IC-NRLF SB 2b 572 'Jk m GIFT OF MICHAEL REESE J ^WWv ; MANUAL OF IRRIGATION ENGINEERING BY HERBERT M, WILSON, C.E. FIRST EDITION, FIRST THOUSAND. NEW YORK: JOHN WILEY & SONS, 53 EAST TENTH STREET. 1893. ,5-0 67$ COPYRIGHT, 1893, BV HERBERT M. WILSON. ROBERT DKUMMOND, Electrotyper. 444 & 446 Pearl Street, New York. PREFACE. THE need of a comprehensive treatise on irrigation has been so frequently brought to my attention during the last few years, that I have undertaken to write this book with the hope that it may help those who are engaged in the study or practice of irrigation engineering. It is chiefly the result of original investigation, the descriptions of works being made from personal observation in America, Europe, and India. Some of the matter contained in Part I is compiled, and in its preparation I am especially indebted for information and suggestions to the valuable work on " Water Supply Engineer- ing," by Mr. J. T. Fanning. There is added, however, much that is new, a portion of which was obtained from, the reports of Mr. F. H. Newell, Chief Hydrographer of the U. S. Geo- logical Survey. The purpose has been to include in Part I only so much of hydraulics as is an indispensable preliminary to the remainder of the book, or is original matter. Wherever the subject has been treated by others the reader is referred to their works. The entire book relates directly to the conditions surround- ing Western irrigation practice. The examples given and the suggestions made apply immediately to Western methods, though many useful hints a**e borrowed from foreign experi- ence. The classification adopted is original, I believe, and follows closely that employed in reports made by me to the Government, which seem to have met with general approval. In this classification the terms "diversion weirs " and "dams* 1 iii *V PREFACE. have been used with special signification. Under the term "diversion weirs" are included all obstructions built across running streams and designed to act as overflow weirs, though their functions may be those either of storage dams or diversion weirs or both. Under the term "dams" are in- cluded all retaining walls, of whatsoever material, which are intended only to impound water and are not so constructed as to withstand the shock of falling water. These classes neces- sarily overlap to some extent. The subject of the application of water to crops is but briefly touched upon. It would in itself require a volume, and is one of more interest to the farmer than to the engineer. Part III, which treats of storage works, contains much new ma- terial never before brought together, and this is especially true of the chapters on Earth Dams and Pumping. The theory of high masonry dams is but briefly considered, as this subject has already been exhaustively treated by previous writers, to whose works reference is made. What little has been said concerning it is partly compiled, the chief source being Weg- mann's admirable treatise on masonry dams. Great care has been taken throughout the volume to avoid the use of mathe- matics, since many of the formulas given on the flow of water in open or closed channels, on the discharge from catchment basins, and on strains in masonry dams are exceedingly faulty and misleading. We have much to learn before we can apply mathematics to these subjects with accuracy. I consider it better to follow practical usage and experience than theory where the latter is founded on doubtful premises and is liable to produce inaccurate results if adhered to closely. The endeavor has been to prepare a work which will be of value to the practical engineer as well as to the student. It was found impossible to include within the covers of one volume the necessary tables on hydraulics and flow of water. It is believed, however, that this book contains much that will be useful to the practical engineer, and that the teacher of irrigation engineering will find the facts assembled in such manner as to be materially helpful. rREFA CE. v The effort has been to illustrate all the important works described, as well as types of works, in order that practising engineers may obtain suggestions from the experience of others. I am indebted to the courtesy of the Director of the U. S. Geological Survey for numerous electrotypes of illustrations, which had been previously published in reports made by me. Several illustrations were also obtained through the courtesy of the Secretary of the American Society of Civil Engineers, being electrotypes of those used in papers read by me before that society. WASHINGTON, D. C., January, 1893. CONTENTS. CHAPTER I. INTRODUCTION. ART. PAGE 1. Extent of Irrigation i 2. Control of Irrigation Works i 3. Value as an Investment 2 4. Incidental Values 2 5. Cost and Returns of Irrigation 3 PART I. HYDROGRAPHY. CHAPTER II. PRECIPITATION. 6. Relation of Rainfall to Irrigation 5 7. General Rainfall Statistics 6 8. Rainfall Distribution in Detail 6 9. Great Rainfalls 7 10. Suddenness of Great Storms 8 1 1 . Precipitation on River Basins 9 12. Rainfall Statistics by States 9 13. Gauging Rainfall " 14. Works of Reference: Rainfall 12 vii Vlll CONTENTS. CHAPTER III. EVAPORATION AND ABSORPTION. ART. PAGE 15. Evaporation Phenomena 13 16. Measurement of Evaporation 13 17. Amount of Evaporation 15 18. Evaporation from Snow and Ice 17 19. Evaporation from Earth 18 20. Effect of Evaporation on Water Storage 18 21. Percolation and its Amount 18 22. Absorption 19 23. Amount of Absorption in Reservoirs and Canals. ... 20 24. Prevention of Percolation 20 25. Seepage Water 21 CHAPTER IV. RUNOFF AND FLOW OF STREAMS. 26. Runoff 22 27. Variability of Runoff 22 28. Formulas for Runoff 23 29. Examples of Runoff s 24 30. Flood Discharges of Streams 25 31. Discharge in Seasons of Minimum Rainfall 25 32. Regimen of Western Rivers 25 33. Mean Discharge of Streams 27 34. Available Annual Flow of Streams 27 35. Works of Reference: Evaporation, Percolation, and Runoff 27 CHAPTER V. SUBSURFACE WATER SOURCES. 36. Sources of Earth Waters 28 37. Sources of Springs and Artesian Wells 28 38. Artesian Wells 29 39. Examples of Artesian Wells 29 40. Supplying Capacity of Wells 30 41. Tunneling for Water , 30 42. Other Subsurface Water Sources 30 43. Works of Reference : Artesian Wells 3 1 CHAPTER VI. ALKALI, DRAINAGE, AND SEDIMENTATION. 44. Harmful Effects of Irrigation 32 45. Alkali 32 CONTENTS. ix ART - PACK 46. Causes of Alkali 32 47. Waterlogging 33 48. Prevention of Alkali and Waterlogging , 33 49. Chemical Treatment and Leaching 34 50. Drainage 34 51. Excessive Use of Water 34 52. Silt 35 53. Amount of Sediment v 35 54. Prevention of Sedimentation in Reservoirs and Canals 35 55. Fertilizing Effects of Sediment 36 56. Weeds 37 CHAPTER VII. QUANTITY OF WATER REQUIRED. 57. Duty of Water 38 58. Units of Measure for Water Duty and Flow 38 59. Measurement of Water Duty 40 60. Duty per Second-foot 40 61. Depth of Water required to Soak Soil 41 62. Duty per Acre-foot 42 63. Linear and Areal Duty 42 64. Percentage of Waste Land 42 65. Works of Reference: Alkali, Sedimentation and Duty of Water 43 CHAPTER VIII. PRESSURE AND MOTION OF WATER. 66. Physical and Chemical Properties of Water 44 67. Weight of Water 44 68. Pressure of Water 45 69. Amount of Pressure of Water 45 70. Center of Pressure 46 71. Atmospheric Pressure 46 72. Motion of Water 46 CHAPTER IX. FLOW AND MEASUREMENT OF WATER IN OPEN CHANNELS. 73. Factors affecting Flow 48 74. Formulas of Flow in Open Channels 49 75. Kutter's Formula 49 76. Discharge of Streams and Velocities of Flow 5* 77. Surface and Mean Velocities 5 2 CONTENTS. 78. Measuring or Gauging Stream Velocities 52 79. Current Meters 53 80. Gauging Stations 54 81. Use of the Current Meter 55 82. Rating the Meter 55 83. Rating the Station 56 84. Measuring Weirs 57 85. Rectangular Measuring Weir 57 86. Francis' Formulas 58 87. Conditions of using Rectangular Weir 58 88. Trapezoidal Weirs 59 89. Weir Gauge Heights 61 90. Measurement of Canal Water 61 91. Methods of Measurement 62 92. The Statute Inch or Module ....-. 62 93. Foote's Water Meter 63 94. Rating Flumes 64. 95. Divisors 65 96. Works of Reference: Hydraulics 65 PART II. CANALS AND CANAL WORKS. CHAPTER X. CLASSES OF IRRIGATION WORKS. 97. Gravity and Lift Irrigation 66 98. Navigation and Irrigation Canals 67 99. Sources of Supply 67 100. Perennial Canals 68 101. Dimensions and Cost of some Perennial Canals 69 102. Parts of a Canal System 69 CHAPTER XI. ALIGNMENT, SLOPE, AND CROSS-SECTION. 103. Location of Headworks 72 104. Diversion Line 72 105. Relation between Lands and Water Supply 72 106. Survey and Alignment 73 107. Obstacles to Alignment 74 CONTENTS. xi ART. PAGE 108. Sidehill Canal Work 74 IOQ. Curvature 75 1 10. Borings, Trial Pits, and Permanent Marks 76 in. Example of Canal Alignment Ganges Canal 76 112. Example of Canal Alignment Turlock Canal 79 113. Slope and Cross-section 85 114. Limiting Velocity 86 115. Grade for Given Velocities 87 116. Examples of Canal Grades 87 117. Cross-sections 88 118. Form of Cross-section 89 119. Side Slopes and Top Width of Banks 91 120. Cross-section with Subgrade 92 121. Shrinkage of Earthwork 93 122. Cross-section in Rock 93 CHAPTER XII. HEADWORKS AND DIVERSION WEIRS. 123. Location of Headworks 95 124. Character of Headworks 96 125. Diversion Weirs 97 126. Classes of Weirs 98 127. Brush and Bowlder Weirs. 98 128. Rectangular Pile Weirs 99 129. Open and Closed Weirs 99 130. Open Frame or Flashboard Weirs 101 131. Open Masonry Weirs, Indian Type , 104 132. Wooden Crib and Rock Weirs in 133. Construction of Crib Weirs 115 134. Composite Gravel and Rock Weir 115 135. Scouring Effect of Falling Water 1 16 136. Weir Aprons 117 137. Rollerway and Ogee-shaped Weirs 118 138. Water-cushions 119 139. Masonry Weirs ... 121 140. Masonry Weirs founded on Piles 122 141. Masonry Weir founded on Piles and Cribs 122 142. Masonry Weir founded on Cribs 123 143. Masonry Weirs founded on Wells 126 144. Weirs founded on Rock. San Diego Weir 126 145. Henares Weir 127 146. Appleton Weir 128 147. Vir Weir 129 148. Other Masonry Weirs 129 149. Diversion Dams I 3 l XI 1 CONTENTS. CHAPTER XIII. SCOURING SLUICES, REGULATORS, AND ESCAPES. ART. PAGE 150. Scouring Sluices 133 151. Examples of Scouring Sluices 135 152. Automatic Sluice Gates 136 153. Mahanuddy Sluice Shutters. ... 137 1 54. Soane Automatic Sluice Gates 138 155. Relation of Weirs to Regulators 139 156. Classification of Regulators 143 157. General Form of Regulator, 144 158. Arrangement of Canal Head 144 159. Wooden Flashboard Regulators 146 160. Wooden Regulator Gate lifted by Lever 146 161. Wooden Gate lifted by Windlass , 147 162. Gate lifted by Travelling Winch 148 163. Gate raised by Gearing or Screw 148 164. Rolling Regulator Gate 151 165. Hydraulic Lifting Gate 153 166. Escapes . 154 167. Location and Characteristics of Escapes 155 168. Design of Escape Heads 156 169. Sand Gates 157 CHAPTER XIV. FALLS AND DRAINAGE WORKS. 170. Excessive Slope 159 171. Falls and Rapids 160 172. Retarding Velocity by Flashboards on Fall Crest 160 1 73. Retarding Velocity by contracting Channel 161 174. Gratings to retard Velocity of Approach 161 175. Simple Vertical Fall of Wood 162 176. Wooden Fall with Water-cushion 165 177. Masonry Falls 167 178. Wooden Rapids or Chutes 167 179. Masonry Rapids 169 180. Drainage Works 169 181. Drainage Cuts 169 182. Inlet Dams 170 183. Level Crossings , 170 184. Flumes and Aqueducts 172 185. Sidehill Flumes 173 186. Construction of Flumes 175 187. Flume Trestles 177 CONTENTS. xiii AKT - PAGE 188. Iron Aqueducts I77 189. Masonry Aqueducts 181 190. Superpassages 181 191. Inverted Siphons 183 192. Inverted Siphon of Wood 185 193. Inverted Siphons of Masonry 187 CHAPTER XV. DISTRIBUTARIES. 194. Object and Types 191 195. Location of Distributaries jgi 196. Design of Distributaries 193 197. Efficiency of a Canal 194 198. Private Watercourses 196 199. Dimensions of Distributaries 197 200. Distributary Channels in Earth 198 201. Wooden Distributary Heads 198 202. Masonry Distributary Heads 201 203. Iron and Steel Distributary Pipes 201 204. Wooden Distributary Pipes 201 205. Rotation in Water Distribution 202 CHAPTER XVI. APPLICATION OF WATER, AND PIPE IRRIGATION. 206. Methods of Applying Water . 204 207. Sidehill Flooding of Meadows 205 208. Flooding by Checks 206 209. Flooding by Checkerboard System of Squares 207 210. Flooding by Terraces 208 211. Furrow Irrigation of Vegetables and Grain 209 212. Combined Flooding and Furrow Irrigation of Orchards 210 213. Irrigating Orchards by Small Furrows 211 214. Subsurface Irrigation 212 215. Sub-irrigation Pipes 212 216. Method of Laying Pipes 213 217. Measuring Sub-irrigation Waters 214 218. Works of Reference: Canals and Canal Works 214 XIV CONTENTS. PART III. STORAGE RESERVOIRS. CHAPTER XVII. LOCATION AND CAPACITY OF RESERVOIRS. ART. PAGE 219. Classes of Storage Works 216 220. Relation of Reservoir Site to Land and Water Supply 216 221. Character of Reservoir Site 218 222. Topography and Survey of Reservoir Sites 218 223. Geology of Reservoir Sites 219 224. Cost and Dimensions of some Great Storage Reservoirs 222 CHAPTER XVIII. EARTH AND LOOSE-ROCK DAMS. 225. Earth Dams or Embankments 223 226. Dimensions of Earth Dams 224 227. Foundations. . . '. 225 228. Foundations of Masonry Core and Puddle Wall 226 229. Springs in Foundations 227 230. Masonry Cores, Puddle Walls, and Homogeneous Embankments.... 227 231. Masonry Cores 229 232. Puddle Walls and Faces 230 233. Puddle Trench 231 234. Construction of Embankment 231 235. Homogeneous Earth Embankment 233 236. Embankment Material 234 237. Interior Slope and Paving 235 238. Earth Embankment with Masonry Retaining Wall 237 239. Earth and Loose-rock Dams. Pecos Dam 239 240. Loose Rock and Earth Dam. Idaho Dam 240 241. Loose-rock Dams 242 242. Walnut Grove Dam 243 243. Crib Dams 244 244. Loose-rock Dam with Masonry Retaining Walls 246 CHAPTER XIX. MASONRY DAMS. 245. Theory of Masonry Dams 248 246. Stability of Gravity Dams 249 247. Stability against Sliding 251 248. Coefficient of Friction in Masonry 252 CONTENTS. XV ART. PACK 249. Stability against Crushing 254 250. Limiting Pressures 255 251. Stability against Overturning 256 252. Molesworth's Formula and Profile Type 259 253. Height and Top Width of Dam 260 254. Profile of Dam 260 255. Curved Masonry Dams 261 256. Design of Curved Dam 265 257. Foundations 267 258. Material of which Constructed. Ashlar Masonry 267 259. Concrete 268 260. Rubble Masonry 270 261. Cement 271 262. Details of Construction 271 263. Submerged Dams 273 264. Construction in Flowing Streams 274 265. Specifications and Contracts 275 266. Examples of Masonry Dams 276 267. Furens Dam, France 276 268. Gran Cheurfas Dam, Algiers 278 269. Tansa Dam, India 279 270. Bhatgur Dam, India 281 271. New Croton Dam, New York 282 272. Periar Dam, India 285 273. Beetaloo Dam, South Australia 287 274. San Mateo Dam, California ... 287 275. Sweetwater Dam, California 289 276. Vyrnwy Dam, Wales 289 277. Betwa Dam, India 291 278. Turlock Dam , California 295 279. Folsom Dam, California 295 280. Colorado River Dam, Texas 297 281. Bear Valley and Zola Dams 298 282. Works of Reference : Storage Works 300 CHAPTER XX. WASTEWAYS AND OUTLET SLUICES. 283. Wasteways 301 284. Character and Design of Wasteways 302 285. Discharge of Waste Weirs 3<>2 286. Classes of Wasteways 34 287. Shapes of Waste Weirs 305 288. Examples of Wasteways 35 XVI CONTENTS. ART. PAGE 289. Automatic Shutters and Gates 306 290. Undersluices 309 291. Examples of Undersluices 309 292. Outlet Sluices 310 293. Gate Towers and Valve Chambers 312 294. Examples of Gate Towers and Outlet Sluices 314 CHAPTER XXI. PUMPING, TOOLS, AND MAINTENANCE. 295. Underground Cribwork or Tunnels 316 296. Tunnelling Underground .... 317 297. Pumping or Lift Irrigation . 317 298. Windmills and Elevators 319 299. Water-wheels 319 300. Steam Pumps 321 301. Centrifugal Pumps 322 302. Huffer and Nye Pumps 323 303. Pumping Engines 323 304. Irrigation Tools 324 305. Scrapers 325 306. Excavating Machines 326 307. Maintenance and Supervision of Canal Works 328 308. Sources of Impairment of Irrigation Works ... 328 309. Inspection 329 310. Works of reference : Pumping Machinery and Water 320 TABLES. I. Extent and Cost of Irrigation 3 II. Precipitation by River Basins 9 III. Precipitation by States 10 IV. Depth of Evaporation per Month in 1887-88 16 V. Depth of Evaporation per Month in Inches 17 VI. Units of Measure 39 VII. Duty of Water 41 VIII. Value of C for Earthen Channels by Kutter's Formula : 50 IX. Discharge over Rectangular Weirs 60 X. Some great Perennial Canals 70 XI. Cost and Dimensions of some Storage Reservoirs 221 XII. Coefficients of Friction in Masonry 252 XIII. Wegmann's Practical Profile No. 3 262 LIST OF ILLUSTRATIONS. PAGB I. Plan and Cross-section of Ganges Canal, Hurdwar to Roorkee, India , 75 II. Kern River Diversion Weir. Head of Galloway Canal 102 III. Cross-sections of Indian Weirs 104 IV. View of Weir and Scouring Sluices, Head of Arizona Canal no V. Cross-section of Croton Dam 124 VI. Automatic Sluice Gate. Soane Canal, India 140 VII. Bear River Canal. Elevation and Cross-section of Weir and Regulator 150 VIII. Cross-section and Elevation of Regulator Gates, Folsom Canal.. 152 IX. View of Fall on Arizona Canal 164 X. Cross-section of Kushuk Fall, Agra Canal, India 166 XI. Plan of Rapids, Bari Doab Canal, India 168 XII. Highline Canal, Colorado. View of Bench Flume. 174 XIII. View of Pecos Flume 176 XIV. View of Solani Aqueduct, Ganges Canal, India 180 XV. Elevation and Cross-section of Nadrai Aqueduct, Lower Ganges Canal, India 182 XVI. View of Ranipur Superpassage, Ganges Canal, India 184 XVII. Central Irrigation District Canal. Elevation and Cross-section of Stony Creek Culvert 186 XVIII. Idaho Irrigation Company's Canal. View of Wooden Siphon on Phyllis Branch 188 XIX. Standard Masonry Outlet for Distributaries, Punjab, India 200 XX. Cross-section of Ashti Dam, India 232 XXI. View of Pecos Dam 23$ XXII. View of Bhatgur Dam, India 280 XXIII. San Mateo Dam. Plan, Cross-section, and Outlet Sluices 286 XXIV. Plan of Sweetwater Dam 288 xvii XV111 LIST OF ILLUSTRATIONS. PLATE PAGK XXV. Cross-section of Svveetvvater Dam 290 XXVI. View of Svveetwater Dam 292 XXVII. Folsom Canal, View of Weir and Regulator 294 XXVI II. Folsom Canal, Plan and Cross-section of Weir 296 XXIX. .Plan, Elevation, and Cross-section of Reinold's Automatic Waste Gate, India 308 FIGURE 1. Rain Gauge n 2. Evaporating pan 14 3. Maximum, Minimum, and Mean Discharge of some Western Rivers.. 26 4. Colorado Current Meter 53 5. Haskel! Current Meter 54 6. Rectangular Measuring Weir 57 7. Foote's Measuring Weir, A. Water Divisor, B 63 8. Canal Cross-sections for Varying Bed-widths 75 9. Turlock Canal. Plan of Diversion Line So 10. Turlock Canal. View of Sidehill Work Si 11. Turlock Canal. View in Tunnel 82 12. Various Canal Cross-sections 90 13. Cross-section of Calloway Canal showing Subgrade. . . 92 14. Rock Cross-section. Tnrlock Canal 93 15. Rock Cross-section. Bear River 94 16. Open Weir, Monte Vista Canal 101 17. Cross-section of Open Weir, Calloway Canal 103 18. Half-elevation and Plan, and Section of Soane Weir, India 106 19. Elevation and Cross-section of Sidhnai Weir, India 108 20. View of Open Weir on River Seine, France 109 21. Cross-section of Arizona Weir 112 22. Cross-section of Bear River Weir 112 23. Cross-section of Hoi yoke Weir .- . 114 24. Cross-section of Little Kukuna Weir 116 25. Diagram of Ogee Curve , 118 26. Cross-section of Norwich Water Power Company's Weir 123 27. Plan, Elevation, and Cross-section of San Diego Weir 127 28. Cross-section of Henares Weir, Spain 128 29. Cross-section of Appleton Weir 128 30. Cross-sections of Newark Dam and Weir 13 31. Cross-section of Lawrence Weir 131 32. View of Highline Canal Weir 134 33. Cross-section of Mahanuddy Automatic Shutters, India 137 34. Plan of Headworks, Ganges Canal, India 142 35. Arizona Canal. Plan of Headworks 143 36. Regulator Gates, Ganges Canal 147 37. Regulator Gates, Soane Canal 148 38. Regulator Gates, Arizona Canal 149 LIST OF ILLUSTRATIONS. . XIX FIGUKB PACK 39. Regulator Gates, Del Norte Canal 149 40. Sliding Regulator Gate, Idaho Canal 151 41. Rolling Regulator Gate, Idaho Canal 153 42. Longitudinal Section of Fall, Arizona Canal 162 43. Plan and Cross-section of Fall, Bear River Canal 163 44. Cross-section of Fall, Turlock Canal 165 45. Plan and Elevation of Big Drop, Grand River Canal 167 46. Plan of Rutmoo Crossing, Ganges Canal, India 171 47. Cross-section of San Diego Flume 175 48. Bear River Canal. Elevation and Cross-section of Iron Flume on Corinne Branch 178 49. Aqueduct, Henares Canal, Spain 179 50. Section of Wooden Siphon, Del Norte Canal 185 51. Soane Canal. Cross-section of Kao Nulla Siphon-aqueduct 187 52. Sections of Sesia Siphon, Cavour Canal, Italy 189 53. Diagram illustrating Distributary System 192 54. View of Distributary Head, Calloway Canal 199 55. Plan of Bifurcation, Del Norte Canal 199 56. Colorado Wooden Pipe 202 57. Diagram illustrating Flooding of Meadows 205 58. Irrigation by System of Check-levees 206 59. Flooding by System of Squares 208 60. Furrow Irrigation of Grain 209 61. Furrow Irrigation of Orchards. . . 210 62. Alessandro Hydrant 214 63. Diagrams illustrating Geology of Reservoir Site 220 64. Cross-sections of Kabra Dam (A) and Ekruk Dam (B), India 237 65. Cross-section of Pecos Dam 239 66. Plan of Idaho Dam 241 67. Cross-section of Idaho Dam 241 68. Elevation and Cross-section of Walnut Grove Dam 244 69. Plan and Cross-section of Bowman Dam 245 70. Elevation, Plan, and Cross-section of Castlewood Dam 247 71. Theoretical Triangular Cross-section of Dam 251 72. Diagram illustrating Wegmann's Formula 256 73. Molesvvorth's Profile Type 259 74. Comparison of Profile Types 261 75. Practical Profile from Wegmann 263 76. View of San Fernando Submerged Dam. 273 77. Cross-section of Furens Dam, France 277 78. Cross-section of Gran Cheurfas Dam, Algiers 278 79. Cross-section of Tansa Dam, India 279 So. Cross-section of Bhatgur Dam, India 281 81. Cross-section of Earth Embankment, New Croton Dam, Cornell's 283 82. Cross-section of Masonry Dam, New Croton Dam, Cornell's 284 XX LIST OF ILLUSTRATIONS. FIGURE PACK 83. Cross-section of Overfall Weir, New Croton Dam, Cornell's 284 84. Cross-^sections of Periar Dam and Waste Weir, India 285 85. Cross-section of Beetaloo Dam, Australia 287 86. Cross-section of Vyrnwy Dam, Wales 291 87. Cross-section of Betvva Dam, India 293 88. Cross-section of Turlock Dam 295 89. Cross-section of Colorado River Dam 297 90. Cross^section of Bear Valley Dam 2gd 91. Plan and Elevation of Bear Valley Dam 298 92. Cross-section of Zola Dam, France 29 ) 93. Cross-section of Shutter on Soane Weir, India 307 94. Cross-section of Earth Dam 312 95. Valve-plug, Sweetwater Dam 313 96. Valve Chamber and Valves 315 97. Gathering-cribs, Citizens' Water Co., Denver. 316 98. View of Water-wheel .... 320 99. Buck Scraper 325 100. New Era Excavator 327 IRRIGATION ENGINEERING. CHAPTER I. INTRODUCTION. 1. Extent of Irrigation. The extent to which irrigation can be practised is enormous. The total area irrigated in India is about 25,000,000 acres, in Egypt about 6,000,000 acres, and in Italy about 3,700,000 acres. In Spain there are 500,000 acres, in France 400,000 acres, and in the United States 4,000,000 acres of irrigated land. This means that crops are grown on 39,000,000 acres of land which but for irrigation would be barren and unproductive. In addition to this there are some millions more of acres cultivated by the aid of irrigation in China, Japan, Australia, Algeria, South America, ,and elsewhere. 2. Control of Irrigation Works. The development of irrigation has resulted in many legal complications, while a diversity of social and physical conditions has given rise to a variety of methods for its control. Practically all the works in India are now under the direct control of the government, which employs its engineers and legal staff, owns the land and the water, constructs the works, and collects the rentals for the use of water and land. In the Piedmont valley of Italy the land is the property of individuals, and in some cases indi- viduals are owners of the irrigation works. In the case of the Cavour canal, however, the government owns and operates the works, and the water is sold to the cultivators. In the United States all irrigation works are the property of individuals who construct and maintain them and collect the rentals for the use of water. In some cases the same individual owns both 2 INTRODUCTION. land and water; but usually farmers and irrigators have no property interest in the irrigation works. These are owned and operated by independent organizations who collect a reve- nue from the sale or rental of water. 3. Value as an Investment. As an investment irrigation works are not always successful. There should be a ready market for the products of irrigation, and the value of land and water must not be so great as to materially reduce the profits derived from crops. The value of irrigation as an investment is especially dependent on the humidity of the climate. In the semi-humid region, where during occasional seasons the rainfall is sufficient to mature the crops, there is little or no demand for water furnished for irrigation, and no profit is derived from its sale. In the arid region, where crops cannot be raised without the aid of irrigation, the demand for water is constant. In the northern provinces of India water is in constant demand for irrigation and returns excellent profits. In Bombay and other places where the demand for water is intermittent, because the rainfall is frequently sufficient to mature crops, the construction of irrigation works has usually resulted in financial disaster. Perhaps the most important factor bearing on this subject in our own country is the degree of habitation. Nearly anywhere that a good market can be found and irrigation is essential to the production of crops, fair interest can be obtained on money invested in irrigation works. Many failures, however, have occurred, due chiefly to the lack of population and consequent lack of demand for water. Where all the water furnished is utilized the works almost invariably pay fair returns on the investment. 4. Incidental Values. Not only is the direct money re- turn from an irrigation investment to be considered, but there are several incidental means whereby profit may be derived from such investments. On broad principles of general gov- ernment and policy the construction of irrigation works is of benefit to the whole country. They furnish homes and agri- cultural pursuits for many who must otherwise be idle or find less substantial support in other ways. Irrigation adds to the COST AND RE TURNS OF IRRIGATION. general wealth of the country by increasing the amount of its agricultural products. It furnishes excellent investment for capital where the projects are well designed. It results in the conversion of barren and desert lands into delightful homes, and aids in the general development of the other resources of the region in which it is practised, as mining, lumbering, graz- ing, etc. One of the great advantages of irrigation is that it becomes practically an insurance on the production of crops. Its practice may not be necessary in the semi-humid or humid regions, but even there occasional droughts occur and crops are lost. Where an irrigation system exists in such cases, it will probably be called into requisition once or twice in the course of a year, and may save vast sums which would other- wise be lost by the destruction of crops. 5. Cost and Returns of Irrigation. The following table compiled from the reports of the U. S. Census of 1890 gives an excellent idea of the extent and cost of irrigation, and of the value of the land and water after irrigation has been pro- vided : TABLE I. EXTENT AND COST OF IRRIGATION. States and Territories employing Irrigation. Crop Irrigated. Acres. 11 S C/J *Ss m > u C <'-' fl 5 ua Average Value of Water per Acre as estimated by Irrigators. Average Annual Cost of Water per Acre. Average Cost of Preparing Land for Cultivation per Acre. Average Value of Land Irrigated per Acre. Average Value of Products from Irrigated Land per Acre. Total U S 3,564,416 6 7 $8.15 $26.00 $0.99 $12.12 $8328 $14.89 Arizona 65,821 1,004,233 890,735 217,005 350,582 224,403 9^745 177,944 263,473 48,800 229,6/6 61 73 92 50 95 192 30 56 27 47 119 7.07 15.84 7-15 4-74 4-63 7.58 5-58 4.64 10.55 4.03 3-62 12.58 52.28 28.46 13.18 15.04 24.60 18.30 15.48 26.84 13.15 8.69 1-55 i .60 79 .80 95 .84 1-54 94 .91 75 .44 8.60 22.27 9.72 9-31 8.29 10-57 11.71 12.59 14.85 10.27 8. 23 $48.68 i 50 . oo 67.02 46.50 49-50 41.00 50.98 57.00 84.25 50.00 31.40 $13.92 19.00 13.12 12.93 12.96 12.^2 12. 80 13 90 18.03 17.09 8.25 California .... Colorado Idaho Montana Nevada New Mexico Oregon . Utah Washington ^Vvoming 4 IN TROD UCTION. From this table it will be seen that while the average first cost of water, that is, the cost of constructing canals to bring the water to the land, is $8.15 per acre, the average value of water per acre as estimated by the owners after they obtain it is $26. This shows clearly the inherent value which the mere fact of possessing the water gives to it. In other words, the water is so scarce and valuable of itself as to increase by threefold the cost of making it available. The average value of the land before irrigation is from $2.50 to $5 per acre, while the same land after a water supply has been provided is valued at $83.28 per acre, and the products from this land have an average value of $14.89 per acre, which represents an unusu- ally large interest on the money invested. PART I. HYDROGRAPHY. CHAPTER II. PRECIPITATION. 6. Relation of Rainfall to Irrigation. In a region where the climate and soil are favorable for the production of agri- cultural crops the necessity of irrigation depends wholly on the amount of rainfall. The necessity of irrigation cannot be judged, however, from the total amount of precipitation in the year. Where the precipitation is less than 20 inches per annum in the United States, irrigation is generally supposed to be necessary, and our arid region is usually considered as includ- ing that portion of the country where the annual precipitation is below 20 inches. This, however, is not a safe gauge in all cases. Thus in Italy, where the annual precipitation averages perhaps 40 inches, irrigation is necessary, because most of this occurs during the winter months or at other times than in the agricultural or cropping season. In India the rain- fall is in some places as high as 100 to 300 inches per annum. Yet nearly all of this occurs in one or two seasons of the year, and the actual rainfall during the winter months, when most of the cropping is done, may be as low as 5 to 10 inches. Generally speaking, the cropping season for our West may be taken as occurring between April and August inclusive, and these are among the dryest months in the year. O PREC1PITA TION. 7. General Rainfall Statistics. Tables II and III show in a general way the extent of precipitation over the arid region. From them it will be seen that the average annual rainfall over the northern portion of the Pacific Coast would be sufficient in amount for the production of crops, pro- viding it fell during the irrigating season. There is also a small area near San Diego, and one on the headwaters of the Gila and Salt rivers in Arizona, where the annual rain- fall is apparently sufficient for the maturing of crops. The amount of precipitation is greatly influenced by altitude. Thus in the same latitude in the region between Reno, Nevada, and San Francisco, California, the average annual precipitation in the bottom of the Sacramento Valley is about 15 inches. To the eastward of this the precipitation increases in amount with the height of the mountains until along their summits it averages from 50 to 60 inches. Still further east it decreases with the diminishing altitude until in Nevada the mean precipitation is from 5 to 10 inches. Every- where throughout the West precipitation in the high mountains is much greater than in the adjacent low valley lands. As a result of this, while the rainfall is frequently insufficient to mature crops in the low lands and valleys, sufficient precipita- tion occurs in the mountains to furnish an abundant supply for the perennial discharge of streams or for the filling of stor- age reservoirs. 8. Rainfall Distribution in Detail. In the lower Colo- rado and Gila river valleys in Arizona the average annual pre- cipitation is between 4 and 6 inches. In the Gila and Salt river valleys in the neighborhood of Phoenix it is between 10 and 15 inches, while on the headwaters of these streams it averages 20 'inches. In Northern Arizona the annual average precipitation is about 10 inches, most of which occurs in win- ter. During the summer or irrigating months the precipitation is from I to 3 inches in the lower Gila and Colorado river val- leys, from 3 to 5 inches in the neighborhood of Phoenix and Florence, and about 5 inches in Northern Arizona. In the lower Rio Grande and Pecos river valleys in New RAINFALL DISTRIBUTION. J Mexico the average annual precipitation is 10 inches. Over the remainder of the agricultural portion of the Territory it averages about 15 inches. In winter the precipitation is comparatively low in the valleys, but comparatively high in the uplands. In the summer or irrigating months it ranges between 4 and 8 inches in the Rio grande and Pecos valleys. In California in the Sacramento valley the annual average pre- cipitation is about 15 inches, and in the San Joaquin valley from 10 to 15 inches. Over the agricultural portions of Southern California it averages about the same. A large pro- portion of this rainfall occurs during the early spring months, but in the latter portion of the irrigating season the rainfall diminishes very rapidly, averaging from May till October scarcely two inches in the Sacramento valley and less than an inch in the San Joaquin valley and in Southern California. Over the plains of Western Nevada the average annual pre- cipitation is between $ and 10 inches, most of which occurs at periods other than in the irrigating season. On the plains of Utah the annual average precipitation is from 10 to 15 inches, while the precipitation during the summer months is but an inch or two. In the upper Missouri and Yellowstone valleys and other principal agricultural portions of Montana the average annual precipitation is from 12 to 20 inches, of which about 5 inches falls during the irrigating season. In the Snake River valley of Idaho the average annual precipitation is about 10 inches, of which about 3 inches falls during the irrigating season. In the Platte and Arkansas valleys of Colorado the average annual precipitation is about 15 inches, of which from 7 to 10 inches fall during the irrigating season. In the eastern portion of Colorado on the plains nearer the Kansas line the precipita- tion is a little less than this and about the same as in the upper Rio Grande valleys. 9. Great Rainfalls. One of the important considerations in designing irrigation projects, and especially storage reservoirs, is the maximum amount of rainfall which may occur. Great floods are the immediate result either of the sudden melting 8 PRECIPITATION. of snow in the mountains or of heavy and protracted rain- storms. In most of the river valleys just considered there are periods of extreme or maximum rainfall, the recurrence and effect of which are worthy of note. In the neighborhood of Yuma, Arizona, the average annual rainfall is about 3 inches, yet in the last week of February, 1891, 2\ inches fell in 24 hours. The average annual rainfall in the neighborhood of San Diego, California, is about 12 inches, yet in the storms of February, 1891, 13 inches fell in 23 hours and 23 j- inches in 54 hours. In the neighborhood of Bear Valley reservoir east of Redlands, California, during the same storm 17 inches of rain fell in 24 hours. Such storms as these may be very destruc- tive both to crops and works. The average annual dis- charge of Salt River in Arizona is about 1000 second-feet, and the average flood discharge is perhaps 10,000 second-feet; yet, as the result of a sudden rainstorm of unusual violence which occurred in the spring of 1891, this river increased to a flood discharge of 140,000 second-feet, and in the spring of 1892, as the result of a still greater cloud-burst, its discharge reached the enormous figure of nearly 350,000 second-feet. Over cer- tain portions of the western region these sudden cloud-bursts are of not uncommon occurrence and must be provided for in the construction of works. 10. Suddenness of Great Storms. Statistics showing the rainfall in 24 hours are often insufficient to give a safe and correct estimate of the suddenness and danger of floods resulting from great storms. The greatest and most sudden storm on record is probably that which occurred on the line of the Lower Ganges canal in the Northwest Prov- inces of India. On the J_3th_of September, 1884, 16 inches fell; on October the 1st 22 inches, on the 2d 22|, on the 3d 18 inches, and on the 4th 17^ inches of rain fell. In some cases and at some times the precipitation was as high as 5 inches per hour. In some of the cloud-bursts in our own West it is not unlikely that the precipitation has reached from 3 to 5 inches per hour. Such storms as these do far greater damage than protracted storms of less violence. PRECIPITATION ON RIVER BASINS. 9 ii. Precipitation on River Basins. The following table of rainfall on a few of the principal river basins of the West shows very clearly the variation in the amount of precipita- tion at different altitudes : TABLE II. PRECIPITATION BY RIVER BASINS. Station. Altitude. Feet. Mean Annual Precipitation. Inches. Rio GRANDE RIVER : Summit, Colorado 11300 29.00 Fort Lewis, Colorado 8500 I 7-I9 Fort Garland, " i 7937 I2 -74 Saguache, " '774 42.60 Santa Fe, New Mexico 7026 14.69 Fort Wingate, New Mexico 6822 14 . 71 Las Vegas, 6418 22.08 Albuquerque, 5032 7 .19 Socorro, " ; 4560 8.01 Deming, " | 4315 8.95 GILA RIVER: Fort Bayard, New Mexico I 6022 14.72 Prescott, Arizona 5389 17.06 Fort Apache, Arizona 5050 21 .04 Fort Grant, " 4914 16.65 Phoenix, " j 1068 7 . 38 Texas Hill, " | 353 3.47 Yuma, " I 141 2.81 PLATTE RIVER : Pike's Peak, Colorado I4 T 34 28.65 Fort Saunders, Wyoming 7180 12.92 Fort Fred Steele, " 6850 11.03 Cheyenne, " 6105 11.32 Colorado Springs, Colorado 6010 14 . 79 Denver, " 5241 14-32 Fort Morgan, " 4500 8.08 MISSOURI RIVER : Virginia, Montana 5480 16.00 Fort Ellis, " 4754 19-60 Helena, " 4266 14.26 Fort Shaw, " 2550 10.22 Poplar, " 1955 I0 -50 12. Rainfall Statistics by States. Table III gives the average annual precipitation, and the precipitation during the irrigating season, from April to August inclusive, for various places in each of the Western States : 10 PRECIPITA TION. TABLE III. PRECIPITATION BY STATES. Locality. Altitude. Feet. Mean Annual Precipitation. Inches. Mean Precipi- tation, April to August. Inches. ARIZONA : Fort Apache 5050 Holbrook 504 7 Casa Grande 1398 Phoenix 1068 Texas Hill 355 Prescott 5389 NEW MEXICO : Springer 576 Las Vegas 6418 Albuquerque 5026 Santa Fe 7026 Fort Wingate 6822 Socorro 4565 Deming 4327 CALIFORNIA : Yreka 2635 Fort Bid well 4640 Redding 556 Oroville 188 - Bowman Dam 54 Summit 7017 Placerville 2110 Sacramento 64 San Jose 94 Merced 171 Fresno 328 Visalia 348 San Bernardino 950 Banning 2317 Los Angeles 330 San Diego 93 Yuma 276 NEVADA : Reno 4497 Winnemucca 4358 Palisade 4840 Fort Churchill 4284 Carson 4628 Pioche 61 10 RADO: "Jreeley 4750 *3reckenridge 9524 ' eadville 10200 'ike's Peak 1 4^34 Canyon City 4700 Pueblo 4753 Fort Lyon 4000 Monte Vista 7765 Trinidad 6070 Denver 5241 21.04 9.29 4.28 7-38 3-47 17.06 11.82 22.08 7.19 14.68 14.71 10.31 8-95 16.34 20.84 34.60 25.14 71.21 43-56 45-17 19.80 14.52 10.30 9.02 8.84 17. 16 14-39 18.31 9.86 3.16 5-17 8.61 8.42 5-3i 11.25 ii. 19 28.25 11.56 28.65 11.52 9.87 11.07 6.91 21 .6l T4-32 10.27 3- 68 1.32 2.27 .66 7-94 8.86 12.70 4.22 8.32 6.97 3.8? 3-90 3-33 4.54 5.61 3.48 8.26 2-73 2.08 1-73 i. 80 1.86 2-37 i. 80 1.81 2-47 i. 06 0.71 2.70 2.17 1.70 2.05 4.41 9. 16 7.01 7.10 8.15 4.18 15.06 9.00 GAUGING RAINFALL. TABLE III. Continued. I 1 Locality. Altitude. Feet. Mean Annual Precipitation. Inches. Mean Precipi- tation, April to August. Inches. UTAH: Ogden .... 414.O ja *{\ Salt Lake 4-3C4 16 85 4. 12 A ,,A Nephi c e co 18 IQ St George . 2880 6 7J 7.4 IDAHO : Eagle Rock 478l 18 67 j* 4 Ark Boise 1108 14 7^ .09 Lewiston. . . . . . . ... 18 25 . II Fort Hall 17 5 T 55 6/1/1 WYOMING : Cheyenne 6105 */ 3 1 I 72 44 Fort McKinnev 55 MONTANA : Fort Benton 2730 1 7 7O 4-45 Miles City 4-772 12 OO 45 See Helena 4266 14 26 55 4d.8 Fort Shaw 2CCQ IO 22 ^5 13. Gauging Rainfall. The common rain-gauge or plu- viometer generally employed in this country in the measure- ment of precipitation is illustrated in Fig. I. It consists of FIG. i. RAIN-GAUGB. three parts, the collector^, the receiver B, and the overflow at- tachment C. A measuring-rod graduated to inches and tenths is furnished with each gauge and is used in measuring the depth of water. This gauge should be placed in an open space, prefer- ably over grass sod, and, to obtain a free exposure to the rain, 1 2 PRE CIPI TA TION. should be at least 30 feet from any building or obstruction. It should be enclosed in a close-fitting box and sunk into the ground to such a depth that the upper rim of the gauge shall be about one foot above the surface, and care should be taken to maintain it in a horizontal position. The sectional area of the receiver being only.i of the area of the collector, the depth of water measured is ten times the true rainfall. In the measurement of snowfall the funnel and receiver should be removed and only the overflow attachment used as the collecting vessel. It should be set as in the case of rain- fall and the snow should be melted after being collected. Where the wind is blowing hard it is advisable to measure the snow in a different manner. After the snow has ceased to fall a spot should be selected where it has an average depth. The overflow attachment is inverted and lowered until the rim has reached the full depth of the newly-fallen snow, when a piece of flat tin or other material is slipped under the rim and the gauge lifted and the snow melted as before. 14. Works of Reference. For fuller information consult : FANNING, J. T. A treatise on Hydraulic and Water Supply Engineer- ing. D. Van Nostrand & Co., New York, 1890. FITZGERALD, DESMOND. Maximum Rates of Rainfall. Transactions Am. Soc. of C. E. 1889, vol. 21. GREELY, Gen. A. W., and GLASSFORD, Lieut. W. A. Irrigation and Water Storage in the Arid Regions. Sist Congress, House of Rep. Ex. Doc. No. 287. Washington, D. C., 1891. GREELY, Gen. A. W. Report of Rainfall. $oth Congress, Senate Ex. Doc. No. 91. Washington, D. C., 1888. NEWELL, F. H. Part II of nth, i2th, and i3th Annual Reports of U. S. Geological Survey. Government Printing Office, Washington, D.C., 1890, '91, '92. CHAPTER III. EVAPORATION AND ABSORPTION. 15. Evaporation Phenomena. The rapidity with which water, snow and ice are converted into vapor is dependent upon the relative temperatures of the water and atmosphere and upon the amount of motion in the latter. Evaporation is greatest when the atmosphere is dryest, when the water is warm and a brisk wind is blowing. It is least when the atmos- phere is moist, the air quiet and the temperature of the water low. In summer the cool surfaces of deep waters condense moisture from the warm air passing across them and thus gain in moisture when they are supposed to be evaporating. When the reverse conditions exist in the atmosphere and the winds are blowing briskly across the water the resultant wave-motion increases the agitation of the body and permits its vapors to escape freely into the large volumes of unsaturated air which are rapidly presented in succession to attract its vapors. Evaporation is constantly taking place at a rate due to the temperature of the surface and condensation is likewise going on from the vapors existing in the atmosphere, the difference between the two being the rate of evaporation. From the above it will be seen that evaporation should be greatest in amount in the desert regions of the Southwest and least in the high mountains. Tables IV and V show this to be the case and that in the same latitude evaporation differs greatly in amount according to the altitude. 16. Measurement of Evaporation. Two or three methods have been devised for measuring evaporation none 13 14 EVAPORATION AND ABSORPTION. of which are wholly satisfactory. Elaborate and expensive apparatus has been employed in evaporation measurements made by Mr. Desmond Fitzgerald, chief engineer of the Boston Water Works ; by Mr. Charles Greeves of England, and others. A simple apparatus and one which is as successful as most of the more elaborate contrivances is that employed by the U. S. Geological Survey. It consists of a pan, Fig. 2, so FlG. 2. EVAPORATING-PAN. placed that the contained water has as nearly as possible the same temperature and exposure as that of the body of water the evaporation from which is to be measured. This evapora- ting pan is of galvanized iron 3 feet square and 10 inches deep, and is immersed in water and kept from sinking by means of AMOUNT OF EVAPORATION. 15 floats of wood or hollow metal. It should be placed in the canal, lake, or other body the evaporation of which it is in- tended to measure in such position as to be exposed as nearly as possible to its average wind movements. The pan must be filled to within 3 or 4 inches of the top in order that the waves produced by the wind shall not cause the water to slop over, and it should float with it srim several inches above the surrounding surface, so that waves from this shall not enter the pan. The device for measuring the evaporation consists of a small brass scale hung in the centre of the pan. The graduations are on a series of inclined crossbars so proportioned that the vertical heights are greatly exaggerated, thus permitting a small rise or fall, say of a tenth of an inch, to cause the water surface to advance or retreat on the scale .3 of an inch. By this device, multiplying the vertical scale by three, it is possible to read to .01 of an inch. In 1888 a series of observations were made with the Piche evaporometer by Mr. T. Russell of the U. S. Signal Service to ascertain the amount of evaporation in the West. While it is probable that results obtained with this instrument are not particularly accurate, comparisons of these results with those obtained by other methods in similar localities show such slight discrepancies that they may be considered of value until superseded by results obtained by other and better methods. Observations were made with this instrument in wind velocities varying from 10 to 30 miles per hour, from which it was dis- covered that with a velocity of 5 miles an hour the evaporation was 2.2 times that from one in quiet air; 10 miles per hour 3.8 times ; 15 miles 4.9 ; 20 miles 5.7 times; 25 miles 6.1, and 30 miles 6.3 times. 17. Amount of Evaporation. In Table IV is given the amount of evaporation by months in the year 1888 in various sections of the West as derived from experiments with the Piche apparatus. As in the case of precipitation, evaporation decreases with the altitude because of the diminished temperature in high mountains. Experiments were made to determine the amount 1 6 'EVAPORATION AND ABSORPTION. TABLE IV. DEPTH OF EVAPORATION, IN INCHES PER MONTH, IN 1887-88. Stations and Districts. 3 " & 00 H fl = 8 - 00 >jf j| fi i- 1? < ' IX a* r I- rcS- r 1 NORTHERN SLOPE : Fort Assiuiboine Fort Custer 0.8 o 6 1.2 I .2 J -3 3- 1 5-4 J'S 4-2 4.9 6.8 6 \\ 4.8 6.1 3-5 3-4 2-5 2.9 i.i 1.5 39-5 52.0 3- 3 3.2 1 6 6.8 i fi 1 R 9 R 2.O i.i 35.8 Helena i fi o 8 o R 2.7 4.9 5.7 6 o 4.4 2. 5 I .7 0.7 OC.A Cheyenne North Platte . ... 3-3 o 8 5'5 4.0 i 8 8.2 5-4 5-2 3-9 0.4 6.9 8.0 6 o 7-7 8.6 3-7 5.8 -> R 6.; 2.3 3-5 i . i 76.5 4 1 3 MIDDLE SLOPE: Colorado Springs Denver .... ? 3-3 3-7 4-1 3-5 6-7 7 6 r 4-3 0.5 6.7 R 7 7.2 8 S 6.8 6 T 46 4-9 4-2 4-2 2.9 3- * 59-4 69.0 Pike's Peak 2. 1 T 8 i .9 3.0 4.0 3- 2.3 7 R i .0 26.8 2 8 i 8 1 8 4-3 T R 47.2 Dodge City Fort Elliott SOUTHERN SLOPE : Fort Sill i-4 i .3 i 6 2.4 1.9 2.8 3-2 2 6 4-1 5-i , 8 J:l 5-4 7-4 8.2 8.3 7.6 A. 8 6.6 6.2 5-5 5-4 5-2 4-7 4.2 4-2 2.1 2.2 54-6 55-4 46 i Abilene i R 3- T 5.0 r 8 9- 5 7-5 6 f 3-4 I . 7 M-4 Fort Davis 5-4 5-7 6.7 8-5 i .0 2.O 11.4 9.0 5-9 S- 2 5-7 o 6 4-9 o g 96.4 SOUTHERN PLATEAU : El Paso 6 o 8 4 5 6 1 6 82 o Santa Fe* 6 8 8 8 0.8 6 6 6 , 5-7 79.8 n f 6 8 6 T 2 6 fie c T y ' Prescott 6 2 8 i 6 6 6 j T 6 Yuma Keeler ... 4-4 5-2 6.6 6 3 9.6 9 6 12.6 ii .0 12 8 1O.2 8.2 10 6 8.2 R R 5-5 ; 95- 7 MIDDLE PLATEAU : Fort Bidwell o 8 8 8 R 1 6 48 o Winnemucca O.Q 2. 6 ? g. Q. 10. T ii .5 12. 9.9 6 6 3.7 i 83.9 Salt Lake City T 9 g 8 Q Q 6 6 r Montrose i 8 6 R 60 0.4 2 .O 68.3 Fort Bridger 6 =; 6 e fi 56 i NORTHERN PLATEAU: Boise City 6 6 CO | , "B i } a 1 S i 1 1889 1890 1889 1889 ,889 1889 1890 1891 1889 1889 1889 1890 1889 1889 ,889 1890 1891 1889 1890 1891 1890 1889 1890 1890 1890 1890 1890 1890 Bozeman, Mont 3-4 4-5 5-3 i. 9 .... 2 6 Great Falls, " Springdale, " 6.8 i:i 3-i 29 .... Hogan, " ( Fort Douglas, near ) < Salt Lake City, >... 7 6 10.5 M I.O ) Utah f.... Nephi and Provo . . . 36.4 .... 3-2 4 .8 5-2 3-9 8.1 7-6 5-o 7-9 6J 4.6 8.6 5-2 !:! 2.5 3-3 4.2 o 6 i-4 2-5 2.2 Cherry Creek, Col Canyon City, " 3-8 4.8 52 7-3 6.0 Lamar, Col Embudo, New Mexico 3-o 2.9 3 6 4.0 10.9 io 8 10.7 9.6 9 6 II.4 7 6 9-2 6.8 4.6 2-9 iFort Bliss, near El \ Ro T 2.O 2.O 7.0 Paso, Texas f " empe, Ariz 6 4 r R e g I fi 5-8 5-2 {.6 3-2 U U 85.5 3-9 3-6 11 J:: "5 13-5 M 1.8 2.5 R 7.2 8-5 7.2 7-i 4-3 Bloods Cal Tuolumne Mead, Cal rto 18. Evaporation from Snow and Ice. From some ex- periments conducted at the Boston Water Works the amount of evaporation from snow and ice was found to be greater than is generally believed. From snow it amounted to about .02 of an inch per day, or nearly 2\ inches in an ordinary season. From ice it amounted to .06 inch per day, or about 7 inches in an ordinary season. The evaporation from snow is greater than this in the arid regions of the West, especially on barren mountain-tops such as those in Arizona, Nevada, and Utah, where they are exposed to the wind and the bright sunshine. 19. Evaporation from Earth. The amount of evapora- tion from earth in the West is a doubtful quantity. The most important experiments bearing on this were made in England between 1844 and 1875. From these it appears that the amount of evaporation from ordinary soil is about the same 1 8 EVAPORATION AND ABSORPTION. as that from water, sometimes exceeding it a little and some- times being a trifle less, though generally averaging about 3 inches less than the corresponding evaporation from water sur- faces. The evaporation from sandy surfaces was found to be only about one-fourth to one-fifth that from water. Thus in the observations of 1873, where the. mean evaporation from water was 20.4 inches, that from earth was 19.7 inches and from sand 3.7 inches. 20. Effect of Evaporation on Water Storage. The value of water storage for irrigation in the West is realized chiefly between May and August inclusive. The only loss due to evaporation which practically affects the amount of storage water is that occurring during these months. Little or no rain falls in the arid region during this period, so that comparatively little of the loss of evaporation is replaced by rain. As an example, take Central California, where the aver- age rainfall during these months amounts to a trifle less than I inch. The evaporation during the same period amounts to about 21 inches. The total resultant deficiency chargeable to evaporation is about 20 inches. 