 99 from Tulare to Famoso, 1901-2 to 1970 __________________________ 32 Hydrographs of three piezometers at 328/28E—30D1 in the center of the Arvin-Maricopa subsidence area and the sub- sidence graph of a nearby bench mark ____________________________________________________________________ 33 Maps showing: 33. Land subsidence, 1965—70, Arvin-Maricopa area ________________________________________________________ 34 34. Average annual rate of subsidence, 1965—70, Arvin-Maricopa area _______________________________________ 35 35. Land subsidence, 1957—70, Arvin-Maricopa area ________________________________________________________ 36 36. Land subsidence, 1926—70, and location of subsidence profiles, Arvin-Maricopa area ______________________ 37 Graph showing rate of subsidence, 1926—70, Arvin~Maricopa area ______________________________________________ 38 Graph showing cumulative volume, 1926—70, Arvin-Maricopa area ______________________________________________ 38 Graph showing relation of magnitude of subsidence to area, 1926—70, Arvin-Maricopa area _______________________ 38 Profiles of land subsidence along US. Highway 99, Bakersfield to Grapevine, 1926—70 ____________________________ 39 Profiles of land subsidence along the Maricopa Road, Maricopa to Mettler, 1935—39 to 1970 ______________________ 40 Map showing proportion of pumpage derived from water of compaction, 1963—66, Los Banos—Kettleman City area____ 41 Map showing proportion of pumpage derived from water of compaction, 1962—65, Arvin-Maricopa area ______________ 42 Pressure diagram for unconfined aquifer and confined aquifer system; head reduction, confined aquifer system only 43 Effective-stress diagrams for a confined aquifer system overlain by an unconfined aquifer ________________________ 44 Graph showing surface-water imports from the joint-use reach of the California Aqueduct to the Los Banos—Kettle- man City area, 1967-72 __________________________________________________________________________________ 45 Graph showing surface-water deliveries from the Friant-Kem Canal to irrigation districts in the Tulare-Wasco area, 1949—7 2 ________________________________________________________________________________________________ 46 Graph showing surface-water imports to the Arvin-Maricopa area, 1962—72 ______________________________________ 46 Diagram of recording compaction gage ________________________________________________________________________ 48 . Map showing location of water-level and compaction measuring sites ____________________________________________ 49 Computer plots showing: 51. Stress change versus compaction at 16/15—34N _______________________________________________________ 51 52. Stress change, compaction, and strain, well 18/19—20P2 _______________________________________________ 51 53. Hydrographs, compaction, and subsidence, 12/12—16H __________________________________________________ 56 54. Hydrograph, compaction, and subsidence, 13/12—20D1 __________________________________________________ 57 55. Hydrograph, compaction, and subsidence, 13/ 15—35D5 __________________________________________________ 57 56. Hydrographs, change in applied stress, compaction, subsidence, and stress-strain relationship, 14/13—11D _ 58 57. Hydrograph, compaction, and subsidence, 14/12—12H1 __________________________________________________ 59 58. Hydrograph, compaction, and bench-mark subsidence, 15/13—11D2 ______________________________________ 59 59. Hydrograph of well 15/14—14J 1, depth 1,010 feet ________________________________________________________ 60 60. Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship, 15/16— 31N3 ____________________________________________________________________________________________ 60 61. Hydrographs, change in applied stress, compaction, subsidence, casing separation, and stress-compaction relationship, 16/15—34N ___________________________________________________________________________ 61 62. Hydrograph and compaction, 17/ 15—14Q1 ______________________________________________________________ 63 63. Hydrograph, compaction, and subsidence, 18/16—33A1 __________________________________________________ 63 64. Hydrographs, change in applied stress, compaction, subsidence, and stress-strain relationship, 18/ 19—20P __ __ 64 65. Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship, 19/16— 23P2 _________________________________________________________________________________ -_ __________ 65 66. Hydrograph, compaction, and subsidence, 20/18—6D1 ____________________________________________________ 66 67. Hydrograph, change in applied stress, compaction, and stress-strain relationship, 20/18—11Q1 ____________ 66 68. Hydrograph, change in applied stress, compaction, subsidence, and stress-strain relationship, 20/18—11Q3____ 67 69. Hydrograph, casing protrusion, and casing separation, 20/ 18—11Q2 and 11Q3 ____________________________ 68 70. Hydrographs, change in applied stress, compaction, subsidence, and stress-strain relationship, 23/25—16N ______________________________________________________________________________________ 69 71. Hydrographs, change in applied stress, compaction, and stress-strain relationship, 23/25—16N3 and N4 __________________________________________________________________________________________ 70 72. Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship, 24/26— 34F1 ____________________________________________________________________________________________ 71 73. Hydrograph and change in applied stress at 25/26—1A2; compaction, subsidence, and stress-compaction re- lationship at well 24/26—36A2 ____________________________________________________________________ 72 74. Hydrograph, change in applied stress, compaction, and stress-compaction relationship, 25/26—1A2 __________ 73 75. Hydrograph of well 25/26—1K2, perforated 1,000—2,200 feet ______________________________________________ 74 76. Hydrograph, compaction, and subsidence, 12N/21W—34Q1 ______________________________________________ 74 77. Hydrograph, change in applied stress, compaction, subsidence, and stress-compaction relationship, 32/28— 20Q1 ____________________________________________________________________________________________ 75 78.. Hydrograph, change in applied stress, compaction, subsidence, and stress-strain relationship,11N/21W—3B1__ 76 ”gnu-l 7F" '1!er W1”. CONTENTS Page Metric conversion table ____________________________________ V Abstract __________________________________________________ H1 Introduction ______________________________________________ 1 The subsidence problem ________________________________ 1 Purpose of report ______________________________________ 3 Acknowledgments ____________________________________ 3 Well-numbering system ________________________________ 3 Reports by the Geological Survey __________________________ 5 Annotated bibliography ________________________________ 5 Valleywide investigations __________________________ 5 Subsidence due to water-level decline ______________________ San Joaquin Valley ____________________________________ Los Banos—Kettleman City area ________________________ Tulare-Wasco area ____________________________________ Arvin—Maricopa area __________________________________ Relation of subsidence to pumpage __________________________ Los Banos—Kettleman City area ________________________ Arvin-Maricopa area __________________________________ Analysis of stresses causing subsidence ____________________ Methods for stopping or alleviating subsidence ______________ Measurement of compaction ________________________________ Los Banos—Kettleman City area ____________________ 5 Tulare-Wasco area ________________________________ 6 Arvin-Maricopa area ______________________________ 6 Special studies ____________________________________ 6 Causes of subsidence ______________________________________ 7 FIGURE 1. DON) ease 8—11. 12—17. 18. 19. 20. 21. 22. 23. 24-27. 