21. Percolation and its Amount. The losses due to per- colation in canals and storage reservoirs are very considerable, and added to those due to evaporation they increase the total loss by from 25 to 100 per cent according to the character of the soil. It is difficult to ascertain the losses due to percola- tion alone. For this reason it is desirable to consider losses from percolation and evaporation together and include them under the joint head of " absorption." From the experiments previously alluded to which were con- ducted by Mr. Greaves in England, it was found that while the evaporation from earth during the period of 23 years was 73.4 per cent of the rainfall, the percolation was but 26.6 per cent. From sand this percentage was nearly reversed, the loss by percolation being about 30 inches, while the loss by evaporation was but 7 inches. There was no loss from percolation at all for several consecutive months. As an average year take that of 1872, when the rainfall amounted to 23.8 inches and the AMOUNT OF ABSORPTION. 19 evaporation from water 20.4 inches, the losses by percolation amounted to 4 inches in earth and 20.1 inches in sand. From observations and experiments made in Bavaria it appeared that in the warm summer months whereas the depth of percola- tion on open bare ground was n per cent of the rain- fall, in forests it amounted to as high as 36 per cent of the rainfall. In our West these quantities will be materially differ- ent. The amount of rainfall is relatively small on the ordi- nary mountain catchment basin. The slopes are steep and gen- erally rocky. As a result of this the percentage of percolation will be low, the amount of runoff being relatively higher. Where there are dense forests, the soil beneath which is covered with a depth of litter, or where the slopes are low, the per- centage of percolation will be relatively high. 22. Absorption. As here considered, absorption is the resultant or total loss due to the combined action of evapora- tion and percolation. From experiments made in India, where the climate is somewhat similar to our western country, it was found that the loss by evaporation on a canal of about 30 miles in length would be a little over 2.5 second-feet, or about 5 per cent of the probable discharge. As this amount is compara- tively small, it appears that the greater portion of the loss is from percolation. Mr. Beresford argues that the losses by percolation are due to capillary attraction and the action of gravity. The latter takes place only through coarse sand or gravel, while the former is a more complicated process acting where the particles are fine and in close contact one with the other. Capillary attraction stops where the absorbing medium is limited, for as soon as water which has been carried by its action through a bank reaches the outer surface, percolation ceases and evaporation comes into play. It is for this reason that banks of sand even when well rammed will retain water. The more extensive the absorbing medium the greater the losses from this cause ; but if its extent be limited by a bed of clay placed under either the reservoir or canal in which per- colation occurs, then the losses due to this cause are rapidly diminished in quantity. The layer next the 'wetted perimeter 20 EVAPORATION AND ABSORPTION. limits the quantity absorbed, and the greater its area the more will it pass through to the still greater area of the next layer ; hence percolation varies as the wetted perimeter. 23. Amount of Absorption in Reservoirs and Canals. The volume of this is very difficult to ascertain and varies greatly with soil and climate. If the bottom of the reservoir is composed of sandy soil, the losses from percolation and evapo- ration combined -will be about double those from the former alone. Whereas, if the bottom of the reservoir be of clayey material, or if the reservoir be old and the percolation limited by the sediment deposited on its bottom, this loss may be considerably less than that of evapoiation. On a moderate-sized canal in India the total losses due to absorption have been found to amount to about one second-foot per linear mile. In new canals these losses are greatest. If the soil is sandy, the losses on new canals may amount for long lines to from 40 to 60 per cent of the volume entering the head. In shorter canals the percentage of loss will be propor- tionately decreased, though they will rarely fall below 30 per cent in new canals of moderate length. As the canal increases in age the silt carried in suspension will be deposited on its banks and bottom, thus filling up the interstices and diminish- ing the loss. In old canals with lengths varying between 30 and 40 miles the loss may be as low as 12 per cent in favor- able soil, though in general for canals of average length the loss will be about 20 to 25 per cent of the volume entering the head. On the Ganges Canal in India, the length of which is several hundred miles, the losses in some years have been as high as 70 per cent. 24. Prevention of Percolation. An excellent method for the reduction of the loss by percolation is that recommended by Mr. J. S. Beresford of India, who advises that pulverized dry clay be thrown into the canals near their headgates. This will be carried long distances and deposited on the sides and bottom of the canal, forming a silt berme. The losses by absorption are greatly increased by giving the canal a bad cross-section. Thus depressions along the line of a new canal SEEPAGE WATER. 21 are often utilized to cheapen construction by building up a bank on* the lower side only, thus allowing the water to spread and consequently increasing the absorption. The least possible wetted perimeter and the least surface exposed to the atmo- sphere will cause the least loss from this cause. 25. Seepage Water. In many instances where canals and reservoirs are bordered by steep hillsides the amount of water lost may prove to be much less than would be expected. This is due to the fact that large amounts of seepage water may enter the canal or reservoir from the surrounding country and thus replenish to a large extent the losses from absorption. Before irrigation becomes universal in any locality it is fre- quently impossible to derive any water from wells. The sub- surface water level may be situated at a great depth below the surface. After irrigation has been practised for some time, however, the soil becomes filled with water and the subsurface level rises so that shallow wells often yield persistent supplies. In portions of California, especially in the neighborhood of Fresno where the subsurface water level was originally from 60 to 80 feet below the surface, wells 10 and 15 feet in depth now receive constant supplies, the result of seepage from the canals. Water used in irrigating is in large part returned to the drainage channels and can be again diverted for irrigation. On the Cache la Poudre Creek in Colorado experiments made in 1889 showed that while the original discharge in the canyon was 127.6 second-feet, the volume at a point considerably lower down on the stream had increased to 214.5 second-feet after supplying fifteen canals and without receiving additional naturald rainage ; an addition of more than two-thirds of the original volume, available to supply canals lower down. Measurement of the volume of water in the Sweetwater reser- voir in Southern California shows that after water ceases to be drawn out of the reservoir in the fall, it begins to fill up while no water is entering it from the streams. This proves that seepage from the hillsides add to the volume in the reservoir faster than water was lost by absorption. CHAPTER IV. RUNOFF AND FLOW OF STREAMS. 26. Runoff. By " runoff " is meant the quantity of water which flows in a given time from the catchment basin of a stream. It includes not only that portion of the rainfall which flows over the surface during storms, but also water which is derived from subsurface sources, as springs, etc. The runoff of a given catchment area may be expressed either as the number of second-feet of water flowing in the stream draining that area, or it may be expressed as the number of inches in depth of a sheet of water spread over the entire catchment. The latter expression indicates directly a percentage of rainfall in inches which runs off. Finally, runoff may be expressed volumetrically as so many cubic feet or acre-feet. 27. Variability of Runoff. As runoff bears a direct rela- tion to precipitation, it appears that, knowing the amount of rainfall and the area of the catchment basin, the amount of runoff can be directly ascertained. This is not the case r however, as the amount of runoff is affected by many varying climatic ard topographic factors. Many formulas, none of which give satisfactory results, have been worked out for obtaining the relation between runoff and precipitation. If the climate be the same over two given catchment basins, the runoff will be affected by the depth of the soil, the amount of vegetation, the steepness of the slopes, and the geologic struc- ture. The climatic influences bearing most directly on runoff are the total amount of precipitation, its rate of fall, and the tem- perature of air and earth. Thus, where most of the precipita- 22 FORMULAS FOR RUNOFF. 2$ tion occurs in a few violent showers the percentage of runoff is higher than where it is given abundant time to enter the soil. If the temperature is high and the wind strong, much greater loss will occur from evaporation than if the ground is frozen and there is no air movement. Within a given drainage basin the rates of runoff vary on its different portions. Thus in a large basin the rate of runoff for the entire area may be low if the greater portion of the basin is nearly level, but at the head- waters of the streams where the slopes are steep and perhaps rocky the rate of runoff will be higher. The coefficient of run- off increases with the rainfall. Thus in humid regions where the rainfall is greatest the rate of runoff is highest. 28. Formulas for Runoff. Several formulas for ascertain- ing the percentage of runoff or the quantity of discharge from a given catchment basin have been obtained both empirically from known measurements and by theoretic processes. Mr. J. T. Fanning found by plotting a curve derived from the flood discharges of some American streams that the resulting equa- tion for flood flow became D= 2oo(My, ....... (i) in which M is the area of watershed in square miles, and D the volume of discharge of the whole area in second-feet. In India Colonel Ryves derived the following formula for runoff, D = C VM*> ....... (2) and Colonel Dickens the formula ....... (3) No such formulas can be strictly applied with the same co- efficient to areas of varying size, and all must be used with discretion, as their results are greatly influenced by different conditions from those under which they were obtained. In regions where maximum recorded rainfalls of from 3 to 6 inches in 24 hours have occurred the following coefficients have been determined : 24 RUNOFF AND FLOW OF STREAMS. Rainfall 3.5 to 4 inches in flat country, C 200; mixed country, C = 250 ; hilly country, C = 300 ; and for a maximum rainfall of 6 inches, C varies between 300 and 350. For Ryves' formula the coefficient varies between 400 and 500 in flat coun- try, and for hilly areas where the maximum rainfall is high it may reach 650. The shape of the catchment basin is an im- portant factor in the formula of maximum discharge. 29. Examples of Runoff. On the headwaters of the Ar- kansas River in Colorado, at altitudes varying between 7000 and 14,000 feet, the depth of runoff varies between 20 and 50 inches. On the Arkansas basin above Canyon City the runoff averages 18 inches. In the Sierras in Western Nevada, on the headwaters of the Truckee and Carson rivers, the runoff ranges between 25 and 45 inches in depth, while the average runoff over larger catchment areas on these streams, above Reno and Genoa, varies between 14 and 25 inches. In nearly every case the depth of runoff is about 60 per cent of the precipitation. In Arizona the slopes are more abrupt and barren ; yet, as the rainfall is less regular and very much less in amount, the volumes of runoff are much smaller. On the upper Gila River basin the total depth of runoff in 1890 for 15,000 square miles of catchment basin was 0.45 of an inch, the discharge amounting to 0.35 second-feet per square mile of catchment area. On the upper Salt River basin above Phoenix the depth of runoff in 1890 was 4.2 inches and the discharge of the stream 3.7 second-feet per square mile of catchment area. In Montana, on the head- waters of the Gallatin and Madison rivers, the total annual depth of runoff averages from 10 to 14 inches, the discharge varying between 10 and 14 second-feet per square mile of catchment area. In the winter it is as low as 0.4 second-foot, and in May and June as high as 3 second-feet. On the Rio Grande basin above Del Norte, Colorado, the in 1890 was annual runoff amounts to about 10 inches in depth or to 10.5 second- feet, while on the entire basin of the Rio Grande above El Paso the runoff amounts to but 0.5 second-feet per square mile of catchment area. On the Bear River at Collision, Utah, the annual depth of runoff is about 6.6 inches, and the discharge 6 DISCHARGE OF WESTERN RIVERS. 2$ second-feet per square mile. On the Provo River above Provo, Utah, the runoff amounts to 10.5 second-feet of discharge per square mile. On the Snake River above Eagle Rock, Idaho, the average annual runoff is 14 inches in depth or 10 second- feet per square mile of catchment area. 30. Flood Discharges of Streams. It is desirable to know the monthly and daily rates of runoff as well as the mean annual runoff of a catchment basin. This is necessary in order that dams and weirs may be provided with ample wasteways. The greatest floods occur either on barren catch- ment basins having steep slopes or where heavy snowfalls are followed by warm, melting rains. On the Gila and Salt river basins in Arizona the percentages of runoff are exceptionally high during occasional severe storms. The highest recorded flood on the Salt River above Phoenix occurred in February, 1891, and amounted to about 350,000 second-feet from a catch- ment basin of 12,260 square miles. This is equivalent to nearly 30 second-feet per square mile of catchment area, while the stream a few days prior to the occurrence of the storm was not discharging over looo second-feet, or one-twelfth of a second- foot per square mile. 31. Discharge in Seasons of Minimum Rainfall. Where the number of storage basins is limited it becomes desirable to save all of the water possible and frequently to impound enough to carry over a period of two or three years of minimum rain- fall. In general it has been found that cycles of mean low rainfall occur every two or three years when the amount of precipitation is less than 0.8 of the mean. The least of these three-year low cycles has been found to average as low as 0.7 of the mean annual rainfall. 32. Regimen of Western Rivers. The Eastern rivers usually drain comparatively level catchment basins, well cov- ered with timber and giass. As a result of this the soil is deep and the rate of runoff is consequently low and the streams are comparatively constant in their discharge, being subject to few and not excessive flood rises. This is because the larger portion of the water reaches these streams from subterranean 26 RUNOFF AND FLOW OF STREAMS. sources by seepage. In the more arid portions of the West the regimen of the streams is the reverse of this. The catch- West Gal latin Madison Missouri Sun Yellowstone Cache la Poudre Arkansas Del- Norte Embudo El Paso Gila Salt East Carson West " Battle Creeklg 3 Collinston J- Ogden Weber American Fork Provo Spanish Pork Sevier Henry Pork Palls Teton Snake Owyhee Malheur Weiser FIG. 3. MAXIMUM, MINIMUM, AND MEAN DISCHARGE OF SOME WESTERN RIVERS. ment basins are precipitous and barren. Little water soaks into the soil to supply the streams from springs. After a FLO W AVAILABLE FOR STORAGE. 2/ heavy storm most of the water runs off in a very short period of time, resulting in great floods. Thus streams which at flood height may reach from 10,000 to 15,000 second-feet discharge for a few hours or days may sink within a week or so to paltry rills of a few second-feet discharge or may entirely disappear. (Fig- 3-) With such streams it becomes necessary to so design works that most of the discharge may be saved by storage within a short period of time. 33. Mean Discharge of Streams. When definite data of the annual discharge of a stream is not available it may be obtained approximately by multiplying the depth of runoff in inches into the area in square miles of its catchment basin. As shown in article 29, the proportion of rainfall which runs off varies between 50 and 80 per cent, according as the slopes are flat or steep, wooded or barren. The discharge ranges be- tween 8 and 20 second-feet per square mile of catchment area. 34. Available Annual Flow of Streams. Where irriga- tion is practised all of the water flowing in the streams is riot available for storage, since much of it is already appropriated by irrigators, and this quantity must be deducted from that available for storage. A large portion of the discharge occurs in winter when the streams are covered with ice which renders it practically impossible to divert the water for storage, though it is available for such reservoirs as may be on the main streams. As nearly all of the flow occurring in the irrigating season is appropriated, only the surplus and flood water is available for storage. 35. Works of Reference. Evaporation, Percolation, and Runoff. BERESFORD, J. S. Memorandum on the Irrigation Duty of Water. Prof. Papers on Indian Engineering, No. 212. Roorkee, India. CRAIG, JAMES. Discharge from Catchment Areas. Trans. Inst. C. E., vol. 80, 1884. FITZGERALD, DESMOND. Evaporation. Trans. Am. Soc. C. E., vol. 15, 1886. GREAVES, CHARLES. Evaporation and Percolation. Trans. Inst. C. E., vol. 45, 1875. NEWELL, F. H. Hydrography. Part II, nth, I2th, and I3th Annual Reports, U. S. Geol. Survey. Washington, D. C., 1890, 1891, 1892. CHAPTER V. SUBSURFACE WATER SOURCES. 36. Sources of Earth Waters. The water which enters the soil by percolation either from rain or from canals, reser- voirs, or lakes finds its way through the soil to some lower level where favorable geologic structure enables it to again reach the surface. This seepage water may move slowly through the particles of subsoil, its motion being rather that due to absorption or capillary attraction than to direct percolation ; or it may enter some seam between two formations from which it may find an exit perhaps at some great distance through a spring or artesian well. The flow of water by percolation is limited not only by the degree of porosity of the strata, but by their inclination. Yet comparatively impervious rocks fre- quently furnish abundant supplies which are the result of capil- lary attraction. 37. Sources of Springs and Artesian Wells. Wells and springs usually derive their water supplies from shallow forma- tions as gravels, sands, and marls. Their temperature may be variable owing to the changes in the temperature of the surface of the soil, while their flow is effected by precipitation of recent occurrence and by evaporation from the surface of the ground. Gravitation tends to draw the water toward the centre of the earth, and it percolates in that direction until intercepted by some impervious stratum along which it finds its way. If the water fills a pervious stratum so surrounded by impervious strata that it is prevented from escaping, and the hydrostatic pressure due to the inclination of the beds is sufficient to bring the water to the surface, the conditions are favorable for the 28 ARTESIAN WELLS. 29 production of an artesian well. All that is necessary is to pierce the upper confining stratum by boring, when the water will escape. Generally artesian supplies exist in the newer sandstones and other equally porous rocks. Waters are fre- quently gathered into such strata from distant catchment basins. Where such a water-bearing stratum approaches the surface in a broad plain it forms an extensive artesian basin. 38. Artesian Wells. Deep wells do not always overflow. The condition of overflow depends on whether the pressure is sufficiently great to force the water above the surface, in which case they are known as artesian wells. Frequently the water will reach within but a few feet of the surface, when an ordi- nary well or" shaft can be excavated and the water pumped to the desired height. In many other cases the pressure is such that the water spouts forth from the well under considerable pressure to great heights. In an artesian area of considerable extent the various wells seriously influence each other. In the San Gabriel and San Bernardino valleys in Southern California it has been found that after a certain number of wells have been sunk, each additional well affects its neighbors by diminishing their discharge. There thus comes a point in the sinking of wells when the number which can be utilized in any given area or basin is limited. 39. Examples of Artesian Wells. Some great wells have been sunk in different parts of the world. The cele- brated Grinnell well in Paris has an 8-inch bore and is 1806 feet in depth. A well is now being bored in the neigh- borhood of Wheeling, West Virginia, which has reached a depth of over 5000 feet. In St. Louis is a well which reaches a depth of 3850 feet ; about 3000 feet below the sea-level. In San Bernardino and San Gabriel valleys in Southern California and in the upper San Joaquin valley in the neighborhood of Bakersfield are some very extensive artesian areas, but the greatest artesian basins of the West are found in the neighbor- hood of Waco, Texas ; Denver, Colorado, and of the James river valley and the neighborhood of Huron in the Dakotas. In 1890 there were 8097 artesian wells on farms in the arid region. Of these 3210 were in California, 2524 in Utah, 596 in 3O SUBSURFACE WATER SOURCES. Colorado, and between 460 and 530 each in North Dakota, South Dakota, and Texas, besides a few in each of the remain- ing States and Territories. Of these wells 48^ per cent were used in irrigating 51,896 acres. Their average depth is 210 feet ; average cost, $245 ; and average discharge, 54.4 gallons per minute. 40. Supplying Capacity of Wells. The supplying capac- ity of common wells is frequently increased considerably by irrigation. As water is applied to the soil through a period of years the subsurface level rises and it may be reached at lesser depths than previously. In this way irrigation water may be used over several times; by pumping it from wells it may find its way by seepage back to the streams from which it may be again diverted. 41. Tunneling 1 for Water. Tunnels are sometimes driven in sloping or sidehill country to tap the subterranean water supplies. These are practically horizontal wells, differing from ordinary wells chiefly in that the water has not to be pumped to bring it to the level of the surface, but finds its way by gravity flow to the lands on which it is to be utilized. Near the Kojah Pass in India is a great tunnel of this kind. This is run near the dry bed of a stream into the gravels for a dis- tance of over a mile. The slope of its bed is 3 in 1000, its cross-section is 1.7 X 3 feet, and its discharge about 9 second- feet. The Ontario Colony in Southern California derive their water supply from a tunnel 3300 feet in length, run under the bed of San Antonio creek through gravel and rock. Its cross-section is 5 feet 6 inches high, 3 feet 6 inches wide at bottom, and 2 feet wide at top. It is partly timbered and partly lined with concrete, having weep-holes in the upper part of the tunnel. Its discharge is about 6 second-feet. The sup- ply from several sub-tunnels has been such as to average nearly 10 second-feet per linear mile of tunnel. 42. Other Subsurface Water Sources. Earth waters may be gathered for irrigation by other means than springs, common or artesian wells, or tunnels. In portions of the plains region, especially in Kansas, subsurface supplies have WORKS OF REFERENCE. 31. been obtained by running long and deep canals parallel to the dry beds of streams or in the low bottom lands and valleys. These canals, acting like drainage ditches, receive a considerable supply of water and lead it off to the lands. In the dry beds of streams in California submerged dams have been built which reach to some impervious stratum and cut off the subterranean flow, thus bringing the water to the surface. In some experi- ments made on two subcanals in Kansas the amount of water obtained was 15 second-feet for each mile in length of excava- tion, which was 6 feet in depth below the subsurface water. It was found that the depth and length were the controlling factors, the breadth of the canal having little effect on the amount of water entering. It was also found that the in- crease of flow due to the deeper cuts was nearly as the square of the depth. 43. Works of Reference. Artesian Wells. CHAMBERLAIN, T. C. The Requisite and Qualifying Conditions of Artesian Wells. Fifth Annual Report, U. S. Geological Survey, Washington, D. C, 1884. GREGORY, J. W., and COFFIN, FRED. F. B. Artesian and Underflow Investigation. Department of Agriculture, Washington, D. C., 1892. HALL, WM. HAM. Irrigation in Southern California. Part II. Sacra- mento, 1888. HAY, Prof. ROBERT, and Others. Geological Reports on Artesian Underflow Investigation. Department of Agriculture, Washington D. C., 1892. HINTON, RICHARD. Artesian and Underflow Investigation. Depart- ment of Agriculture, Washington, D. C., 1892. NETTLETON, E. S. Artesian and Underflow Investigation. Depart- ment of Agriculture, Washington, D. C., 1892. NEWELL, F. H. Artesian Wells for Irrigation. U. S. Census Bulletin No. 193. Washington, D. C., 1890. POWELL,]. W. Artesian Wells. Part II, nth Annual Report, U. S. Geological Survey. Washington, D. C., 1890. CHAPTER VI. ALKALI, DRAINAGE, AND SEDIMENTATION. 44. Harmful Effects of Irrigation. When irrigation is practised without proper attention to drainage it is liable to result in the following evils: (i) production of alkali or floc- culent salts on the surface of the ground ; (2) souring or waterlogging of the soil due to supersaturation ; (3) fevers and other injurious effects the result of the same cause. 45. Alkali. The white efflorescent salt known as "alkali " is to be found in many portions of the West both as a result of irrigation and occurring naturally over extensive areas. These salts have been analyzed and are found to consist chiefly of chlorides, carbonates, and sulphates of sodium. Sometimes a small amount of potassium salts, sodium phosphate, or man- ganese sulphate are present. In most cases sodium sulphate predominates, ranging in amount from 5 to 75 per cent. The effect of this alkali on the surface of the ground is to kill all vegetable growth and to render the soil barren and unproduc- tive. 46. Causes of Alkali. Where the natural drainage of the country is defective and the strata underlying the surface are impervious or the soil not deep, irrigation or rainfall causes the subsurface water plane to rise to such a height that finally the soil becomes saturated. Evaporation then takes place from the surface, and as this process continues there is left on the soil the salts contained in the water. Thus the more water that evaporates from the surface the more alkali will be de- posited, and increased rainfall or irrigation will increase the amount of alkali. It is thus seen that the direct cause of the production of alkali is the rise of the subsurface water plane 32 ALKALI AND WA TER LOGGING. 33 due to defective drainage. Seepage from badly constructed canals is a great producer of alkali. Thus where the velocity of the canal is slow, time is given for water to soak into the soil and permeate it. 47. Waterlogging. Where the rise of water from the sub. surface or its addition to the surface from natural causes or irrigation is more rapid than the losses by evaporation or drainage, the water stands in pools and the soil becomes soft and marshy, producing the effect known as "swamping" or " water-logging." Like alkali, waterlogging is directly traceable to defective drainage and the careless use of water. Where the conditions are sufficiently well balanced for drainage to prevent the rise of the subsurface water to within 10 or 15 feet of the surface, continued irrigation produces good results by soaking up the lower strata and giving an abundance of water near the surface for wells and for moistening the deeper rooting plants. 48. Prevention of Alkali and Waterlogging. Several preventatives for the rise of alkali or the excessive soaking of the soil have been recommended, and some have been employed with success. Where it is impossible to entirely remove the alkali, the cultivation of deep-rooting or such plants as shade the soil and reduce the amount of evaporation may permit some use to be made of the land. Irrigating only such lands as have good natural drainage, and exercising care not to interfere with this, is one of the best and surest preventives of the production of alkali and waterlogging. The introduction of artificial drainage produces the same effect, while in a lesser degree the same result may be obtained by the use of deep ditches or furrows which themselves act as drainage channels. When the quantity of alkali is small the evil effects resulting from its presence may be mitigated by the application of chemical anti- dotes, and lastly relief may be obtained in some cases by watering the surface and drawing off the water without allow- ing it to soak into the ground. This system of reclaiming the land by surface washing and drawing off the salt-impregnated water is known as " leaching." 34 ALKALI, DRAINAGE, AND SEDIMENTATION. One of the most effective methods for the prevention of alkali is the judicious and sparing use of water in irrigation. If the least amount of water necessary for the production of crops is applied to the soil, the soaking of this with water will be a much slower process and may not result in oversatu- ration, even though the drainage be defective. 49. Chemical Treatment and Leaching. A cheap anti- dote for most alkaline salts is lime, while neutral calcareous marl will answer in some cases. When the alkali consists of car- bonates and borates the best antidote is gypsum or landplaster sown broadcast over the surface. Leaching may be practised by building temporary embankments around the land and flooding, then rapidly drawing or pumping off the salt-im- pregnated waters. 50. Drainage. Generally the drainage of irrigated land will take care of itself if the natural drainage channels are not interfered with or obstructed. Where the surface has a mod- erate though sufficient slope to allow the water to flow off, or the soil is underlain by deep beds of gravel or porous rocks which will carry off the percolation water, irrigation may be practised for all time, and even an excessive amount of water may be used without seriously affecting the crops. In a few cases the drainage may be improved by digging drainage chan- nels or ditches or laying drainage pipes under the surface. Such methods as these, however, are usually too expensive. In many portions of the West, and especially in the San Joaquin Valley in California, old sloughs and abandoned natu- ral drainage lines have been utilized as irrigation channels. The effect of this is bad, as the natural drainage lines thus be- come overloaded, resulting in* waterlogging the soil. In this way large areas in Fresno County and its neighborhood have been rendered uncultivatable, whereas with a proper system of irrigating channels, providing the natural drainage channels had been left open, no evil effects would necessarily have resulted. 51. Excessive Use of Water. This is one of the greatest evils at present noticeable in our Western irrigation methods. Almost invariably too much water is employed in irrigating SILT AND SEDIMENTATION. 35 crops. The result is the waste of water and the oversaturation of the soil. As the value of water rises it will be used with less extravagance. Proper care in the location and construction of the canal banks will aid greatly in reducing the evil effects of irrigation. If the location is bad, the natural drainage chan- nels may be interfered with. If the construction is bad, the loss by seepage from the canal into the soil becomes great. 52. Silt. Great volumes of silt are transported by Western rivers in times of flood. This is the result of the erosion of the alluvial banks of the streams. The heavier sand and gravel is soon deposited in the upper reaches of the river, and only the finest silt reaches the canals. As the velocity in these is relatively low, much of this sediment is deposited near the canal head, in storage reservoirs or in other slack water, thus choking the canal or diminishing the volume of the reservoir. 53. Amount of Sediment. The quantity of this sediment which is carried in suspension during floods is frequently greater than is generally appreciated. From investigations made by the U. S. Geological Survey on the Rio Grande in 1889 it was found to range from J to \ of I percent of the volume of flow. It was estimated that in about 150 years the amount of this sediment would seriously impair a reservoir 60 feet in depth. On the American River at Folsom, California, in one year a depth of nearly 10 feet of wet silt was deposited in a reservoir at that point ; much of this, however, was heavy matter,- as gravels and boulders carried by the swift current of the stream. 54. Prevention of Sedimentation in Reservoirs and Canals. There are practically but two methods of mitigating the injury due to sedimentation in reservoirs. One is by build- ing higher up on the stream cheap settling reservoirs which may be destroyed in the course of a number of years, or the dams be increased in height as they silt up. The other method is by the construction of under- or scouring-sluices in the bottom of the dam. These have not as yet proved effectual, as their in- fluence is felt at but a short distance back from the opening. Experience has shown that they do not remove silt which has already been deposited, but, providing their area is large com- 36 ALKALI, DRAINAGE, AND SEDIMENTATION. pared with the flood volume of the stream, they may effectively prevent the deposition of sediment by permitting the silt-laden waters to flow through the reservoir ; the latter only being filled after the flood has subsided and the waters become less turbid. Canals should be so designed that the angle at which they are diverted from the main stream shall be such as to cause the least back eddy in front of the headgates and the least deposit at that point. Where a canal is taken off at right angles to the line of the stream and scouring-sluices are placed in the weir immediately adjacent to the headgates, the main stream may be so trained as to have a straight sweep past the headgates and thus scour out any deposits occurring at that point. In designing a canal the endeavor should be to so change the grade with the cross-section that a constant velocity shall be maintained throughout the main line and all its minor branches. In this event the silt will be maintained in suspension and will be carried through the minor ditches and not deposited until it reaches the fields. It thus becomes valuable, as it acts as a fertilizer. As the velocity of the current is generally diminished in the upper portion of the canal in its passage from the main stream, the deposit of silt is likely to occur at this point. It may be well to encourage this by increasing the cross-section of the canal and reducing its grade so that its capacity shall remain the same but its velocity be diminished. Then the de- posit of silt will occur all at once in the first half-mile or less of the canal, and it may be either dredged out or perhaps scoured out by an escape. 55. Fertilizing Effects of Sediment. The value of silt- bearing water as a fertilizer is well known. Where it is possi- ble to keep the silt in suspension until the water reaches the fields, such waters are especially valued for purposes of irriga- tion. In the valley of the Moselle, France, on land absolutely barren and worthless without fertilization, the alluvial matter deposited by irrigation from turbid water renders the soil capable of producing two crops a year. In the valley of the Durance, France, the turbid waters of that stream bring a price for irrigation which is ten and twelve times greater than WEEDS. 37 that paid for the clear cold water of the Sorgues River. It has been estimated that on the line of the Galloway Canal in Cali- fornia land which has been irrigated with the muddy river water gives 18 per cent better results after the fifth year than the same land which has been irrigated with clear artesian water. 56. Weeds. When from any cause it becomes necessary to give a canal a low velocity, the growth of water weeds and the deposition of silt are encouraged. Water-plants grow most freely where the current has a slow velocity and the depth is such that the sunshine reaches the bottom. They thrive in shallow reservoirs, thus diminishing their capacity. Brush, willows, weeds, and rushes may encroach on the chan- nels of canals where the slopes of the banks are low and so diminish the water-way as to greatly reduce their carrying -capacity. Providing a high velocity cannot be given the only possible way of remedying this is to draw off the water and destroy the plants. CHAPTER VII. QUANTITY OF WATER REQUIRED. 57. Duty of Water. The duty of water may be defined as the ratio between a given quantity of water and the amount of land which it will irrigate. In order to determine what amount of water is sufficient to supply a given area of land it is first necessary to at least approximately determine its duty for the specific case under consideration. On the duty of water depends the financial success of every irrigation enterprise, for as water becomes scarce its value increases. In order to estimate the cost of irrigation in projecting works, it is essential to know how much water the land will require. In order to ascertain the dimensions of canals and reservoirs for the irrigation of given areas the duty of water must be known. 58. Units of Measure for Water Duty and Flow. Be- fore considering the numerical expression of water duty, the standard units of measurement should be defined. For bodies of standing water, as in reservoirs, the standard unit is the " cubic foot." In the consideration of large volumes of water, however, the cubic foot is too small a unit to handle conven- iently and the " acre-foot" is the unit employed by irrigation engineers. This is the amount of water which will cover one acre of land one foot in depth, that is 43,560 cubic feet. In considering running streams, as rivers or canals, the expression of volume must be coupled with a factor representing the rate of movement. The time unit usually employed by irrigation engineers is the second, and the unit of measurement of flow- ing water is the cubic foot per second, or the " second-foot " as it is called for brevity. Thus the number of second-feet flow- 38 UNITS OF MEASURE FOR WATER DUTY AND FLOW. 39 ing in a canal are the number of cubic feet which pass a given point in a second of time. A unit still generally em- ployed in the West is the " miner's inch." This differs greatly in different localities and is generally defined by State statute. In California one second-foot of water is equal to about 50 miner's inches, while in Colorado it is equivalent to about 38.4 miner's inches. The period of time during which water is applied to the land for irrigation from the time of the first watering until after the last watering of the season is usually known as the " irrigating period." This is generally divided into several " service periods," by which is meant the time during which water is permitted to flow on the land for any given watering. Thus the irrigation period in the majority of the Western States extends from, say, April I5th to August 1 5th, about 120 days. The service period, or the duration of one watering, is generally from 12 to 24 hours, according to the soil and crop. The number of waterings making up the irrigation period vary between 2 and 5, according to the soil, climate and crop. In the following table are given some few convertible units of measure. TABLE VI. UNITS OF MEASURE. second-foot = 45 gallons per minute. cubic foot = 7-5 gallons. cubic foot weighs 62$ pounds at average temperature. second-foot = 2 acre-feet in 24 hours (approx.). ,000,000 cubic feet = 23 acre-feet, (approx.). loo California inches = 4 acre feet in 24 hours. 100 Colorado inches = 5* acre-feet in 24 hours. 50 California inches i second-foot. 38.4 Colorado inches = i second-foot, i Colorado inch = 17,000 gallons in 24 hours (approx.). 1 second-foot = 59* acre-feet in 30 days. 2 acre-feet = i second-foot per day or .03^ second-feet in 30 days. 100 California inches = 3-97 acre-feet per 24 hours, i acre-foot = 25.2 California miner's inches in 24 hours. 4O QUANTITY OF WATER REQUIRED. 59. Measurement of Water Duty. The duty of water may be variously expressed by the number of acres of land which a second-foot of water will irrigate ; or by the number of acre-feet of water required to irrigate an acre of land; or in terms of the total volume of \vater used during the season. It may also be expressed in terms of the expenditure of water per linear mile of canal, though this form can only be satis- factorily employed when the location of the canal line has been previously determined. In considering the duty of water care should be taken to show whether it is reckoned on the quantity of water entering the head of the canal or the quan- tity applied to the land, since the losses by seepage, evapora- tion, etc., in the passage of water through the canal are con- siderable. Thus, if in a long line of canal the duty is esti- mated at 150 acres per second-foot and the losses by seepage and evaporation are 33^ per cent, the duty would be reduced to 100 acres at the point of application. 60. Duty per Second-foot. The duty of water in various portions of the West is a matter of extreme doubt. As re- cently as in 1883 it was estimated in Colorado to be from 50 to 55 acres per second-foot. In Montana and portions of Colorado the farmers still state the duty as being one miner's inch to the acre, or 38.4 acres per second-foot. Recent experi- ments show that the duty is rapidly rising, for as land is irrigated through a series of years it becomes more saturated, and as the subsurface water plane rises the amount of water necessary to the production of crops is diminished. The culti- vation of the soil causes it to require less water. The adoption of more careful methods in designing and constructing dis- tributaries and care and experience in handling water increase its duty. The State Engineer of Colorado now accepts 100 acres per second-foot as the duty for that State. In Utah 60 acres per second-foot is accepted as the present duty. In Montana it is about 80 acres per second-foot. In the following table the duty of water is given for a few foreign countries and for various portions of the West, These duties cannot be taken as fixed. They are apt to be increased DEPTH OF WATER REQUIRED TO SOAK SOIL. 41 with experience, and in the same State or even in the same neighborhood they will differ according as the crops, soil, alti- tude, and the skill in handling the water vary. TABLE VII. DUTY OF WATER. Northern India 250-300 Valencia, Spain , 200-325 Northern Chili 190 Italy 65-70 Colorado 80-100 Utah ; 60-80 Montana So-ioo Wyoming 70 Idaho , 60 New Mexico 60 Southern Arizona loo San Joaquin Valley, Cal 100-150 Southern California, surface irrigation 150-300 sub-irrigation 300-500 The reason for the high duty given for such an arid region as Southern California is because the water there, being valu- able, is handled with great care. Where sub-irrigation is em- ployed the duty has in some cases reached as high as 1000 acres per second-foot. In Wyoming, where care was taken on an experimental farm in handling water, its duty was found to be as high as 94 acres on oats and 230 acres on potatoes. 61. Depth of Water required to Soak Soil. Experi- ments conducted in India have shown that a good heavy rain amounting to about 5j inches soaks into the earth to a depth of from 16 to 18 inches. If this amount of water were applied three times in the season, it would be equivalent to a total depth of 16^ inches to the crop. Experiments made in Colorado showed that good crops could be raised by the application of a depth of 1 8 inches of water, while in Wyoming 12 inches applied to potatoes and 24^ inches to oats proved sufficient. In Idaho the depth of water necessary is now assumed to be about 2 feet, while in Montana 15 to 18 inches is believed to be sufficient. 4 2 QUANTITY OF WATER REQUIRED. 62. Duty per Acre-Foot. An average depth of 3 inches of water on the surface is sufficient to thoroughly water an average soil. In sandy soil 4 inches is required. This is equivalent to 10,454 cubic feet, or about \ of an acre-foot per acre. The average crop requires about four waterings in the season. This at the above rate would be equivalent to 42,500 cubic feet, or nearly an acre-foot per acre. From the results shown in article 61 it will be seen that from \\ to 2 acre-feet in depth applied to the land is sufficient to irrigate it. In estimating the duty of water stored in a reservoir allowance must be made, however, for the loss due to evaporation and absorption in conducting the water to the fields. As this will rarely average below 25 per cent it follows that where a duty of one acre-foot per acre is possible i acre-feet must be stored in the reservoir, and where 2 acre-feet per acre is the duty 2|- acre-feet must be stored. 63. Linear and Areal Duty. From experiments made in India it was found that from six to eight second-feet of water should be allowed per linear mile of canal. This quantity, of course, depends on the area on either side of the canal which it will command. On the Soane Canal in India a more con- venient unit was employed, it having been discovered that about three fourths of a second-foot was sufficient for a square mile of gross area. As the net area irrigated, however, is rarely more than two thirds of the gross area commanded, perhaps about one half a second-foot is sufficient to irrigate a square mile when the most economic use is made of the water. 64. Percentage of Waste Land. In every irrigated area it has been discovered that but a small percentage of the total area commanded is irrigated in any one season. Some of the land is occupied by roads, farm-houses, or villages. Some is occupied by pasture lands which receive sufficient moisture by seepage from adjoining irrigated fields ; and some by barn- yards, while occasionally fields are allowed to lie idle for a season. In this way it has been discovered in India that gen- erally but two-thirds to four-fifths of the total area commanded has been irrigated, though in some localities this percentage is WOKA'S OF REFERENCE. 43 a trifle larger. This is particularly so in the neighborhood of the Soane Canals in India, where about 500 acres out of every 640 are irrigated. From estimates made of the'area under cul- tivation in well-irrigated portions of the West it has been dis- covered that if water is provided for 500 out of every 640 acres, it will be sufficient to supply all the demands of the cultivators. Keeping this in mind, it will be seen that the actual duty of water when estimated on large areas is at least 20 per cent greater than the theoretic duty per acre. 65. Works of Reference. Alkali. Sedimentation and Duty of Water. BERESFORD, J. S. Duty of Water and Memoranda on Irrigation. Pro- fessional Papers, Second Series, No. 212. Roorkee, India CARPENTER, L. G. Third Annual Report on Meteorology and Engin- eering Construction, State Agricultural College of Colorado, 1890. Fort Collins, Colorado. DEAKIN, ALFRED. Royal Commissioner on Water Supply. First Prog- ress Report, Irrigation in Western America. Melbourne, 1885. FLYNN, P. J. Irrigation Canals and other Irrigation Works. Denver, Col., 1891. FOOTE, A. D. Report on Irrigation of Desert Lands in Idaho. New York, 1887. HALL, WILLIAM HAM. Report of the State Engineer to Legislature of California. Sacramento, 1880. HILGARD, E. W. Alkali Lands. Report of University of California. Sacramento, Cal., 1886. NEWELL, F. H. Various Bulletins of the nth Census on Irrigation in Arid States. Washington, D. C, 1892. WILSON, H. M. Irrigation in India. Part II, I2th Annual Report of the U. S. Geological Survey. Washington, D. C., 1891. American Irrigation Engineering. Part II, isth Annual Report of the U.S. Geological Survey. Washington, D. C., 1892. CHAPTER VIII. PRESSURE AND MOTION OF WATER 66. Physical and Chemical Properties of Water. Water is composed of an infinite number of minute particles, each of which has weight and can receive and transmit this in the form of pressure in all directions. The particles composing water move upon and among each other with an inappreciable amount of friction. Water is composed of at least two atomic substances, oxygen and hydrogen, combined in the ratio of one of oxygen to two of hydrogen, the whole forming a molecule of water. These molecules are so fine that it has been esti- /v* W m ^" '^ o co in CO co in CO * o CO ft in "? m OJ IO in CO '* 111 a * R co O oo Tf m R vO 8, o O co co en CO II cT | 1 1 O N -t m 8 CO 5 m O O o o in O 1 m N C C c in C 10 c O C C C C c O c c C O Tf c c CO c c Jjl m CO in -r of 8 8 1 8 1 -t CO of 8 1 1 CO 8 O w in HI ON 01 r^ o in Ol co s in en C4 H O O -r CO r^ r> w CO co P "- 1 ^1- IT) in " CO ||| 8 8 8 8 8 8 8 8 8 8 8 O co 8 8 1 lO CO 8 i co S 8 CM co ei 8 co c7 1 bj, I HJ JB 2 2 -S D 2 o 'x OJ .5 'c 15 U = 2 Arizona Colorado : .5 -5 c : ; : I C 15 3 13 m U U c J O U 3 U "o "* tl 1 [ : c o C 1 c <*J Cj ^ II Jl c (4 U o Turlock Canal. *J V - > 5 t/5 'b/C C i5 M C ci" Z Arizona Canal. 5 E c Q c U 03 cd > O V | c be < Soane Canal. . Carpenteras Ca Henares Canal Cavour Canal . PARTS OF A CANAL SYSTEM. 7 1 miles of diversion line, where numerous difficulties are fre- quently encountered, calling for variations in the form and con- struction of drainage works and canal banks. The headworks consist usually of the diversion weir with its scouring sluices, of the head regulating gates at the canal entrance, and of the head or first escape gates. The control works consist of regulating gates at the head of the branch canals, and of escapes on the line of the main and branch canals. The drainage works consist of inlet or drainage dams, flumes or aqueducts, superpassages, inverted siphons, and drainage cuts. In addition to these works there are usually constructed falls and rapids for neutralizing the slope of the country, and tunnels, cuttings, and embankments. Modules or some form of measuring box or weir are necessary for the measurement of the discharge. CHAPTER XL ALIGNMENT, SLOPE, AND CROSS-SECTION. 103. Location of Headworks. The headworks of a canal are almost invariably located high up on the supplying stream, in order to command a sufficient area and to tap the stream where the water is clear and contains the least amount of silt. By so locating the headworks it is usually possible (owing to the greater slope of the country) to reach the water-sheds or interfluves with the shortest possible diversion line. The dis- advantages of this class of location are serious, since the canal line is sure to be intersected by hillside drainage, the passage of which entails great difficulties ; and as the adjacent slopes of the country are heavy-, much expensive hillside cutting is required. 104. Diversion Line. By diversion line is meant that por- tion of the canal line which is required in order to bring it to the neighborhood of the irrigable lands. It is that waste construction which does not command any irrigable land. The endeavor should always be made in locating the canal to re- duce the length of diversion line to a minimum, so that the canal shall command irrigable land and derive revenue at the earliest possible point in its course. 