28. Interrelations of water-level change, compaction, and subsidence __________________________________________ Examples of stress-strain graphs ______________________ Computer plots of field records ________________________ References cited __________________________________________ ILLUSTRATIONS Map showing pertinent geographic features of central and southern San Joaquin Valley and areas affected by subsid- ence ____________________________________________________________________________________________________ . Diagram showing well—numbering system ____________________________________________________________________ . Map showing network of leveling by the National Geodetic Survey and three areas of detailed studies of land subsid- ence ____________________________________________________________________________________________________ Map showing location of selected observation wells, nearby bench marks, and boundary of principal confining beds__ Map showing land subsidence, 1926—70, San Joaquin Valley ____________________________________________________ . Graph showing cumulative volume of subsidence in the San Joaquin Valley, 1926—70 ____________________________ . Profiles of apparent subsidence and water-table decline along the Southern Pacific Railroad between the San Joaquin and Kings Rivers ________________________________________________________________________________________ Graphs showing: 8. Subsidence and artesian-head change 10 miles southwest of Mendota ____________________________________ 9. Subsidence and artesian-head change near Cantua Creek ________________________________________________ 10. Subsidence and artesian-head change near Huron ______________________________________________________ 11. Subsidence and head change in two zones near Hanford ________________________________________________ Maps showing: 12. Land subsidence, 1966—69, Los Banos—Kettleman City area ______________________________________________ 13. Average yearly rate of subsidence, 1966—69, Los Banos—Kettleman City area ____________________________ 14. Land subsidence, 1955—69, Los Banos—Kettleman City area ______________________________________________ 15. Land subsidence, 1926—69, Los Banos—Kettleman City area ______________________________________________ 16. Land subsidence, 1969—72, Los Banos—Kettleman City area ______________________________________________ 17. Land subsidence, 1926—72, Los Banos—Kettlemen City area ______________________________________________ Graph showing rate of subsidence, 1926—72, Los Banos—Kettleman City area ____________________________________ Graph showing cumulative volumes of subsidence and pumpage, 1926—69, Los Banos—Kettleman City area ________ Graph showing relation of magnitude to area of subsidence, 1926—69, Los Banos—Kettleman City area ____________ Profiles of subsidence, 1943—69, Tumey Hills to Mendota __________________________________________ W ___________ Profiles of subsidence, 1943—69, Anticline Ridge to Fresno Slough ______________________________________________ Profile and graph showing subsidence and water-level fluctuations northeast of Delano __________________________ Maps showing: 24. Land subsidence, 1962—70, Tulare—Wasco area __________________________________________________________ 25. Average yearly rate of subsidence, 1962—70, Tulare-Wasco area __________________________________________ 26. Land subsidence, 1948—70, Tulare-Wasco area __________________________________________________________ 27. Land subsidence, 1926—70, and location of subsidence profile, Tulare-Wasco area __________________________ Graph showing rate of subsidence, 1926—70, Tulare-Wasco area ________________________________________________ III Page H8 8 14 24 30 36 36 38 39 44 47 48 48 51 53 10 11 12 13 14 14 15 16 17 18 19 20 21 22 23 23 23 24 25 26 27 28 29 30 31 SUBSIDENCE, IN FEET SUBSIDENCE, IN FEET DEPARTMENT OF THE INTERIOR PROFESSIONAL PAPER 437—1 AQUEDUCT MILES VERTICAL EXAGGERATION X10,560 LAND SUBSIDENCE ALONG THE CALIFORNIA AQUEDUCT FROM MILE 174 TO MILE 218, SOUTH OF KETTLEMAN CITY, 1967 TO 1978 PROFILES OF LAND SUBSI IDENCE ALONG THE CALIFORNIA AQUEDUCT IN T AQUEDUCT MILES VERTICAL EXAGGERATION X10,560 LAND SUBSIDENCE ALONG THE CALIFORNIA AQUEDUCT FROM MILE 238 TO MILE 287 (SOUTHWEST OF WIND GAP PUMPING PLANT) IN THE ARVIN—MARICOPA AREA, 1970 TO 1978 LOS BANOS-KETTLEMAN CITY AREA, SOUTH OF KETTLEMAN CITY, AND IN THE ARVIN—MARICOPA AREA, CALIFORNIA U. s. GEOLOGICAL SURVEY PLATE 1 :1- "-12 5% 32" w\ 219- I.” ii I II A 4 .- 3 m: 8 B 8:9 2 «=2 are w. «s . I I I I I on o 8,; oarsN 93 m I I m N NN'KI‘ a: N N N“ N NNNN mm m m 0" m m 0’) comm FEE ;2 225 PP.— catch .2 #55 8558 g B I; |§ g g 8 O m 0') . ' E: E3 333% 3 ll 5 I ‘ I. I { E 5 $38 §§s eggs 82-38 8% 8 8§888 I I I ‘ ggg 8 22°53 2252 g 2 2 mg- g c; 2 W N 22 ~ ~ 2 E6 EGSK .9 §m§ 2 § m Em 2 2 a 8 ° ‘0 FD ; 3X>§ 25 U E I >4 5 Z E§°= m m m N< E ”‘3“ ”I“ * 2 ° E2" _ _ ' \11’IVSCIENG‘Qr—«*' 5 8'8 3 E 5’ IH HII I «553 3' 8' <5 :35 2 2 :' 2 II III IWII III II I I I III FREEBOARD RAISED '5 g g s s 33 BB§2§ 2 g 82.9 olg \~-——~ ; UIU ; " E PRECONSOLIDATED 2 U '— " " " " x 5‘ L '— P ; x > 5 ; 5 E E 5 o m "' O '7 D > g 8'0 D (I) 8% L HYDROCOMPACTION AREA J L P R E C O N S O L I D A T E D H Y D R O C O M P A C T I O N A R E A :l 5|: mu: F m|_ "m II II I II I III II II III II I I I III I E” Eu. NOVEMBER—DECEMBER I967 BASE NOVEMBER—DECEMBER 1967 BASE I 0 “\- \ /‘ / ' \_/’ /,-\ \.___ .— \ / .\ ____,._. //~\\ \\\ \_ ._ \ _/ / \\ W — \. .K / // V“ \ \__/ - . ,_ . // / \\ \\ ’ \ //' \\\ \._’,.-—— \,/ \ '/./- \_\ \. December1968‘Januarv14969 / /,_.//_ \\’/// \\\ fi/ \ V ///‘\\ \\ .— \ [\Vf—V - / /—"\\ \_ _/' \ __, /. i . : / \\ /, \ ~ ~\_____ \ / ‘ /// z \\ ’___\ \\\// ll \\ \_ ,/ \ __ /-\ \ /’—\~ \\ \ / October—November 1969 / /’/ /// '— ‘\/ \ ,/ \ I \ \v/ \/ // \ / ’F———-——/ / / / U-I \ \_’ \ / \\ \\ ’ /’T‘\ \\ ,— \' /——-——_—’/ / / / E \ /-\ \ / I \ JanuaI’Y'March, /_.\ _\ \\///\\ // \ _ \\ / / \- \ \ , I \ ‘ L //'—‘\\975 x \ / \ ,/ ~-" A \ \ 71 ’ / \\\TT/ / \ _’ 19 \\\\"’// \\\ T TTTTT ’/ \ JI //’ \\\ \\ N vember1970‘JanuaWI/9’/ // E \ embeL 77L . , // ‘x\ \ __ \ __ \\ 0 " _ _ _ \\ I \th/ ~\AEr/l 197 / \\ \\_,/ // \ |//-‘ \\—” ‘\\\ \_/ - _ _/’ -FebruaTY1972 /// // LU —— y’ \ 8 / \ / I ‘—‘\ / er1971 / o \_, ,———J \ I, \ \ \ , N vemb ,/’ \ / I\\ II ~\‘\ \ ” _________ / E \/ \ \J/ \\ I \ / ————————— ’z / D I _\\\\ \ / / ” / (T) / \\/ I \ \--/ I] (/‘~———’/ g \ \\ / ,__,-—/ “3 EXPLANATION \ \ / /’\_// 3 '— \\ \\ // // I Bench markonaqueduct structure \ / \._’ \\ / A Bench mark adjacent to the aqueduct See fig.6 for location of profiIe \ / \\ // Note: all other bench marks are in the \./ l aqueduct lining 95 100 105 110 115 120 125 130 135 140 145 150 155 160 165 170 AQUEDUCT MILES VERTICAL EXAGGERATION X10,560 LAND SUBSIDENCE ALONG THE CALIFORNIA AQUEDUCT FROM MILE 92 TO MILE 174 IN THE LOS BANOS—KETTLEMAN CITY AREA, 1967 TO 1978 (6 v— V m: 2 “FE < 32 i 2g ‘5 Z to B E CD «IE :1: 5?: ARROYO PINO CREEK I LOST HILLS OIL FIELD J PRECONSOL'DATED 7‘5 E E E 3 U E PRECONSOLIDATED 1 E ”YDROCOMPACT'ON AREA «>5 2‘ E 3 g I» E g E PRECONSOLIDATED HYDROCOMPACTION AREA c ._ ,_ c» I '53 " g3 If PRECONSOLIDATED HYDROCOMPACTION AREA ET: 3 JL HYDROCOMPACTIONAREA V) L. E §§ m In common mmmm mm": 0“ FE ‘3 m m m ”mm” mm B m m m m '33” m “'5:QO ‘9 mm mm 5 agaaem‘fi g grg and: a: man mmmmmm mmmmmMmmmzammmmmm mml‘mmmmmmmmm mm mmmmmmmmmmmm mm m mm mm mgmmmmmmmmmm%§!mm :- ’II‘I I 322%8 8 3 $3282228388828 2322838255q£332222 339-5353533528 85”‘”‘°3253-9fi* 888Es§SS§888283§388833288885888§2§8222$8288883 88233888888885 88888 88 83.938888898826338 g§ a. g A..- . «_/\\/ \7———\_/\, -<;=—\ ,2 ’ /\ ,§ 1975//’ \f \\,/ /—‘—-——/ ‘\ \\ ,_\ / \\\\~,//—~ ‘\\\\ ’91:” // \_’,—\\\ \ /.——— \ \“‘Y)& / - / \f\4 \\ / f\\ / _—-‘ \ ’___‘ l/ \ / \/ \ '/s \ . . ,,_L\ ___, \ _/,——/ “I, A I \I \ 973 \ ,/;—\ \ / \ / \, \91 \\ \"\'\" ._ -/ /’ \\ . —March1 ,—__/.’/'_ '9)§\~-/ I ’\ ' \V’VJ ‘ \"// \ \\ // \ / \ \ ___\~ / \_/ // \\ Jaw' f.{75 . ‘// I I \\/ \j / \_\ // \/ \~——~2\ 'v-/ \“ / \\ ‘\ /'\ /‘ mbEIJQU-ApriLBZEV / I ' ~_/ \\-’/ \/ —— \\\ __ ,r"\\\__,/’/ \\ \J ‘ “(f/6’/ \T/ \——// _ 1 _ I I Regional subsidence1926—70 greaterthan 1.0ft \ __ \\ //” ‘\_,// \\ ,/“\\ // H (see fig. 38) " V \___z \ / \_’/ II \ / u \\\—/ T Turnout structure \ I __ ——2I—- _» _ Hydrocompaction area L (seefig.38) See Ii .6forlocutionof rofiIe See f' .6forlocation of rofile Hydrocompaction area Hydrocompaction area 9 p I9 P F (see fig. 38) I (see fig. 38) J 3 | I I I ’1 175 180 185 190 195 200 205 210 215 240 245 250 255 260 265 270 275 280 285 filNTERIOR—GEOLOGICAL SURVEY, HESTON, VIRGINIA—1984—682717