105. Relation between Lands and Water Supply. In designing an irrigation work the first consideration is the land to be irrigated. The projector must consider the area of this, its nearness to market, the quality of the soil, the climate, and the character and value of the crops which it will produce. In 72 SURVEY AND ALIGNMENT. 73 addition, the value and ownership of the land must necessarily be considered. All of these quantities having been satisfac- torily determined and the necessity of supplying water for irri- gation having been ascertained, the next question is the source of supply and its relative location to the lands. This supply may be found in some adjacent perennial stream, or it may be necessary to transport it across an intervening ridge from a neighboring water-shed, or it may be necessary to conserve in storage reservoirs the intermittent flow of minor streams. The relation of the water supply to the land, the extent of the latter, and the volume and permanency of the former are the most im- portant items to be ascertained in the preliminary investigation of any irrigation project. 106. Survey and Alignment. Having determined the source of water supply and its relation to the irrigable lands, the third question in order of importance is the alignment of the canal. This should be so made that the canal shall reach the highest part of the irrigable lands with the least length of line and at a minimum expense for construction. The line of the canal should follow the highest line of the irrigable land, preferably skirting the surrounding foothills and passing down the summit of the water-shed dividing the various streams. In order that the best possible alignment may be obtained, careful preliminary and location surveys are necessary. That all possible locations may be examined, it is desirable, first, to construct a general topographic map on some large scale, perhaps 800 to 1500 feet to the inch, and with contour lines showing differences of elevation of from 5 to 10 feet. On such a map as this it is possible to at once lay down with a near de- gree of approximation the final position of the canal line. It is also frequently possible from inspection of such a map to save many miles of canal by the discovery of some low divide or some place in which a short but deep cut or a tunnel will save a long roundabout location. Having laid down this line on the map, the final location may be made on the ground, with the aid perhaps of a few short trial lines to determine its exact position. 74 ALIGNMENT, SLOPE, AND CXOSS-SECTION. 107. Obstacles to Alignment. Such obstacles as streams, gullies, ravines, unfavorable or low-lying soil or rocky barriers are frequently encountered in canal alignment. The best method of passing these must be carefully studied. It may be cheapest to carry the canal around these obstructions, or it may be better to at once cross them by aqueducts, flumes, or inverted siphons, or to cut or tunnel through the ridges. Careful study should be made of each case and estimates made of the cost not only of first construction, but of ultimate maintenance. In crossing swamps or sandy bottom lands it may be cheaper, be- cause of the losses which the water will sustain from evapo- ration and absorption, to carry the canal in an artificial channel through such places. If water be abundant it may be less expensive on hillside work to simply build the canal with an embankment on its lower side, permitting the water to flood back on the upper side according to the slope of the country. In such cases the losses by evaporation and absorption will be great in the beginning, but ultimately these flat places maybe- come silted up and a permanent channel made through them. The relative cost of building a sidehill canal wholly in excava- tion or partly in embankment should be considered. If the hillside is steep and rocky, the advisability of tunnelling, of building a masonry retaining wall on the lower side of the canal, or of carrying it in an aqueduct or flume will have to be considered. 108. Sidehill Canal Work. It is extremely difficult to carry a large canal along steep sidehill slopes. In order to get a sufficient cross-section to carry the volume required without unduly increasing the velocity demands the exercise of careful judgment. It is possible to get the same cross-sectional area by employing different proportions of depth to bed width. The less the cross-sectional area of a channel, the less its cost and the expense for maintenance. It is therefore first necessary to choose the highest possible velocity which the resistance of the material and the necessity of commanding land will permit, and then to give the canal such a cross-sectional area as will produce the required discharge. The great difference in ex- CURVATURE. 75 cavation of two canals of equal capacity but different propor- tions of bed width to depth is graphically shown in Fig. 8. In one case many times the amount of material will have to be removed than in the other, while the surface exposed to evap- oration and absorption is greatly increased. Where the mar c FIG. 8. CANAI. CROSS-SECTIONS FOR VARYING BED-WIDTHS. terialis suitable and not too liable to cause loss by percolation, it is well to equalize the cut and fill. In this way still less material will have to be moved, for, as shown in the illustration, the depth of excavation is diminished by raising the lower bank. 109. Curvature. A direct or straight course is the most economical, as it gives the greatest freedom of flow and causes the least erosion of the banks. It also greatly diminishes the cost of construction and the losses by absorption and evaporation consequent on the increased length of a less direct location. It is an error in alignment to adhere too closely to grade lines following the general contour of the country. By the insertion of an occasional fall it is frequently possible to obtain a more desirable location and to diminish the cost of construction by the avoidance of some natural obstacle. One of the most serious errors in alignment is the careless location of curves, to which detail too little attention is ordi- narily paid. The insertion of sharp bends inevitably results in the destruction of the canal banks, or requires that they shall be paved or otherwise protected to prevent their erosion. Instances have been noted where engineers have inserted great curves carefully constructed on some fixed radius of absurd length, as though the canal were a railway line. Curva- ture diminishes the delivering capacity of the canal, and too 76 ALIGNMENT, SLOPE, AND CROSS-SECTION. sharp a curve endangers the structure itself. In large canals of moderate velocity it will be safe in most cases to take the radius of curvature at from three to five times the depth of the canal. As the cross-section becomes smaller or the velocity is increased, the radius of curvature should be correspondingly increased. To keep up the discharge of a canal either its cross-section or grade should be increased in proportion to the sharpness of the curve. 1 10. Borings, Trial Pits, and Permanent Marks. In finally locating an expensive work, borings and trial pits should be made, the former with a light steel rod and the latter by simple excavation in order to discover the character of the material to be encountered. In making the final survey of a canal it is well to place at convenient intervals permanent bench marks of stone or other suitable material. The estab- lishment of these along the side of the canal in some safe place will give convenient datum points to which levels can be re- ferred whenever it may be necessary to make repairs or run branch lines. Mile or quarter-mile posts or permanent stakes should also be set in the canal banks so that future surveys and changes in the line may be referred to these. in. Example of Canal Alignment Ganges Canal. An excellent example of a typical alignment on one of the great Indian canals is that of the Ganges canal, which heads in the Ganges river at Hurdwar, where the stream issues sud- denly from between the foothills of the Himalayas on to the broad level plains. In the first 20 miles of its course the canal encounters considerable sub-Himalayan drainage, and the works for the passage of this and for the reduction of slope in the canal by means of falls are important (PI. II). The slope of the river bed and country averages from 8 to 10 feet per mile. At the site of the headworks the river is divided into several channels, one of which, about 3 feet in width, follows the Hurdwar shore and rejoins the main stream half a mile below that town. As the discharge of the canal is 6700 sec- ond-feet and that of the river never falls below 8000 second- GANGES CANAL. 77 feet, only a portion of the water is required at any time. This is diverted to the Hurdwar channel by means of training works and temporary bowlder dams, and the current has deep- ened the channel until it now has a uniform slope of 7^ feet per mile to the canal head. The regulator is about half a mile below the first training works, and consists of a weir and scour- ing sluices across the channel. In the first few miles the canal crosses several minor streams which are admitted by means of inlets. At the sixth mile it is crossed by the Ranipur torrent, which is passed over it in a masonry superpassage 195 feet in breadth (PL XVI). In the tenth mile the Puthri torrent, having a catchment basin of about 80 square miles, or twice that of the Ranipur, is carried across the canal by a similar superpassage 296 feet in breadth. The sudden flood dis- charges in these torrents are of great violence, the Puthri discharging as much as 15,000 second-feet and having a velocity of about 15 feet per second. In the thirteenth mile the canal encounters the Rutmoo torrent (Article 183), which has a slope of 8 feet per mile and a catchment basin half as large again as that of the Puthri. This torrent is admitted into the canal at its own level, and in the side of the canal opposite to the inlet is an open masonry out- let dam or set of escape sluices. Just below this level crossing is a regulating bridge by which the discharge of the canal can be readily controlled ; thus in time of flood, by opening the sluices in the outlet dam and adjusting those in the regulator so as to admit into the canal the volume of water required, the remainder is discharged through the scouring sluices, whence it continues in its course down the torrent. In the nineteenth mile, near Roorkee, the canal crosses the Solani river and valley on an enormous masonry aqueduct (Article 189). The Solani river in times of highest flood has a discharge of 35,000 second-feet and the fall of its bed is about 5 feet per mile. The total leagth of the aqueduct is 920 feet. The banks of the canal on the up-stream side are revetted by means of masonry steps for a distance of 10,713 feet, and on the down-stream side for a distance of 2,722 feet. ALIGNMENT, SLOPE, AffD CROSS-SECTION. TURLOCK CANAL. 79 For if miles the bed of the canal is raised on a high embank- ment previously to its reaching the aqueduct, and for a dis- tance of half a mile below it is on a similar embankment. The greatest height of the canal bed above the country is 24 feet (PL XIV). The aqueduct proper consists of fifteen arches of 50 feet span each. In addition to these great works there are in the first 20 miles of the canal five masonry works for damming minor streams and a number of masonry falls. Beyond Roorkee the main canal follows the high divide between the Ganges and the west Kali Nadi, and continues in general to follow the divide between the Ganges and the Jumna rivers to Gopalpur, a short distance below Aligarh, where the main canal bifurcates, forming the Cawnpur and Etawah branches. The former tails into the Ganges river at Cawnpur and is 170 miles in length. The Etawah branch is also 170 miles long and tails into the Jumna river near Humerpur. The Vanupshahr branch leaves the main line at the fiftieth mile, and flows past the towns of Vanupshahr and Shahjahanpur. It formerly terminated at mile 82^-, emptying into the Ganges river ; but it is now continued to a point near Kesganj, where it tails into the Lower Ganges canal. The first main distribu- taries are taken from both sides of the canal a short distance below Roorkee. The nature of the country offers abundant facilities for escapes from the canals, of which five are con- structed on the main line, four on the Cawnpur branch, and three on the Etawah branch, besides numerous small escapes to the distributaries. 112. Example of Canal Alignment Turlock Canal. A typical American canal alignment is that of the Turlock canal, which is diverted from the Tuolumne river in Cali- fornia at a point where it emerges from the Sierras between high rocky canyon walls. For the first 5 miles the canal is built along steeply sloping hillside, and it crosses numerous drainage channels in its endeavors to surmount the bluffs bor- dering the river and gain the irrigable lands. The topography is so irregular that the first attempts which were made at diver- sion were unsuccessful. The present location was discovered 8o ALIGNMENT, SLOPE, AND CROSS-SECTION. only after a careful detailed topographic map had been made of the entire region, and from this the canal line was laid down (Fig. 9). The headworks of the Turlock canal consist of a masonry dam which is constructed as a common diversion weir for the FIG. 9. TURLOCK CANAL. PLAN OF DIVERSION LINE, Turlock canal and the canal of the Modesto Irrigation district, which latter heads on the opposite or north bank of the river. This weir (Article 278) is located between high canyon walls, two miles above the town of La Grange, at a point where the abutments and foundation of the weir consist of firm homo- geneous dioritic basalt, in which scarcely any excavation is required. The canal is diverted from the south bank of the TURLOCK CANAL. 81 river at a point about 50 feet above the end of the main weir. Owing to the great floods which occur in this narrow canyon the water may rise as much as 15 feet in an hour and the maximum height which it is estimated to reach above the sill of the canal is 16 feet. The pressure of this height of water on the regulator head would be so great as to materially in- crease the cost of its construction. Accordingly the canal heads in a tunnel 560 feet in length, blasted through the rock FIG. 10. TURLOCK CANAL. VIEW OF SIDEHILL WORK. of the canyon walls, and having no regulating apparatus at its entrance. Where it discharges into the open cut, which is the commencement of the canal, regulating gates and scouring or escape sluices are placed. The entrance tunnel is 12 feet wide at the bottom, 5 feet in height to the spring of the arch, above which it is semicircular with a 6-foot radius. Its slope is 24 feet per mile and it is excavated in a firm dioritic rock which requires no lining. The regulator in the canal head below the exit of the tunnel consists of six gates, each 3 feet wide in the clear and 12 feet in height. These gates are constructed of timber and iron, and slide on angle-iron bearings let into the rock and firmly set in concrete. The escape is set at right 82 ALIGNMENT, SLOPE, AND CROSS-SECTION. angles to the canal line heading immediately above the regu- lator, between it and the end of the tunnel, and tailing back into the Tuolumne river a short distance below the subsidiary weir. Like the regulator, the escape consists of six gates, each 3 feet wide in the clear, 12 feet high, and constructed of simi- lar material and in like manner. It is estimated that whereas FIG. ii. TURLOCK CANAL. VIEW IN TUNNEL. a maximum flood of 16 feet over the sill of the tunnel will give a discharge in front of the regulator and escape of about 4000 second-feet with a velocity of 20 feet per second, the wasting capacity of the escape will be at least 6000 second-feet, thus fully insuring the canal against accident from this source. Below the regulating gates the main canal proper begins, having a capacity of 1500 second. feet. For the first 6200 feet TURLOCK CANAL. 83 it is excavated in slate rock on a steep hillside (Fig. 10). It has a bed width of 20 feet, depth of water 10 feet, the upper rock slope being ^ to I, while the lower bank or downhill slope, where gullies are crossed, is built up with an inner slope of J- to I and is faced with 18 inches of dry-laid retaining-wall inside and outside, the interior of the bank consisting of a well- puddled earth core 12 feet in top width (Fig. 14). Where this portion of the canal is on ordinary sloping ground, not cross- ing gulches, its dimensions are the same but the inner face only has the 18 inches of riprapping the downhill slope of the bank consisting of dirt and other soil. The top width of the bank in such places is 5 feet and the puddle wall 5 feet in thickness. This portion of the canal line has a grade of 7.92 feet per mile, which gives a velocity of 7^ feet per second. At the end of this slate-rock work the canal empties into Snake ravine, up which the water of the canal runs for 940 feet. This is effected by constructing an earth dam across the mouth of the ravine just below the entrance of the canal, which raises the surface of the water so as to form a small settling reservoir and produces a flow up the course of the ravine for the dis- tance above mentioned. The earth dam is 20 feet wide on top, 318 feet long on the crest, with slopes of 2 to I and a maximum height of 52 feet. This dam was partly constructed of material borrowed from its abutments and the canal exca- vation and partly by a silting process from material washed out of a hydraulic cut at the upper end of the ravine. This hydraulic cut, which is utilized as the canal bed, is 800 feet in length and 45 feet in maximum height, with slopes of I to I and a grade of 5 feet per mile. Owing to the abundance of water procurable this cut was more cheaply excavated by the hydraulic process than it could have been by other means. At the far end of the cut the canal enters an old hydraulic wash- ing which is utilized for its channel for a length of 2380 feet, after which it enters a rock cut 860 feet long, with a maximum depth of 45 feet and a similar cross-section to the cut first described. At the end of this rock cut the canal water is discharged 84 ALIGNMENT, SLOPE, AND CROSS-SECTION. into Dry creek, down which it flows for a distance of 6500 feet on a grade of 12 feet to the mile, and from which it is diverted by means of an earth dam 460 feet long. This dam has a maximum height of 23 feet with side slopes of 3 to I, and is riprapped to a depth of 3 feet on its upper face. At its south end the dam abuts on sandstone rock in which a waste-way is cut 50 feet wide with its sill 4 feet below the crest of the dam, and which will discharge back into the creek 180 feet below the toe of the dam. Between the waste-way and the end of the dam is a waste-gate which it is intended shall be used in the time of freshets, for Dry creek has a maximum discharge of 4000 second-feet and as the freshets are quick and violent a large wasting capacity is necessary. These waste-gates are ten in number, each 3 feet wide in the clear and 10 feet in depth. They fall automatically outward or down-stream, being hinged at the bottom to a concrete floor laid on the bed-rock, and when raised they are attached by chains to the piers. For about a mile below Dry creek the canal is excavated in heavy, sandy loam, in which it has a bed width of 30 feet, with slopes 2 to I, a depth of 10 feet and a grade of i feet per mile. At the end of this excavation the canal crosses Dry creek in a flume 62 feet in height and 450 feet long, after crossing which the canal enters a series of three tunnels, the cross-sections of which are nearly similar to that of the first tunnel, while they are excavated in a tufa and sandstone which will require no timbering. The first tunnel (Fig. n) is 2ii feet in length, the second 400 feet and the third 400 feet in length, while they are separated by short, open cuts exca- vated in hardpan and clay, which are respectively 250 and 300 feet in length. The last tunnel discharges into Delaney gulch, which is crossed by constructing a high bank or earth dam below the canal, the total length of which is 180 feet, its maxi- mum height being 40 feet and its top width 20 feet. The volume of discharge of this gulch is so trifling that it was unnecessary to provide a waste-way or escape at this point. Immediately after crossing the gulch the canal enters a cut 8 SLOPE AND CROSS-SECTION. 85 feet in maximum depth, with the same cross-section and grade as the first cut and having a length of 3300 feet. The canal is then widened to a bed width of 35 feet and depth of 10 feet and is given a grade of i foot per mile. At the end of a mile and a half Peasley creek is crossed on a trestle and flume 60 feet in height and 360 feet long, the water-way on which is 20 feet wide and 7 feet in depth. This flume is provided with an escape constructed in its bottom and discharging into two small sloping flumes which lead the water down into the bed of Peasley creek (Article 168). At the end of the flume the main canal is reached and traversed for a distance of II miles, in which are two rock cuts, each 3000 feet long and respectively 20 and 30 feet wide on the bottom, depth of water 7^ feet and grade 5 feet per mile. The remainder of this length of the canal varies in cross-sec- tion according to the soil, but most of it has a bottom width of 70 feet and depth of water of 7^ feet, slopes 2 to I and a grade of I foot per mile. The main canal as outlined above consists for the 18 miles of its length of a purely diversion channel, the object of which is to bring the water to the irrigable lands included within the area of the Turlock district. At the terminus of this diversion line the canal begins at once to do duty by watering the lands, and below this point the main line is divided into four main branches, each of which has a bottom width of 30 feet, depth of water 5 feet, and grade .of 2 feet per mile, their aggregate length being 80 miles. In addition to these main branches minor distributaries, havingatotal length of 180 miles,lead the water to each section of land. The discharge of the branches is so designed as to give a uniform velocity of 2^ feet per second, in order that any matter carried in suspension will be held up until deposited on the agricultural lands instead of in the canals. 113. Slope and Cross-section. These two quantities are nearly related and are interdependent one upon the other. Having determined the discharge required, the carrying capac- ity for this quantity can be obtained by increasing the slope 86 ALIGNMENT, SLOPE, AND CROSS-SECTION. and consequent velocity and diminishing the cross-sectional area ; or by increasing the cross-sectional area and diminishing the velocity. The determination of the proper relation of cross-section to slope requires considerable judgment. If the material in which the excavation is to be made will permit, it is well to give a high velocity, as the deposition of silt and the growth of weeds are thus reduced to a minimum. A steep slope may result, however, in bringing the canal to the irri- gable lands at such an elevation that it will not command the desired area. Again, it may be inadvisable to give too great a cross-section if the construction is in sidehill or in rock, of other material which is expensive to remove. Other things being equal, the correct relation of slope to cross-section is that in which the velocity will neither be too great nor too slow, and yet the amount of material to be removed will be reduced to a minimum. Where the fall will permit, the slope of the bed of the main canal should be less than that of the branches, which should be less than that of the distributaries and laterals, the object being to secure a nearly uniform veloc- ity throughout the system, so that sedimentary matter carried in suspension may not be deposited until the irrigable lands are reached. 114. Limiting Velocity. In order that the proper slope may be chosen, one which will produce a velocity that shall not cause silt to be deposited on the one hand, or erode the banks on the other, the amount of such velocities for different soils should be known. In a light, sandy soil it has been found that a surface velocity of from 2.3 to 2.4 feet per second, or mean velocities of 1.85 to 1.93 feet per second, give the most satisfactory results. It has been discovered that velocities of from 2 to 3 feet per second are ordinarily sufficiently swift to prevent the growth of weeds or the deposition of silt, and, other things being equal, this velocity is the one which it is most desirable to attain. In ordinary soil and firm sandy loam velocities of from 3 to 3^ feet per second are safe, while in firm gravel, rock, or hardpan the velocity may be increased to from 5 to 7 feet per second. It has been found that brickwork or EXAMPLES OF 'CANAL GRADES. 87 heavy dry-laid paving or rubble will not stand velocities higher than 1 5 feet per second, and for greater velocities than this the most substantial form of masonry construction should be em- ployed. 115. Grades for Given Velocities. The grade required to give these velocities is chiefly dependent on the cross-sec- tional area of the channel. Much higher grades are required in small than in large canals to produce the same velgcity. The velocity which is required being known, the grade can be ascertained from Kutter's or some similar formula. In large canals of 60 feet bed width or upwards, and in sandy or light soil, grades as low as 6 inches in a mile produce as high veloci- ties as the material will stand. In more firm soil this grade may be increased to from 12 to 18 inches to the mile, whereas smaller channels will stand slopes of from 2 to 5 feet per mile, according to the material and dimensions of the channel. 116. Examples of Canal Grades. On the Ganges canal, the bottom width of which is 170 feet and the depth 7 feet, a slope of 14 inches per mile given in sandy soil produces such a velocity that the current just ceases to cut the banks or to de- posit silt, showing that this is the correct slope for that canal and material. In another portion of the same canal slopes of from 15 to 17 inches have been found too great, and much damage has been done to the banks. A velocity of 3 feet per second given to the Soane canals is found too great for the material, as much damage was caused by erosion. Care- ful observations of the slope on the Ganges canal show that a current apparently perfectly adjusted to light, sandy soil was produced by a surface velocity of about 2.4 feet per second, or a mean velocity of about 1.9 feet per second. In one of the distributaries in sandy soil having some clay in it a mean velocity of 1.93 feet per second caused slight deposits of silt, but did not permit the growth of weeds. On the western Jumna canal silt was deposited in small quantities with a ve- locity of from 2 to 2.75 feet per second, while in sandy soil the latter velocity was the highest permissible for non-cutting of the banks. 88 ALIGNMENT, SLOPE, AND CROSS-SECTION. In the light, sandy loam soils of the San Luis valley in Col- orado a slope of 6 inches to the mile given on the Citizens' canal has proven very satisfactory. So low a slope as this is possible, because the water is comparatively free of silt and there is little chance of its deposition, while the temperature is so low that there is little likelihood of the growth of weeds affecting the canal bed. In the gravelly clays through which the Turlock canal runs a satisfactory grade has been found to be 1.5 feet per mile, though the grade is changed on portions of this canal according to the character of the soil, until in the cut through loose shale near the canal head a grade of 7.9 feet per mile is given, producing a velocity of 7^ feet per second with satisfaction. On the main line of the canal, the bed width of which is 70 feet and depth of water 7^ feet and the soil a light alluvial loam, the grade adopted is one foot per mile. Perhaps the highest grade on any canal is that on a short portion of the Del Norte canal in Colorado, where the fall is 35 feet per mile through a rock cut. On several miles of this canal the grade is 8 feet per mile, but after it reaches the earth soil in the valley it is reduced to 1.2112. 117. Cross-sections. The most economical channel is one with vertical sides and a depth equal to half the bottom width, but this form is only applicable to the firmest rock. The best trapezoidal form is one in which the width of the water surface is double the bottom width and equal to the sum of the side slopes. Such a cross-section as this, however, would call for an unusually compact material. In the interest of economy the side-slopes above water-level should be as steep as the nature of the soil will permit. As before shown, the cross-sectional area depends on the velocity and slope and their relation to the quantity of water to be discharged. The exact form of this cross-section is dependent on the topography and the material through which the canal passes. The greater the depth the greater will be the velocity and consequent dis- charge for the same form of cross-section. Very large canals, such as some of those in India, have been given a proportion of depth to width similar to that of the FORM OF CROSS-SECTION. 89 great rivers. This proportion has been found to be most nearly attained when the bed width is made from 13 to 16 times the depth. In sidehill excavation the greater the propor- tion of depth to width the less will be the cost of construction (Art. 108.), and in all rock and heavy material it is desirable if possible to make the bottom width not greater than from 2 to 3 times the depth. Such a proportion as this, however, is rarely practicable. In a large canal, one for instance having a capac- ity of 2000 second-feet, with a velocity of 2 feet per second, the cross-sectional area should be 1000 square feet. If the proportion of 2 to I were maintained, this would call for a bed width of about 45 feet to a depth of 22\ feet. Such a depth as this unless in very hard material, is readily seen to be absurd, as the cost of construction would be greatly increased over that of a canal having a lesser depth. In this case a fair proportion would be 125 feet bed width to about 8 feet depth. A rule which has been proposed and which will prove fairly good on moderate sized canals, is to make the bottom width in feet equal to the depth in feet plus one, squared. This, how- ever, will not apply to large canals and is not altogether true for any size of canal. 118. Form of Cross-section. The cross-section of a canal may be so designed that the water may be wholly in excavation, wholly in embankment, or partly in excavation and partly in embankment (Fig. 12). The conditions which govern the choice of one of these three forms are dependent primarily on the alignment and grade of the canal, and second- arily on the character of the soil. For sanitary reasons it is sometimes desirable to keep a canal wholly in cutting, for if the material of which the banks are constructed is porous the water may filter through and stand about in stagnant pools on the surface of the ground. If the material is impervious to the passage of water and will form good firm banks, it may be well to keep the canal in embankment where possible, though this may necessitate the expense of borrowing material. In order to lessen the cost of construction, it is desirable, where the surface will permit, to keep a canal half in cut and half in 90 ALIGNMENT, SLOPE, AND CROSS-SECTION. fill, thus reducing to a minimum the amount of material to be moved. Ordinarily the surface of the ground is irregular and undulating, and in order that the grade may be maintained the canal will of necessity be sometimes wholly in cut and at others wholly in fill, and at others at all intermediate stages between these. Where the canal is wholly in embankment there is always considerable loss from leakage, and consequent WITHOUT BERMS W.L. BELOW C.L SIDELONG GROUND .W.L./XBOVE C.L. FIG. 12. VARIOUS CANAL CROSS-SECTIONS. danger of breaches. Where the canal is wholly in cut, care must be taken to discover the character of the soil in which the excavation is to be made, as rock may be encountered at a few inches below the surface, thus increasing the cost of excavation, or a sandy substratum may be discovered which would cause excessive seepage. Most main canals follow the slope of the country on grade contours running around sidehill or mountain slopes. In such cases it is necessary to build an embankment on one side only, when the cutting will be entirely on the upper side. If there is -a gentle slope on the upper side, and consequently an embankment on that side, it is desirable to run drainage chan- nels at intervals from this embankment to keep the water from making its way thro.ugh it to the canal. These drainage chan- SIDE SLOPES AND TOP WIDTH OF BANKS. 9 1 nels may be taken through the embankment into the canal, or may be led away to some natural watercourse. In designing the cross-section of a canal it maybe desirable to give a berm, and this may be above or below the water- level (Fig. 12). Ordinarily the berm is left at a level with the ground surface, though it may be constructed in excavation or embankrnent, an unusual practice, however. The chief object of the berm is to provide against the destruction of the slopes in the lower part of the banks by giving a terrace or bench on which the upper bank may slide, providing it fails to maintain the slope originally given ; it also serves in some cases as a tow-path or foot-path. The width of berm varies between 2 and 6 feet, and it is common to change the slopes at the point of junction between cut and embankment, making the slope of the latter a little flatter than that of the former. 119. Side Slopes and Top Width of Banks. In large canals it is always desirable to have a roadbed on at least one bank, and the width of this will determine the top width of the bank. The inner surfaces of the canal are usually made smooth and even, while the top is likewise made smooth, with a slight inclination to the outward to throw drainage away from the canal. The inner slopes of the banks vary in soil from i on i to i on 4, according to the character of the mate- rial. In firm clayey gravel or hardpan slopes of i on i are sufficiently substantial for nearly any depth of cutting or embankment. On the Turlock canal in California is a cut 80 feet in depth with side slopes of I on i, while on the Bear river canal in Utah are similar slopes in disintegrated shale in coarse gravel. In ordinary firm soil mixed with gravel or coarse loamy gravel slopes of i on I j- are sufficient. In firm soil and slightly clayey loam slopes of I on 2 may be required ; on lighter soils these slopes may be increased until the lightest sand is reached, when slopes of i on 4 may be necessary. The top width of the canal bank is generally from. 4 to 10 feet, according to the material, depth, and whether or not the water is in embankment. If there is to be no roadway on the top of the embankment, and the surface of the water does not 92 ALIGNMENT, SLOPE, AND CROSS-SECTION. rise more than a foot or so above the foot of the embankment, a top width of 4 feet is sufficient. Where the depth of water on the embankment is greater, this width should be 6 or 8 feet, and if the soil is light it should be at least 10 feet. It is sometimes necessary to build a puddle wall in the embank- ment, or to make a puddle facing on its inner slope where it is particularly pervious to water. The same effect is obtained by sodding or causing grass to grow on the bank. It may be well to puddle the entire bank during construction by laying and rolling it in layers. The carrying capacity of a canal should be so calculated that the surface of the water when in cut shall not reach within one foot of the top of the ground surface. In fill the depth of water carried should be such that the surface shall not rise higher than within \\ feet of the top of the bank, while if the fill is great it is often unsafe to let the water rise within 2 feet of the top of the bank. 120. Cross-section with Subgrade. In the light soils of the San Luis valley in Colorado and in Kern valley in Cali- fornia it has been found advantageous to use a different form of cross-section than that above described. Experience in the regions above cited has shown that the subgrade produces a form approaching that of the ellipse. This cross-section tends to keep the current in the centre of the channel, and to keep up its flow with the least exposure to friction and seepage when the volume of water in the canal is low. The sub- grade (Fig. 13) is given by practically designing the canal as FIG. 13. CROSS-SECTION OF GALLOWAY CANAL SHOWING SUBGRADB. if it were to have a trapezoidal cross-section with berm, and then evening off the slope by removing the berm and continu- ing the slope from the bottom of the canal toward the centre to a depth or subgrade of from I to 2 feet below the original bed of the canal. In such construction as this it has some- times been found desirable to give the bank practically no top CXOSS-SECTION IN ROCK. 93 width, simply rounding it off from the inner to the outer sur- face, where the waste is carelessly scattered, allowing the soil to assume its natural slope. 121. Shrinkage of Earthwork. It is well known that when -soil which has been removed from an excavation is formed into embankment it settles or shrinks in volume. That is to say, the excavated and embankment soil occupies a less space than it did in the ground ; while, on the contrary, rock or loose stone occupies a greater space, depending on the dimensions of the fragments. The percentage of this shrinkage differs according to different soils. The following list gives an idea of the amount of this shrinkage for different soils : Sand, about 10 per cent ; in other words, after excavation sand will ultimately occupy 10 per cent less space than it did in its natural bed. Sand and gravel shrink 8 per cent. Earth, loam, and sandy loam shrink 10 to 12 per cent. Gravelly clay shrinks 8 to 10 per cent. Puddled clay and puddled soil shrink 20 to 25 per cent. Rock expands or increases in volume from 25 per cent in the case of small or medium fragments and road-metalling to 60 or 70 per cent in large fragments carelessly thrown. 122. Cross-section in Rock. In firm rock it is desirable to make the proportion of depth to width about as i to 2, FIG. 14. ROCK CROSS-SECTION. TURLOCK CANAL. with side slopes of about 4 on I. In less firm rock lighter slopes and a less proportional depth are desirable. In friable 94 ALIGNMENT, SLOPE, AND CROSS-SECTION. shale, as on the Turlock canal in California, a different cross- section is desirable (Fig. 14). In this instance a retaining-wall of hand-placed stones, with an outer slope of 4 on I and a top width of 2,\ feet, is built on the lower side. Inside this is a puddled earth bank, riprapped on the water surface with 10 inches in thickness of loose stone. The upper or excavated slope is about 2 on i, the depth 10 feet, and the bed width 20 feet. On the Bear River canal in Utah, the cross-section W/M FIG. 15. ROCK CROSS-SECTION, BEAR RIVER CANAL. shown in Fig. 1 5 was given in order to avoid too much exca- vation in extremely rocky sidehill. > CHAPTER XII. HEADWORKS AND DIVERSION WEIRS. 123. Location of Headworks. The headworks of a canal are generally placed where the stream emerges from the hills. At such a point the slope of the country and of the stream is steep, making it possible to conduct a canal thence to the irrigable lands with the shortest diversion line. Moreover, the width of the channel of the stream is generally contracted, and it flows through firm soil or rock, thus permitting a reduc- tion in the length of the weir and in the cost and character of its construction. When the volume of flood water occurring in the stream is great it is sometimes necessary to locate the headworks at a point where the width between banks is greatest, in order that the depth of water flowing over the weir may be reduced to a minimum and danger of its destruction reduced accord- ingly. While such a location may be the most permanent, it is also most costly for construction. The site of the headworks should be such that the most permanent weir can be con- structed at the least cost, and yet they should be so located that the diverting canal can be conducted thence to the irri- gable lands at a minimum cost. The location of the head- works high up on the stream is usually antagonistic to the last object, since it generally results in the canal having to en- counter heavy rock work and difficult construction until it gets away from the river banks. 95 96 HEADWORKS AND DIVERSION WEIRS. 124. Character of Headworks. The headworks of a canal consist 1. Of the diversion weir, in which is usually built : 2. A set of scouring sluices ; 3. Of a regulator at the head of the canal for its control ; 4. Of an escape for the relief of the canal below that point. Sometimes to these are added river training or regulating works for the .protection of the banks of the stream above and below the obstruction formed by the >headworks. Too careful attention cannot be given to an examination of the stream at the point of diversion. Soundings and borings should be made to ascertain the depth of water and character of the foundation. The velocity of the stream and its flood heights should be studied, as should the material of which the banks are composed. Where possible, a straight reach in the river should be chosen for the location of the headworks in order that the stream shall have a direct sweep past them, thus reducing to a minimum the deposition of silt in front of the regulating gates. If possible, a point should also be chosen where the velocity in the river will not exceed that in the canal, so that the deposition of silt shall be further reduced. There has been too great a tendency in American construc- tion to build works of a temporary and transient character. The headworks of a canal are the most vital portions of its mechanism ; they are to a canal system what a throttle-valve is to a locomotive. Through them the permanency of the supply in the canal is maintained, and any injury to them means paralysis to the entire system. They should therefore he most substantially and carefully designed throughout. The employment of wood is altogether too common in the United States. It is very well to make use of wood as a temporary makeshift until money and time can be found for substituting more substantial material. It may be generally laid down as a principle, however, that only iron and masonry should enter into the construction of the headworks. It is impossible to form wood, with the addition of little or no iron or masonry, into permanent and substantial headworks. The best and DIVERSION WEIRS. 97 most abundant examples of substantial headworks must still be sought in Europe and India. In some cases it has been found unnecessary to construct diversion weirs as a part of the headworks of a canal. This has been the case especially where the discharge of the stream was great relative to the discharge of the canal, and only when a portion of the water in the stream was re- quired. Thus, on the Central Irrigation District canal in Cali- fornia no diversion weir is required. The canal heads in a simple cut, its bed being a few feet below the lowest water- level in the Sacramento river. At the head of the Ganges and Jumna canals in India there are no permanent diversion works, the water being turned into the canal head by means of temporary structures of bowlders, or by means of training the water of the river so that it shall flow directly against the canal head. 125. Diversion Weirs. In this book the word weir as distinguished from dam is generally employed to mean a structure intended either for the impounding or diversion of water and over which flood waters may safely flow. Thus weirs are usually built at the heads of canals for the diversion of the waters of the streams into their heads, while the surplus water is permitted to flow over the weir and to pass on down the stream. In some cases, however, dams over which it would be unsafe to permit flood waters to pass are used for the purpose of diversion, and a wasteway is constructed at one end of the dam for the passage of surplus waters. A weir across a stream is analogous to a bar and should be located and treated as such. If it is placed at the widest part of the stream the cost of construction may be increased. In the great rivers of India where diversion is made in the level and sandy plains below the hills and where permanent foundations cannot be obtained, weirs have generally been placed in the broadest reaches of the streams. This is the case at Okhla at the head of the Agra canal, and at Narora at the head of the Lower Ganges canal. In our own country diversion for canals has generally taken place in the foothills, 98 HEADWORKS AND DIVERSION WEIRS. and accordingly the narrower portions of the streams have been chosen for this purpose. 126. Classes of Weirs. Weirs may be divided into two classes according to the mode of building their foundations. Thus they may rest directly on some permanent material ; or they may rest on some unstable material, as quicksand, gravel, or clay, in which case an artificial foundation of piles, caissons, or wells or blocks must be constructed. Where, in western practice, a firm foundation has not been found piling has usu- ally been employed. In India and Egypt wells or blocks are employed for foundations in unstable material. These consist of rectangular boxes or cylinders of brick, which rest on a sharp cutting edge, and from the interior of which the earth is excavated as the well sinks. After it has reached a suitable depth it is filled in with concrete, the whole depending for its stability chiefly on the friction of its sides against the surrounding material. The most convenient classification of diversion weirs is according to the construction of their superstructures. These may be 1. Temporary brush or bowlder barriers ; 2. Rectangular walls of sheet and anchor piles filled with rock or sand ; 3. Open weirs ; 4. Wooden crib and rock weirs ; 5. Masonry weirs. 127. Brush and Bowlder Weirs. The simplest and crudest form of weir is the brush and gravel barrier, which was originally used by the Mexicans and is still employed in the West on minor streams. These weirs are formed by driving stakes across the channel and attaching to them fascines or bundles of willows from three to six inches in diameter at the butts, which are laid with the brush end up-stream, and are weighted with bowlders and gravel. More willow or cotton- wood branches are laid on the top of these and again weighted with bowlders, this operation being continued until the struc- ture is built to a height of three or four feet. Such structures OPEN AND CLOSED WEIRS. 99 are of the crudest character and can be built without any en- gineering knowledge or supervision. 128. Rectangular Pile Weirs. These have been em- ployed in wide sandy rivers like the Platte, in Colorado. They consist of a double row of piling driven into the river bed, the two rows being about 6 feet apart, and the piles about 3 feet apart between centres. Between these is driven sheet piling to prevent the seepage or travel of water through the barrier, and the upper portion of the structure is planked so as to form a rectangular wall the interior of which is filled in with gravel, sand, etc. Such walls, are usually low, rarely exceeding 8 feet in height, and after the upper side is backed with the silt deposited from the stream they form substantial barriers which may last for many years. Such structures cannot be employed where the flood height is great, as they would soon be undermined unless substantial aprons were constructed. 129. Open and Closed Weirs. Diversion weirs may again be classified as open or closed. A closed weir is one in which the barrier which it forms is solid across nearly the entire width of the channel, the flood waters passing over its crest. Such weirs have usually a short open portion in front of the regulator known as the " scouring sluice," the object of which is to maintain a swift current past the regulator entrance, and thus prevent the deposit of silt at that point. An open weir is one in which scouring sluices or openings are provided throughout its entire length. The advantage of the closed weir is that it is self-acting, and if well designed and constructed requires little expense for repairs or maintenance. It is a substantial structure, well able to withstand the shocks of floating timber and drift ; but it interferes with the normal regimen of the river, causing deposit of silt and perhaps changing the channel of the stream. Open or scouring sluice weirs interfere little with the normal action of the stream, and the scour produced by opening the gates prevents the deposit of silt, while their first cost is generally less than that of closed weirs. 100 HEADWORKS AND DIVERSION WEIRS, The closed weir consists of an apron properly founded and carried across the entire width of the river flush with the level of its bed, and protected from erosive action by curtain-walls up and down stream. On a portion of this is constructed the superstructure, which may consist of a solid wall or in part of upright piers, the interstices between which are closed by some temporary arrangement. This portion of the weir is called the scouring sluice. The apron of the weir should have a thickness equal to one half and a breadth equal to three times the height of the weir above the stream bed. During floods the water backed against the weir acts as a water cushion to protect the apron, and as the flood rises the height of the fall over the weir crest diminishes, so that with a flood of 16 feet over an ordinary weir its effect as an obstruc- tion wholly disappears. An open weir consists of a series of piers of wood, iron or masonry, set at regular intervals across the stream bed and resting on a masonry or wooden floor. This floor is carried across the channel flush with the river bed, and is protected from erosive action by curtain-walls up and down stream. The piers are grooved for the reception of flashboards or gates, so that by raising or lowering these the afflux height of the river can be controlled. The distance between the piers varies between 3 and 10 feet, according to the style of gate used. If the river is subject to sudden floods these gates may be so constructed as to drop automatically when the water rises to a sufficient height to top them. It is sometimes necessary to construct open weirs in such manner that they shall offer the least obstruction to the waterway of the stream. This is necessary in weirs like the Barage du Nil below Cairo, Egypt, or in some of the weirs on the Seine, in France, in order that in time of flood the height of water may not be appreciably increased above the fixed diversion height. Should the height be increased in such cases the water would back up, flooding and destroying valuable property in the cities above. Under such circumstances open weirs are sometimes so constructed that they can be entirely removed, piers and all, OPEN FRAME OR FLASHBOARD WEIRS. IOI leaving absolutely no obstruction to the channel of the stream, and in fact increasing its discharging capacity, owing to the smoothness which they give to its bed and banks. 130. Open Frame or Flashboard Weirs. A form of cheap open weir which has been commonly constructed in the West is the open wooden frame and flashboard weir. This type of structure is used only on such rivers as have unstable beds and banks, where any obstruction to the ordinary regimen of the stream would cause a change in its channel. It con- sists wholly or in part of a foundation of piling driven into the river bed, upon which is built an open framework closed by horizontal planks let into slots in the piers. These weirs are constructed of wood, and are temporary in character, their chief recommendation being the cheapness with which they can be built in rivers the beds of which are composed of a considerable depth of silt or light soil. Two varieties of this weir are in common use. One (Fig. 16), which has been employed at the heads of the Del FIG. 16. OPEN WEIR. MONTE VISTA CANAL. Norte, Monte Vista and other canals in the San Luis valley of Colorado, is partly open and partly closed. An earth bank or dam is built for a portion of the way across the stream and of such height that it will not be topped by floods. The remainder of the weir consists of a framework of rough- hewn logs founded on piles, the abutments of which are pro- tected by wooden planking built against the earthen dam. The openings between the frames or piers are about 6 feet apart, and the crest of the weir rarely exceeds 5 feet in height above the normal water surface. Between the piers horizontal planks or flashboards can be inserted one at a time, thus IO2 HEADWORDS AND DIVERSION WEIRS. OPEN FRAME OR FLASHBOARD WEIRS. 103 closing the waterway to any desired extent up to the level of the weir crest. A more common and finished type of frame or flashboard weir is that employed on the Kern river in California, at the heads of the canals in that neighborhood. An example of these is the weir at the head of the Galloway canal (Fig. 17), which consists of 100 bays, each separated by a simple open tri- angular framework of wood founded on piles, the width of FIG. 17. CROSS-SECTION OF OPEN WEIR, GALLOWAY CANAL. each, opening or bay being 4 feet. In constructing this weir the area to be built upon was inclosed in sheet piling and covered with a floor placed 2^ feet below the bed of the stream. Above this floor is a second floor, about 2 feet in height, the walls forming compartments which are filled with sand, thus making a sand box apron, on which the waters fall. This apron is carried up and down stream for a distance of about 10 feet in each direction. The weir proper is formed of frames or trusses of 6 by 6 inch timber, placed transversely IO4 HEADWORKS AND DIVERSION WEIRS. NARORA WEIR-LOWER GANGES CANAL length 1260 metres H.F.I ofStver OKHLA WEIR-AGRA CANAL. 743 metres H.r,L DEHREE WEJR-SOANE CANAL length d825 metres -JET" BEZWARA WEIR - KISTNA CANAL. length 1150 metres. 1{ I 60DIVERY WEIR. length 6274 metres. PLATE III. CROSS-SECTIONS OF INDIAN WEIR OPEN MASONRY WEIRS, INDIAN TYPE. IO5 4 feet apart. These frames consist of 2 pieces, the up-stream piece being 7 feet 2 inches long and set at an angle of 38 degrees, while the other supports it at right angles and is 5 feet 4 inches long. The lower ends of these rafters thrust against two pieces of 6 by 2 inch timber running the whole length of the weir and nailed to the flooring. These frames are sup- ported directly on anchor piles, one at each end joiced into the framing. These trusses are kept in vertical position by means of a footboard running transversely the entire width of the stream.. On the up-stream face of the trusses planks or flashboards which slide between grooves formed by nailing face-boards on the trusses are laid on to the required height. This weir is 10 feet in height above the wooden floor, which is flush with the river bed. 131. Open Masonry Weirs, Indian Type. A substantial form of open masonry weir is that generally constructed on Indian rivers, where the banks and bed are of sand, gravel, or other unstable material. These weirs generally rest on shallow foundations of masonry, in such manner that they practically float on the sandy beds of the streams. The foundation of such a weir is generally of one or more rows of wells sunk to a depth of from 6 to 10 feet in the bed of the river, the wells and the spaces between the rows of wells being filled in with con- crete, thus forming a masonry wall across the channel. This form of construction is illustrated in PL III, which exhibits several different types of such works. The weir at the head of the Soane canals, which is typical of this class of structure, consists of three parallel lines of masonry running across the entire widtrijthe stream, and varying from 2^- to 5 feet in thick- ness. The main wall, which is the \ipper of the three and the axis of the weir, is 5 feet wide and 8 feet high, and all three lines of walls are founded on wells sunk from 6 to 8 feet in the sandy bed of the river. Between these walls is a simple dry stone packing raised to a level with their crests, thus form- ing an even upper surface. The up-stream slope is I on 3, and the down-stream slope i on 12, the total length of this lower io6 HEADWORKS AND DIVERSION WEIRS. slope being 104 feet, while the total height of the weir includ- ing its foundation is 19.3 feet. The Soane weir has a total length across stream of 12,480 feet, of which 1494 feet consists of open weir disposed in three sets of scouring sluices (Fig. 18), one in the centre and two Elevation. \Z 470' Cross Section of Weir . 3o' *4>t 70' - FIG. 18. HALF ELEVATION AND PLAN, AND SECTION OF SOANE WEIR, INDIA. adjacent to either bank and in front of the regulating gates at the head of the canals. These scouring sluices consist of three parts, the foundation, the floorway or apron, and the super- structure. The floor is deep and well constructed of substan- tial masonry, and is continued for a short distance above the weir and for a considerable distance below it. It is 90 feet wide parallel to the river channel, and is founded on wells, the OPEN MASONRY WEIRS, INDIAN TYPE. IO/ ashlar pavement of the floor being 15 inches thick in the bottom of the scouring sluices between the piers, and 9 inches thick over the remainder of the apron. Up-stream from the sluice floor for a distance of 25 feet is a line of wells sunk to a depth of 10 feet as a curtain-wall to the apron. Twenty-five feet down-stream from the flooring of the sluices is a similar line of wells formed into a wall, and the spaces between these two curtain-walls and the main ashlar flooring of the sluice- way is packed with dry-laid bowlders and rubble covered with a pavement of masonry 9 inches in thickness. Down- stream from the lower curtain-wall a paving of large bowl- ders stretches for 50 feet further, the whole of this sluice floor parallel to the river channel being 200 feet in length. This is a typical floor to an Indian open weir or sluiceway, on top of which, in line with the centre of the crest of the weir, are built up masonry piers at regular intervals of from 6 to 12 feet apart, grooved for the reception of planks or flashboards, or closed with lifting or automatic drop-gates. A peculiar form of open weir is that constructed at the head of the Sidhnai canal in India. At the point where the vveir is built the bed of the river gives a good clay foundation for a short distance from either bank, while in the centre of the channel the bed is of sand for a considerable depth. Sheet piling 10 feet long was driven into the sandy bed of the river to prevent excessive percolation. On these piles (Fig. 19) rests a series of piers which support masonry arches, the piers being 16 feet between centres and filled between with clay. Above this masonry arch is built a continuous wall across the entire width of the streem from 4 to 6 feet wide on top and from 3^- to 8| feet in height. Over this wall, parallel to the channel of the river, is built a masonry flooring, the upper slope of which is I on 3, while its lower slope varies between I on 5 and I on 10, according as it is near the centre or ends of the weir. The total width of this floor parallel to the channel of the stream is 12 feet above the axis of the weir and 40 feet below it, the lower toe terminating in a series of wells. On top of this flooring are erected a series of piers 23 feet apart between 108 HEADWORKS AND DIVERSION WEIRS. centres, and projecting 2\ feet up-stream from the central wall and 9 feet down-stream, their total length parallel to the channel being 1 5^ feet and their width on top 6 feet. The crests of these pillars are 6 feet in height above the crest of the floor, while the total height of the weir above the summit of the pile foundation is about 21 feet. It will thus be seen that this weir offers a clear waterway across the entire channel, ob- structed only by the piers, which are 6J feet above the stream- bed. The openings between these piers are closed by means iiillljl FIG. 19. ELEVATION AND CROSS-SECTION OF SIDHNAI WEIR, INDIA. of needles, which consist of a heavy beam laid along the crest wall from pier to pier, against which rest wooden sticks or needles inclined at a slight angle. These needles are each / feet long by 5 inches wide and 3^ inches in thickness, and are laid along the upper face close together so as to form a close paling or barrier when in place. The weirs on the river Seine in France differ materially from the open Indian weirs. They consist of a series of iron frames of trapezoidal cross-section, somewhat similar in shape to the frames of the open wooden flashboard weirs of Cali- OPEN MASONRY WEIRS, INDIAN TYPE. 109 fornia. On these frames rest a temporary footway, and on their upper side is placed a rolling curtain shutter or gate which can be dropped so as to obstruct the passage of water across the entire channelway of the stream, or can be raised to such a height as to permit the water to flow under them. In FIG. 20. VIEW OF OPEN WEIR ON RIVER SEINE, FRANCE. times of flood the curtains can be completely raised and re- moved on a temporary track to the river banks, the floor and track can then be taken up, leaving nothing but the slight iron frames, which scarcely impede the discharge of the river and permit abundant passageway of the floods over, around, and through them (Fig. 20). m t WOODEN CRIB AND ROCK WEIRS. Ill 132. Wooden Crib and Rock Weirs. This type of weir is generally built where the bed and banks of the river are of heavy gravel and bowlders, or of solid rock, and it may be employed for diversions of greater height than is possible with open weirs. Crib weirs consist essentially of a framework of heavy logs, drift-bolted or wired together, and filled with broken stone and rocks to weight and keep them in place. Such works may be founded by sinking a number of cribs one on top of the other to a considerable depth in the gravel bed of the stream, or they may be anchored by bolting them to solid rock. They may consist of separate cribs built side by side across the stream and fastened firmly together as in the case of the weir at the head of the Arizona canal, or they may be made as one continuous weir, as in the case of the structures at the heads of the Kraft Irrigation District canal in California, and the Bear river canal in Utah. After its completion the weir is planked over on its exposed faces and forms one con- tinuous wall across the channel of the stream. The weir at the head of the Arizona canal (PL IV) con- sists of crib boxes of hewn logs about 9 by 9 feet, the logs being fastened with drift-bolts, and the whole wired together and filled with rocks. This weir was constructed by laying mudsills in a trench excavated in the bed of the stream, and on these was built up the cribwork. In the central and deepest portion of the river channel the weir was sunk to a depth of 33 feet in the gravel bed of the stream, while its crest is every- where 10 feet above mean low-water. The base of this weir in the deepest part of the channel is from 36 to 48 feet in width parallel to the course of the stream, and the mudsills, which are 8 by 12 by 48 feet, were wired together with i-inch cable to act as a hinge between the sections. Each section was floored and cribbed and built up as a box, only the alter- nate sections being closed at first, the others being left open for the passage of water. These openings were planked on the bottoms and sides. The alternate sections were closed by dropping timbers into place. Instead of bringing up the face batter, as is ordinarily done, the weir was built in four sections 112 HEADWORKS AND DIVERSION WEIRS. transversely to its axis (Fig. 21). The first section consisted of two rows of cribs, the upper faces of which were given a slight '4 r FIG. 2T. CROSS-SECTION OF ARIZONA WEIR. batter, and on them silt has since deposited and helps to weight the structure. Immediately below the crest and with its upper surface 2J- feet lower is another row of cribs which drop off 2j feet to the third row of cribs, below which at a distance of 2^ feet still lower are a couple of depths of swinging cribs wired to the projecting part of the dam. The whole of this upper surface is planked over and forms a series of steps upon which the water falls, its force being thus broken. The crib weir at the head of the Bear river canal in Utah FIG. 22. CROSS-SECTION OF BEAR RIVER WEIR. is 370 feet in length on its crest, which is 17^ feet in maximum height above the river bed, while the greatest width at its base parallel to the course of the stream is 38 feet (Fig. 22). The up-stream face has a slope of I on 2 while, that of the down- WOODEN CRIB AND ROCK WEIRS. 113 stream face is I on J, the water falling on a wooden apron an- chored by bolts to the bed-rock of the river. This weir con- sists of heavy 10 by 12 timbers, drift-bolted to the rock and firmly spiked together. The interstices between these timbers are filled with broken stone, and it is backed by silt deposited from the river. Sometimes crib weirs are founded on piles, as in the case of the weir across Stony creek, at the head of the Kraft Irrigation District canal. This is composed of timber cribs sheathed with 3 inches of plank on the up-stream face and 7 inches on the lower face, and it rests on two rows of piles driven across the entire width of the stream, 6 feet apart between centres. One of these rows of piles is driven to a depth of 12 feet under the toe of the apron, while 8 feet below this is a row of sheet piling and 22 feet above the upper row of piles is another row of sheet piling, both of these being of 4-inch double piling 8 feet in length or driven to bed-rock. The crib weir across the Connecticut river at Holyoke, Mass., is about 1017 feet in length, its ends abutting against heavy masonry wings at either extremity. Between these the crib weir is composed of 12 by 12 timbers, built in such a way as to present on the upper face a surface of planking inclined at an angle of 21 degrees to the horizon. These tim- bers are separated by transverse timbers at distances of 6 feet apart, and the whole is drift-bolted to the solid rock of the channel. The cribwork is filled with loose stone to a height of about 10 feet, and the upper surface of the weir is planked over. On the upper toe of the weir rests a bed of concrete to prevent seepage, and over this is a filling of gravel to a height of about 10 feet (Fig. 23). The down-stream face of this structure consists of an apron or rollerway of similar crib timbers, a little more substantially built. Origi- nally the down-stream face was nearly vertical, but the water soon so undermined the structure that it was found necessary to add this rollerway to prevent its. destruction. This addi- tion has the same slope on the down-stream face as has the up-stream face for a distance of about 50 feet below the HEADWORKS AND DIVERSION WEIRS. CONSTRUCTION OF CRIB WEIRS. COMPOSITE WEIRS. 11$ crest of the weir, at which point it falls away vertically, its end being nearly level with the surface of the river, though its vertical height at this point is about 25 feet. As the water rolling over this drops immediately into a water cushion of considerable depth, no injury is done the structure from its impact. 133. Construction of Crib Weirs. A crib weir should never be left hollow, as was the upper part of the Holyoke weir, but should be completely filled in with gravel or rock. Many engineers advise against rock filling, as this permits the passage of air to the wood, and thus promotes its decay. The action of air in causing decay is still more marked if the weir is left hollow. Gravel well puddled around the wood- work becomes air-tight, and protects every timber which it encases. This material is therefore the most desirable filling. No timbers should butt on top of the course next beneath, as this gives each timber 6-inch bearing at the most, and if the lower timbers become decayed the strength of the bearing is speedily reduced. The shape of such a weir should always be such as to prevent the water which falls over it from excavating beneath its toe, especially if the foundation is of gravel or soft rock. In such cases a roller apron should be built, backed still lower down by a horizontal apron which will take up the scour- ing force of the water. Even on a firm rock foundation a clear overfall should not be given unless a deep water cushion can be furnished or the bed of the river can be laid dry for exam- ination and the repair of the weir. 134. Composite Gravel and Rock Weir. There are several varieties of mixed weirs other than those described which have given satisfaction in the West. One of these is built across the Lower Fox river at Little Kukuna. The foundation of this weir (Fig. 24) is of gravel and loose ma- terial, and the structure is held in place by two parallel rows of piling driven across the entire width of the stream. One of these rows runs through the centre of the weir, its sum- mit being on a level with the crest ; the other is 10 feet further down-stream, and forms the edge of the lower portion i6 HEADWORKS AND DIVERSION WEIRS. of the apron. These piles were driven 14 feet into the gravel and bowlder bed, and the two rows were braced together by 10 by 10 timbers and the intervening space filled with broken stone. On 'the upper side of the upper row 4-inch planking was spiked to within 2 feet of the river bed, below which sheet piling was driven against this piling 4 feet into the gravel bed FIG. 24 CROSS-SECTON OK LITTLE KUKUNA WHIR. to prevent seepage. On the upper side of this barrier, against the planking and sheet piling, alternate layers of clay and gravel were laid, at a slope of I on i, and on top of this was placed a thickness of i^ feet of loose stone, the whole being faced with large flat stones 4 inches thick. The top surface of the down-stream face between the two rows of piling has an incli- nation of about i on 3-J-, and is faced with 4 inches in thickness of planking, below which the loose rock is given a slope of I on \\. 135. Scouring Effect of Falling Water. In the con- struction of weirs various subterfuges have been employed to deliver the falling water so quietly that it shall not erode the stream-bed below. The erosive force of falling water is such that it is capable of wearing away even the hardest rock. The principal forms which have resulted from the endeavor to re- duce this action are: I, aprons, 2, sloping roller-ways, 3, ogee curves to the lower side of the weir, and 4, water cushions. Each of these forms has its advocates, and each is especially adapted WEIR APRONS. II/ to certain conditions, dependent chiefly upon the height of over- fall and the character of the material of which the stream-bed is composed. Under similar conditions aprons are employed in all countries. Ogee shapes appear to have originated in India, and are very popular there. They have been adopted to a limited extent in this country. 136- Weir Aprons. Where the foundation of the weir is of some unstable material, as earth, sand, or gravel, an apron is built below its down-stream toe. These aprons are made of wood, of dry-laid masonry, or of masonry in cement. They form a substantial artificial flooring to the stream-bed on which the force of the falling water is taken up, thus protecting it from erosion and preventing undercutting of the weir. Where an apron is employed, the weir depends on its efficient con- struction and careful maintenance for its security. Such works are built of masonry in the most substantial manner in India, where a rough general rule is to give the masonry apron a thickness equal to one half and a length parallel to the stream channel equal to from three to four times the vertical height of the obstructive part of the weir. Beyond this a loose stone apron is generally added, with a length equal to one and one half times, and a depth equal to two thirds of the height of the weir. Another rule adopted in India is to give the apron a width equal to from six to eight times the square root of the maximum depth of water above the weir crest, and a thickness equal to one fifth to one fourth of the overfall height of the weir plus the depth of water on the crest. According to the American standards both of these rules seem to give unnecessarily substantial results. With us wooden aprons are generally employed which rarely exceed from 2 to 6 feet in thickness for the greatest height of overfall. Aprons, however, cannot be used with security with weirs in which the drop is considerable. No limit, other than that of expense, can be set to the height for which aprons are serviceable, for a point is ultimately reached where an ogee-shaped or rcllerway weir or a water-cushion will be less expensive and more serviceable. Il8 HEADWORKS AND DIVERSION WEIRS. 137. Rollerway and Ogee-shaped Weirs. Ogee-shaped weirs probably originated as a development of roller aprons. The first ogee weirs of any magnitude were those built on the falls in the eastern Jumna canal in India. The original sloping apron or rollerway is still largely employed, the chief objection to it being the amount of material required in its construction and its consequent cost. Such structures are the weirs of the Soane and Agra canals, illustrated in PL III. In these the lower slope of the weir is made extremely flat, so that the friction of the water rolling over it shall retard its FIG. 25. DIAGRAM OF OGEE CURVE. velocity and diminish its erosive action. In our own country a similar long sloping rollerway is that on the Holyoke weir (Fig. 23). The ogee shape is an improvement on the rollerway. It reduces to a minimum the amount of material required, while producing nearly the same effect. The object of the ogee shape is to cause the water to slide instead of to fall over the weir, and the exact moment when water ceases to slide and commences to fall is shown by its losing its bluish color and commencing to become whitish. The ogee curve is best understood from the accompanying diagram (Fig. 25). Bisect AE, and from the point of bisection at A draw a per- pendicular cutting the perpendicular let fall from A at C. Join CE and prolong this line until it cuts the perpendicular WA TER- CUSHIONS. 1 1 9 projected on B at D. From the points C and D as centres, draw the curves of the ogee A good example of ogee-shaped weir is shown in plate V. 138. Water-cushions. The principle involved in the water-cushion is that which nature has laid down for herself on all natural falls, namely, that of having a deep enough cis- tern below the fall to take up the shock of the falling water and reduce its velocity to the normal. It has been noticed below cataracts and falls, for instance, that they erode a cistern the depth of which bears a certain relation to the height of the fall. The method of constructing a water-cushion is not to excavate such a cistern below the weir, but to create a corre- sponding depth by building a subsidiary weir below the upper weir. This subsidiary weir backs the water up against the lower toe of the main weir to the required depth, at the same time practically reducing the height of the fall by the height of the subsidiary weir. It is difficult to find any set rule for determining the depth of water-cushion for a given height of fall. From observa- tions of several natural waterfalls it has been discovered that the height of fall is to the depth of the water-cushion as from 5 or 7 to I. In an experimental fall constructed on the Bari Doab canal in India it was found that, with a height of fall to a depth of water-cushion as 3 to 4 the water had no injurious effect on the bottom of the well. On canals where the height of fall is not great it has been discovered that the depth of the water-cushion may be approximately determined from the formula D = c Vh 3 Vd, in which D represents the depth of the water-cushion below the crest of the retaining wall ; c is a coeffi- cient the value of which is dependent on the material which is 120 HEADWORKS AND DIVERSION WEIRS. used for the floor of the cushion and varies between .75 for compact stone and 1.25 for moderately hard brick; // is the height of the fall, and d is the maximum depth of water which passes over the crest of the weir. The breath of the floor or the bottom of the cistern of the water-cushion parallel to the stream channel is dependent on the section of the weir and will not exceed 8. \ FIG. 37. REGULATOR GATES, SOANE CANAL. of wood, cross-braced, and to its top are attached chains which run over the windlass of the travelling winch. Above these gates is a bridge, and on the parapet immediately over the gates is a simple railroad track on which a handcar is run. On this is placed a simple hand winch, and by turning this each gate can be successively raised or lowered and the winch pushed along to the next gate. 163. Gate raised by Gearing or Screw. This type of gate is common both in this country and abroad. They are gen- erally employed where there is pressure to be overcome and are slow in their operation. As a consequence a few simple lifting gates are generally inserted in a few of the openings, to be used when the pressure is light, and a few geared gates are employed to be operated under pressure. Such a gate is that at the head of the Arizona canal (Fig. 38), which is constructed GATE RAISED BY GEARING OR SCREW. 149 of wood framed with iron. Above it projects a heavy steel screw, i inches in diameter, and this passes through a female FIG. 38. REGULATOR GATES, ARIZONA CANAL. screw of malleable iron on which the wear is taken up. As the pressure which this gate has to withstand is great, the FIG. 39. REGULATOR GATES, DEL NORTE CANAL. simple screw is not sufficient, and the female screw forms the inner surface or axis of a geared or cogged wheel, and this is I5O SCOURING SLUICES, REGULATORS, AND ESCAPES. Scale i i i i i i i ~ i& 4 " ^g.,, . _>. . ,. 21' 2 Ji ^ PLATE VII. BEAR RIVER CANAL. ELEVATION AND CROSS-SECTION OF WEIR AND REGULATORJJ ROLLING REGULATOR GATE. turned by a smaller cog operated by a hand wheel ; thus the gate, while moving very slowly, can be raised with the appli- cation of but a trifling amount of power, owing to the multi- plicity of gearing employed. A simpler gate of the same general type is that at the head of the Del Norte canal in Colorado. As shown in Fig. 39, the lifting screw is attached to the gate and turns in a female screw attached to the overhead bridge. A more substantial gate is that at the head of the Bear River canal in Utah, which is set between firm masonry abutments and slides in an iron frame. This gate is of iron and to it is attached an upright screw which works in a female screw the outer circumference of which is cogged, and is turned by an FIG. 40.- -SLIDING REGULATOR GATE, IDAHO CANAL, endless wheel operated by a hand lever (PL VII). An ingenious method of operating gates is that employed on the Idaho Mining Company's canal at the head of the escapes and smaller regulators. To the upper part of the gate are attached two uprights (Fig. 40) on which are plain iron cogged racks. On these work cogged pinions turned by hand levers, which cause the gates to move up and down. 164. Rolling Regulator Gate. This form of gate (Fig. 41) is employed at the head of the Idaho Mining Company's canal, and is similar to that employed on the open weirs on the river Seine in France (Fig. 20). The regulator consists of eight open- ings, each 8 feet wide and 19 feet high, and is constructed of substantial masonry, surmounted by a bridge the height of which is 21 feet above the canal bed. The gates which close the openings are separated by masonry piers 3 feet in thickness, 152 SCOURING SLUICES, REGULATORS, AND ESCAPES, HYDRAULIC LIFTING GATE. 153 and consist of roller curtains made of steel plates and angle iron to a height of 10 feet from the bottom, above which the curtain is constructed of pine slats, each 6 inches wide. There are 20 steel slats and 8 of wood, and the bottom of the curtain FIG. 41. ROLLING REGULATOR GATE, IDAHO CANAL. is fastened to a cast-iron roller, on which it is wound up from above, in the form of a spiral, by means of a chain operated from the overhead bridge by a winch. 165. Hydraulic Lifting Gate. At the head of the Folsom canal in California the regulating gates (PL XXVII) are oper- ated by hydraulic power from an accumulator fed by water 154 SCOURING SLUICES, REGULATORS, AND ESCAPES. power from a fall in the canal. This regulator is constructed in the most substantial manner of granite masonry, and has a total width of 66 feet between the abutments. The gates (PL VIII) are three in number, each 16 feet in width and 14 feet in height to the crest of a semi-circular arch, and are separated by masonry piers 6 feet in thickness. They are of wood, well braced, and slide vertically in grooves let into the masonry piers separating them. One hydraulic jack is attached to each gate, and its cylinder is fastened to the masonry above. In this works a steel plunger having a 14-foot stroke and directly connected at its lower end with the gate. 166. Escapes. In order to establish a complete control over the water in a canal channel, provisions should be made for disposing of any excess which may arise from sudden rains or floods or from water not required for irrigation. This is effected by means of escapes, or, as they are more com- monly called in this country, wasteways. These are short cuts from the canal to some natural drainage way into which the excess of water can be discharged. Escapes perform the addi- tional service of flushing the canal and thus preventing or scouring out silt deposits. If the heads of distributaries be opend they relieve the main canal, and the former are in turn relieved by opening the escapes ; hence the distributary heads act as the safety-valves and the escapes as the waste-pipes of a canal system. Escapes should be provided at intervals along the entire canal line, the lengths of the intervals depending on the topography of the surrounding country, the danger from floods or inlet drainage, and the dimensions of the canal. On large canal systems in India it is customary to place them at intervals from 20 to 40 miles. In our own country they are placed more frequently, usually 10 to 20 miles apart. Where the regulator head is placed back from the river a short distance, as in the case of the Cavour, Pecos, and Turlock canals, an escape should be provided immediately above the regulator head for the dis- charge of surplus water and in order that the channel may be kept free from silt. The first or main escape on the canal LOCATION AND CHARACTERISTICS OF ESCAPES. 155 line should always be constructed at a distance not greater than half a mile from the regulator, in order that in case of accident to the canal the water may immediately be drawn off. This main escape has the additional advantage of acting as a flushing gate for the prevention and removal of silt deposits. Where used for the latter purpose it is customary to decrease the slope of the canal between its head and the escape, in order that the matter carried in suspension may be deposited at that point. 167. Location and Characteristics of Escapes. Escapes should be located above weak points, as embankments, flumes, etc., in order that the canal may be quickly emptied in case of accident. Their position should be so chosen that the escape channels through which they discharge shall be of the shortest possible length. These must have sufficient discharge to carry off the whole body of water which may reach them from both directions, so that if necessary the canal below the escape may be laid bare for repairs while it is still in opera- tion above. The greatest danger from injury to canals is during local rains, when the irrigator ceases to use the water, thus leaving the canal supply full, while its discharge is augmented by the flood waters. Hence it is essential where a drainage inlet enters the canal that an escape be placed opposite it for the discharge of surplus water. During floods the escape acts in relieving the canal of surplus water as though the head regu- lator of the canal had been brought so much nearer the point of application. In order that the escape way may act most effectively the slope of its bed should be increased by at least 12 inches immediately below its head; in addition to which the slope of the remainder of the bed should be a little greater than that of the canal, and it should tail into the drainage channel with a drop of a few feet. It is common in this country to build escapes in the sides of flumes, thus taking advantage of the wooden construction as an escape head and avoiding the expense of constructing an escape cut, as the water is discharged immediately into the drainage channel be- SCOURING SLUICES, REGULATORS, AND ESCAPES. neath the flume. While this practice is economical and may serve well where cheap construction is necessary, it is far from the best method unless great care is taken. The water falling from the flume may damage its foundations while the escape does not add to the security of the structure in which it is placed, as it does not shut off the water above it. 168. Design of Escape Heads. Escape heads and the regulators placed in the canal adjacent to and below them are built on similar designs to the main regulating gates at the head of the canal. A maximum limit is given to the dimen- sions of each gate, and as many are inserted as are necessary to pass the entire discharge of the canal without obstructing its velocity. These gates may be of wood or iron, and may be framed between timber, iron, or masonry piers and abut- ments. They are operated as are the head regulating gates; but as the pressure on them is never great, some simple form of lifting apparatus, as flashboards or sliding gates raised by hand lever, windlass, or simple screw, is sufficiently effective. On the Galloway canal in California wooden flashboard escape gates are used which are similar to the Galloway falls and regulating gates (Fig. 17). The escapes on the Idaho canal consist of cylindrical pipes let through the banks, the entrance to each being closed by a sliding gate raised by rack and pinion (Fig. 40). On the Highline canal in Colorado the first main escape is in the bench flume 600 feet below the head regulator, and consists of a set of four wooden gates, each 3 by 4 feet, set into the side of the flume and raised by simple rack and pinion. In the flume below and adjacent to this escape head are a set of flashboard checks for regulating the discharge of the canal, or, if necessary, of closing it and forcing all the water through the escape. In addition to this there are several other escapes along the line of the canal, a few at drainage inlets, and one in each of the important flumes on the line. For complete con- trol of the water on the Bear river canal there are two head escapes, one 1200 feet and the other 1800 feet below the head regulating gates, and discharging back over the canyon sides into the river. Each of these escapes has 12 feet of clear open- DESIGN OF ESCAPE HEADS. 1 57 ing closed by three wooden gates sliding between iron posts and raised by screw gearing. Below and adjacent to the lower escape is a set of regulating gates in the canal. On the line of the Turlock canal abundant escape way has been provided, as the canal flows in natural drainage channels for a portion of its course. One of these, Dry creek, has a large catchment basin, and the diverting dam which turns the water back into the canal is provided with an escape weir 51 feet in length, besides an escape way 30 feet in length. An interesting escape on the line of this canal, however, is that at the bottom of the flume crossing Peasley creek. This flume is 20 feet wide and 7 feet deep and is carried on a trestle 60 feet in height above the stream bed. In the bottom of the flume is built an escape which is of sufficient capacity to dis- charge the full volume of water flowing in the flume. It is built by laying an iron beam across the flume bed, and this re- volves on an axis turned by means of a hand wheel, thus con- verting a portion of the floor into a revolving gate by opening the bottom of the flume for its entire width. Beneath this gate is a receiving box which discharges up and down stream into two inclined wooden flumes which lead the water into the creek. 169. Sand Gates. Sand gates are practically escape gates, though they are so designed and arranged in some canals as to be of service only in scouring or removing silt deposits. The main or head escape on a canal system acts as a sand gate, and is generally built as much for the purpose of flushing and scouring sediment as for the control of water in the canal. The gate in the Highline flume acts effectively as a sand gate, because a board check from I to 2 feet in height is placed across the flume below the escape head. This causes the de- posit of silt immediately above it, whence it can be removed by the scour through the escape. Careful provision has been made for the removal of silt on the Folsom canal. Immediately in front of and above the regulating head is a set of four sand gates placed 6 feet below the grade of the canal and discharging directly back into the 158 SCOURING SLUICES, REGULATORS, AND ESCAPES. river. These are practically undersluice gates, and are each 5 by 6 feet in the clear and set in substantial masonry. Sediment which is dropped into the subgrade in the canal opposite these gates is scoured out through them. In addition to these sand gates, seven others are placed in the first 1700 feet of the canal. These are all similar in construction, 5 feet wide by 10 feet high, framed in substantial masonry, and consist of iron gates sliding vertically and raised by means of a hand wheel and endless screw working on ratchets set on the back of the gate. Across the bed of the canal opposite and below each of these sand gates is a subchannel and catch-basin I foot in depth, the object of which is to collect silt which is afterwards scoured out through the gates. CHAPTER XIV. FALLS AND DRAINAGE WORKS. 170. Excessive Slope. As the natural fall of the country through which a canal runs is usually greater than the slope of the canal, the tendency of the water in the latter is to erode its bed. In a small section of the line the erosive action of the water on the bed is noticeable providing the velocity of the stream be great. When this erosive action is extended to long reaches of the channel it produces what is known as re- trogression of levels, which is the direct result of too great a slope and consequent too high velocity. If the canal is straight little harm is done by this, other than to cause the level of the water to sink below the ground surface and prevent its diversion. Where it is necessary to divert the water or where there are curves which the increased erosive action of the water would injure, it becomes necessary to compensate for the dif- ference between the slope of the country and the canal-bed, so as to reduce the velocity. This is done by concentrating the difference of slope in a few points where vertical falls or rapids are introduced. The location of these is usually fixed by the place where the canal comes too high above the surface of the ground, while their distance apart is so arranged that they shall not have an excessive height or fall. If a canal can be so lo- cated and aligned that it will skirt the slopes of the country on a grade contour, it becomes possible to give it the most de- sirable slope throughout its length without the introduction of falls ; but where it runs down the slope of the country, compen- sation must be made for the difference between the excessive ground slope over that of the canal. 159 l6o FALLS AND DRAINAGE WORKS. 171. Falls and Rapids. There are two general methods of compensating for slope: one is by the introduction of verti- cal drops or falls, and the other by the use of inclined rapids or chutes. Falls and rapids are of various kinds and may be generally classified according as they are of wood or masonry. In design the fall maybe of three general types: I, it may have a clear vertical drop to a wooden or masonry apron ; 2, the lower face of the fall may be given 'an ogee-shaped curve (Article 137) with the object of diminishing the velocity and consequent erosive action of the water; 3, the water may plunge into a water-cushion (Article 138). To prevent the scour above the fall induced by the increased velocity of ap- proach ; i, a flashboard weir may be erected at the crest ; 2, the channel may be contracted, or 3, gratings may be introduced. To prevent the erosive action in the lower level at the foot of the fall a water-cushion may be employed, or the channel may be increased in width, terminating in wings which shall deflect the eddies back against the fall. 172. Retarding Velocity by Flashboards on Fall Crest. The effect of a fall is to increase the velocity and to diminish the depth of water for some distance above it. This increase of velocity produces a dangerous scour on the bed and banks of the canal, which in a properly constructed fall is guarded against by means of flashboards or by narrowing the width of the channel. The height to which it is necessary to raise the crest of the fall is found by the following formula devised by Colonel Dyas of the Indian Engineers : r ~ 12 S- 8I22 7' ' ' ' ' 0) in which h = height in feet of the water surface above the crest of the fall ; a = the sectional area of the open channel in square feet; r =. the hydraulic mean depth of the same in feet ; / = the length of the crest of the fall in feet ; f= the length of slope to a fall of one in the same. RETARDING VELOCITY OF APPROACH. l6~I This formula has been somewhat simplified and modified by Mr. P. J. Flynn in order to make it agree with Kutter's formula. Mr. Flynn finds the discharge over the fall complete to be in which Q = the discharge in second-feet ; c = the coefficient of discharge of open channel ; /;/ coefficient of discharge over a weir, and varies between 2.5 and 3.5 ; s = the sign of slope ; and finally he gives the fol- lowing : If from this value of // we deduct the depth of water in the channel, we have the height to which the weir must be raised above the bed of the canal in order that the water shall not increase in velocity in approaching the crest of the fall. 173. Retarding Velocity by contracting Channel. If, instead of raising the crest of the fall, it is desired to narrow the channel above the fall in order to diminish the velocity of approach and the consequent erosive action, the amount of narrowing may be calculated by the common weir formula (No. 2) above given, and substituting for Q its value ac(rs}^, and transposing we finally get _ 2agc 2grs_ } -^ < (2g/i + Sr7)*' in which / is the length of the weir crest or the width of the channel immediately above the fall, in feet. 174. Gratings to retard Velocity of Approach. Gratings have not been employed on American canals for the purpose of retarding the velocity of approach to the crest of falls, but are used with excellent results on some canals in India. They 162 FALLS AND DRAINAGE WORKS. consist of a number of inclined wooden bars placed just above the crest of the fall, and the method of spacing them is such that the velocity of no one part of the stream shall be either increased or retarded by the proximity of the fall. The wooden bars which rest on one or more overhead cross-beams, are laid at a slope of about I on 3, and are made of such length that the full supply level in the canal is half a foot below their ends. In canals with 6J feet depth of water the following dimensions have been used for the bars : lower end \ inch broad by f of an inch deep ; upper end \ inch broad by f of an inch deep. They are supported on 12 X 12 inch beams, and are placed such dis- tance apart that 18 go into one lo-foot bay. According to the experience had in India vertical falls ter- minating in a water-cushion and having gratings above them are the best form that has yet been devised, the erosive action being diminished to a minimum. 175. Simple Vertical Fall of Wood. On the line of the Galloway canal in California simple flashboard checks sim- ilar to the regulating heads are used for the falls. By increas- ing or diminishing the number of flashboards inserted in these FIG. 42. LONGITUDINAL SECTION OF FALL, ARIZONA CANAL. checks the height of fall can be increased or diminished as desired. These checks are inclined at a slight angle to the vertical, and the water drops to a wooden apron or flooring resting on mudsills and protected by sheet piling at its ends, SIMPLE "EKT1CAL FALL OF WOOD. I6 3 while the bank is protected by wings. On the line of the Arizona canal (Plate IX) a somewhat similar fall is used though the check is vertical. There are a number of these falls, averaging about 5 feet in height each and varying from FIG. 43. PLAN AND CROSS-SECTION OF FALL, BEAR RIVKK CANAL. 1 8 to 21 feet in length on the crest. They consist (Fig. 42) of wooden fluming, the flooring of which is 12 feet in length above the fall, which rests on sheet piling, while the floor be- low the fall is continued for a length of about 16 feet. A somewhat similar fall is that employed on the Fresno canal, only in this the flooring of the apron below the fall is WOOD EX FALL WITH WATER-CUSHION. depressed i feet below the bed of the canal and an earth fill- ing is placed above this, thus giving a sand box on which the water falls. Above the crest of the fall instead of the hori- zontal flooring is an inclined apron 12 feet in length and slop- ing downwards at an angle of 45 degrees. 176. Wooden Fall with Water-cushion. On the Bear river canal are a large number of falls, ranging from 4 to 12 feet in height (Fig. 43). In these the flooring has been made es- pecially heavy, and above and below the apron it slopes down into the bed of the canal to prevent percolation. On the line of the Turlock canal in California are falls varying from 4 to 1 1 feet in height. Immediately above these the canal is con- tracted from its ordinary bed-width of 70 feet to a clear width of 40 feet at the fall crest in order to reduce the velocity and prevent the scour above it. These falls (Fig. 44) are con- <--- 3 < 9N. Pi %W.I// b i 1 x FIG. ROSS-SECTION OF FALL, TURI.OCK CANAL. structed of wood much as are those just described, while below the fall is a depressed water-cushion of such dimensions that for a 5-foot fall the water-cushion is 4 feet in depth, while the i i-foot fall has a water-cushion of 6 feet in depth. Below the water-cushion a wooden apron is carried out for 16 feet, while a similar apron 16 feet in length extends above the fall crest. The falls are divided into four bays of 10 feet each by means of vertical rows of planking in order to direct the current and prevent back eddies. MASONRY FALLS WOODEN RAPIDS. i6 7 177. Masonry Falls. In all the falls employed in India masonry work alone is used. These falls have sometimes sim- ple vertical drops, at others they terminate in water-cushions. It is invariably csutomary, however, in the case of wide canals to divide the falls into bays of 10 feet each, or thereabouts, by means of vertical partitions of masonry in order to prevent scour and back eddy and keep the water moving in a direct course. By this means each may be separately closed and repaired if necessary. An interesting series of two falls ter- minating in water-cushions on the Agra canal is shown in cross- section in Plate X. 178. Wooden Rapids or Chutes. A notable wooden rapid is the " Big Drop " on the Grand River canal in Colo- rado. The canal above the rapid is 30 feet wide and 4 feet deep and is narrowed down at the head of an inclined flume PLAN Of PENSTOCK FIG. 45. PLAN AND ELEVATION OF BIG DROP, GRAND RIVER CANAL. which forms the rapid to a cross-section of 5 by 4 feet. The flume descends with a total fall of 35 feet in a length of 125 feet (Fig. 45), the water being discharged against a solid bulkhead of timbers which throws it back into a wooden penstock. From this it escapes over a riffled floor 16 feet in length, be- yond which is an additional flooring 16 feet in length, whence it emerges in the open canal. 1 68 FALLS AND DRAINAGE WORKS. DRAINAGE WORKS DRAINAGE CUTS. 169 Wooden rapids similar to those just described are em- ployed on the line of the Phyllis branch canal in Idaho. These are practically inclined wooden flumes with slopes of from I to 5 in 100 and ranging in height from 12 to 50 feet. 179. Masonry Rapids. On the Bari Doab canal in India rapids paved with loose bowlders have been used with great success. The floors of these rapids (PI. XI) are confined be- tween low masonry walls so as to prevent the movement of the loose bowlders, and the banks are protected by masonry wings. Bowlders form a better material for the flooring of a rapid than does brickwork, which could not safely be used with velocities exceeding 10 feet per second. The bowlder floors are grouted in mortar and will safely withstand a ve- locity of 15 feet per second. The tail walls of these rapids are peculiarly carved in order to turn back the current and pro- tect the canal banks from the direct action of the water. 180. Drainage Works. Where the diversion line of a canal is carried around the sides of hills or sloping ground, great difficulties are sometimes encountered in passing side drainage. The higher the canal heads up on a stream the more liable is it to encounter cross drainage. On low slopes much may be done by diverting the watercourses by cuts emptying into natural drainage lines. When this cannot be done it may be passed in one of the following ways : 1. By simple inlet dam ; 2. Level crossing ; 3. Flume or aqueduct ; 4. Superpassage ; 5. Culvert or inverted siphon. 181. Drainage Cuts. An instructive example of diversion by means of a drainage cut is the case of the Chuhi torrent on the Bari Doab canal in India. This torrent had two out- lets, one running into the Beas and the other into the Ravi river just above the canal crossing. The latter was embanked close to the bifurcation by a bowlder dam, and by this means the water was forced down the Beas and the expense of cross- ing the canal saved. On the Betwa canal in India is another I7O FALLS AND DRAINAGE WORKS. interesting diversion cut. The first six miles of this line are protected by a drainage channel 15 feet wide at the bottom and 6 feet deep, which runs parallel to the canal and catches the minor drainage from small streams, which it discharges into the Betwa river above the point of diversion of the canal. 182. Inlet Dams. Where the drainage encountered is intermittent and its volume is small relatively to that of the canal, much expensive construction may be saved by admitting the water directly into the canal and permitting it to be dis- charged through the first escape on its line. If the canal crosses a depression in the hillside, a heavy bank will of neces- sity be built on its lower side to keep the level of its crest at the desired height. The result will be to back the water up the drainage depression, thus causing wastage where water is scarce, as the area of surface exposed to evaporation and seepage is increased. In such a case an inlet dam should be built at the mouth of the depression to confine the canal chan- nel within reasonable limits. Inlet dams may be of wood, masonry, or loose stone. If the depth of the canal is small and the consequent height of overflow from the crest of the dam to the canal bed small, a wooden fluming or flooring may be laid in the bed of the canal and a barrier or dam of piles and sheet piling be built across the upper side. In the course of a short time the sediment carried by the stream will fill in behind the dam to a level with its crest and the water will simply fall over it onto the wooden apron. The inlet dam may be made as a loose rock retaining- wall when the bed and banks of the canal below and opposite should be riprapped with stone to protect them from erosion. In case the drainage torrent is of some magnitude more sub- stantial works than this may be required, and it may be neces- sary to build a masonry inlet dam and perhaps to build a portion of the canal channel of masonry, revetting the opposite bank with loose stone. 183. Level Crossings. When the discharge of the drain- age channel is large and it is encountered at the same level as the canal, it may be passed over, under, or through the latter. LEVEL CROSSINGS. 171 In the latter case the water is admitted by an inlet dam on one side and discharged through an escape in the opposite bank. The discharge capacity of the escape must be ample to pass the greatest flood volume likely to enter, and a set of regulat- ing gates must be placed in the canal immediately below the escape in order that only the proper amount of water may be permitted to pass down the canal. The inlet dam must be constructed as described in Article 182, while the escape and regulators should be built of the usual pattern. On the line of the Turlock canal in California are several level crossings of peculiar design, built where the canal skirts PPR^j^v^v^ >' f*o ' 6r r/te' Jn/ef. FIG. 46. PLAN OF RUTMOO CROSSING, GANGES CANAT., INDIA. steep sidehill slopes, causing the embankment on the lower side to become practically a high earthen dam. The top of the bank is made a little higher, firmer, and wider than else- where along the canal line, and in the case of two of these drainage crossings no inlet dam has been constructed. As a result the water is retained on the upper side of the canal as in a large reservoir. With a new canal this has no great disadvan- 1/2 FALLS AND DRAINAGE WORKS. tage, as such construction saves considerable expense in the beginning, while in the course of a few years, and by the time the canal water becomes valuable, this reservoir will have silted up and the canal can then be confined between proper limits. These earthen drainage dams are of considerable height, one 23 feet and the other 40 feet high, and in them are constructed escapes, or wasteways for the discharge of surplus waters. The most interesting level crossing built is that of the Rutmoo torrent on the Ganges canal in India. This consists of a simple inlet at the torrent entrance, of a masonry outlet dam, of an escape regulator in the opposite canal bank, and of a regulating bridge across the canal channel just below the inlet (Fig. 46). The escape dam consists of 47 sluiceways, each 10 feet wide, with their sills flush with the canal bed and flanked on either side with overfalls of the same width with their sills 6 feet higher, while on the extreme flanks are plat- forms 10 feet above the canal-bed. The closing and opening of these sluiceways is accomplished by means of small flash- boards fitting into grooves. 184. Flumes and Aqueducts. These structures are prac- tically the same, the term flume being more commonly em- ployed in this country to mean a wooden structure for carrying the waters of a canal either around steep rocky hillsides or across drainage lines. The word aqueduct may be more properly applied to those flumes which are of some magnitude and are built of permanent material, as iron or masonry. Where the drainage encountered is at a lower level than the bed of the canal, it may most conveniently be passed under the latter, which crosses over it in a flume. Care must be taken to study the discharge of the stream crossed in order that the water- way under the flume may be made amply great to pass the largest flood which may occur. The foundations of the flume must be substantial, and the area of water-way must not be greatly impeded ; otherwise the velocity in the drainage chan- nel will be so great as to cause scour of its bed and perhaps the destruction of the work. Care must be exercised in con- SIDE HILL FLUMES. 1 7 3 necting the ends of the flume with the canal banks on either side so that leakage may not occur at these points. As the flume or aqueduct is built across a depression, ex- pense in construction is usually saved by limiting the length of the structure as much as possible. This is done by making its approaches on either side of earth embankments, thus causing the canal at either end of the flume to flow on top of an em- bankment which must be carefully constructed and of ample width in order that it may not settle greatly or be washed away. This embankment must be faced with abutments and wing walls at its junction with the flume in order to protect it against erosion. That the dimensions of the flume may be as small as possible, its cross-section is generally diminished and it is given a slightly greater slope than the canal at either end to enable it to carry the required volume. 185. Sidehill Flumes. The simplest form of wooden flume is what is generally known as a bench flume, built on steep sidehill to save the cost of canal excavation. Such flumes are common in the West, notable examples of which are the bench flume on the Highline canal in Colorado (PI. XII) and the great San Diego flume in California. The former was built to avoid expense in construction, its length being a little over half a mile. It is 25 feet wide and 7 deep, its grade being 5j feet per mile, and its. discharge 1184 second-feet. The San Diego flume, on the other hand, was built chiefly to give the -canal the most permanent form of water-way and one least, liable to the losses of evaporation and absorption. In this case fluming is employed for the entire length of the canal, which is 36 miles. Such structures should never be built on embankments; they should rest everywhere on excavated material or trestles to avoid the danger of subsidence and consequent destruction. This excavated bench should be several feet wider than the flume, in order to give a place on which loose rock from the sidehills may lodge without injury to the structure, and the flume itself should rest on a permanent foundation of mudsills or posts. CONSTRUCTION OF FLUMES. 175 186. Construction of Flumes. The boxing of flumes is generally of three types : 1. The floor may be built directly on stringers and the planking be laid at right angles with the current of the stream. 2. The floor beams may be laid on stringers braced at in- tervals calculated to bear the water pressure ; the standard and floor beams being boxed in and bolted to the outside braces, the whole forming the foundation for putting on the inside sheeting or boxing. 5. The floor beams and stringers may be formed in cross beams yoked to receive the boxing. The lumber forming the boxing of the flume should be from i to 2 inches in thickness, according to the dimensions of the flume, and all joints should be calked with oakum. An FIG. 47. CROPS-SECTION OF SAN DIEGO FLUME. excellent example of bench flume is that of the San Diego Flume Company (Fig. 47), which is 6 feet wide in the clear and 4 feet high ; the bottom and sides are planked with 2-inch redwood, and the boxing rests on transverse sills of 2-inch planking laid 4 feet apart, and upon these are 4 by 6 longi- tudinal stringers, above which is constructed the framework of FLUME TRESTLES IRON AQUEDUCTS. .177 the flume, consisting of 4 by 4 scantling placed at intervals of 4 feet and braced by diagonal uprights 2 by 4 inches and 3 feet in length. 187. Flume Trestles. Where the flume crosses a depres- sion it rests on trestles. These are constructed as are the ordinary trestles on railway lines, and are built of various de- signs. Where the trestle rests on dry ground it may be founded on mudsills or on short posts let into the soil, but where it crosses drainage channels it must be substantially founded on cribs or piling. The superstructure of a flume crossing a drainage line is similar to that of bench flumes. A large and imposing flume is that across the Pecos river in New Mexico (PI. XIII). The approaches to this flume consist of a terre plein or raised embankment 105 feet wide at the base, 24 feet in maximum height, and 80 feet wide on the top, while the top width of the canal is 70 feet, thus giving 5 feet in width of embankment for the canal channel. The flume ter- minates at either end in substantial wooden wings extending for 12 feet into the earth embankments and well braced and supported by sheet and anchor piling. This flume is 40 feet in height above the river, 25 feet wide, 8 feet deep, and 475 feet long, and rests on a substantial trestlework, the spans of which are 16 feet in length. 188. Iron Aqueducts. But few of these have been con- structed, though it is probable that they will continue to grow in favor and will be largely substituted for wood. The chief difficulty encountered in constructing long aqueducts of iron has been the expansion and contraction of the metal, though in fact this has proven to be an imaginary rather than a real danger. In practice it has been found that the metal of the structure has approximately the same temperature as that of the water, and as this is somewhat uniform but little change takes place in the dimensions of the aqueduct. On the Bear River canal in Utah are two aqueducts, one of which consists of a wooden flume resting on iron trestles founded on masonry columns. The other is a simple iron aqueduct resting on iron trestles. The floor of this is 37 feet above the bed of the 1/8 FALLS AND DRAINAGE WORKS. stream, and its length is 1 30 feet (Fig. 48), disposed in three bents the centre span of which is 60 feet long, the other two being respectively 25 and 45 feet long. This aqueduct is essentially a plate-girder bridge resting on iron columns and founded on iron I "_'?< ". x . "_, .130' HI I I I [ , J i M 1 1 n LI FIG. 48. BEAR RIVER CANAL. ELEVATION AND CROSS-SECTION OF IRON FLUME ON CORINNE BRANCH. cylinders filled with concrete and resting on piles. The plate girders forming the sides of the aqueduct are 5^ feet in depth, the available depth of water being 4 feet. The sides of the girder are braced by vertical angle-iron riveted to it every 5 feet apart, while the top is cross-braced by similar angle-iron. IRON AQUEDUCTS. 179 These angle-irons vary between 3 and 4 inches in width, while the web of the sides of the aqueduct consists of -f-inch iron. On the Henares canal in Spain is an iron aqueduct over the Majanar torrent. This aqueduct is 70 feet long with a clear span of 62 feet. Its water-way is 10.17 ^ eet wide, its capacity being 177 second-feet. The sides are composed of box girders 6.2 feet deep (Fig. 49), and each girder is calculated Half 5/evarion of Aqueduct 1-t-HtHjfl FIG. 49. AQUF.DUCT, HENARES CANAL, SPAIN. to bear 200 tons or the entire structure to carry 400 tons. To prevent leakage the ends of the aqueduct rest on stone tem- plates, and 4 inches from each end is a pillow composed of long strips of felt carpet 9 inches wide and soaked in tallow, which is let into the stone below the aqueduct. This presses on it with its full weight, thus making a water-tight joint. In addition to this lead flushing is riveted to the aqueduct and let into a recess of the stone abutments. This recess is 12 inches deep and 4 inches wide, and around it is poured, hot, a MASONRY AQUEDUCTS SUPERP A SSAGES. l8l mixture of tar, pitch, and sand, which allows slight play during its expansion and contraction and yet is water-tight, 189. Masonry Aqueducts. In general design masonry aqueducts are planned and constructed much as are those of wood or iron. One of the greatest structures of this kind is the Solani aqueduct on the Ganges canal in India (PL XIV). This consists of an earth embankment approach or terre plein 2f miles in length across the Solani valley, its greatest height being 24 feet. This embankment is 350 feet wide at the base and 290 feet wide on top, and on this the canal banks are formed, the width of the banks being 30 feet on top and the bed-width of the canal 150 feet. The aqueduct is 920 feet in length with a clear water space between piers of 750 feet, dis- posed in fifteen spans of 50 feet each. The breadth of each arch parallel to the channel of the river is 192 feet audits thick- ness 5 feet. The greatest height of the aqueduct above the river valley is 38 feet, and the walls of the water-way are 8 feet thick and 12 feet deep. This structure is founded on masonry piers resting on wells sunk 20 feet in the river bed. Perhaps the most magnificent aqueduct ever built is that carrying the Lower Ganges canal across the Kali Nadi torrent in India (Plate XV). The present structure was built to replace another of similar design which was destroyed by a flood which the water-way under the aqueduct was too small to pass. This was calculated to discharge 30,000 second-feet, \vhereas the flood which destroyed it amounted to 135,000 second-feet in volume. The present aqueduct consists of fif- teen masonry spans each 50 feet in width and supported on masonry wells sunk to a maximum depth of 50 feet. Under the aqueduct is built up a concrete floor 5 feet in thickness to prevent erosion and destruction of the foundation. 190. Superpassages. Where the canal is at a lower level than the drainage channel, a superpassage is employed to carry the latter over the canal. A superpassage is practically an aqueduct, though there are some elements entering into its design which are different from those affecting aqueducts. The volumes of streams which are to be carried in superpas- 182 FALLS AND DRAINAGE WORKS. HEM. O PLATE XV. ELEVATION AND CROSS-SECTION OF NADRAI AQUEDUCT, LOWER GANGES CANAL, INDIA. SUPERPA SSA GES. 1 8 3 sages are variable ; at times they may be dry, while at others their flood discharges may be enormous. No provision has to to be made for passing flood waters under the structure, since the discharge of the canal beneath it is fixed. On the other hand, the water-way of the superpassage must be made amply large to carry the greatest flood which may occur in the stream, and much care must be taken in joining the superpassage to the stream bed above and below to prevent? injury by the violent action of the flood waters. No instances can be cited where superpassages have been constructed in the United States. In nearly every case where these would have been required the canal has been taken under the stream-bed in an inverted siphon. In India, however, superpassages have frequently been used on the canals, where they have been employed in preference to inverted siphons chiefly because of the requirements of navigation. It would probably be a dangerous experiment to attempt to construct a superpassage of wood, because it would be so constantly sub- jected to alternate drying and wetting, according as there was or was not water flowing in the stream, that it would soon decay. A small iron superpassage has been constructed across the Agra canal in India which is 99 feet long, 30 wide, 10 feet deep, and is constructed of boiler-iron strongly cross- braced. It is well built and is supported on masonry piers. Its slope is steep, thus giving a high velocity. The connection between its ends and the abutments is made by means of heavy sheet lead to accommodate the changes due to expan- sion of the iron. This precaution is more necessary in a super- passage than in an aqueduct, as it is more subject to changes of temperature when empty. On the Ganges canal in India are two of the largest and most interesting superpassages ever constructed. One carries the Puthri torrent and the other the Ranipur torrent over the canal. The discharge of the former amounts in times of flood to as much as 15,000 second-feet. The Ranipur superpassage (PI. XVI) is built of masonry founded on wells, and its flooring, which is given a steep slope in order that the velocity shall INVERTED SIPHONS. 185 prevent its filling up with sediment, is 3 feet in thickness above the crown of the arches and is bordered by parapets 7 feet wide and 4 feet high. The flooring and parapets continue inland from the body of the work a distance of 100 feet on each side, the latter expanding outward so as to form wings to keep the water within bounds, The superpassage is 300 feet long and provides a water-way 195 feet wide and 6 feet deep. 191. Inverted Siphons. Where the canal is not used for purposes of navigation and encounters drainage at a relatively low level, the most convenient and usual form of crossing is by means of inverted siphons. The ordinary method of using these is to carry the water of the canal in the siphons under the stream, though sometimes the stream is carried in the siphon and the canal is taken over this in a half aqueduct. The di- mensions of the siphon are to be computed by means of one of tlje many formulas for the flow of water through pipes, though the formula for flow through channels may also be used in some cases. Many examples of these are to be found in works on hydraulics, and therefore they will be but briefly referred to here. To find the velocity of flow in a pipe, given its diameter, length, fall, and value of n, or the coefficient of roughness, we can use the formula v = c Vrs. To determine the discharge we can use the formula Q = av, or the velocity into the cross- section. The various other dimensions of the pipe, such as the velocity and grade given to find its diameter, are obtained in like manner from these formulas by looking up their equivalent values in published tables. 192. Inverted Siphon of Wood. An excellent example of a small work of this kind is the wooden culvert or inverted siphon used on the Del Norte canal in Colorado (Fig. 50). This consists of two parallel wooden boxes, each 4 feet 6 inches wide by 3 feet high, supported on piling and framed and braced with 6 by 8 scantling. The bottom and sides are floored with 2-inch plank, while the top, which has to bear the weight of the superincumbent earth and water, is covered with 6-inch plank- ing laid crosswise. 1 86 FALLS AND DRAINAGE WORKS. A most interesting wooden- siphon is that which carries the Central Irrigation District canal under Stony creek in Colusa county, California. In addition to acting as a conduit for the waters of the canal it is so arranged as to act as an escape and regulating gate to the canal, while its crest acts as an in- let from the creek. The length of the siphon is 650 feet, and it ter- minates at either end in an inlet and outlet masonry well protected by;substantial walls and approaches, as shown in PL XVII. This siphon consists of seven parallel lines of semicircular wooden tubing fastened under a horizontal platform of wood the top of which is level with the stream-bed. Above and below the platform in the creek-bed are wooden aprons, while light training works keep the current of the stream in its channel. At the inlet to the culvert are a set of simple flash- board regulating gates which act as an escape to the canal. The outlet culvert-well is planned as a simple inlet to the canal. As shown in the illustration, the semicircular wooden culvert rests on a bed of concrete l\ feet in thickness. The tubes of the culvert are each 5 feet 5 inches in diameter and consist of 2^-inch staves laid longitudinally and bound together by semicircular iron hoops which terminate in bolts above the platform floor. INVERTED SIPHON OF WOOD. I8 7 r PLATE XVII. CENTRAL IRRIGATION DISTRICT CANAL. ELEVATION AND CROSS-SECTION ot STONY CREEK CULVERT. PLATE XVIII. IDAHO IRRIGATION COMPANY'S CANAL. VIEW OF WOODEN SIPHON ON PHYLDS BRANCH. 1 88 INVERTED SIPHONS OF MASONRY. I8 9 Instead of this form of built-up wooden inverted siphon, ordinary wrought-iron, cement, or wooden pipes are frequently employed, especially where the head is great. These wooden Gaoutio Sutrrxee FIG. 51. SOANE CANAL. CROSS-SECTION OF KAO NULLA SIPHON-AQUEDUCT. pipes may be of the ordinary wrought-iron hydraulic mining type or of the same type as the Colorado wooden pipe de- scribed in article 204 (PL XVIII). 193. Inverted Siphons of Masonry. An interesting struc- ture of this kind which is practically a siphon aqueduct, since the waters of the stream are carried under those of the canal, is that carrying the Kao torrent under the Soane canal in India (Fig. 51). This work is built of the most substantial masonry, the area of the superstructure being contracted and given a slightly increased grade to carry the waters of the canal, while the waters of the torrent flow over a masonry floor which is depressed a few feet. The most magnificent masonry siphon ever built is that carrying the waters of the Cavour canal under the Sesia river in Italy. Its total length is 878 feet and it consists of five oval orifices (Fig. 52) each 7.8 feet in height by 16.2 feet in width, the amount of depression of the water surface in the canal be- UNIVERSITY ) d/.r ,,,A // 190 FALLS AND DRAINAGE WORKS. ing 7^ feet. The siphon consists of a substantial concrete floor or foundation iijfeet in thickness under the river bed, its roof forming the floor of the river channel and being about 3 FIG. 52. SECTIONS OF SESIA SIPHON, CAVOUR CANAL, ITALY. feet in thickness. Another large siphon is that on the Sirhind canal in India crossing the Hurron torrent. The total length of this is 212 feet, and it consists of two openings each 4 feet high by 15 feet wide. The water drops from the canal almost vertically into a well the floor of which is on a level with the floor of the siphon, while at its exit it is raised again to the level of the outlet canal up an incline built in steps. CHAPTER XV. DISTRIBUTARIES. 194. Object and Types. Distributaries are to a main ca- nal system what service pipes are to the mains in city water service. The minor ditches or laterals which are owned by the irrigators and from which water is directly applied to the crops should never be diverted from the main canal nor from its upper branches. It is desirable to have as few openings in the bank of the main canal as possible, so as to reduce to a minimum the liability of accident. The water is drawn at proper intervals from the main line into moderate-sized branches which are so arranged as to command the greatest area of land and to supply the laterals and small ditches of the irrigators in the most direct manner. Wherever water has not a high intrinsic value it is conducted to the lands in open distributaries and laterals excavated in the earth. Where, however, its value is relatively high and it is scarce it is desir- able to reduce the losses from percolation and evaporation to a minimum. In such cases the distributaries consist of wooden flumes or of paved or masonry-lined earth channels, while in extreme cases, such as are frequently encountered in Southern California, water is conducted underground to the point of application in pipes, and is applied to the crops from these instead of being flowed over the surface. By such methods of handling the highest possible duty is obtained and the most effective use made of the water at command. 195. Location of Distributaries. Distribution from a canal is most: economically effected when it runs along the summit of a ridge so that it can supply water to its branches 191 I Q2 DIS TRIE U TA RIES. and to private channels on either side. In the case of main canals this location can be made only in occasional instances ; but the distributaries taken from these mains should be made to conform to the dividing lines between watercourses. The capacity of the distributaries which then traverse the separate drainage divides are proportioned to the duties they have to perform, the natural bounding streams limiting the area they have to irrigate. In designing a distributary system too little care and atten- tion are ordinarily paid to its proper location and survey ; yet it is in the distribution and handling of water that the greatest losses occur, and accordingly it is there that the greatest care should be taken in its transportation. Careful surveys should be made of the area to be traversed by the distributaries, as described in Chapter XI for the location of main canals, and the greatest care should be taken to balance cuts and fills and to so locate the distributaries that the least loss of water shall occur from percolation. In Fig. 53 is shown an ideal distributary system. The con- FIG. 53. DIAGRAM ILLUSTKATING DISTRIBUTARY SYSTEM. tour lines and drainage courses show the general slope and lay of the country, and the main canal and its tributaries should be run down the divides between these drainage lines as indi- DESIGN OF DISTRIBUTARIES. 193 cated. Such an arrangement enables the least mileage of channels to command the greatest area of country by furnish- ing water to both sides of its line. At the same time perfect drainage is obtained by the water flowing in both directions into the natural watercourses. t" 196. Design of Distributaries. For the more complete and efficient distribution of water the engineer treats distribu- taries as of as much importance as the main branches. At- tention is devoted to the character of the soil traversed, to the alignment, to the safe and permanent crossing of natural drainage lines, and especially to so maintaining the surface of the canal with relation to the ground as to command the largest irrigable area. In all well-designed distributary sys- tems the capacity of the channels is exactly proportioned to the duty to be performed, the cross-sectional area being dimin- ished as the quantity of water is decreased by its diversion to private watercourses. The distributary should be taken off from the main canal as near the surface of the latter as possible. That is, the bed of the distributary should not be on a level with the bed of the canal, but should be placed with reference to the full supply of the main canal, in order to get the clearest water, and in order that the bed of the distributary may be kept at a high level and admit of surface irrigation throughout its length. In leyel country great care should be taken in designing distributaries that the natural drainage lines into which they tail shall be sufficiently large to accommodate any flood volume it may be necessary to pour into them ; otherwise the stream courses might become clogged and flood the surround- ing country. In order to avoid the construction of costly em- bankments and to insure the surface of the water being above that of the country, the slope of the distributary should be made as nearly parallel as possible to that of the land it trav- erses. To effect this alignment falls must be frequently in- troduced ; and to dispose of storm-waters escapes into natural drainage lines should be provided at least every 10 miles in the course of the distributary. . s 1 94 DIS TRIE UTA R1ES. 196. Efficiency of a Canal. According to Mr. J. S. Beres- ford, an Indian engineer, we may look upon a great canal sys- tem as a machine composed of four parts and calculate its efficiency in the same way as that of a steam-engine. These parts are : 1. The main canal ; 2. The distributaries; 3. The private irrigating channels ; 4. The cultivators who apply the water to the soil. Each cubic foot of water entering the canal head is ex- pended in five ways : 1. In waste by absorption and evaporation in passing from the canal head to the distributary head. 2. In waste from the same causes between the distributary head and the head of the private channel. 3. In waste from the same causes in passing from the pri- vate channel to the field to be watered. 4. In waste by the cultivators in handling the water, both by causing losses from evaporation or from percolation where an unnecessary amount is applied. 5. In useful irrigation of the land. The object is plainly to increase the last item by the reduc- tion of all the rest. Calling D l the theoretic duty of a foot of water entering the canal head, we have the actual duty of the canal D = C me X D\ (i) where C me represents the mean efficiency of the main canal. Now if the efficiency of water entering a distributary head for use in watering a field from an outlet is called E, the duty of water used in this field will be D = EX& (2) and E = E d XE w XE c , (3) where E d is the efficiency of the distributary, E w is the effi- ciency of the private watercourse between its head and the EFFICIENCY OF A CANAL. 1 95 field, and E c is the efficiency of the cultivator who waters the field. The efficiency of any distributary is the fraction whose de- nominator is the quantity entering the distributary head, and the numerator this same quantity minus the loss down to the point in question. If W represents the waste down to any outlet, Q the discharge at the head of the distributary, and E the efficiency at the point under consideration, then . Q - w w The waste W, down to any point may approximately be ex- pressed as the product of the loss of the first mile into some function of the length, or L*; ....... (5) or substituting in the above equation, we get APxL* ,,, E Q - > ...... (6) where AP is the ascertained loss by absorption and percolation in the first mile and L* is some function of the length, which will be found by experiment to be about \ or f of L in most cases, or near the head of the distributary Z- 1 . Taking / as the length of the private watercourse, q as its discharge, and /* as the same function of its length as in the case of L x , we have the efficiency of the private channel w The efficiency of the cultivator E e varies between .5 and .9 where unity represents his efficiency at the theoretical limit. Now for an outlet at the head of the distributary and with the irrigating field close to this outlet. Z o and /=o. 1 96 DIS TRIE U TA RIE S. Therefore the second terms of the equations (6) and (7) van- ish and E and E = o. An application of these rules as laid down by Mr. Beres- ford is given in the following cases : Say the discharge Q = 50 cubic feet ; that the outlet is at the loth mile, whence L= 10; the losses from percolation, etc., being 1.25 in the first mile and x = $. The discharge of the watercourse q = i cubic foot, / = 6 furlongs, and ap = .03 of a cubic foot per furlong. Then say '=75; and E = .829 X .82 X -75 = -5 1 5 or leaving out the cultivator, this is equal to .68. That is, of each cubic foot entering the distributary head only .68 of a cubic foot is available at the loth mile and 6 furlongs. What- ever the actual amount of loss in either distributary or private channel, it varies directly with L and /; it also varies directly with AP and ap, and great waste is due to the cultivator if he is careless. It will thus be seen from the above that every effort should be made to reduce the value of AP and to induce the cultivator to use the greatest possible care in handling the water. 198. Private Watercourses. As a result of Mr. Beres- ford's experiments it is evident that the widest field for improvement is in the private watercourses. As generally constructed these are much longer than is necessary, and are usually so constructed as to avoid low lands, whereas flumes or proper alignment would remedy this. They often run long distances through sandy soil, which absorbs the water, and frequently parallel each other, thus adding to the losses by absorption by unnecessarily increasing the wetted perimeter. DIMENSIONS OF DISTRIBUTARIES. 1 97 Where sandy soil is encountered or depressions are to be crossed the channels should be puddled or flumes employed. 199. Dimensions of Distributaries. Experiments made in India show that the greater the amount of water discharged by a distributary the smaller will be the proportion of cost of maintenance. Thus a channel 12 feet wide discharges more than double the volume discharged by two channels each 6 feet wide, while the cost of patrolling and repairing the banks would be half that of both the smaller ones. Experience has proved that irrigation can be most profitably carried on from channels 18 feet wide at the bottom and carrying about 4 feet in depth of water. Thus on the eastern Jumna canals during the years 1858 to 1860, inclusive, the expenditure of water on all the distributaries of 12 feet bed-width and upwards was 0.123 of the revenue, while on all those below 12 feet it was 0.223 or nearly double that of the first. From the same ex- aminations the relative value per cubic foot per annum on channels of respectively 12, 6, and 3 feet in bed-width was as 10 : 7 : 4- The increased action of absorption in small chan- nels with diminished volumes and velocities accounts for the difference. The depth of water should accordingly seldom be less than 4 feet and the surface of the water should be kept at from I to 3 feet above that of the surrounding country ; not only to afford gravity irrigation, but because the loss by absorp- tion is thereby diminished. The principle which is so commonly employed in the West on minor private channels of diverting the water by raising it to the surface of the country by means of earth check-dams, or by introducing plank stops in grooves, is to be condemned. It converts freely flowing streams into stagnant pools, encour- ages the growth of weeds and the deposit of silt, and produces an unhealthy condition of the neighborhood. It is moreover extremely wasteful of water, since much of the latter is dis- sipated because of loss of head and because of absorption and evaporation. Where these stop planks or checks are used in private channels with a view to diverting the water to the irri- gable fields, little or no damage is done, since the planks re- 1 98 DIS TRIE U TA KIE S. main in but a short time, during which no damage is likely to occur. 200. Distributary Channels in Earth. The cross-section of the main or larger distributaries should be relatively the same as for main canals (Articles 117 to 120.) In designing the canal banks their top width should be sufficient to admit of easy inspection. On moderate-sized distributaries 3 feet may be taken as the minimum width. Should the cut not be so deep that a berm is necessary, it is always well to let the latter slope away from the canal and be drained off through the bank. The top of the bank likewise should not be level but should drain away from the canal. For smaller distributaries or minor private channels a small trapezoidal cross-section both for the bank and the canal will usually be sufficient, and as far as possible the larger portion of this cross-section should be in embankment, thus keeping the water above the level of the surrounding country. In such small channels it is not neces- sary to construct berms, to give subgrades or other complex cross-sections. 201. Wooden Distributary Heads. Distributary heads on Western canals are arranged much as are the heads of main canals and escapes. They consist essentially of two parts, a regulator or check below the head on the main canal, in order to divert the water into the distributary, and a regulating gate in the latter to admit the proper amount of water. These heads usually consist of a wooden fluming, which is practically an apron to the bed of the distributary and planking to protect the banks. Inthis fluming are inserted the gates, which con- sist either of flash boards, as in Kern county, California, or of simple wooden lifting gates, as in most other portions of the West. In Fig. 54 is shown a distributary head on the line of the Calloway canal in California. Immediately below the regu- lator is shown a minor headgate leading to a private channel, while a sort of well is formed in the distributary flume just be- low this minor headgate to retard the velocity of the current. On the line of the Idaho canal the distributary heads are WOODEN DISTRIBUTARY HEADS. I 99 FIG. 54. VIEW OF DISTRIBUTARY HEAD, CALLOWAY CANAL. designed much as are the main heads on the same canal (Fig. 40). On the Del Norte canal in Colorado a few of the distribu- FIG. 55. PLAN OF BIFURCATION, DEL NORTE CANAL. taries are diverted by practically bifurcating the main branch, the latter thus terminating in two distributaries, in the heads of which are placed regulating gates (Fig. 55). 2OO DISTRIBUTARIES. DISTRIBUTARY HEADS DISTRIBUTARY PIPES. 2OI 202. Masonry Distributary Heads. In Europe and India masonry is employed almost exclusively in the construction of distributary heads. These are generally so built that the water passing from them can be measured and the volume turned into the private channels thus ascertained at any time. In PL XIX is shown the type of distributary head used on the canals of the Punjab. On the Mutha canals in Bombay a V- shaped weir is placed in the head of each private channel or lateral for the purpose of water measurement, while a water- cushion is built in the lower portion of the distributary head in order to diminish the shock of the falling water. The rules for the dimensions of water-wells or cushions are about the same as those given for main canals (Article 138). Distribu- taries are passed over or under each other or the country drain- age in flumes or siphons as are main canals (Chapter XIV). 203. Iron and Steel Distributary Pipes. Where water is conveyed in pipes instead of open channels, these are gener- ally of iron, steel, wood, or occasionally of cement. The iron or steel pipes are constructed of sheet metal, the varieties being spiral riveted pipe, converse lock-joined kalamined lap- welded pipe, and straight double-riveted pipe. The dimen- sions of these distributary pipes range from 6 to 30 inches in diameter, and the thickness of the metal is trifling, varying between No. 8 and No. 10 plate. With straight riveted pipe the distance apart of rivets in the rows ranges from 1.33 to 1.40 inches, and the distance between any two rows is about f of an inch. This wrought-iron or steel pipe is invariably coated with hot asphaltum by inserting the pipes in a tank of refined asphaitum fluxed with crude oil heated nearly to burning point. This class of pipe will bear pressures of from 100 to 200 pounds per square inch. In laying it air-valves are attached at all high places, and an air standpipe generally at the highest point, besides which blow-offs are placed at proper intervals. 204. Wooden Distributary Pipes. There are several types of patented wood pipe. That which is now finding most favor is the invention of Mr. C. P. Allen of Denver and is known as the Colorado wooden pipe (Fig. 56). It is made 202 t DISTRIBUTARIES. of varying sizes from 20 to 36 inches in diameter, the walls of the pipe being formed of longitudinal staves braced together with iron or steel bands. These staves are shaped on the broad sides to cylindrical circles and the edges to true radial lines, so that when put together they form a perfectly cylin- drical pipe. To join the ends of the staves, a thin metallic tongue is inserted which is a trifle longer than the width of the stave and cuts into the adjoining ones. The confining FIG. 56. COLORADO WOODEN PIPE. bands are of round or flat iron or steel of from f to f inches in diameter and are shipped from the factory as rods, provided at one end with a square head and at the other with a thread and nut. They are bent on the ground on a bending-table and coated with mineral paint or asphalt varnish, and are cut about 6 inches longer than the outside circumference of the pipe, on which they are slipped loose. These confining bands are placed at varying distances apart, according to the press- ure which the pipe has to bear. 205. Rotation in Water Distribution. The water in dis- tributaries can be most economically handled if a system of rotation be employed in admitting it to the heads of the private channels. It is more convenient and economical to ROTATION IN WATER DISTRIBUTION. 2O3 move water in as large volumes as possible. This may be done by regulating the amount admitted to the private chan- nels and the periods of time in which they shall receive it. Thus the outlets to these channels may be closed in the first length of the canal for four days, in the second for three days, and so on ; and then this order may be reversed, the period of rotation being such as to change the length of closure along the various portions of the canal. It is better to impose these systems of rotation on long portions of the distributary at once, as the effect in forcing the water down to the tail of the distributary is then more noticeable. Thus if a distributary be 20 miles in length and all the outlets in the first 5 miles be closed, those in the second 5 miles opened, those in the third 5 miles closed, and those in the fourth 5 miles opened at the same time, the effect will be to produce a stronger head and to carry the desired amount into all the channels in the last portion of the canal ; then for a period of a few days this order may be reversed and without difficulty the maximum duty obtained from the water in the distributary. To make this system effective rules should be made compelling irrigators to accept water when their irrigation heads are open, and refusing it to them when their turn has gone by. CHAPTER XVI. APPLICATION OF WATER, AND PIPE IRRIGATION. 206. Methods of Applying Water. The cultivator ap- plies water to the crops by various methods, depending chiefly on the nature of the crop and the slope of the surface of the ground. These methods are : 1. By absorption from water sprinkled over the surface. 2. By filtration of a sheet of water downward through the surface of the soil. 3. By lateral percolation from an adjacent source of sup- ply. 4. By absorption from a subsurface supply. The first method includes irrigation by nature in the form of rain, or by sprinkling with a watering-pot or hose. This method is of such simple character as to require no further consideration here. The second method of irrigation is called flooding, and is accomplished in three ways, depending on the character of the crop and on the slope of the soil : 1. Flooding of meadows by simply conducting a ditch along the upper slope of the land and allowing the water to flow from this completely over the meadow. 2. Flooding by checks, by dividing gently sloping surfaces into level benches by means of check levees and permitting the water to stand in these as in still ponds. 3. Flooding by the checkerboard system, by dividing nearly level ground into squares by surrounding levees and allowing the water to stand in these. The third method of application is generally called the furrow method and is accomplished in four ways : I. By running small ditches close to fruit-trees and vines, and allowing the percolation from these to moisten their roots. 204 SIDE HILL FLOODING OF MEADOWS. 205 2. By letting a large number of small streams flow from flumes" through ditches between fruit-trees and vines, and allowing the water to percolate from these to their roots. 3. By flowing the water in small streams through the fur- rows between such crops as potatoes and corn, and thus grad- ually moistening them. 4. By drilling grain in rows or shallow furrows and running the water through these. This is practically a combination of flooding and sidewise soakage. The fourth method of irrigation is conducted by laying pipes underground and having outlets in these under each fruit tree ; or by so placing these outlets that the water escaping there- from shall moisten the roots of vines and trees near by. 207. Sidehill Flooding of Meadows. This method is the most wasteful of water, but it is that most commonly practised FIG. 57. DIAGRAM ILLUSTRATING FLOODING OF MEADOWS. in the cultivation of grass and cereals. Wild meadow lands and hayfields are flooded by simply turning the water on them 2O6 APPLICATION OF WATER, AND PIPE IRRIGATION. when the slope of the ground is sufficient and allowing it to sink into the soil. To accomplish this the water is made to enter the field at its highest point in a ditch conducted around an upper contour of the field. Breaks are made at intervals in the side of the ditch, and the water being allowed to flow through these, finds its way in a thin sheet over the field (Fig. 57). This method is very expensive of water and can be employed on but few soils, since clayey soils bake or parch, forming a thin crust which kills the growth of plants. Instead of making breaks in the side of the ditches checks are sometimes formed by little dams of earth or wood. 208. Flooding by Checks. This method consists in run- ning check levees around the slope of the land on contour lines. These are low ridges of earth about I foot in height, turned up with a plough or scraper and placed at such distances apart that the crest of each shall be on a level with the base of the check above it (Fig. 58). If properly built these checks CROSS SECTION Oft a-b a & FIG. 58. IRRIGATION BY SYSTEM OF CHECK-LEVEES. will last for many years, and the field may be ploughed and re- ploughed without injury to them or their in any way affecting the handling of the crops. In comparatively level country like FLOODING BY CHECKERBOARD SYSTEM OF SQUARES. 2O? i that in Kern county, California, the distributary ditches are placed as much as a quarter of a mile apart, their banks form- ing two of the bounding ridges or levees, the third or lower boundary being a contour levee connecting the ditch banks. The less the height of this levee the better, because the quan- tity of water spread over the land will be of more uniform depth and will interfere less with ploughing and harvesting; the greater the width of the levee base the better. From 6 to 12 inches is the best height and from 15 to 20 feet the best width of base. In such country as that described the checks range from 10 to 50 acres each in area and require from 12 to 20 miles of levee per square mile of check, while a mile of levee contains about 3000 cubic yards of earth. The water is run through the ditches (Fig. 58) and admitted by gates into each separate check. When the latter is full the water is drawn off to the next lower level, or if the soil is porous it is allowed to stand until it has been absorbed. 209. Flooding by Checkerboard System of Squares. This method is practised extensively on the level plains of Southern Arizona and in India. The fields are divided into squares of from 20 to 60 feet on each sicje (Fig. 59), and these are separated by ridges or levees of from 10 to 12 inches in height from which openings are made leading from one square to the other. In some cases the fields are divided into much larger squares, often of an acre in extent, depending on the slope of the ground. Again, especially in India, very small squares are employed, and the height of the dividing ridges is made as low as 6 inches, so that these do not interfere materi- ally with the harvesting and ploughing of the fields. The chief objection to this method is the obstruction created by the check levees. When these can be placed far enough apart they interfere but little with the operations of the cultivator: other- wise he must use spade and hoe instead of plough. Water is admitted to one square at a time and is either permitted to soak into the soil or is drawn off to be used in the next square below, much as in the check method. The chief crops irrigated by this method are hay, grain, and vege- 208 APPLICATION OF WATER, AND PIPE IRRIGATION. tables. Where flooding is practised by checks or squares, any- where from 4 to 12 inches in depth of water is let on at a single watering. The number of these waterings may range between two and five in a season, according to the crop, soil, and climate. Rice and sugar cane are irrigated in India and uuitpniNMHraflQmflMmi ' . . jpffii " %IWiDW|T!lOipJimV|liJl!l3Jii ^; 1; Cross Section on a - h. FIG. 59. FLOODING BY SYSTEM OF SQUARES. South America by squares. These crops require a very large amount of water, and as a consequence the height of the levees is rarely less than a foot and is often greater. These are filled with water and it is allowed to stand on them for long periods of time, the soil being seldom permitted to dry. 210. Flooding by Terraces. This method is employed chiefly in India and China, and has recently been adopted on a small scale in the neighborhood of Newcastle, California. It FURRbW IRRIGATION OF VEGETABLES AND GRAIN. 2OQ consists of laying out steeply sloping sidehill ground in terraces, the lower sides of which are surrounded by high levees. These are practically exaggerated forms of checks, and as employed in California are maintained and operated on the sa:"2 general principle, though they receive a large proportion of their water supply from the drainage of the hillsides above. As employed in india or China, these terraces also receive their water supply chiefly from the drainage above, and hold it as in a small tank or reservoir of a few feet in depth. As the water soaks into the soil of the terrace, rice or similar crops are sown, and the amount of moisture retained in the earth by such a volume of water entering it is sufficient, with the addition of what may be received from occasional rains, to irrigate the crops. 211. Furrow Irrigation of Vegetables and Grain. This method is practised by laying the field off in shallow ditches run around its upper slope. From these ordinary plough or V-- shaped furrows radiate down the slope of the field, and between FIG. 60. FURROW IRRIGATION OF GRAIN. these the vegetables, potatoes, or grain are planted. Where the country slopes more irregularly or steeply the furrows are run at various angles down the slope in such manner that their grade shall not be too steep. The water is then turned into a few of these furrows at a time by blocking the ditch above with a clod 2IO APPLICATION OF WATER, AND PIPE IRRIGATION. of dirt or a board (Fig. 60), and the water penetrates by sidewise soakage to the crops. Corn is irrigated by the furrow method by ploughing a ditch along the upper slope of the field as above described, and by drilling the grain down the slope of the field radially from this ditch and permitting the water to enter a few of the drill rows at a time. Grain fields are sometimes pre- pared for this method of combined flooding and furrow irriga- tion by roiling the field after the grain is planted with a heavy roller on the surface of which are angular projections of from ~J to I foot apart and a few inches in height. These make grooves in the surface of the soil in a direction parallel to the ^lope, and the water is admitted to these and permitted to flow through them as in the case of ploughed furrows or drill rows. 212. Combined Flooding and Furrow Irrigation of Or- chards. Where orchards are directly flooded the tendency ..of the water is to bring the roots to the surface and thus en- feeble them. To prevent this furrows are run from the upper FIG. 61. FURROW IRRIGATION OF ORCHARDS. ditches, generally in a double row, one on either side of and at a short distance from the trees or vines (Fig. 61). By this means the water percolates into the soil and reaches the roots of the tree by sidewise soakage at some depth beneath IRRIGATING ORCHARDS BY SMALL FURROWS. 211 the surface, thus moistening and encouraging their growth. Another method of flooding orchards is to protect the trees by earth ridges thrown up so as to prevent the water from reach- ing within 3 to 4 feet of them. In this method the entire field is flooded with the exception only of the areas immedi- ately adjacent to the trees. This practice is wasteful of water, as much more is employed than is required. Olive and orange trees are watered from three to four times in a season, vines once or twice and often not at all after the first few seasons. 213. Irrigating Orchards by Small Furrows. This method is practised as yet chiefly in the neighborhood of San Bernardino valley, California. The principle underlying this method is that the ground shall be put in the condition which it would be in after several days of long soaking rain, rather than in the condition which it would be in after a small cloud-burst, which is the condition resulting from most other methods of surface irrigation. This is done not by running large streams of water through the furrows for a short period of time, but by running small streams through them for a long time. It is accomplished (Fig. 61) by running a number of ploughed furrows between the rows of trees, the nearest furrow not being closer than 3 feet from the trees, and the distance between furrows from 2 to 3 feet. The volume of each of the streams running through these does not exceed one four-hundredth of a second-foot, and the water is run through them for two and three days at a time. Where the soil is not too loose or sandy this method seems to give the best results for fruits and vines and may be used with some success on grain and corn. , In order that the method shall be successful, the laterals from which the furrows are filled and which come from the main distributary must have a uniform depth and slope to a degree which cannot be secured in open earth. This is accomplished by running wooden laterals or flumes along the surface of the ground down its slope. These simple flumes are but a few inches in cross-sectional area, generally the width 212 APPLICATION OF WATER, AND PIPE IRRIGATION. of a plank at base and on the sides. They are given a suffi- cient grade to produce a good velocity and where the natural slope is too great falls are introduced. The water escapes from these flumes into the furrows through auger-holes bored in their sides opposite each furrow and on a level with the bottom of the flume (Fig. 61). The flow through these holes is regulated by wooden buttons or plugs which are inserted in them. For small orchards, these flumes generally have a capacity of about -J a second-foot. Fruit trees thrive well on from three to five waterings and vines on from two to three waterings when supplied by this method. 214. Subsurface Irrigation. Irrigation from beneath the surface, or sub-irrigation, is the most perfect method of supply- ing water to plants. The idea is to replace soakage from above by means of flooding or furrows, by absorption from below, which, to be perfect, should not wet the surface. This is effected by laying pipes underground, and these derive 'their supply from distributaries which are usually sheet-iron or steel pipes. While the cost of preparing land for this method of irrigation is relatively great, it is more than repaid by the sav- ing in water charges, since the duty of water is great, reaching from 500 to 1000 acres per second-foot. This method has been most extensively employed among the valuable fruit lands of Southern California, and where these lands are di- vided into and sold in orchard lots of from 10 to 20 acres in area, the distributing pipes are carried to the highest point in each one of these lots, and from this the sub-irrigation pipes are conducted through the orchards. 215. Sub-irrigation Pipes. These are made of sheet-iron or steel or of some porous or glazed material, the former being usually a combination of cement, lime, sand, and gravel, with a small admixture of potash and linseed oil, and are known as asbestine pipes. Glazed earthenware pipes are becoming more popular than any other form. Asphalt-concrete pipes have been successfully employed for sub-irrigation and have the advantage over simple concrete pipes of being impervious to water. These are united by heating so as to form a continu- SUB-IRRIGATION PIPES. 213 ous pipe. These distributing pipes are usually made in various dimensions, according to the circumstances under which they are to be used and the area which each is to control. In some cases they are as small as 2 inches in diameter, and from this they range to 6 inches where the principal distributaries are reached. 216. Method of Laying Pipes. Sub-irrigation pipes are laid in open trenches at a depth of I to \\ feet below the sur- face, parallel to the rows of trees or vines in the orchard, and the trench is then filled in with earth. A method has been attempted of laying the pipes by means of machinery, though as yet this has not met with success. Irrigation is effected from these pipes sometimes by cutting a hole on the upper side and inserting therein a wooden plug opposite each tree or vine. Each plug is surrounded by a larger standpipe set loosely on top of the distributary pipe, open at the bottom and reaching to the surface of the ground for the purpose of keeping the dirt away from the outlet and rendering it acces- sible at all times for inspection. The process of irrigation consists in simply turning the water off or on from the main pipe, when it finds its way through the outlets, fills the standpipe, and slowly percolates to the surface of the ground. One of the great objections to the use of pipes for sub-irrigation is the necessity for having these small holes or openings from which water can escape, and the resultant danger to the pipe of roots growing into the open- ings and clogging or destroying them. If muddy water is let into the pipe there is danger of clogging unless sufficient pressure can be used to flush them. One of the most satisfac- tory methods of letting the water escape consists in cutting a section several inches in length out of the continuous pipe where the plug-hole should be inserted, and by replacing it by a U-shaped shoe placed below the cut in the pipe. A tile a little longer than the gap covers it and water escapes between the two surfaces. By this method of irrigation plants do not re- ceive the fertilizing elements brought to them by the sediment carried in surface waters. On the other hand, the pipes have 214 APPLICATION OF WATER, AND PIPE IRRIGATION. the advantage of acting as drains to carry off surplus water and thus prevent the rise of alkali and other evils attend- ing supersaturation, especially as the water, when properly handled, does not reach the surface and evaporate there. 217. Measuring Sub-irrigation Waters. In the Ales- sandro district in California a water-measuring apparatus is em- ployed which consists of a 4-inch iron standpipe resting on the 6-inch vitrified service-pipe (Fig. 62). At the top of the stand- FIG. 62. ALESSANDRO HYDRANT. pipe a scale is so arranged that the amount of water flowing through can be measured by simply reading it. A valve inside the standpipe, which can be locked by a simple device, is oper- ated by a screw attachment and admits the proper amount of water. On the outer surface of the standpipe is a pressure- gauge which shows the head of water on the measuring-slot. The unit of measure used on these pipes is the miner's inch. This device has met with some favor, but is open to the same objection as all similar water meters, namely, that it is expensive and troublesome, requiring much attention for its proper management. WORKS OF REFERENCE. 218. Works of Reference. Canals and Canal Works. BAROIS, J. Irrigation in Egypt. Paris, 1887. Translated by Major A. M. Miller, U.S.A. War Department, Washington, D. C. BIRCHA. Distribution of Water from Irrigation Canals. Proc. Inst. C. E.,vol. 72. London, 1882. BUCKLEY, ROBERT B. Keeping Irrigation Canals Clear of Silt. Proc. Inst. C. E., vol. 58, Part IV. London, 1879. Movable Dams in Indian Weirs. Proc. Inst. C. E., vol. 60, Part II. London, 1880. CAUTLEY, COL. SIR PROBY T. Ganges Canal Works. 3 vols. London, 1860. DERRY, J. D. Victoria Royal Commission on Water Supply. Fourth Progress Report. Melbourne, 1885. FLYNN, P. J. Irrigation Canals and other Irrigation Works. San Francisco, Cal., 1892. HALL, WM. HAM. Report of the State Engineer to the Legislature of California. Part IV. Sacramento, Cal., 1881. Irrigation in Southern California. Sacramento, Cal., 1888. HERSCHEL, CLEMENS. The Holyoke Dam. Trans. Am. Soc. C. E., vol. 12. New York. LEVINGE, H. C. Soane Canal. Professional Papers, VII. Roorkee, India, 1870. MONCRIEFF, COLIN C. SCOTT. Irrigation in Southern Europe. E. & F. N. Spon, London, 1868. MULLIN, LiEUT.-GEN. J. Irrigation Manual. E. & F. N. Spon, New York and London, 1890. MEDLEY, LIEUT.-COL. J. G. Manual of Irrigation Works. Thomason Civil Engineering (College, Roorkee, India, 1873. NAVIGATION DE LA SEINE, Exposition Universelle Internationale de 1889, Paris. Imprimerie Nationale, Paris, 1889. RONNA, A. Les Irrigations.' Firmin-DidotetCie. 2 vols. Paris, 1889. SCOTT, JOHN. Irrigation and Water Supply. Crosby, Lockwood & Co., London, 1883. STEWART, HENRY. Irrigation for the Farm, Garden, and Orchard. Orange Judd Co., New York, 1889. VERNON-HARCOURT, T. F. Fixed and Movable Weirs. Proc. Inst. C. E., vol. 60, Part II. London, 1880. WEISBACH, P. J., and Du Bois, A. JAY. Hydraulics and Hydraulic Motors. John Wiley & Sons, New York, 1889. WHITING, J. E. The Nira Canal. Proc. Inst. C. E., vol. 77, p. 423. WILCOX, W. Egyptian Irrigation. E. & F. N. Spon, London and New York, 1889. WILSON, H. M. Irrigation in India. Twelfth Annual Report U. S. Geological Survey, Part II. Washington, D. C., 1891. PART III. STORAGE RESERVOIRS. CHAPTER XVII. LOCATION AND CAPACITY OF RESERVOIRS. 219. Classes of Storage Works. A storage work is any variety of natural or artificial impounding reservoir or tank for the saving of superfluous or flood waters. Storage works are employed to insure a constant supply of water during each and every season regardless of the amount of rainfall. They may be classified according to the character and location of the storage basin, or the design and construction of the retaining wall or dam which closes it. Under the former classification are: 1. Natural lake basins; 2. Reservoir sites on natural drainage lines, as a valley or canyon through which a stream flows ; 3. Reservoir sites in depressions on bench lands ; 4. Reservoir sites which are in part or wholly constructed by artificial methods. Under the second classification are: 1. Earth dams or embankments; 2. Combined earth and loose-rock dams ; 3. Hydraulic-mining type of dam, or dams constructed of loose rock or loose rock and timber ; 4. Combined loose-rock and masonry dams ; 5. Masonry dams. 220. Relation of Reservoir Site to Land and Water Supply. There are several modifying considerations affecting 216 RESERVOIR SITES. 2 1/ the value of the reservoir site. Among the more important of these are : 1. The relation of the site to the irrigable lands ; 2. The relation of the site to its catchment basin or source of supply ; 3. The topography of the site ; 4. The geology of the site. The cost of water storage depends chiefly on the last two, while the value of the site for storing water and the possibility of filling the reservoir depends on the first two. In considering the relation of the reservoir site to the irri- gable lands, the former should be situated at a sufficient alti- tude above the latter to allow of the delivery of water to them by natural flow. The area of these lands should be sufficient to require the entire amount of water stored, that the maximum return may be derived from water rates, and the reservoir should be as near as possible to the irrigable lands in order that the loss in transportation shall be a minimum. It not infrequently happens, however, that the reservoir is of neces- sity located at some distance from the irrigable lands, thus requiring either a long supply canal or that the water be turned back into the natural drainage channel, down which it will flow till diverted in the neighborhood of the irrigable lands. This is very wasteful of water, since the losses by absorption, percolation, and evaporation are great, especially if the bed of a natural channel is used as a portion of the supply line. As related to the source of supply, the reservoir site may be on a perennial stream the discharge of which is more than sufficient to fill it, in which case the supply is assured. It may be on a stream the available perennial discharge of which is sufficient to fill it in times of flood. It may be on an intermit- tent stream subject to occasional flood discharges of sufficient volume to fill the reservoir so as to enable it to tide over a couple of seasons of moderate supply. Or the reservoir site may be situated above and away from any natural drainage line, in which case it will receive its supply either by a canal diverted from some perennial stream or from artesian wells or springs. 218 LOCATION AND CAPACITY OF RESERVOIRS. 221. Character of Reservoir Site. If situated in a natu- ral lake basin, a short drainage cut or a comparatively cheap dam or both may give a large available storage capacity. Such sites are usually the best and cheapest, costing for construction as low as 20 cents per acre-foot stored, and in unfavorable cases rarely exceeding $3 per acre-foot. The most abundant reser- voir sites are those on natural drainage lines, though these are usually the most expensive of construction owing to the precautions which it is necessary to take in building the dam to provide for the discharge of flood water. Almost equally abundant are those reservoir sites found in alkaline basins or depressions on bench or plain lands, especially on the plains sloping to the eastward of the main Rocky mountains and in the foothills of the Sierras in California. The utilization of such basins as reservoir sites is comparatively inexpensive; they can be converted into reservoirs by the construction of a deep drainage cut or of a comparatively cheap earth embank- ment. Scarcely any provision is necessary for the passage of floods. The heaviest item of expense in connection with these sites is the supply canal for filling them from some adjacent source. Artificial reservoirs are occasionally constructed where water is valuable, by the erection of an earth embankment above the general surface of the country or by the excavation of a reservoir basin by artificial means. Such constructions are usually insignificant in dimensions, as the expense of building large reservoirs of this kind would ordinarily be prohibitive. Shallow reservoirs should not be constructed. The loss from evaporation and percolation is proportionately great, and the growth of weeds is encouraged where the depth is less than seven feet, by the sunlight penetrating to the bottom. 222. Topography and Survey of Reservoir Sites. Knowing the position of the irrigable lands, a careful prelimi- nary survey should be made of the entire neighborhood to dis- cover all possible reservoir sites, and the outlines of the catch- ment basins of each of these should be mapped, while stream gauging should be conducted and examinations and inquiries TOPOGRAPHY AND GEOLOGY OF RESERVOIR SITES. 219 made to ascertain the minimum discharge of the streams and their flood heights, as well as the amount of evaporation and percolation (Chapters III and IV). Having determined in a general way upon the location of the reservoir site, a detailed survey of it should be made. This can ordinarily be best done by means of a plane table. The highest possible point to which the dam may reach may be taken as a basis and a top contour run out closing around the entire site. In addition to this a main traverse should be run through the central or lowest line of the site from the dam to the extreme end where it will connect with the top contour. Cross-section lines may be run from this with the plane table, and the topog- raphy of the site sketched in 5-foot contours and plotted to some large scale, preferably 500 to 1000 feet to the inch. Where the country is open and unobstructed by timber the site may be triangulated from one side, as a check on the cross-section lines, and where the slopes are even these may be best determined by means of gradienter lines run up and down them from a base contour. Such a map will enable the engineer to deter- mine the capacity of the reservoir for various depths of water. The dam site should be surveyed in greater detail, several possible sites being cross-sectioned and mapped in i-foot con- tours and at a scale of perhaps 100 feet to the inch. This work should be done with transit and chain, whereas in the reser- voir survey the -stadia may be satisfactorily employed on most of the cross-section lines. With such a knowledge of the topog- raphy of a catchment basin and of the reservoir and dam sites as the resulting map will give, the engineer may readily com- pute the cost of construction of dams for various heights as well as the contents of the reservoir for these heights, and thus determine what height of dam will be most economic of con- struction, for there is always some height which will render the cost of storage a minimum. 223. Geology of Reservoir Sites. Having ascertained the desirability of the reservoir site topographically and hydro- graphically, a few test borings or trial pits should be sunk at various points on the reservoir basin, and especially at the dam 220 LOCATION AND CAPACITY OF RESERVOIRS. site, to ascertain the character of the soil and the dip of the strata underlying the proposed reservoir. The geological con- formation may be such as to contribute to the efficiency of the reservoir, or it may prove so unfavorable as to be irremediable by engineering skill. A reservoir site which is situated in a synclinal valley as shown in A, Fig. 63, is the most favorable. FIG. 63. DIAGRAMS ILLUSTRATING GEOLOGY OF RESERVOIR SITE. In this the strata incline from the hills towards the lower lines of the valley, and any water which may fall on to these hills will find its way by percolation through the strata into the reservoir, thus adding to its volume. An anticlinal valley is the least favorable for a reservoir site (Fig. 63, B). In such a valley as this the strata dip away from the reservoir site and would permit of the escape of much of the impounded water, percolation through the strata leading it off to adjoining valleys. A class of geological formation intermediate between these two is that represented in C, Fig. 63, in which the valley has been eroded in the side of strata which dip in one direc- tion. Here the upper strata lead water from the adjoining COST AND DIMENSIONS OF STORAGE RESERVOIRS. 221 |i O co m CO *^" O w O co O O CO M P o in ^ *^ co co ** m . CO N a> N o *i- TJ- co CM CO M M Length on Top, Feet. cS CO O in co O O O^corj-c CON c* O cowinmm m O O r^ o O co in O O O oo O O^ o C^ N m 8 \n o Tfr 111 J in m *t- "tO m r-. f-' -3- O Oco' sO m m c* O co M r** Q\ vO O O' *t co W co o 8 SB! -^ 1 ooooooooo m OvOOOOOO mO O moo cofinco 828888 g n CO cTco OOO cooo mrj- ^J-COONCO MMM M a in W O >n M CO M CO I-x i : 1 : : L ; t o : : : : : 8 : : : : S timber. . "o i : : : : "S * c n m c c ='**'" V V* 1 3 . rt Locality. rt 'c :::::: 2 :: (rt 3 "c ' : g :ornia . . . i! "fl U -O - ^ 3 tC a c o. ~? ~H {/)(/){/)< "3 ^ - "o U ^ U < 'cd U of Reservoi . ' i ' ' ' "** j> ^ : : : g rt : : ' : -g 1 ; V i i Sweetwat ^ > u a; M tiiigissc 2i^5^^=2 PQD:(XOQ2QO S - 2 i > -s ;. ! rt bo u 'w 3 & 8 I 1 U J S < W U Walnut G Bowman . 222 LOCATION AND CAPACITY OF RESERVOIRS. hills into the reservoir, while the strata on the lower side tend to carry it off from the reservoir by percolation. In such a case it is probable that the reservoir would neither gain nor lose. If the surface proposed reservoir site is composed of a deep bed of coarse gravel or sand or even limestone, crevices in the latter or between the interstices of the former will tend greatly to diminish the capacity of the reservoir by seepage from it. Again, the geologic formation may be most unfavorable, yet if the surface of the reservoir site be covered with a deep deposit of alluvial sediment or of clay or dirty gravel or other equally impervious material, little danger may be apprehended from loss by seepage. 224. Cost and Dimensions of some Great Storage Reservoirs. In Table XI are given the capacities, material, dimensions of dam, and cost per acre-foot stored of some of the great storage reservoirs which are used for purposes of irrigation. CHAPTER XVIII. EARTH AND LOOSE-ROCK DAMS. 225. Earth Dams or Embankments. The choice of t*he material of which the dam shall be constructed, whether it shall be of earth, masonry, or loose rock, is dependent largely upon the character of the foundation and the cost of transportation. Earth dams when well constructed are fully as substantial as those of masonry, and in many cases they are far more so. In countries subject to earthquakes, or where the rock foundation is not thoroughly homogeneous, an earth dam is decidedly preferable to one of masonry. They are usually cheaper, and where transportation is expensive they are very much cheaper. Providing a substantial and abundant wasteway of a sufficient capacity to carry the greatest possible flood be provided, an earth dam is generally to be preferred in mild, damp climates. In warm, dry climates they are liable to dry and crack.- For reservoirs over 100 feet in depth masonry dams are to be pre- ferred, as earth dams are nearly as expensive when transporta- tion is cheap, and are more liable to be badly built. As before stated, the choice between the two depends largely on the foundation. A substantial masonry dam can- not be founded on loose gravel or soil ; an earth dam should rarely be founded on rock, owing to the difficulty of making a tight joint between it and the earth. There are three general types of earth dams: 1. Earth dams having a central core or wall of puddled earth ; 2. Earth dams having a central core of masonry or wood ; 3. Earth dams built up in layers of homogeneous material, without central core or puddle facing. 223 224 EARTH AND LOOSE-ROCK DAMS. 226. Dimensions of Earth Dams. An earth dam may be supposed to fail in two ways, either by yielding to the hori- zontal pressure of the water overturning it, or by sliding on its base. The simplest form of calculation clearly demonstrates what is fully acknowledged by all engineers, namely, that the dam will not be destroyed by overturning or revolving about its lower toe ; hence the only theory as to its destruction is that it may slide on its base. The conditions of stability will be satisfactory when the horizontal component of the water press- ure against the bank equals the weight of the latter plus the vertical pressure exercised by the water to hold it down, and multiplied by the coefficient of friction. Such a case is rarely or never apt to occur. In point of fact such structures usually fail, not by overturning or sliding on their bases, but by the disintegration of their particles due to the percolation of water. When subjected to the contact of water earth loses a cer- tain amount of its stability, and therefore it is customary to give the inner slope of an embankment a greater inclination than the outer slope. These slopes depend on the character of the material, When the outer slope will stand with an in- clination of I on 2\ the inner slope should be I on 3. The interior and exterior slopes of earth dams may be con- sidered as planes forming together an angle of not less than 90 degrees, and the figure should be so formed in order to in- crease its stability, that lines of pressure passing from the interior faces at right angles may fall within its base. As one cubic foot of rammed earth weighs about 100 pounds and a cubic foot of water 62^ pounds, we find the base of a prism resisting the lateral thrust of the water does not require to be more than two thirds of the depth of the column it supports. Hence all quantities above that are due to the natural slopes, the stability of the dam, and the prevention of percolation. In large works it is frequently a matter of close calculation to determine which will be the more economical, dams exclusively of earth or those whose inner slopes are supported by retaining walls of masonry. The outer slope of the dam may vary be- tween I on i-J and I on 3^, according to the character of the DIMENSIONS OF EARTH DAM S FOUNDATIONS, 22$ material. Light sand requires the flattest slope. A firm mix- ture of gravel and clay will stand a slope of about I on i. The inner slope of the darn should be about on I greater than the outer slope. It is not unusual, as in the case of the Ashti dam (PI. XX), to make the inner slope near the top a little steeper than the lower portion of the slope, the object being that a steep slope from i on i to i reflects the waves, while a flatter slope breaks them up. The top width of the dam depends somewhat on circum- stances. A top width of 6 feet is perhaps the minimum which should be employed, and for a high dam this is usually too small. A good rule as to the minimum top width of earthen dams 50 feet in height and over is to make their breadth 10 feet. For dams under 50 feet the top width should be 8 to 6 feet. As the dam settles in course of time, its top should be built up by adding material to the required height. The dam should always be several feet higher than the highest flood mark in order to prevent waves from topping it. Thus the height of the dam above the crest of the discharge weir should be in which D equals the depth of water in the reservoir above the v/eir crest at maximum flood ; ^equals the height of the top of the stone pitching above the surface of the maximum flood ; C is a constant equal to 2 or 3 feet according to cir- cumstances, and is equal to the vertical height of the top of the dam above the top of the pitching. 227. Foundations. The foundation of an earth dam should be examined with great care. The best material on which to found it is sandy or gravelly clay, fine sand or loam. Such a structure should never be built on shale or slate or on firm rock. Great care should be taken in searching for springs or quicksands in the foundation. Sometimes a quicksand may be discovered at some little depth beneath a hardpan or other suitable foundation. In such a case it is sometimes possible to 226 EARTH AND LOOSE-ROCK DAMS. seal over the quicksand under the embankment, and found the latter on the upper stratum. Such an expedient is not entirely free from risk, and great care should be taken in joining the toe of the embankment to the foundation material, if necessary spreading earth and clay over the surface of the valley for some distance on either side of the dam. The first thing to be done in preparing the site of the dam is to clean off all soil, removing it to a depth equal to that penetrated by the roots of the grasses, bushes, and trees. If firm and impervious, the soil may be scored by longitudinal trenches, which will give the proper adhesion between the foundation and the embankment, and prevent the slipping of the latter. If a puddle wall or masonry core is to be built into the dam, the foundation for this should be sunk to a suf- ficient depth to secure its permanence. If a homogeneous dam is to be built and the foundation material exposed is not im- previous, a trench should be dug, and this filled with some puddle material, as clayey gravel or gravelly loam, moistened and rolled or packed in layers. 228. Foundations of Masonry Core and Puddle Wall. No rule can be laid down for the depth to which the founda- tions for the centre wall, if one is built, should be carried. If a rock foundation is encountered the problem is simplified, as the wall may be founded on this after removing the loose and disintegrated surface ; if the test pits or borings reveal only the existence of coarse or permeable strata, the masonry core must be carried well down. In some cases it has to be carried to great depths, though when this is the case a foundation con- sisting of a puddle wall would appear to be preferable. The finer the material, the better it is adapted for a foundation for the centre wall. Fine gravel and sand and clay, or even quick- sand when at a sufficient depth to prevent its being forced up, form good foundations. Where a puddle wall is employed instead of a masonry core or heart-wall, the same general precautions with regard to its foundation are necessary as for the foundation of the latter. Every care should be taken to insure it a firm seat on some impervious stratum. SP KINGS IN FOUNDATIONS PUDDLE W 'ALLS, ETC. 227 229. Springs in Foundations. It is a very common oc- currence to encounter springs in the excavations for the foun- dations of dams either of masonry or of earth. These springs are a great menace to the integrity of the structure, and it is due to their presence that some of the most disastrous failures of dams have occurred. Some engineers recommend that springs be taken up and carried away in proper drains securely puddled. This, however, is a very difficult operation and one rarely possible of accomplishment. When a single large spring is discovered this mode of treatment may be easily resorted to by following it back in a cutting until it can be taken up in a pipe. But ordinarily the foundation is underlain by a number of small springs, since water appears in such cases to rise from all over the surface of the stripped foundation. The best method of dealing with such cases is to strip the foundation of the inner embankment down to good firm earth, and then commence placing that part of the embankment which is next to the centre wall and advance it outward toward the toe of the slope with a view of smothering down the springs. Large springs frequently give trouble in closing the gap in the foun- dation of the centre wall. They may sometimes be carried up with the wall until a point is reached above which they do not rise, or they may be handled by reducing the width of the gap left in the wall until it becomes too narrow for the passage of the water. There are several methods of treatment, but the rule is to get the wall built up so that the water does not wash out the mortar and run through it. 230. Masonry Cores, Puddle Walls, and Homogeneous Embankments. There is still a wide difference among engi- neers as to the best type of earth dam. Occasionally in Eng- land and in a few cases in our own country earth dams have been built up homogeneously, the front or water face being covered with a deep layer of some puddle material, as clayey loam. This practice, however, is falling into disuse, and engi- neers now rarely trust to a puddle face alone for protection against leakage. A wooden or plank core should never be employed. The 228 EARTH AND LOOSE-ROCK DAMS. material is sure to rot and decay, while the smooth surface of the boards offers a most excellent line along which leakage water will travel until it finds an outlet. Again, it is impossible to make a wooden wall sufficiently substantial and heavy to withstand leakage and the tendency to rupture which may re- sult from the settling of the bank. The masonry core is in great favor with many engineers, both in Europe, India, and America. A central core of puddled earth is subject to rupture from the settlement of the embank- ment. Both are practically impervious to leakage. In build- ing them they must be carried sufficiently deep to reach some impervious stratum, and far enough into the side walls of the valley to prevent the passage around their ends of seepage water which would travel along their impervious faces. The construction of a dam composed for a portion of its length of earth and for the remainder of loose rock or masonry is dangerous, and the writer is opposed to such combinations. Moreover, masonry, either as a retaining wall, core, or culvert, is rigid, while the other material is flexible, and any settlement in the latter leads to rupture in the former. Furthermore, masonry offers a smooth surface for the travel of seepage water. The earth dam with masonry core is probably the most popular at present, but engineers to a limited extent in India and to a large extent in our western irrigation region are com- ing to favor the earth dam built up in homogeneous layers, each carefully rolled or tramped over in such a manner that the whole dam is a puddle wall. This character of construction has all the advantages of imperviousness to leakage if the work is well done, while it is free from the disadvantages possessed by dams with central cores, namely, a smooth surface along which water may travel, and liability to rupture in the wall. To be sure, the liability to rupture is very trifling, and is a mat- ter of sentiment and theory rather than fact, as probably no case is on record of such an accident occurring in a well-built dam. Still, a homogeneous earth dam (Art. 235) is one of the sim- plest and cheapest to construct, and may be so built up as to be practically indestructible. With such a form of dam a puddle MASONRY COKES. , 229 trench is usually excavated in the centre of the foundation and filled with puddle material to prevent leakage under and around the dam, and the material as laid down may be so selected as to get the finest and least pervious constituents in the front portion of the dam, leaving the heavier and coarser material to the rear to give stability. Such a form of construction practi- cally converts the dam into one having a puddle face of great thickness. 231. Masonry Cores. The primary object of a masonry centre wall is to afford a water-tight cut-off to any water of per- colation which may reach it through the bank. Where the masonry wall is employed, it is the dam proper, for it is this which retains the water in the reservoir, the earth embankment surrounding it on either side being only of service in keeping the centre wall from being thrown down. One of the great ad- vantages of the masonry core is that it affords an excellent op. portunity for making the connections with the outlet tower and the culverts for the discharge sluices. These masonry culverts running through the centre of an earth dam constitute one of the weakest points in its construction, and offer the greatest opportunity for the passage of seepage water. They can be so bonded with the masonry core as to form a part of it, and pre- clude the possibility of the water following along the culverts. The masonry core should be carried to a height equal to that of the sill of the escape-way, while in very high dams it is well to raise it to the extreme flood height. It should be as thin as possible in order to reduce its cost, yet as some move- ment may take place in the embankment owing to settlement, it should be sufficiently heavy to be self-supporting. A safe and usual rule is to give it a top width of 4 to 5 feet, and to increase its thickness toward the bottom at the rate of about I foot in 10. Sometimes this thickness is increased beyond the amount here stated. This centre wall should be composed of the best hydraulic masonry, preferably of concrete composed of sharp broken stone mixed with clean sand and Portland cement. Concrete, however, is not essential : rubble in cement is equally good, and ordinarily quite as convenient and satis- 230 EARTH AND LOOSE-ROSK DAMS. factory. When such material is used, however, stones of mod- erate size should be employed which shall not run through the wall from side to side, and for purposes of economy the rubble should be uncoursed, though very compactly and carefully laid. An excellent example of a masonry core or centre wall for an earth dam is that in the New Croton dam at Cornell's (Fig. 81). This masonry core is 18 feet thick at the base, where it is founded on rock, and retains the same dimensions for a height of 89 feet, above which it tapers to 6 feet in thickness at the top, which is 20 feet below the top of the embankment. 232. Puddle Walls and Faces. The puddle wall is not considered as satisfactory nor as efficient as the masonry wall, though it is much cheaper of construction in some portions of the West, where transportation is expensive. The proper ma- terial for a puddle is not always obtainable, while water for moistening it is frequently difficult to obtain in the arid region. It is difficult to prepare, and requires careful manipulation in placing it. A good puddle should, when placed, resemble in character and composition an unburnt brick. Where too much responsibility is rested in the imperviousness and security of the puddle wall it is frequently a menace to the structure, as it is rarely built with sufficient care. A puddle wall should have a thickness of 8 or 10 feet at the level of the water line, and should increase in thickness downward to the surface of the ground at the rate of about I foot in 10. Where a puddle wall is employed, the material of which it is constructed is usually clay, or gravel and clay moistened and puddled in layers of about 6 inches in thickness, and permitted to dry slowly. On either side of it selected material is usually placed, the remainder of the dam downward consisting of the poorer and most available material. As before stated, a puddle face is rarely employed. Where it has been used it consists generally of a covering on the whole inner face of a layer of puddle 8 or 10 feet in thickness at the base and 2 or 3 feet in thickness near the summit, and on the whole is placed a layer of common soil on which the rip- rap is laid. In a few instances the puddle face has been mixed PUDDLE TRENCH EMBANKMENT. 231 with small stones or furnace cinders as an obstruction to the passage of moles, gopher, or other vermin. 233. Puddle Trench. This is employed only where the dam is built up in homogeneous layers without a central wall. 1 1 consists of a trench excavated longitudinally the entire length of the dam down to some impervious stratum, or if none can be found, for a very considerable depth. This trench is then filled either with puddle material built up the same as is a puddle wall or with a wall of masonry built up as a core wall, and the material filling this trench is carried up several feet above the surface of the ground. The trench should be carried up the slopes of the surrounding hills till it terminates at a level with the top of the embankment, and its bottom should be level in all directions, all changes of level being made by means of ver- tical steps. The same rule applies to the foundation of a pud- dle wall or masonry core. One of the most excellent examples of a puddle trench is that illustrated in Plate XX, and employed in the Ashti dam in India. This trench was carried down to a hard bed of trap- rock, and in some places to consolidated clay. In this a puddle was laid in layers 4 inches thick which were reduced to 3 inches by watering and rolling. This puddle trench is rectan- gular in cross-section, 10 feet in width throughout, and gener- ally 1 6 feet in height to the summit of the material filling it. The crest of the material filling the puddle trench was raised to a height of I foot above the surface of the ground so as to form a water-tight junction with the earthwork of the dam. Across the bed of the river along the centre line of the dam the trench was made but 5 feet in width, and was carried down to bed-rock and extended 100 feet into the banks of the river on either side, and was filled with a wall of concrete. 234. Construction of Embankment. As ordinarily built the earth embankment changes outward from the central core, as before described, to a body of selected material on each side of it, the remainder of the dam being constructed of the most available common material. The result is a dam composed of 5 layers, each of different density and weight and HOMOGENEOUS EARTH EMBANKMENT. 233 each likely to settle in different amount. This material is car- ried up generally in layers of a foot or so in thickness, and the result is a structure not homogeneous in character and with a series of horizontal surfaces with cleavage and vertical lines on which settlement and shrinkage may occur. The material, when laid in the embankment, should be disposed in layers which are thicker at their outer edges than at the centre. When well built the centre third of the dam is composed of the best selected material, while on either side of it is laid com- mon soil, which is usually not so impervious to water as that in the centre. On the lower side of the dam is laid any heavy material available. The main object in constructing an earth dam which has some impervious central core is to make this central wall and a small portion of the bank in the rear and a large section in front impermeable to the percolation of water ; then the remainder of the bank to the rear is put in merely with the object of giving stability to the water-tight portion. 235. Homogeneous Earth Embankment. This type of dam is considered by the writer and many other engineers as the most safe and efficient as well as economic. It is gen- erally preferable in the arid region because of the saving in transportation of cement, rock, or selected materials for a pud- dle wall. Such a dam .should be of the same density through- out, and composed of material practically impervious to water. It should form in itself and with the natural material on which it rests a perfectly homogeneous mass. Practically it is diffi- cult to obtain such a structure, though the engineer should come as near as possible to the ideal. A puddle or masonry core is considered by some Western engineers as an element of weak- ness in the structure. They say that in a homogeneous earth dam the up-stream face is that point at which the water press- ure ceases either by the water ceasing to penetrate the body of the dam or by its having free egress from the down-stream side. The puddle or masonry wall will stop the small amount of water coming through a new dam, and this will accumulate in the earth against the core, and will finally permeate the whole body of the dam above the wall, thus causing the water 234 EARTH AND IOOSE-ROCK DAMS. pressure which should be exerted against the up-stream face to be exerted against the core. The whole duty of the dam is then performed by the masonry core and the material below it. If enough impervious material cannot be had to build the whole structure up homogeneously in layers, the up-stream third or half should be built of the best material available, the poor- est and heaviest being put in the lower side. These two classes of material should be well worked into one another so as to give a perfect bonding. This practically converts the principal third of the dam into a puddle face, only the whole structure is built up at the same time in irregular layers of I or 2 feet in thickness, and well tramped over or puddled. By not building it in uniform layers a better bond is given to the structure. With such a form of construction any water which may soak through the upper third will find free egress from the dam on its lower side. The result will be to keep water out of the dam if possible, but when it enters to pass it through quickly. In building a dam up in irregular layers in this way these layers should be so disposed that the outer edges or extremities of each layer shall be higher than the centre of the layer by from 2 to 4 feet. As built in the West with teams and scrapers, no runways should be provided, the teams being driven over the whole surface, thus adding to the density and compactness of the structure. As each layer is built up it is well to drag or harrow it, and then pass a heavy roller over it. The same re- sult can be produced by rolling it with a heavy roller having annular projections or rings on its surface. 236. Embankment Material. The ideal material of which to construct an earth dam is such a mixture of gravel, sand, and clay that all the coarser interstices between the particles of the former shall be filled by the sand, and that all the mi- nute openings between the particles of this material shall be filled by the still finer particles of clay. This would give such a composition that water would pass through it with the great- est amount of resistance, and the bank would be practically impervious. In practice, with proper care to mix the materials EMBANKMENT MATERIAL INTERIOR SLOPE. 235 so as to thoroughly incorporate them one with the other, the following proportions should be used : Coarse gravel i.oo cubic yard Fine gravel 0.35 " Sand 0.15 Clay 0.20 " Giving a total of about 1.70 cubic yards, which when well mixed, compacted, and rolled can be reduced to about \\ cubic yards in bulk. These proportions will rarely be obtained, but the effort should be to approach as nearly to them as possible in order to produce the best combination of materials. Weight is a valuable property in an earth embankment, and such a combination as above given possesses the greatest amount of weight obtainable with earth. The sand and gravel lack cohesiveness but have stability, while clay though cohesive is liable to slip if unsupported. The combination above given possesses the qualities of weight, cohesiveness, stability, and imperviousness, while the angle of repose or the slope which can be given is about midway between that possible with fine sand and that to be obtained with shingle or a mixture of sand and clay. If judgment be used in choosing materials, dirty gravel, or that possessing a large amount of soil and sandy matter, may often be found which will give nearly the propor- tions above specified. 237. Interior Slope and Paving. The interior slope of an earth dam is rarely made uniform, while the exterior slope though usually uniform is sometimes broken by a level bench (Fig. 81), the object of which is to prevent serious effect from the sliding of the embankment. This bench is usually made from 4 to 6 feet in width. On the interior slope one or more similar benches are sometimes introduced, though rarely more than one. In the case, however, of the great dam being built for the Citizens' Water Company in Denver the slope is to be broken by a number of benches. In addition to this break in the slope, it is not uncommon to give a lighter slope below 236 EARTH AND LOOSE-ROCK DAMS. the bench and a steeper inclination for the last 5 to 7 feet at the top of the inner slope (PL XX). This steepness at the top is to prevent waves at flood height from slopping over the crest of the embankment, the sharp angle breaking the waves up and reflecting them back. The bottom of the inner slope is some- times made steeper if the material will stand it, as it is not exposed to the air by the drawing off of the water as is the upper portion of the embankment. This interior slope is invariably paved with cobble-stones or dry rubble tightly driven home and carefully placed (PL XX). The object of this pitching is to protect the embankment against the erosive action of the waves, and its thickness de- pends on the height and violence of these. The maximum height of the waves depends on the fetch or distance from the shore where their formation commences, and may be determined by Stephenson's formula, X= i. 5 ^+2.5 where X equals the height of wave in feet and F equals the fetch in nautical miles. Rankine states that where an embank- ment of loose stone is exposed to the action of the waves it should be faced with blocks set by hand, the least dimension of any block in the facing being not less than two thirds the greatest wave height. The best way in which to lay the stones is to place them with broad ends downwards, rough squared stones being preferable, in order that they shall fit fairly close one to the other. The interstices should be packed with small stone chippings and finished off with earth (Fig. 81). The entire height of the inner slope need not be protected by a stone pitching. That portion of the slope which is below the level of the outlet sluices requires no pitching at all, as it will not be subjected to wave action. The lower portion of the exposed slope need be pitched with a lesser thickness than the upper portion, as the fetch will be less, and consequently the wave height less and its erosive action proportionately diminished. At the upper portion of the slope the pitching should be carried quite to the top of the embankment, and for EMBANKMENT WITH MASONRY RETAINING WALL. safety might be carried across the top, in order that any spray falling on the top of the embankment should do the least pos- sible amount of damage. It is customary to give the top of the embankment a slight inclination toward the reservoir, so that it will drain into it and not outward over the unprotected lower slope. For better protection of this exterior slope it should be planted with grass, or, better still, sods of consider- able size should be placed upon it a few feet apart, in order that the roots of these may spread and entirely protect it from the erosive action of rain and spray. 238. Earth Embankment with Masonry Retaining Wall. It is sometimes necessary to economize reservoir space, in which case one side of the embankment may be A FIG. 64. CROSS-SECTIONS OF KABKA DAM (A) AND EKRUK DAM (.5), INDIA. faced with masonry, though this combination is rarely success- ful or advisable. It has all the disadvantages of both earth and masonry dams without any additional advantages. The Kabra embankment in India (Fig. 64, A) is an example of this class of structure. It consists of a masonry wall on the front face of an earth embankment and having a steep batter of about 12 on I, while the outer portion of the embankment and the lower slope have the natural slope of the earth,, which is merely used to give stability to the masonry facing wall, the latter being the dam proper. 1 PECOS DAM, 239 The masonry may be put in as in the case of the Ekruk tank in India (Fig. 64, B). This consists of a masonry core of such dimensions as to practically form the entire dam, the earth being merely added to the bottom of the slopes to give stabil- ity. In this case the masonry dam has an inner slope of 12 on I, an outer slope of 2 on I, and a total height of 68 feet. Against it, on its upper side, is an earth embankment with a slope of I on 3, reaching to about 25 feet in height, and on the outer slope another earth embankment with a slope of I on 2, reaching to about 35 feet in height. Above this the masonry is unsupported. Still another method of using masonry with earth is where the inner slope of the dam is of earth, its water face being rip- rapped as before described and a puddle wall placed through its centre to prevent percolation. On the outer slope, in place of the usual mass of material intended to add stability, is built up a rubble retaining wall, the stones being set in mortar, the object of the wall being merely to retain the embankment, and not to prevent percolation ; also to avoid covering land below the dam which may be of value. 239. Earth and Loose-rock Dams. Pecos Dam. The dam at the head of the Pecos Irrigation Company's canal, in New Mexico (PL XXI), furnishes an excellent example of this combined construction. This dam is shaped in plan like the letter L, the re-entrant angle of which points up-stream. The <5 FIG. 70. ELEVATION, PLAN. AND CROSS-SECTION OF CASTLEWOOD DAM. is possible that in the future such a type of dam as this may become popular. It possesses all the good qualities of the loose-rock dam and need be no more expensive, since its slopes may be made a little steeper. It is doubtful if so steep a slope as 10 on i for the upper face is safe : probably 5 on i would be better, while i on i for the rear face is ample to give stability. In such a structure as this great care should be taken to firmly found it on solid rock or on a deep bed of hard and impervious clay, while the loose-rock centre should be carefully laid to prevent any inclination to slide or thr.K'- outward against the confining walls. CHAPTER XIX. MASONRY DAMS. 245. Theory of Masonry Dams. Masonry dams are employed both for diversion and storage works, and may be so constructed as either to permit flood water to pass over their crests or have it passed around one end. If the dam is to be used for storage purposes only, and a sufficient wasteway can be provided, it may be designed according to one of the theo- retical formulas or from one of the type profiles given here- after. Dams constructed by these formulas contain the mini- mum amount of material necessary to enable them to perform their functions of holding up the storage water, and are not sufficiently substantial to withstand the shock produced by water falling over their crests. Where a masonry dam is used as a diversion weir or as an overflow weir, it is impossible to design it on any of the theoretical profiles. The chief calcula- tion then requisite in its design is, that the pressure of the masonry on the foundation shall not pass the limit which the material can withstand, and also that its cross-section shall be more ample and substantial than that which would be required by one of the theoretical profiles. The first and most vital rule in building a masonry dam is that it shall rest on solid and practically homogeneous rock. A masonry dam is practically an absolutely rigid structure, and settlement in any portion of its foundation will result in cracks and ultimate rupture in its mass. There are two ways in which a masonry dam may resist the thrust of water : first, 248 THEORY OF MASONRY DAMS. 249 by the inertia or weight of its mass, and, second, as an arch. Its safety depends upon compliance with the conditions 1. That the horizontal thrust of the water must be held in equilibrium by the resistance of the masonry to sliding forward or overturning ; and, 2. That the pressure sustained by the masonry or its foun- dation must never exceed a certain safe limit. The thrust of the water may be resisted by being transmit- ted to the abutments, the dam acting as an arch. But three dams have as yet been built which depend in any degree for their stability on arch action, and the laws governing this action in a dam are as yet so uncertain that they cannot be depended upon with any degree of security. Some attempt at solving the rules on which a dam is dependent for its stabil- ity as an arch are given in Articles 255 and 256. According to J. B. Krantz, a dam which is curved in plan, with a radius of 65 feet or less will transfer the pressure of the water to the sides of the valley whatever the height of the structure. This, however, does not lessen the effect of the weight of the masonry, so that whether the structure be curved in plan or not, its weight must be supported in the same way, and the height must be such that this weight will not exceed the limit of pressure permissible on the base. In France, and in the case of the Fife dam near Poona, India, and elsewhere, reservoir walls have been reinforced by means of masonry counterforts. If the wall is strong enough by itself the counterforts are a useless expense, and if the wall is not sufficiently strong they will not prevent it from yielding. The masonry intended for the counterforts would always be better used if spread over the mass of the dam. 246. Stability of Gravity Dams. The author will make no attempt here to enter into a tedious mathematical discussion of the theory of the stability of masonry dams. This question is one which has been investigated with great thoroughness within the past 15 years, and nothing which could be stated in this place will add to the value of the theories now held. For the benefit of students who desire to enter into the mathematics 250 MASONRY DAMS. of this subject a list of authors is appended at the end of this chapter. Sufficient of the principles of the subject may be obtained from the works of Baker, Fanning, Wegmann, Mc- Masters, Church, and Merriman, who are the more modern American writers on the subject. The conditions on which the stability of gravity dams are calculated are : 1. The hydrostatic principles involved in the pressure of a volume of liquid on an immersed surface ; the fact that this pressure is perpendicular to the surface ; and that for rectangu- lar surfaces it may be considered as a single force applied below the water surface at a distance equal to -f of its depth. 2. That a gravity dam may fail: I, by sliding on a hori- zontal joint ; 2, by overturning ; or 3, by crushing of the masonry or foundation. The stability of the dam against its liability to destruction, as enumerated in condition 2, page 249, must be determined 1. When the reservoir is full; and, 2. When the reservoir is empty. These two conditions give the extreme positions of the lines of pressure in a dam. The first causes the maximum pressure in any horizontal plane to be at the down-stream face of the wall, and the second produces them at the up-stream face. When the reservoir is empty the wall supports only its own weight, but if the wall has a uniform thickness the pressure per square inch will be about 85 pounds if the height of the struc- ture is 85 feet. If the faces be inclined so as to reduce the mean thickness, the pressure on the base diminishes and the height can be accordingly increased. From this it is clearly seen that it is absolutely necessary to widen the base of the dam by inclining its faces if the wall is to have any great height ; otherwise it would rupture from the pressure of the material composing its own mass. When the reservoir is full, however, the water contained in it bears upon the up-stream face with a pressure that increases with the square of the depth. In deep reservoirs this pressure is great, and exerts its effect in a re- sultant which is nearly horizontal in direction and carries the STABILITY OF MASONRY DAMS. 251 maximum load to the down-stream toe of the wall. For sta- bility this resultant must pierce the base in front of this lower edge. From these considerations arises the necessity of giving the down-stream face a greater batter than the up-stream face. The tendency of the water pressure to produce overturning or sliding and the weight of the material are greater for each suc- cessive layer of the mass of the dam from the top downwards. As a result of this the width of the dam at the top might theoretically be nil, and should be increased downwards in such a proportion as to render the dam capable of resisting tenden- cies to crushing, sliding, and overturning. From theoretical examinations of the effects of these forces it has been found, keeping constantly in view the necessity of making the batter of the down-stream face the greater, that the dam should have a triangular profile, somewhat similar to that represented in Fig. 71. FIG. 71. THEORETICAL TRIANGULAR CROSS-SECTION OF DAM. 247. Stability against Sliding. The tendency of the water pressure to slide any portion of the dam forward on a given horizontal plane is resisted by the friction due to the weight of the mass above it. The dam is necessarily founded 252 MASONRY DAMS. on firm rock the disintegrated and weaker portions of which must be removed, and as a result the base is usually sufficiently rough to offer considerable resistance to sliding. If this is not the case steps must be cut for a few feet in depth in the foun- dation rock, or this must be irregularly cut in such manner as to leave trenches in which projections of the dam will fit. The dam, if properly constructed, is safe against any liability to slide providing its profile is such that it will resist overturning ; therefore the usual computations entered into to determine whether it will resist sliding are practically unnecessary. If it be constructed of rough rubble masonry without regular beds, and so built as to form a monolithic mass, sliding is impossible. It is well known that the force required to make two pieces of smooth stone slide upon each other when dry or joined by fresh mortar is equal to about .75 of the normal pressure. Hence sliding would only be possible when the horizontal was equal to of the sum of the vertical pressures. In none of the formulas or profile types ordinarily employed is the ratio of the thrust to the pressure beyond .7, while it more ordinarily ranges between .3 and .5 248. Coefficient of Friction in Masonry. In the follow- ing table are given the coefficients of friction in dry masonry of various kinds : TABLE XII. COEFFICIENTS OF FRICTION IN MASONRY. Coefficient. Point-dressed granite on like granite 70 Point-dressed granite on brick 63 Point-dressed granite on smooth concrete. 62 Fine-cut granite on like granite 60 Fine-cut granite on be" ton block 60 Dressed granite on granite with fresh mortar 50 Beton blocks on bton blocks 65 Common brick on common brick 65 Common brick on common brick with wet mortar 50 Common brick on dressed limestone 60 Dressed hard limestone on limestone 65 Dressed soft limestone on like limestone 75 COEFFICIENT OF FRICTION IN MASONRY. 2$$ According to J. T. Fanning, let 6" = the symbol of friction of stability; x = the horizontal water pressure resultant ; c = the coefficient of friction of the given section ; w = the weight of masonry above that section ; e = the vertical downward water pressure resultant ; z = the maximum upward water pressure resultant ; c 1 = the ratio of effective upward water pressure to the maxi- mum. Then, when 5 and x are equal to each other, the wall is on the point of motion and 5 must be increased. This has to be done by adding more weight to the wall. This weight should be increased until it is able to resist a thrust of at least 1.5^, when The wall has a small margin of fractional stability when x 2.2$ tons. Ordinarily the weight or pressure of the wall far exceeds this figure, and is usually from 5 to 12 tons per square foot. For equilibrium, let x < cw -{- ml, in which m is the cohesion of the masonry per square unit and / the length of the joint at the section above x. The value of m is so considerable that ml may be considered as a margin of safety, when we have x = cw. To find what value of c will x prevent sliding, we have c = - . A masonry wall must be founded upon solid rock which is either naturally uneven or must be made so, and it must be made of rubble masonry or concrete not laid in courses. As there can therefore be no smooth planes to slide one upon 254 MASONRY DAMS. the other, the coefficient of friction in the mass must be many times the superincumbent weight ; and we may con- clude, therefore, that there is no possible danger of failure from sliding. 249. Stability against Crushing. According to the method given by Debauve, when the reservoir is full and the resultant of the pressure of the water and the weight of the masonry intersects the base at one third of its width from the down-stream toe, the maximum pressure is at this toe, and is double what the pressure per square inch would be if the weight were uniformly distributed over the whole base. When the reservoir is empty the conditions are reversed, the maxi- mum pressure being at the up-stream toe and equal to double the average pressure on the base. From this proposition Mr. James B. Francis differs. He believes that the pressures near the base of the wall are prac- tically zero, and that these pressures are transferred to the cen- tral part of the mass, where the resistance to crushing is greatest. In other words, that the masonry is not perfectly rigid, and that it becomes accordingly unnecessary to take account of crushing pressures in a dam less than 200 feet in height. In this opinion other authorities agree with Francis to a limited extent, though all prefer to Calculate the limit of pressure in the usual manner, namely, to measure the pressures near the face of the wall, as that gives a safer factor, though it may be unnecessarily high. As parts of the dam are built at different times in the year and under different conditions, the structure cannot be truly homo- geneous. The absence of fractures at the thin portion near the toe of the dam indicates the absence of excessive strains at that point ; it is therefore more probable that the real point of dis- tribution of pressure lies somewhere between the extremes enumerated by Debauve and Francis. Up to the limit of 200 feet in height there is no doubt that the crushing strength of well-laid masonry need not be considered. The following, from Wegmann, is a brief synopsis of a simple formula for finding the distribution of pressure at any point in a dam : LIMITING PRESSURES. 2$$ Let W = the total pressure on the base ; u = the distance of W from the nearest edge ; / = the maximum pressure on the foundation ; q = the minimum pressure on the foundation ; / = the length of the joint or base under considera- tion. 2 W When u = , or in other words the 2 W pressure is within the middle third of the base, / = - . If the pressure is without the middle third there will be tension in the mass. As it is unsafe to depend on the tension in masonry, it would be best to neglect this in calculating the 2\V pressure on the foundation, and this will become / . An- other simple formula for determining the pressure on the base, and one which leads to practically similar results, is the follow- ing, given by Ira O. Baker: W 250. Limiting Pressures. The limiting pressures which it maybe safe to permit in masonry differ considerably accord- ing to various authorities. From actual tests these pressures differ according to the dimensions of the masonry blocks, and it is probable that much greater pressures can be sustained per unit of area in the interior of large masses than in the smaller experimental blocks or near the surface of the mass. The fol- lowing pressures are ordinarily accepted: Brick, 120 pounds; sandstone, 130 pounds; limestone, 152 pounds; granite, 155 pounds per square inch. It is not advisable to allow either a direct or resultant pressure exceeding 140 pounds per square inch within I foot of the face of rubble masonry or exceeding 200 pounds per square inch in the heart of the work. On some of the great structures already built limits of pressure as low as 85 pounds have been adhered to, while pressures exceeding 200 256 MASONRY DAMS. pounds per square inch have been permitted in the Almanza and the Gros Bois dams in Europe. Among the great dams which have been constructed the pressures vary between 5.8 tons per square foot in the Verdon dam in France and 14.6 tons per square foot in the Gros Bois dam, while the proposed Quaker Bridge dam, in New York, was designed for a maximum pressure of 16.6 tons per square foot. It is probable, however, that a safe average limit is that already given of from 140 to 200 pounds per square inch. 251. Stability against Overturning. To insure ample safety against all the causes of failure in a dam in addition to the other conditions already fixed, the lines of pressure must lie within the centre third of the profile, whether the reservoir be full or empty. This last condition precludes the possibility of tension, and insures a factor of safety of at least two against overturning. In Fig. 72 suppose the lines of reaction R and H l FIG. 72. DIAGRAM ILLUSTKATING WEGMANN'S FORMULA. W to intersect the joint / at the limit of its centre third. Taking the moments of the three forces, H, R, and W, which Hd Wl are in equilibrium at about the point e, we find -- = , in o o which d = the depth of water at the joint above the plane of /. If the moments are taken about the front edge a, the lever arm of ^will be double, while that of H remains un- changed ; the factor of safety against overturning is therefore two. It is equally evident that if the line of reaction of W or R should intersect /within its centre third, the factor of stabil- ity would be greater than two. STABILITY AGAINST OVERTURNING. The following formulas are taken from the treatise of Edward Wegmann, Jr., on Masonry Dams, because the author considers them simple and accurate. For their deduction; and discussion the student should refer to this work.. The mass of the cross-section of the dam should be rectangular and will contain an excess of material as regards resistance to the hydrostatic pressure of the water ; P will pass through the centre of the rectangle, and P will gradually ap- proach the front face eventually reaching some joint x = a where u = . The depth of this joint below the top of the J dam is d = a Vr, where P= the line of pressure, reservoir full ; P' = the line of pressure, reservoir empty; x = the unknown length of the joint ; u the distance of P from the front edge of the joint x ; a the top width of the dam ; d the depth of water at the joint x\ r = the specific gravity of the masonry. For the next course below the joint x, where the dam- begins to assume a trapezoidal cross-section, we have in which w = equals the total weight of masonry resting on the joint /. / = the known length of the joint above x ; h = the depth of a course of masonry^ assumed as 10 feet ; m = the distance of P' from the back edge of the joint /; d* M -7 = the moment of H on the joint x ; d? H = = the horizontal thrust of the water. 2r Equation (2) may be used for a series of joints down to a depth where the back surface of the dam begins to slope or until a joint is found where n = - ; n being the distance of P' from 258 MASONRY DAMS. the back edge of the joint x. For the next course both faces x will have to be sloped, and u = n , when we obtain 6M In applying equation (3) for finding the value of x> the maximum pressure must be obtained both with reservoir full and empty. This may be done by the formula 6M in which / = the limiting pressure per square foot at the front face of the dam. This equation may be employed until the limiting pressure is reached at the back face, when the following formula must be used : 2 * + = 6M > - (5) in which q is equal to the limiting pressure per square foot at the back face of the dam, and is generally assumed to be greater than /. These equations give the successive lengths of the joints, but do not give their position. This may be found by deter- mining the value of y = the batter of the back face ; the formula being _ and for equation (5), - 6m) + lh(x - The theoretical profile resulting from calculating the dam by the above formulas will have polygonal faces. It only MOLESWORTH'S FORMULA AND PROFILE TYPE. 2 59 becomes necessary then to make the value of h sufficiently small to determine a profile with a smooth surface which will fulfil all of the conditions. 252. Molesworth's Formula and Profile Type. Mr. Guilford L. Molesworth has worked out the following formula, the application of which gives the profile shown in Fig. 73 : 8 M. W. -^-^i-q^- ~ = *^=-=- \A \_ t y or SfHW/ort \ '-^ \ 8 oil i -""T\| /9 ' 7 \* "ft ***^ 00; 1 ^ Vl X i i lOQl-i _ fjM. -V9+. ^' r - - V J.1 - - 30.80- -\A 1 % \ *\ \ * X Tt ^T woH : | I V. \>o X I2O>H d co co co co co Ol M O OGO O M M co "^- to in u->o OOOOOOOOO inmtn 6 6 6.6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 1-1 O CO CO O vnO Tj- N CO vr> CO -1-QO "tf-CO CO > CO CO r^coomwo Wv O O O O *i ui ' - r>-co 6 ~> MOO r--O moo o^ ex *- r}-co m '^O O co M ^MO t^inN O>t-> rj-o o c< u-i a> coco co t^o -^- ci a cotnnc>O couic>ao rfO inTtoo Oco oo M t^r>.co u->vn^i-io noo inr^ CO CO* CO 6 T OO N OO ' O^O >-iO r^co oo ^ SOOO O O O t^r^coco M ^- mo r^ M o "i M a -.i-.NN OO vr>O t^ON -cooOi-iNcotnv jo jaaj oiqno co m O m O ^" m m O ^t" O ^ O O O m O *o O ^t" MTtoomTl-OW MincoOO >-Ir^OM xoO^tOu-ii-cco i^ M M M c ei (O ^t-^ in XJUOSBJ^ jo 133J jo O OO cocovn-i OO ^t i-" '^oo Ncooo O m Oco >-i OI-ICGCO cocoo *-co ~f >-> Or>>u-> '^-'^ vr>O O r~CO }33J UI 'tnep jo do^ MO\ OOOOOOOOOOOOOOOOOOOOO M w cOTfino r^co OO >-> N coTinvo t^oo OO CURVED MASONRY DAMS. 26 3 dam of the pure arched type relies solely on the arched form for stability, in which case the pressure of the water is trans- mitted laterally to the abutments. If our knowledge of the laws governing masonry arches were more complete, the arched or curved dam would probably be the best type, since SCALE OF FEET 5 10 IS 19098 FIG. 75. PRACTICAL PROFILE FROM WHGMANN. it will contain the least amount of material. As it is, we know something of the laws governing such true masonry arches as those supporting bridges. In thece the two extremities of the arch are raised at their springing on some firm abutment 264 MASONRY DAMS. and the whole is keyed together at the centre ; but in a masonry dam of arched form not only is the arch supposed to transmit the pressures laterally to the side of the abutments, but as the dam rests on the bottom of the valley it is sus- tained again at that point, so that it cannot act as a true arch, nearly perfect arch action only occurring at the top, where the pressure is a minimum, while near the bottom, where the pressure is greatest, probably very little of this is transmitted to the abutments. For this reason it is not yet considered safe to build a dam depending purely on the arched form, and such few dams as have been constructed on this principle have been given somewhat of the gravity cross-section, increasing downward in width, so that they presumably resist the press- ure both by gravity and arch action. The three best existing types of such works are the Zola dam in France and the Bear Valley and Sweetwater dams in California (Arts. 275 and 281). That a masonry dam constructed across a narrow valley can resist the water pressure by transmitting it to its abut- ments is proved by the dams above cited. The question then arises, can the profile be reduced from what would be required if the plan were straight? As stated at the beginning of this chapter, Krantz asserts that a dam curved in plan and con- vexed up-stream with a radius 65 feet or less will transfer the pressure of the water to its abutments. Dams, however, of even greater radius than this do transfer the pressure to the abutments. The radius of the Zola dam is 158 feet and its length on top is 205 feet. The length of the Bear Valley dam, which depends almost wholly on its arched form for its. sta- bility, is 230 feet, the radius at the top being 335 feet and at the bottom 226 feet. The Sweetwater dam is 380 feet in length on top, its radius at the same point being 222 feet. M. Delocre says that a curved dam will act as an arch if its thick- ness does not exceed one third of the radius of its up-stream or convex side. M. Pelletreau fixes the limiting value of the thickness at one half of this radius. When a dam acts as an arch it only transmits the water pressure to the sides of the valley; its own weight must still be borne by the foundation. DESIGN OF CURVED DAMS. 26$ 256. Design of Curved Dams. Mr. Wegmann gives th2 following formula for calculating the thrust in curved dams of circular plan : in which / = the uniform thrust in the circular rings of any plane of the masonry ; / = the pressure per unit of length of this section of the ring ; r = the radius of the rings of the outer surface. Arch action can only take place by the elastic yield of the masonry ; but little is known of the elasticity of brick, stone, etc., and nothing of the elasticity of masonry; hence it is im- possible to determine the amount of the arch action. It may be shown theoretically that in the case of a narrow valley a profile of less area may be employed for a dam which is curved in plan than one in which the plan is straight. An excellent theoretical discussion of this subject has been pub- lished by Messrs. Hubert Vischer and Luther Wagoner. The result of the investigations of these gentlemen goes to show that arch action, as usually understood, adds little to the strength of a curved dam. Notwithstanding this, the curved form may to a marked degree afford additional resistance, and this in a manner less dependent on the radius of the curve than the arched theory implies. The general conclusion reached by these gentlemen is, further, that the rate of effi- ciency of a curved dam over the straight decreases with the increased length of the dam ; that very narrow cross-sections are not justifiable ; and they ascribe the high duty of the Bear Valley dam to a favorable combination of conditions which could not have held good if the span had been considerably longer or the workmanship less excellent. Engineers are now generally agreed upon the advantages of the curved plan. Its chief disadvantage is the increased length of the dam over a straight plan, and the consequent increase in the amount and cost of material to within certain limits of top length and radius. Though the cross-section of a 266 MASONRY DAMS. curved dam should unquestionably be somewhat reduced, it would be unsafe to reduce it as much as has been done in the case of the Bear Valley and Zola dams, though these have withstood securely the pressures brought against them. It might with safety be reduced to the dimensions of the Sweet- water dam, thus saving largely in the amount of material em- ployed. All of the more conservative writers, as Wegmann, Rankine, and Krantz, recommend that the design of the profile be made sufficiently strong to enable the wall to resist water pressure simply by its weight, and to curve the plan as an additional safeguard whenever the topography makes it advisable. American engineers, and especially those of the West, however, are prone to be more liberal ; and the tendency is toward a slight reduction in the cross-section where a curved plan is practicable. An additional advantage of the arched form of dam is that the pressure of the water on the back of the arch is perpendicular to the up-stream face, and is decom- posed into two components, one perpendicular to the span of the arch and the other parallel to it. The first is resisted by the gravity and arch stability, and the second thrusts the up-stream face into compression, which has a tendency to close all vertical cracks and to consolidate the masonry trans- versely. An excellent manner in which to increase the efficiency of the arch action in a curved dam is that employed in the Sweetwater and Buchanan reservoir dams, the latter of which has recently been designed for construction in California. This consists in reducing the radius of curvature from the centre towards the abutments. The good effect of this is to widen the base or spring of the arch at the abutments, thus giving a broader bearing for the arch on the hillsides. In the Sweetwater dam the effect of this is seen in projections or rectangular offsets made on the down-stream face of the dam (PL XXIV), the centre of the dam sloping evenly, while the surface is broken by steps where it abuts against the hillside. In the Buchanan dam, the length of which is 780 feet on top, the maximum radius at the centre is 1146 feet, and this is FOUNDATIONS. 267 diminished gradually to 736 feet at the abutments. These changes in the radii are made gradually, and are not shown in the surface of the dam in projections, as the entire outer surface is smoothed off evenly. 257. Foundations. Masonry dams must be founded on solid rock, and great care and judgment are required in deter- mining just when the excavation for the foundation has pro- ceeded sufficiently far. If the looser and partially decomposed surface rock is not entirely removed there is danger of leakage under the dam, and consequent liability of its destruction. If the excavation is carried too far into the underlying rock much money may be wasted. Frequent cases might be cited where it has been found necessary to make unusually deep excavations in order that a sufficiently firm foundation might be reached. In the case of the Turlock dam the average depth of excavation in the large bowlders and underlying porphyry was from 5 to 10 feet to the homogeneous material. In one or two cases, how- ever, seams full of huge bowlders weighing several hundred tons apiece were encountered, which necessitated excavation to a depth of 25 to 35 feet in order that they might be worked out and homogeneous rock reached. A masonry dam is an abso- lutely rigid structure, and the least unequal settlement in any portion of it tends to produce a crack. A clay or hardpan foun- dation is almost sure to yield under the weight of a masonry dam, and be the loose material ever so little in amount, if it offers opportunity for subsidence it will result in the rupture of the dam. The safe load on the lower courses of a masonry dam depends on the character of the material of which it is composed, and may reach from 10 to 15 tons per square foot, and nothing but the most substantial rock will bear such a weight as this. 258. Material of which Constructed. Ashlar Masonry. Reservoir dams may be built of cut masonry, of rubble or concrete with dressed-stone facing, or of random rubble. The first would be the best for the purpose on account of its strength, but while only twice as strong as rubble, it costs three or four times as much. As the form of the upper part 268 MASONRY DAMS. of the dam depends on the positions of the lines of pressure and not on the strain in the masonry, the great strength of cut- stone work would only avail in the lower portion of the dam. Great care would have to be employed in the use of cut ma- sonry in order that it should not be laid in horizontal beds, which might permit of shearing or sliding, and in order that it should break joints with a proper degree of irregularity. Neither the vertical nor the horizontal joints in a dam should be continuous ; therefore if made of cut or ashlar masonry or of square stone the joints should be carefully broken. Rubble or concrete with cut-stone facing is not a desirable material of which to construct a dam, because of the difference in settling of the two kinds of masonry, which might result in the formation of cracks and seams. Where the facing becomes detached in this manner from the remainder of the body of the wall the strength of the structure is reduced to that of the uncoursed or concrete centre. The most prominent examples of the use of cut-stone facing with rubble or concrete interior are to be found in the Vir, Bhatgur, and Betwa dams of India, which are briefly described in Articles 270 and 277, and the new Croton dam in New York (Art. 271). In each of these the cut stone is laid as headers and stretchers, and the former are well bonded into the mass of the dam. The use of this form of construction is condemned by many Indian engineers, and is not approved in this country. 259. Concrete. Some engineers consider concrete too pervious a material to be placed in a dam. It has, however, been successfully employed in four of the greatest dams yet constructed, namely, the San Mateo dam in California, 170 feet in height; the Periar dam in India, 155 feet high ; and in the Geelong and Betaloo dams in Australia, respectively 60 and no feet in height (Articles 272-274). The Periar and Betaloo dams are two of the best examples of the homogeneous use of concrete. The great disadvantage in using this material, aside from engineering considerations, is the added cost of cement where the latter is expensive. The great advantage of the use of concrete and that which determined its employment in CONCRETE. 269 the Periar dam is the saving effected in labor; for concrete can be mixed and handled entirely by machinery worked by water-power furnished by the reservoir while under construc- tion. In the Beetaloo dam for 46 feet above the founda- tion the concrete was made of one part Portland cement, two parts washed sand, and four parts broken stone of 2-inch gauge. In building the structure great care was taken to have the surface of the set concrete picked, washed, and brushed before a fresh layer was deposited, and the new concrete was kept shaded from the sun while setting. This dam was built up as a monolithic mass, the concrete being laid between boards or framing bolted in the body of the dam. After re- moval these boards left their imprint on the sides of the struc- ture, which marking still remains. In choosing concrete as the material to be employed in the construction of the Periar dam in India the engineer held that concrete is nothing more than uncoursed rubble reduced to its simplest form. As regards resistance to crushing or percola- tion, he holds that the value of the two materials is identical, unless it be considered as a point in favor of concrete that it must be solid, while rubble may, if the supervision be defective, contain void spaces not filled with mortar ; he holds that the selection between the two depends entirely on their relative cost. The proportion of materials employed in this dam were : for every 100 cubic feet of concrete, 60 cubic feet of solid stone plus 10 per cent for wastage, 25 cubic feet of native hydraulic lime, and 30 cubic feet of sand. The San Mateo dam in California was not built up as a monolithic mass of concrete as were those just described, but is composed of great concrete blocks of uniformly irregular dimensions. These blocks (PL XXIII) weigh 9 tons each, and were built up in the body of the dam in such manner as to key in with each other both in horizontal and vertical plan, so as to produce a nearly homogeneous mass and create the greatest amount of friction between blocks. The material was mixed at the site of the dam, and run out in a tramway and built in place inside of a wooden boxing which was afterwards re- 2/O MASONRY DAMS, moved. The blocks were left surrounded by the boxing for one week, during which time they set sufficiently for the wood to be removed and to permit of other blocks being built against them. The concrete consists of 2-inch-gauge metal mixed in the proportion of 6 of broken stone to 2 of sand and i of Portland cement. In mixing concrete one of the best proportions to use, measured by volume, is I part of cement, 2 of clean sharp sand, and 3 to 4 of broken stone. This concrete should be laid im- mediately after mixing, and should be thoroughly rammed and compacted until the water flushes to the surface. It should be allowed to stay for 12 hours or more before any further work is laid upon it. 260. Rubble Masonry. Rough random rubble masonry is considered the best material that can be used for building a dam. It possesses strength, can be readily adapted to any form of profile, and is relatively cheap. In building a dam the main object is to form as nearly homogeneous a monolithic mass as possible. Horizontal and vertical courses must there- fore be avoided, and the stones interlocked in all directions. The sizes of these stones may differ greatly. The mass of the wall may be composed of stones of such a size as may be car- ried between two men, as is the case in India, where machinery is rarely employed ; or it may consist of cyclopean rubble measuring from one to several cubic yards in volume, each block perhaps weighing several tons. To prevent leakage, all spaces between the stones must be completely and compactly filled with impervious mortar or cement. To prevent sliding, the blocks must be irregularly bedded, and as each course is laid a large proportion of the stones must be permitted to pro- ject above the general surface. The spaces between the larger stones may be filled with concrete or small rubble. Grouting must never be permitted, and the best stones are generally reserved for the facing, in which they are laid as headers in such manner as to give an even contour to the outer surface. CEMENT DETAILS OF CONSTRUCTION. 2J\ 261. Cement. The center of a large work may be of some cheaper variety of cement, as Rosendale or other natural or American cement. Portland cement should be used in the facing stones and in pointing. All cement used should be hydraulic and of some well-known brand, whether natural or Portland. The cement should be carefully enclosed in a tight shed with a close floor set above the ground to protect it against dampness, and should be subjected to strict inspection and tests. All mortar used should be prepared from the best qual- ity of cement of the kind above described, and of clean sharp river sand well washed and free from dirt. They should be mixed dry. in the proper proportions, and then a moderate amount of water should be added and the whole thoroughly worked together. Portland cement and mortar should gen- erally be mixed in the proportion of about I of cement to 2 of sand in laying the puddle work ; while for laying the rubble work and concrete I of cement to 3 of sand may be used. In laying masonry great care should be taken that water shall not interfere, and in no case should it be laid in water. No masonry should be built in the winter time during freezing weather, un- less exceptional precautions be taken to cover it and protect it from frost. 262. Details of Construction. Rubble stone masonry should always be made of sound clean stone, of suitable size, quality and shape for the work. All awkward projections should be hammered off so that the stones shall become rectangular in form. Their beds should present such even surfaces that when the stones are lowered on the surface pre- pared to receive them there can be no doubt that the mortar will fill all spaces. The stones should be well rammed into the bed of mortar if they are light, and this should be at least one inch in thickness. Where large stones are employed a moderate quantity of spawls may be used in the prepara- tion of suitable surfaces for receiving them. Especial care must be taken to have beds and joints full of water, as no grouting or filling of joints should be allowed after the stones are placed. The work must be thoroughly bonded, and if 2/2 MASONRY DAMS. mortar joints are not full and flush they should be taken oivt to a depth of several inches and properly repointed. In such work various sizes of stones should be employed, and regular coursing should be avoided in order to obtain both vertical and horizontal bonding. The sizes of the stones may vary with the character of the quarry, but where the thickness of the masonry is great a considerable proportion of large stones should be used. Where exceptionally large stones are em- ployed the joints may be filled with concrete instead of mortar. In such cases only so much water should be employed as can be brought to the surface by ramming. In carrying out the construction of rubble-masonry work it should not be built in horizontal courses ; at the same time it must be built in beds, and these should be irregularly stepped, and various parts of the structure worked upon and allowed to set at different times. The surface of these horizontal steps or courses should bristle with projecting stones, so as to secure a perfect bond in every direction. This is done by working up the mortar or concrete between the stones to about half their height, and wherever the work is stopped over night or for a period of time these projections insure bond with the next layer to be worked. No stones should be deposited or dressed upon the wall, but on platforms or planking, so that no dirt shall be brought in contact with the material. The same pre- caution must be taken in handling concrete and mortar. The rubble facing stones should be of large size, not less than 2 feet deep, with frequent headers. Where especial jar is brought on the masonry work, as in overfall weirs, facing stones should be of range rubble, of the soundest and most durable quality, and should be cut so true that joints not exceeding inch shall be necessary for 3 inches from the surface, the remain- der of the joint not exceeding 2 inches in thickness at any point. In such work it is well to alternate about two stretchers for one header, and to make the former not less than 3 feet in length, while the header should not have less than 12 inches lap under ordinary circumstances. The concrete used in work of this character should be made SUBMERGED DAMS. 273 of rough broken stone metal, and of clean river gravel not ex- ceeding from 2 to 2j- inches gauge. This material should be washed free of dirt before being used, and be mixed in boxes, or mortar mixers with mortar of a proper quality. The pro- portions used in mixing differ greatly, and are described in technical books treating on this subject. 263. Submerged Dams. In a few instances submerged dams have been constructed for the purpose of stopping the underground or underflow water in the beds of streams. This FIG. 76. VIEW OF SAN FERNANDO SUBMERGED DAM. has been resorted to particularly in a few streams in the moun- tains of Colorado and California, where the surface flow is large, but as the streams reach the plains the water sinks and disap- pears. Its downward course then is stopped by some imper- vious bed of clay or rock, and there is created practically a slow- moving river under a bed of deep gravel. This can be brought to the surface by sinking a dam entirely across the stream bed to the impervious substratum, when the water will be raised, forming an underground reservoir ; or a series of cribs may be 2/4 MASONRY DAMS. built on the impervious stratum under the gravels, and these will catch the water and lead it off, whence it may be removed by an open cut or by pumping (Art. 295). The former method is employed on the San Fernando Land and Water Company's property on Pacoima creek in Califor- nia. At the site of the dam the canyon walls are about 800 feet apart and the bed-rock about 75 feet below the gravel surface of the stream. Through this a trench was excavated, and in this a masonry wall was built up, its bed width being about 3 feet and its top width 2 feet, its greatest depth being 53 feet and rising to a height of from 2 to 3 feet above the stream bed (Fig. 76). On the line of this wall are two large Wells, and on its upper face pipes are laid in open sections, so that the seepage water caught by the dam might enter these and be led through them into the wells, from which it is drawn off for purposes of irrigation. 264. Construction in Flowing Streams. In building any variety of dam across a flowing stream the expense of con- struction is considerably increased by the necessity of hand- ling the flowing water and keeping it away from the work of construction. Several methods are pursued, depending largely upon the discharge of the stream. If this is small, one of the simplest methods is to build an under or scouring sluice in the dam and construct this portion of the work first, so that the water may be permitted to flow off through it Avhile the remainder of the work is being built. If the stream is subject to violent floods or its discharge is too large to be conveniently handled in this manner, wasteways at varying heights may be left in the crest of the dam over which the floods may fall. It is frequently necessary to build a temporary dam above the main structure with a view to retaining the water until the latter is completed ; or a temporary channel may be built for the stream around the dam, and through this the water may be carried off. In the great Tansa and Bhatgur dams in India, where the floods discharged are very large, a portion of the masonry adjacent to either abutment was maintained at a SPECIFICATIONS AND CONTRACTS. 2?$ lower height than the rest in order that the floods might flow over it as over a wasteway. In commencing the construction of a dam where flowing water has to be controlled, if the discharge is not too great the stream may be diverted temporarily while the main por- tion of the dam is being built ; or if undersluices are to be provided for the discharge of the water, these should be built first, the stream being passed to one side during their con- struction, after which it may be turned back through them, and the remainder of the structure carried up. If no under- sluices are to be constructed, pumping may be resorted to if a temporary channel cannot be provided, though this method is not advisable and should rarely be resorted to. In founding a dam in quicksand two or three methods may be employed. Pneumatic caissons may be sunk, and the foundation built in these as would be done for a bridge pier ; or if the sand is comparatively dry and semi-fluid, it may be frozen by the Poetsch process, and the excavation for the foundation can then be made within the frozen walls. 265. Specifications and Contracts. There are many trivial details of construction which must be considered by the engineer in designing earth, crib, and masonry dams. It is customary to have such structures built by contract, and for this purpose careful specifications are drawn up by the en- gineer, detailing the character of material and construction. For those who are unfamiliar with such forms of specifications, such books on the subject of specifications and contracts as those of Gould and Haupt can be purchased ; or specifications which have been used by other engineers can be obtained through them. The usual form of specification opens with a general de- scription of the work and its location, a statement of the methods and appliances to"be used in construction, a descrip- tion of the protective work, highways, bridges, and diverting works, as well as pumping plant and other temporary work to be employed during construction. For earth dams the speci- fications then go into a description of the soil to be used, and 2/6 MASONRY DAMS. where it is to be obtained ; the depth of excavation and its character, and the method of retaining it ; a description of the refilling of excavations and the building of embankments ; and the question of sodding and paving or revetting the em- bankments. If the dam is to be of timber or loose rock, a description of the timberwork and cribwork is given, and the character of the rock excavation and explosives to be employed is entered into. If of masonry, the matter of excavation for foundation, measurement and disposal of the material removed, and method of stepping the foundation are first considered. Then the hydraulic masonry is described, the cement and its tests, the proportions used in mixing mortar and concrete, the char- acter of the brickwork and of the stone masonry, whether of dry rubble, rubble masonry, range-rubble facing, or cut-stone. In addition to these there is usually some iron work connected with the superstructure and gate-houses. 266. Examples of Masonry Dams. In Table XI on page 222 were given the general dimensions of several of the largest masonry dams which have been built. An account of the construction of masonry dams would be incomplete with- out a few examples of the larger and more typical of the modern dams, and accordingly brief descriptions and illustra- tions of some of these are given here. These are divided for convenience into two general classes : I, those which act as re- taining walls for the water and over which the latter is not ex- pected to flow ; and 2, those which act both as retaining walls and overflow weirs. The older and less typical forms of dams, such as those built in Spain in earlier days, and a few of those built in France and elsewhere, do not require description here, as no such works are likely to be designed in the future. For those who are interested in their study, descriptions and cross- sections of these can be found either in Wegmann's "Design and Construction of Masonry Dams," Krantz's " Reservoir Walls," or in the I2th and I3th Annual Reports of the U. S. Geological Survey. 267. Furens Dam, France. This is one of the largest FURENS DAM, FRANCE, 277 and first of the great dams built according to modern formu- las (Fig. 77). It is 170.6 feet in maximum height above bed- rock, the maximum depth of water being 164 feet ; its thick- ness at top 9.9 feet, and at the base 161 feet. The maximum pressure on the masonry is 6.82 tons per square foot while its 45.9 4908 FIG. 77. CROSS-SECTION OF FURENS DAM, FRANCE. total length is 328 feet on top. In plan it is curved with a radius of 828.4 feet, and it is built entirely of rubble masonry, the facings being of the same material. The top of the dam is finished off as a roadway 9.8 feet wide, and this is protected by two parapets, one on either side, each 1.6 feet in height. 278 MASONRY DAMS. 268. Gran Cheurfas Dam, Algiers. This dam (Fig. 78) was built in 1882, and has a total height above its foundation of 98.4 feet. Its width at top is 13.1 feet, at the base 72.2 feet, and its top length is 508.4 feet. It is built practically in two parts, the first consisting of a trapezoidal-shaped foundation 4.00 FIG. 78. CROSS-SECTION OF GRAN CHEURFAS DAM, ALGIERS. mass of rubble, on which is built the dam, the upper and lower surfaces of which are parabolic. The depth of water which this dam will hold is 132.2 feet, and the maximum pressure on the masonry within it is 6.14 tons per square foot. In plan it is straight. TANSA DAM, INDIA. 279 269. Tansa Dam, India. This great dam is built through- out of uncoursed rubble masonry. It is designed to have a total height of 133 feet, though it has as yet been completed only to a height of 118 feet (Fig. 79). At this height its maximum top width is 15.2 feet, while its maximum width at *,/*/ fp. /acA FIG. 79. CROSS-SECTION OF TANSA DAM, INDIA. base is 96.5 feet. Its total length on top is 9350 feet, while in plan it is built in two tangents, the apex pointing up-stream. Near the south end is built a wasteway 1800 feet in length, its crest being 3 feet below that of the dam. This wasteway is built in a portion of the dam where its height is but a few feet, and it discharges back directly into the river channel below the toe of the structure. Near the base of the dam BHATGUR DAM, INDIA. 281 is a large outlet tunnel, which discharges into the conduit which carries the water to Bombay for the supply of that city. FIG. 80. CROSS-SKCTION OF BHATGUR DAM, INDIA. 270. Bhatgur Dam, India. This dam (PI. XXII) is 4067 feet in length, and is constructed throughout of the best un- 282 MASONRY DAMS. coursed rubble masonry in cement. On the faces the dressed rubble is laid up. in courses. It is 127 feet in height, 74 feet in width at the base, and 12 feet wide on top (Fig. 80). When full the pressure on the lower toe is 5.8 tons per square foot, and when empty the pressure at the upper toe is 6.7 tons per square foot. In plan the dam curves irregularly across the valley, following an outcrop of rock. Portions of either end of the dam, where it is not high, are left 8 feet lower than the remainder so as to act as wasteways. The total length of these wasteways is 810 feet, and they are arched over in such manner as to leave a roadway across their tops. Below the dam and jutting from it are masonry walls which lead the waste water off in such manner that it flows clear of the foot of the dam and passes off through separate channels to the main stream below. For the purpose of scouring silt which may be deposited in the reservoir, fifteen undersluices are constructed near the centre of the dam, at its deepest part. These are placed 17 feet apart and are 4 by 8 feet in dimen- sions, their sills being 60 feet below high-water mark. Above these are two other undersluices for discharging the water to be used in irrigation when the reservoir is full. One of these is 20 feet and the other 50 feet above the main row of under- sluices. 271. New Croton Dam, New York. This monster dam will be of composite construction. For about 530 feet from the left bank it will be of earth. The next 630 feet of its length will consist of a high masonry dam designed on a theoretic profile. Thence to the left bank the structure will consist of a masonry overfall weir of heavy cross-section and 1020 feet in length on the crest. The capacity of the reservoir will be 92,000 acre-feet. The earth dam will be 245 feet in extreme height above its foundation and 120 feet above the ground surface (Fig. 81). Its top width will be 30 feet and will be 20 feet above high- water. Through its centre will be built upon a rock foun- dation a masonry core-wall 18 feet wide at the base and sloping on both faces to a top width of 6 feet at a level with NEW CROTON DAM, NEW YORK. 283 high-water. The upper or water face will have a slope of i on 2, and will be paved with from if to 2 feet of cobbles laid on I to I J feet of broken stone. The lower slope will be I on FIG. 81. CROSS-SECTION OF EARTH EMBANKMKNT. NEW CROTON DAM, CORNELL'S. 2, and will be broken by three benches. each 5 feet wide and paved to make a gutter to catch drainage. This slope will be carefully sodded. The main dam will be connected with the earth dam by heavy masonry wing walls and the masonry core wall. It will have an extreme height of 248 feet above its foundation and will be 163 feet in height above the river bed. The high- water level or crest of the overfall weir will be 14 feet below the crest of the dam. Its extreme width at base will be 185 feet and at its top 18 feet, surmounted by a 4-foot coping. This structure will be built throughout of the best rubble-stone masonry, faced above the ground surface with coursed stones set in Portland cement. In plan the earth and masonry section will be straight to the masonry overfall weir, which will curve up-stream nearly at right angles to the main structure. The water falling over this weir will spill into an artificial channel excavated in the hillside and emptying into the main channel below the toe of the dam. The extreme height of the weir will be 150 feet and its extreme width at base 195 feet. It will have a very slight 284 MASONRY DAMS. TlG. 82. CROSS-SECTION OF MASONRY DAM. NEW CROTON DAM. CORNELLS. |^-i-. CL^rf^^.-z ^ FIG. 83. CROSS-SECTION OF OVERFALL WEIR. NEW CROTON DAM, CORNELL'S. PERIAR DAM, INDIA. 28 5 batter on the up-stream side, while its lower side will have a slightly ogee-shaped curve and will be broken by 25 steps varying from 2 to 10 feet in height. This weir will be con- structed, like the dam, of an uncoursed rubble masonry interior and coursed faces. FIG. 84. CROSS-SECTIONS OF PKRIAR DAM AND WASTH WEIR, INDIA. 272. Periar Dam, India. This dam, which is constructed throughout of concrete, is 1230 feet long on top. It has a maxi- mum height (Fig. 84) of 173 feet (the numbers on the illustra- tion being incorrect as they were taken from a preliminary 286 MASONRY DAMS. BEETALOO AND SAN MATEO DAMS 287 design for the dam). Its crest is surmounted by a parapet $ feet in height, the maximum depth of water which the dam will hold being 160 feet, and its width at base 138 feet 9 inches, its top width being 12 feet. At either end are two wasteways built in solid rock, forming the abutments of the dam and separated from it, their aggregate length being 920 feet. The maximum capacity of the reservoir will be 306,000 acre-feet, its available capacity being 157,000 acre-feet. 273. Beetaloo Dam, South Australia. This structure (Fig. 85) is no feet in maximum height, no feet wide at the base, and 14 feet wide on top. Its length on top is 580 feet, and it is curved in plan, the convex side facing up-stream. It is FIG. 85. CROSS-SUCTION OF BEETALOO DAM, AUSTRALIA. constructed throughout of concrete, and in one end of the dam is built a set of three wasteways, their total length being 200 feet with their crests 5 feet below that of the main structure. These wasteways are separated by masonry walls, which lead the flood waters back into the river below and clear of the structure. 274. San Mateo Dam, California. This structure is built throughout of concrete, not as a monolithic mass, as is the case with the Beetaloo and Periar dams, but as described in Article 259, it was built up in blocks set in place, the weight of each being about 9 tons. In cross-section this structure is heavier than theory alone would require. As shown in PI. XXIII, its maximum height is 170 feet, its crest being 5 feet above high-water mark, at which level is a wasteway built a 288 MASONXY DAMS. SWEEl^WATER DAM, CALIFORNIA. 289 short distance above the north end of the dam and separated from it by a low ridge. The top width of the dam is 25 feet and its width at the bottom is 176 feet. Its upper slope has a uniform batter of 4 on I, while the lower slope, beginning with a batter of 2^ on I at the top, curves to within a few feet of the bottom, where the batter becomes I on I. In plan this structure is curved up-stream. 275. Sweetwater Dam, California. This dam (PI. XXVI) is slighter in cross-section than theory would require, and de- pends to a certain extent on its curved plan for its stability. As shown in Plates XXIV and XXV, it is 90 feet in maximum height, 380 feet long, 12 feet wide on top and 46 feet wide at the base. The radius of its curvature is 222 feet, and as the length of the radius is small and the curvature great, this adds considerably to its stability. The structure is built throughout of large uncoursed rubble masonry, the greatest care having been used in every detail of construction. At its southern end are a set of seven escape-ways 40 feet in aggregate width, so arranged that the water issuing through them drops first into a series of water cushions, and is then led off by a directing wall so as to clear the dam. Near its base is a discharge sluice, operated from a water tower in the reservoir. 276. Vyrnwy Dam, Wales. This structure is peculiar in cross-section (Fig. 86), being unusually heavy, and much greater than theory would demand. The reason for this is that the crest of the whole dam acts as a waste weir, which is sur- mounted by arches on which rests a roadway, and beneath these arches the waste waters are permitted to flow. Its lower face is given an ogee-shaped curve so as to reduce to a mini- mum the shock of the falling water, and there is a depth of 45 feet of back-water on its toe, which forms a sort of water cushion. Its maximum height is 136 feet, while the greatest depth of water is 129 feet. Its width at base is 1 17.7 feet, and the upper curved portion rests on a massive pedestal nearly rectangu- lar in cross-section and 43 feet in height. This dam is straight in plan, its total length on top being 1350 feet, and it is built 2QO MASONRY DAMS. VYRNWY DAM, WALES. throughout of large cyclopean rubble, the stones weighing from. 2 to 8 tons apiece. FIG. 86. CROSS SECTION OF VYRNWY DAM, WALES. 277. Betwa Dam, India. This structure, which has an- unusually heavy cross-section (Fig. 87), performs the functions of a weir, the flood waters passing over the entire crest to an extreme depth of 6 feet. In plan it is built in three tangents, following the line of an outcrop of rock. Its total length is, 3296 feet, its top width being 15.2 feet, and its maximum height about 64 feet. The down-stream face of this weir is. supported by a buttress or block of masonry 15 feet in width I BE 7 'W 'A DAM, INDIA. 293 and 20 feet in height, while above it the back-water in the river rises to an additional height of about 10 feet, so that the flood waters will fall on a water cushion of this depth and then on the solid buttress. This structure is built throughout of un- coursed rubble masonry, its faces, however, being coursed with dimension stone and the coping being of ashlar. In the river some distance below its highest portion is built a subsidiary FIG. 87. CROSS-SECTION OF BETWA DAM, INDIA. or smaller weir, which backs the water up against the toe of the main weir in such manner as to form the water-cushion on which the floods may fall. The extreme height of this sub- sidiary weir is 1 8 feet, and the height of overfall from the main weir to the surface of the water cushion is 2\\ feet, though in time of greatest flood this will be reduced to 8 feet. The top width of the subsidiary weir is 12 feet, and its walls are nearly vertical on the down-stream side, with a slope of 10 to I on the up-stream side. TURLOCK AJVD FOLSOM DAMS. 295 278. Turlock Dam, California. This structure (Fig. 88) is a little heavier in cross-section than theory alone would demand, as it is expected that the flood waters of the Tuo- lumne river will pass over its entire crest to a possible maxi- mum depth of 1 6 feet. About 200 feet below the main dam is built a subsidiary weir 20 feet in height and 120 feet in length, its top width being 12 feet. This weir will back the water up against the toe of the main weir to a depth of 15 FIG. 88. CROSS-SECTION OF TURLOCK DAM. feet, thus giving a water cushion on which the floods may fall. The main weir is straight in plan, 310 feet in length on top, 96 feet in width at the base, 20 in width on top, and 130 feet in maximum height, and is built throughout of uncoursed rubble masonry. There is no escape-way, while there are a couple of undersluices which served to pass water during con- struction. 279. Folsom Dam, California. This structure (PL XXVII), like that just described, acts only as a diversion weir. It is 69^ feet in maximum height on the up-stream side, and 98 feet in height on the down-stream side. Its cross-section is unusually heavy, as flood waters to a depth of over 30 feet are expected to flow over its crest (PL XXVIII). Its top width is 24 feet and its extreme width at base 87 feet, the toe termi- nating in a heavy buttress of masonry. Its total length on the crest is about 520 feet, a large portion of which consists of a retaining wall leading to the canal entrance. One hundred and eighty feet in length in the centre of the main dam is lowered a depth of 6 feet to form a wasteway over which the MASONRY DAMS. CROSS SECTION QF'WEIR PLATE XXVIII. FOI.SOM CANAL, PLAN AND CROSS-SECTION OF WEIR. COLORADO RIVER DAM, TEXAS. 297 floods jnay pass, and this wasteway is closed by a single long shutter, consisting of a Pratt truss backed with wood, which can be raised and lowered by means of hydraulic presses, operated from a power-house near by. The dam is constructed throughout of uncoursed rubble masonry. 280. Colorado River Dam, Texas. This dam is built .-.cross the Colorado river for the supply of water and water- power to the city of Austin, Texas. Its interior is of rubble masonry, faced on both sides and on top with large cut blocks of coursed granite. It is 1275 feet long on top, 1125 feet of which are constructed as an overfall wasteway, and 66 feet in maximum height, its upper face being vertical. The lower face has an easy ogee-shaped curve (Fig. 89), calculated to pass the FIG. 89. CROSS-SECTION OF COLORADO RIVER DAM. waters with such ease that the erosive action at the base will be reduced to a minimum. The structure is practically a great overfall weir, the maximum flood to be passed being estimated at 250,000 second-feet from a catchment basin of 50,000 square miles. The cross-section is somewhat heavier than theory would demand if the dam were built to act as a retaining wall only. The lower portion of the down-stream face is curved with a radius of 31 feet tangent at the bottom to low-water surface, so as to deliver the floods away from the toe and against the back-water in the river. The upper end of the curve is tangent 2 9 8 MASONRY DAMS. to the main slope, which has a batter of 3 in 8, and ends on top in a curve of 20 feet radius. This top curve is tangent to the horizontal crest line, which is 5 feet wide. The total top width is 16 feet, and the maximum width at base 68 feet. 281. Bear Valley and Zola Dams. The most notable curved dams are the Bear Valley dam in California, and the FIG. 90. CROSS-SECTION OF BEAR VALLEY DAM. Zola dam in France, the cross-sections of which are unusually light, as they depend chiefly on their curved plan for their FIG. 91. PLAN AND ET.KVATION OF BEAR VALLEY DAM. stability. The former (Fig. 90) is but 3.2 feet in width on top, and at a depth of 48 feet below its crest its width is but 8.4 feet. At this point an offset of 2 feet is made on each side, BEAR VALLEY AND ZOLA DAMS. 299 and its width thence increases to 20 feet at its base, which is at a point 64 feet below its crest. This structure is 450 feet in FIG. 92. CROSS-SECTION OF ZOLA DAM, FKANCK. length on top, and in plan it is curved with a 3OO-foot radius (Fig. 91). It is built throughout of the best uncoursed rubble 3OO MASONRY DAMS. granite masonry, and depends almost wholly on its curved plan and the excellence of its construction for its stability, since the lines of pressure with the reservoir full fall from 13 to 15 feet outside of its base. The Zola dam (Fig. 92) is 123 feet in maximum height, 19 feet in width on top, and 41.8 feet in width at the base. Its length on top is 205 feet, and it is curved with a radius of 158 feet. Like the Bear Valley dam, it depends chiefly on its curvature and the excellence of its construction for its stability. The material of which it is built is uncoursed rubble masonry. 282. Works of Reference. Storage Works. BAKER, IRA O. A Treatise on Masonry Construction. John Wiley & Sons, New York, 1890. CHURCH, IRVING P. Mechanics of Engineering. Fluids. John Wiley & Sons, New York, 1889. FANNING, J. T. Hydraulic and Water-supply Engineering. D. Van Nostrand & Co., New York, 1890. FRANCIS, J. B. High Walls or Dams to resist the Pressure of Water. Trans. Am. Soc. C. E., New York, vol. xix, 1888. GOULD, B. SHERMAN. Contract and Specifications for Building a Masonry and Earthen Dam. Engineering News Pub. Co., New York. HALL, WM. HAM. Irrigation in Southern California. Report as State Engineer of Cal. Sacramento, 1888. JACOBS, ARTHUR. The Designing and Construction of Storage Reser- voirs. D. Van Nostrand & Co., New York, 1888. KRANTZ, J. B. A Study on Reservoir Walls. Translated by F. Mahan. John Wiley & Sons, New York, 1883. MERRIMAN, MANSFIELD. Text-book on Retaining Walls and Masonry Dams. John Wiley & Sons, New York, 1892. MCMASTERS, JOHN B. High Masonry Dams. D. Van Nostrand & Co., New York, 1876. RONNA, A. Les Irrigations. 2 vols. Firmin-Didot et Cie, Paris, 1889. VISCHER, HUBERT, and WAGONER, LUTHER. On Strains in Curved Masonry Dams. Trans. Tech. Soc. Pacific Coast, vol. xi, 1890. WEGMANN, EDWARD, JR. Design and Construction of Masonry Dams. John Wiley & Sons, New York, 1889. WEISBACH, P. J., and Du Bois, A. JAY. Hydraulics and Hydraulic Motors. John Wiley & Sons, New York, 1889. CHAPTER XX. WASTEWAYS AND OUTLET SLUICES. 283. Wasteways. Wasteways, escapes, or spillways as they are sometimes called, are an essential adjunct of every dam. They are to a reservoir what a safety-valve is to a steam- engine ; the means of disposing of surplus waters due to floods and preventing these from topping the dam and possibly caus- ing its destruction. Water should not be permitted to flow over the crest of a masonry dam unless it has been built in an unusually substantial manner calculated to withstand the shock of this overfall. It should never be permitted to flow over the face of a loose-rock or earth dam. The outer slope of an earth dam is its weakest part, and if water is permitted to top it it will speedily cut it away and cause a breach. Too many of the great floods which have occurred in recent years bear testimony to the necessity of constructing substan- tial and ample wasteways. Moreover, an ample wasteway being provided, the greatest care should be exercised to maintain it always open and ready for use, independent of all undersluices and other discharge outlets which may be closed by valves or other mechanical means. To the lack of one or both of these precautions was due the destruction of the South Fork dam in Pennsylvania in 1889; of the Walnut Grove dam in Arizona in the spring of 1890, and many other similar catastrophes. Had the wasteway of the South Fork dam been ample, as it origi- nally was, the water would not have flowed over the crest of the dam and have caused its destruction. But the wasteway was barred by fish-screens, and these not only obstructed the pas- 301 302 W 'A S TE WA YS A ND O U TLE T SL UICES. sage of the water but caught floating timber and logs brought down by the flood, which so diminished the area of the spill- way as to cause the waters to top the dam. In the case of the Walnut Grove dam the area of the wasteway was unquestion- ably insufficient, resulting consequently in the passage of much of the flood water over the dam crest and resulting in the destruction of the work. 284. Character and Design of Wasteways. In design- ing a wasteway for a reservoir data relating to the greatest floods likely to occur must be sought for in its catchment basin, and the dimensions of the wasteway must be proportioned for the extraordinary floods. The methods of determining the great floods and the necessity for looking for signs of these in the valleys has already been discussed in Chapter IV. Should other reservoirs exist above that under consideration provision should be made for the discharge of their contents lest their embankments give way; this can only be done by considering their volume and calculating the velocity and consequent quantity which will reach the dam at any one time. Having fixed on the area of the wasteway from a knowledge of the maximum flood to be discharged, the chief consideration to be borne in mind is the relation of its depth to its length. A long wasteway may permit the loss of too great a volume of water if exposed to the action of the wind, whereas a short one renders it necessary to give the dam an increased height in order that it may have the required capacity. The depth of the wasteway will be largely regulated by the probable wave- height, and this will depend on the depth and fetch of the res- ervoir (Article 237). The difference in height between the crest of the dam and the wasteway will generally vary between 3 and 10 feet as limits. Care should always be taken in designing a wasteway to rapidly increase the slope of its bed immediately below the crest of the waste weir, so that there shall be no piling or banking up of water to retard the discharge. A quick drop beyond the crest considerably enhances the discharging capacity. 285. Discharge of Waste Weirs. For the calculation of DISCHARGE OF WASTE WEIRS. 303 discharge the wasteway can be considered as a measuring weir subject to the weir formulas. If the crest of the wasteway has a sharp square edge or falls away with considerable suddenness on the lower side, Francis' formula (Art. 86) may be applied with approximate results, and we have ...... (i) The mean velocity of flow o'ver the crest is and multiplying the depth of water on the weir h into its length / we get the volume of discharge. When the overfall from the crest is not sudden (2) in which m is a coefficient of contraction with the value of about .62. Where the overfall weir has a wide crest the follow- ing formula, suggested by Mr. Francis, is the most accurate for depths between 6 and 18 inches, viz., 0=3.012/7* ''53 ......... ( 3 ) Another formula and one commonly used in India for deter- mining the discharge of wasteways is Q = I X \c X 8.02 in which c is a coefficient which varies with the form of the weir and rarely exceeds .65, though with a majority of weirs it is about equal to .62. In which case where d is the maximum depth in feet of water to be permitted to pass over the weir. Ordinarily there is no velocity of ap- proach to a reservoir wasteway, though should the water reach the latter by a cut it may be necessary to take the velocity of approach into account. 304 WASTEWAYS AND OUTLET SLUICES. 286. Classes of Wasteways. Wasteways maybe divided into three general classes, depending upon the character of the dam and the topography of the site. First, the entire struc- ture, if of masonry, may be utilized as a wasteway. This can only be done by making the cross-section of the dam unusually heavy and providing it against the shock of falling water as in the case of the Folsom, Turlock, Betwa, Colorado River, and Vyrnwy dams (Articles 276 to 280). Second, if the dam is of masonry it may be given the theoretical cross-section and the wasteway made in one end of it, if the dam at this point is sufficiently low not to subject it to great shock from the falling water. This is the case with the Bhatgur, Tansa, and New Croton dams (Articles 269 to 271). It is never advisable to build a wasteway in earth or loose- rock dams, as it is difficult to make a safe bond between the masonry wasteway and the earth dam, and unless extraordi- nary circumstances demand it such an arrangement should be avoided. In some cases, however, this has been done, great care being taken in connecting the two classes of work and the wasteway being carefully lined with masonry and provided with masonry wing walls for the protection of the earth em- bankment. The third general class of wasteways is where these are built in the hillsides at some distance from the dam. If on the slopes adjacent to one end of the dam, the discharge water must be so directed by retaining walls that it will flow back into the stream channel clear of the toe of the dam. Such wasteways may be excavated in the solid rock, or if in earth they should be paved or lined with masonry. The safest dis- position for the wasteway is at some favorable point in the rim of the reservoir entirely free and away from the dam. This may be through some low saddle, which if too low may be filled in with a waste weir of masonry, or if too high may be excavated to the proper elevation. Such an isolated channel is frequently found beyond some spur immediately adjacent to one end of the dam and discharging back through a separate channel. This is the case in the Oak Ridge reser- EXAMPLES OF WASTEWAYS. 30$ voir dam in New Jersey, the Ashti and Periar dams in India, and the Pecos and Idaho dams in the West. 287. Shapes of Waste Weirs. The forms of waste weirs for dams vary considerably with the circumstances under which they are constructed. Their general design is very sim- ilar to that of weirs used for purposes of diversion and thor- oughly discussed in Chapter XII. It is therefore unnecessary here to enter into any general discussion of the thickness and dimensions of waste weirs or their shapes. They may be given the ogee shape (Article 137) in order that the water falling over them shall produce the least vibration in the structure ; or water-cushions may be employed to deaden the effect of the falling water (Article 138). 288. Examples of Wasteways. Brief descriptions and illustrations of wasteways were given in Articles 269 to 273. The wasteway of the Sweetwater dam is peculiar. It is built as a continuation of the main dam and, as shown in Plates XXIV and XXV, the water from the reservoir enters the several separate passageways over a waste weir and drops into a shallow water-cushion. Thence it flows through a chan- nel partly excavated in the side of the ravine and partly con- structed by means of an artificial wall which carries the water clear of the toe of the dam. The wasteways to the Periar dam are two in number, one at either end of the structure ; both are separated from the main dam by means of low sad- dles of rock. That on the right bank is cut down for a length of 420 feet till its crest is 11 feet below that of the main dam. On the left bank the solid rock is 50 feet below the crest of the dam, and the saddle is closed with a waste weir of ma- sonry (Fig. 84) built up to the same level as that of the wasteway on the other bank. At a distance of 60 feet from this waste weir is built a low subsidiary weir 10 feet in height with its crest 30 feet below the upper wall, thus forming a water-cushion on which the floods fall. This escape weir is so designed that the lines of pressure fall within the middle third when a depth of 12 feet of water is passing over the crest, and 3O6 WAS TE WA YS A ND OUTLET SL VICES. so that the water shall fall clear of the weir to the water-cushion below. A similar waste weir to that just described and one some- what similarly situated is that at the Idaho Mining and Irriga- tion Company's dam described in Article 240. The wasteway of the Ashti tank in India consists of a channel having a clear width of 800 feet excavated through a saddle in the high ridge bounding the reservoir on its western side. The bed of this channel at its entrance forms the weir crest and is level for a length of about 600 feet and then falls away with a slope of I in 100 to a side drainage channel. The dam is 12 feet in height above the crest of the wasteway and the greatest flood anticipated would raise the water in this wasteway to 7 feet above its crest or to within 5 feet of the top of the dam just sufficient to prevent waves from topping it. 289. Automatic Shutters and Gates. The use of flash- boards or any similar permanent obstruction in a wasteway in order to increase the storage capacity of the reservoir is greatly to be condemned. Such obstructions must be removed at the time of great floods or else these will top the dam. The result of their use is that the area of the wasteway is diminished below the point of safety, while the integrity of the structure depends upon the careful attention of the watchmen, who should remove the flashboards. Automatic shutters, however, have been used with considerable success in a few instances. These, however, should only be employed where water is of the greatest value and the saving of every drop is essential. One of the most desirable forms of these is that shown in Fig. 93. It consists of a row of upright iron shutters, each 1 8 feet long and 22 inches high. These are supported by struts or tension rods hinged to the crest of the weir on the up-stream side and to the upper side of the shutter at about two thirds of the distance from its crest, or, in other words, below its centre of gravity. As soon as the water level ap- proaches the top of the shutter it causes its lower end to slide inward and the whole falls flat against the top of the weir, offering no obstruction to the passage of the water. AUTOMATIC SHUTTERS AND GATES. 307 An ingenious form of automatic weir gate (PL XXIX) was devised and patented by Mr. E. K. Reinold for use on the Bhatgur reservoir in India. This gate is of value where water is precious, and can be utilized with considerable safety to retain water to the full storage capacity of the reservoir. The gate falls automatically as soon as the water reaches its crest, and continues to fall as the flood rises until the full discharge capacity of the wasteway is brought into action. The gate then closes as the flood subsides, enabling the reservoir to retain the maximum amount of water. The gate slides vertically on two contact surfaces one of which is the face of the wasteway against which it presses while the other surface is attached to the face of the gate. These surfaces slide parallel to each other and are the sur- faces of inclined planes. The gate rests on wheels running on rails, and the axes of the wheels are parallel to the line of the rails and at a slight angle to the contact planes (PL XXIX), Up stream slope FIG. 93. CROSS-SECTION OF SHUTTER ON SOANE WEIR, INDIA. so that the latter do not touch until the gate is fully raised or closed, thus permitting by leakage a large amount of flood water to run out of them until the last moment. The gates are operated by means of counterpoises balanced in water cisterns, the weight of these counterpoises exceeding the weight of the gate by a little more than the amount of friction, and they act by displacing their volume in the water cisterns in which they plunge, thus lessening their weight by that volume of water. As the water flows over the top of the gate it simultaneously enters the cast-iron cisterns in which the counterweights hang. When the water ceases to enter the cisterns owing to its level having fallen below that of the inlets, 3O8 WASTE WAYS AND OUTLET SLUICES. to/.*" ' UNDERSLUICES. 309 it runs out from holes in the bottom and the weights then be- come heavier than the gate and raise it. 290. Undersluices. Undersluices perform the same func- tion for storage dams as do scouring sluices in diversion weirs. Their object is to remove or to prevent the deposition of sedi- ment in the reservoir. Undersluices have little effect in pre- venting the deposition of silt unless the area of their opening is great compared to the area of the flood, while they are use- less for the removal of silt already deposited. This is shown by the manner in which such reservoirs as Lake Fife and the Vir reservoir in Bombay, India, and the Folsom reservoir in California have silted up in spite of them. If the dam is high and the discharge through the undersluices will keep the flood level below the full supply level, they may be efficient in preventing the deposit of silt by carrying it off in suspension. If the dam is low and the area of the undersluices will not en- able them to keep the flood-level below full-supply level, they will have but little effect. This has been partly proved at the Betwa and Bhatgur reservoirs in India, where experience shows that their scouring or preventive effect is felt but a few feet to either side of the sluice, and silt will deposit close to the entrance. In other words, undersluices do little more than keep an open channel above them. 291. Examples of Undersluices. The most successful attempt to utilize undersluices for the clearance of silt is at the Bhatgur reservoir in India. There are fifteen undersluices in the centre of the dam near its bottom, their sills being 60 feet below high-water mark (PL XXII). Each of these undersluices is 4 by 8 feet in interior dimensions, and they are lined through- out with the best ashlar masonry. Under a full head they will discharge 20,000 second-feet, and the velocity through them is 36 feet per second. Each undersluice is closed by a heavy iron gate which slides vertically and weighs about 2 tons. They are operated by steel screws worked from above by a female capstan screw turned by hand levers. Stout wooden gratings protect the gates from injury by floating objects. The undersluices are placed about 30 feet apart, and this 310 WASTE WAYS AND OUTLET SLUICED. space was filled with sediment shortly after the completion of the dam. In the bottom of the Folsom dam in California there is a set of three undersluices, the object of which is to remove silt depos- ited in the reservoir (PL XXVIII). These undersluices are built in the centre of the weir near its bottom and are under a head of 60 feet, the area of each one being 4 by 4 feet. While these undersluices have not impaired the integrity of the structure, they have been of little service in preventing the deposit of silt, as their area compared with that of the floods is compara- tively small. Where undersluices have been employed to carry away silt-laden waters from in front of a canal head they have proved more effective. In the bottom of the Idaho Mining Company's dam an undersluice is projected the sill of which will be 13 feet below the headgates of the canal and 24 below the crest of the dam. It will be 4 feet wide by 8 feet high inside, closed by a gate operated by a screw from the top of the dam. A similar under or scouring sluice is built in the bottom of the Pecos dam adjacent to the entrance to the canal head. 292. Outlet Sluices. As the object of a storage dam is to impound water that it may be drawn off when wanted, one or more outlet sluices must be constructed at the level at which water can be drawn off. These outlet sluices either terminate in pipe lines which carry the water to the point of distribution or discharge directly into the canal head or back into the stream channel, to be again diverted lower down. The greater the depth at which these sluices are placed, the greater the available capacity of the reservoir. They may either be built in the body of the dam or through the confining hillsides independently of the dam. The latter is by far the better and safer method, and wherever practicable should be employed, as anything which breaks the homo- geneity of the dam is a menace to its integrity. With an earth dam this is especially true, and its greatest source of weakness is the masonry discharge conduit passing through it. Simple pipes should never be laid through an earth embank- ment, as under the pressure of the water in the reservoir this OUTLET SLUICES. 311 is certain ultimately to find its way along the line between the pipe and the earth embankment or through a loose joint in the pipe, and the water which enters the embankment in this manner will rapidly increase in quantity until the structure is destroyed. It is essential that the outlet sluices, valves, pipes, etc. r should always be accessible for inspection and repair in order that the constant use of the reservoir may not be interrupted. When they must be placed in the embankment a masonry con- duit should be built through it, and for convenience of inspec- tion an iron pipe should be placed in this. The conduit should be of such dimensions that a man can pass through it, and the pipe should be so placed within it as to be easily seen and re- paired. In order to prevent the travel of seepage water along the outside of the conduit, rings of masonry should be placed at short intervals along its length, and these should project not less than from I to 2 feet from its surface. The chief objection to laying a conduit through a dam is its liability to fracture through settlement. Better and safer than this is to lay the discharge pipes in a trench dug under the foundation of the dam in the surface rock or soil. Such a trench should be substantially lined and roofed with concrete, and will offer little inducement for travel of seepage water. The best method of all, however, for the placing of outlet pipes is to build them through the surface rock or soil of the country, excavating a tunnel for this pur- pose and laying the pipes in it, the whole being away from and independent of the dam. This insures them against any damage from settlement in the structure. Sometimes the entrance to the outlet culvert is not placed at the lowest level of the reservoir, but at about two thirds the way up the embankment from the bottom, or at such height that the pressure will enable a siphon to draw water off from the lowest depths of the reservoir. This siphon pipe is carried down to the bottom of the reservoir and passes up through the culvert in which is placed the main pipe con- nected with the valve chamber and supplied directly from 312 WASTEWAYS AND OUTLET SLUICES. orifices above the level of the conduit (Fig. 94). Where a reservoir embankment is very low say 25 feet or under it may be discharged by simply carrying a siphon pipe over the top of the embankment with no outlet pipe or conduit through the embankment. FIG. 94. CROSS-SECTION OF EARTH DAM 293. Gate Towers and Valve Chambers. The valves .or controlling the admission of water to the outlet sluice are either operated from a valve chamber let into the body of the dam or from a gate tower situated in the reservoir at a point vertically over the inlet to the discharge conduit. In order that these valves shall not be worked under too great pressure, water is usually admitted to the tower or well from orifices placed at several depths, and in this well the conduit heads. At its exit at the lower side of the dam is generally placed a second valve chamber or gatehouse for the control of water which is admitted to the distributing pipes or canal. The orifices ad- mitting water to the well tower are closed on the outside by plugs or close-fitting valves which can be operated from the top of the tower or valve chamber ; while the valve admitting the water from the bottom of the well to the outlet sluices is operated either from the tower or from the bottom of the well pit by screws and hand gearing. In this manner the attendant in charge has full control of the whole outlet works, and all pipes and valves are under perfect control so that the supply can at any time be arrested for the repair of pipes. In case a gate tower is constructed independently of and away from the body of the dam, great care must be taken to make it suffi- ciently substantial to withstand the thrust of ice, or it should be buttressed against the side of the dam. GATE TOWERS AND VALVE CHAMBERS. 313 The outlet sluicepipe which passes through the embank- ment may be connected on the inside of the reservoir by a flexible joint with another pipe of the same diameter, to the end of which is attached a float. This pipe can thus be moved vertically, and admits of the water being drawn off from the surface where the pressure on the valve is the least. Where the expense will permit, the better method is that of admitting the water to a valve well through orifices situated at varying heights. One of the great difficulties encountered is to insure a constant discharge from the reservoir with a constantly vary- ing head in it or in the gate well. The usual method of insur- ing a constant discharge is by opening the valve gates control- ling the admission of water to the outlet sluice to a greater or less extent according to the amount of water required, though automatic systems of maintaining a constant discharge irre- spective of the head have been used with more or less success in a few cases. The inlets to the valve chamber are of two general classes. That illustrated in Fig. 95 is of the kind em- FIG. 95. VALVE-PLUG, SWEETWATER DAM. ployed on the Sweetwater dam in California, and consists of a simple cast-iron plug let into the top of the pipe, the end of which is bent upward. This plug is held in position by the pressure of the water and is removed by a chain operated from above by a windlass. In Plate XXV is shown the method of placing the valves at varying heights and the arrangement of air valve and gatehouse at the lower end of the dam. Another method of admitting water to the valve chamber is by means of rectangular openings in the side of the chamber on the inner surface of which stop valves are bolted. These are usually of cast-iron, the seat and bearing of the valve being faced with bronze composition. Above this projects a screw WASTEWAYS AND OUTLET SLUICES. stem which is operated from above by means of a female cap- stan screw. Where the area of such valves exceeds 4 or 5 square feet or the pressure is more than 20 to 25 pounds, some geared motion is usually necessary to enable a single man to operate it. The intake valve permitting the water to pass from the valve chamber to the outlet sluice is usually a sliding valve, working on bronze bearings and operated from above by a screw and hand gearing. It is not unusual to employ more than one such valve, according to the amount of water to be admitted and the consequent number of outlet pipes required. The foundations for gate towers must be of the most substan- tial character, especially where they are attached to loose rock or earth dams, in which case the foundation must be carried down to a sufficient depth to insure stability. 294. Examples of Gate Towers and Outlet Sluices. Owing to the low inclination of the inner surface of earth em- bankments or loose-rock dams, it is necessary to construct the gate tower controlling the outlet sluice at some little distance in the reservoir so that it shall come above the entrance to the sluice. This method of construction is occasionally employed on masonry dams, and an excellent example of such a work is that illustrated in Plates XXIV and XXV, showing the gate tower to the Sweetwater reservoir. In Fig. 96 are shown in plan and cross-section the arrangement of the valve chamber and intakes of the proposed Bear Valley dam in California. As will be noticed, the valve chamber or tower is built of masonry as a projection on the inner surface of the dam, thus becoming practically agate tower attached to the centre of the dam. The intake valves in this case are similar to those em- ployed in the Sweetwater dam, and discharge directly into a valve well. A much better practice, however, is that followed on the Vyrnwy dam in Wales and the San Mateo dam in California. In the case of the former there are two discharge sluices operated from valve-houses built in the body of the dam for discharging compensation water back into the stream. The main valve chamber, however, for the supply of water to the aqueduct is situated at a point on the shore of the reservoir GATE TOWERS AND OUTLET SLUICES. 315 about three fourths of a mile distant from the dam ; entirely independent of it, and out in the lake at such a distance as to control water at nearly the maximum depth. The valves and other mechanisms employed in this tower are all operated by hydraulic power furnished from a water-wheel supplied by a small mountain reservoir. In the case of the San Mateo dam (PL XXIII), and the proposed Citizens* Water Company dam in Colorado, the valve tower is situated at a point quite independ- FIG. 96. VALVE CHAMBER AND VALVES. ent of the dam, and the outlet conduit passes through the country rock at a sufficient distance from the abutments of the structure to be entirely free from the pressure of its possible subsidence. As shown in the illustration, water is admitted at three different elevations through inle^ pipes which discharge directly into a main iron standpipe passing vertically through a shaft which is the entire height of the dam. The entrance of this water to the standpipe is controlled by plunger valves operated by hand wheels and approached by a stairway passing through the tower. At the outer end of the discharge pipe is another gate-well where the main supply is regulated. CHAPTER XXI. PUMPING, TOOLS, AND MAINTENANCE. 295. Underground Cribwork or Tunnels. Submerged cribs have been satisfactorily employed by the American Water Company on Cherry creek in Colorado, and by the Citizens' Water Company on the South Fork of the Platte river in Colorado. The former enterprise consists of a sub- merged open crib dam sunk in the gravel bed of Cherry creek, FIG. 97. GATHERING-CRIBS, CITIZENS' WATER Co., DENVER. and resting on solid rock which is 73 feet below the surface of the stream. This cribwork is 70 feet in height, and its crest is 3 feet below the bed of the stream. This is not a dam, as it. 316 T UNNELLINGP UMPING. 3 1 / does not extend across the entire channel of the stream, but it stops the movement of that portion of the subsurface water which enters the cribwork. This is open on the upper side but closed on the down-stream side, and consists of timbers 14 inches in dimension at the bottom of the dam, which is de- creased to 8 inches at the top. These timbers are placed 4 feet apart across stream, and are planked on both faces with interstices of 3 inches on the upper face. The water caught in this cribwork is pumped to the surface. The Citizens' Water Company develope the underground waters of the Platte river by means of a series of gathering galleries, consisting of perforated pipe and open cribwork laid at a depth of from 14 to 22 feet below the surface of the gravel bed of the stream. The cribs (Fig. 97) are 30 inches square, and about a mile of these have been built running up the bed of the stream, besides about a mile of perforated pipe 30 inches in diameter. The average daily yield obtained by these gal- leries is nearly 10 acre-feet of water, which is led off through the pipes by natural flow. 296. Tunnelling Underground. For the development of underground waters, tunnelling, which is a little different from the cribwork just described, has been resorted to in a few in- stances. For the development of the water supply of Ontario Colony (Art. 42), and at the mouth of the Santa Anna river in California, tunnels have been built under the stream bed, the cross-section of these being trifling, and the tops roofed by open lagging, while the sides and bottom are formed into an imper- vious channel by a framing of woodwork or a cement lining. The seepage water which enters these tunnels is led off through open cuts, and is let into the irrigating ditches. 297. Pumping or Lift Irrigation. The methods of irri- gation heretofore considered are those in which the water reaches the irrigable land by means of gravity or natural flow. Frequently, however, there are large volumes of water which are situated at such low levels that gravity will not carry them to the field to be irrigated, and this water must be raised or lifted by means of pumps or other lifting devices. Lift 3l8 PUMPING, TOOLS, AND MAINTENANCE. irrigation may be employed to utilize the water from wells or from natural streams flowing at a lower level than the field worked, or it may be employed to raise water from the canals to higher levels than those reached by them. When the gravity sources of supply have been entirely utilized, large areas of land may still be brought under cultiva- tion by the employment of pumps. As irrigation is practised the subsurface soil becomes saturated, the ground-water level is raised, and much of the water which is delivered by gravity systems may by pumped up and re-employed for irrigation, thus greatly adding to the duty of the ultimate sources of water supply. The value of pumping for this purpose has been recognized in the older European and Asiatic countries for ages. A very large proportion of the irrigation in Europe, China, Japan, India, and Egypt is by means of lifting. Among the various methods more commonly practised in Asia for lifting water from wells are the Mot of India, which consists of a rope passing over a pulley down into the well and to the bottom of which a bucket or other receptacle is attached. This is raised by two bullocks walking away with the rope and raising the bucket to the top of the well, where it is emptied into the distributing ditches. One of the more common methods of pumping is by means of the Persian Wheel, which consists of a vertical wheel on the outer rim of which are at- tached buckets which dip into a well, and as they reach the upper circumference of the wheel spill their water into a trough which leads it to the fields. This wheel is made to revolve by means of bullock walking in a circle and drawing a sweep attached to rough, cogged gearing. By this means two bullocks are estimated as capable of lifting 2000 cubic feet of water per day. Still another method of lifting water is by means of the Paecottah, which is simply the old-fashioned well-sweep of this country. By its use from 400 to 2000 cubic feet of water can be raised a day, while with the Mot, two bullocks working 10 hours a day will raise about 3f acre-feet of water in a season of 90 days. In this country the value of pumping as a means of irri- WINDMILLS AND WATER-WHEELS. 319 gation is not yet fully appreciated : a few windmills and water wheels are utilized for this purpose, and some small amount of pumping is done by steam-power, though the value of the water supply to be derived from the latter mode of lifting is destined to increase greatly in the near future. 298. Windmills and Elevators. Windmills have been extensively used in the San Joaquin valley in California and in a few places in the Colorado plains and elsewhere in the West for raising water for purposes of irrigation. As yet they have been employed chiefly for pumping for domestic uses, but as water becomes more valuable windmills are rinding greater favor. Most of these machines are patented, and the makers furnish all the information desired relative to their cost, capacity, and duty. A modern ten-foot wheel will average about one eighth horse-power developed for a stiff breeze and will cost about six cents per horse-power per hour. Larger wheels are much cheaper. A fifteen-foot wheel will irrigate about seven acres at a cost of $8 per acre per annum. A link-belt water elevator manufactured in Chicago has been successfully employed in the West for raising water for irrigation. It is operated by horse-power, and consists of a link belt erected at a slight inclination from the vertical and revolving over two wheels, one pivoted a little below the level of the water surface and the other at the summit of the height to which the water is to be lifted. On this belt are a number of iron vanes attached at intervals of about 8 inches apart, and these pass up through a closed wooden boxing, so that each vane acts as a lift and raises the water above it, as does the old chain pump used in shallow wells. This water is emptied out through a lip to a flume, from which it runs to the irrigated lands. With a belt speed of 300 feet the smallest of these elevators will raise about 20 cubic feet per minute to a height of 10 feet ; the largest will elevate nearly 5 second-feet of water to the same height. 209. Water-wheels. Lifting water by means of under- shot water-wheels has been practised ever since the early placer operations in California, while in the older countries 320 PUMPING, TOOLS, AND MAINTENANCE. this method of lifting water is extremely ancient. The Noria of Italy is simply an undershot water-wheel of this description. As used in a few occasional instances in the West, these wheels are very similar in appearance to an old steamboat paddle- wheel, varying from 15 to 20 feet in diameter, the width of the wheel or the length of the paddles being from 6 to 10 feet. Such a wheel (Fig. 98) will rest either on cribwork abutting on the shores and in the river, or if the change in the flood height of the river is considerable it may rest on some variety of FIG. 98. VIEW OF WATER-WHEEL. anchored float which will permit it to rise and fall with the stream. On the outer circumference of these wheels are placed a series of buckets, one attached to each blade or paddle. These buckets may be constructed of tin, as old tin cans, or sometimes are constructed of wood, and as the wheel revolves they are filled as they are successively immersed* STEAM PUMPS. 32T When they reach such a point in their revolution that the water begins to spill out of them, it is caught in a trough suitably placed, and from this runs into a flume which leads it to the fields. Some of the water-wheels of this variety which have proved most successful on the Green river in Colorado are from 20 to 30 feet in diameter, the wooden axle being 5 inches in diame- ter, while the paddles dip about 2 feet into the water of the stream. The buckets, which are of wood, have an air-hole in the bottom closed by a suitable leather valve which permits of the bucket being rapidly filled by forcing out the air. These buckets are of wood, about 6 feet in length and 4 inches square, the capacity of each being about 5 gallons. There are sixteen paddles, to each of which is attached a bucket, thus enabling one revolution of the wheel to lift So gallons. The wheels make about two revolutions a minute, but as a large percentage of the water raised is spilled in emptying into the flume, each wheel has been found to handle about 4000 cubic feet a day. 300. Steam Pumps. The value of steam pumps for pur- poses of irrigation is not fully appreciated. There are many places where water can be pumped at comparatively small cost, and yet where the land it will serve must otherwise remain uncultivated but for water obtained by this means. Steam pumping for irrigation has been practised to a limited extent in Colorado, in Arizona, and in California, and many varieties of pumps have been employed for this purpose. It is not the intention in a work of this sort to describe the mechanical details of pumps, the value of each type, or the theories and formulas on which its operation and coal consumption depend. These can all be found fully discussed in the many books and pamphlets which have been written, more particularly on the subjects of " Mine Pumping" and " Pumping for Waterworks," or they can be obtained from the trade catalogues of pump makers. The chief point of difference between pumping for irrigation and pumping for mines and waterworks is in the height to which the water has to be forced. For purposes of irrigation it has rarely to be lifted to heights exceeding 25 or 322 PUMPING, TOOLS, AND MAINTENANCE. 30 feet, the water having to be raised generally from a well or river merely to a sufficient height to enable it to flow to the fields by the action of gravity. In a few notable instances it has been necessary to force the water to greater heights. In one case near Tucson, Ari- zona, the depth of the well is about 70 feet, and the water has to be raised this height to bring it to the surface of the ground. Perhaps the most remarkable instance of pumping for irriga- tion is in Italy, above Saluggia, on the Cavour canal. In this case the river Dora Baltea runs between rather high banks, and it was found impossible to bring water to the highest levels by means of natural flow. Accordingly the water that is taken from the river by one of the canals is pumped to the high level, whence it flows through a gravity system to the fields. There .are in all four canal levels along the hillside. Between the two lower is placed an extensive pumping plant operated by turbines, which receive their water from the upper of these two and tail into the lower canal, whence the water is distributed to low-lying fields. The lower of the two upper canals supplies water by means of an immense wrought-iron pipe 3 feet in diameter, with a head of 66 feet, to the pumps below, and these force it through another pipe of the same dimensions a total height of 140 feet to the high-level or distributive canal. The head of 66 feet on the pumps practically counterbalances that height in the 140-foot force-pipe. The varieties of pumps more commonly employed in the West are : I. Centrifugal pumps, which for their operation re- quire small steam-engines ; 2. Vacuum pumps, pulsometers, and a variety of patented pump made in Greeley, Colorado, known as the Huffer and Nye pumps ; and, 3. Pumping engines. 301. Centrifugal Pumps. The ordinary centrifugal pumps employed for irrigation have capacities varying between 500 and 1 500 gallons per minute, the height raised ranging from 20 to 80 feet. The average pump handles about a thousand gallons a minute or 2 second-feet, with heights of from 25 to 40 feet. Such a pump will irrigate from 5 to 10 acres per day, .and in the course of an irrigation season will handle about too PUMPING ENGINES. 323 acres. It is easily operated by one man, and the cost of maintenance for a season of three months amounts to $2.50 per acre, a relatively low water rate. A plant of this kind erected, including engine, boiler, and pumps, costs about $1500 equivalent to a first cost of about $15 per acre. 302. Huffer and Nye Pumps. These pumps have been used in large numbers in Colorado, Wyoming, and other por- tions of the West. Their capacity is small, averaging about 400 gallons a minute, or about one second-foot of water. They are capable of lifting water to heights of 15 to 20 feet, and of forcing it to low heights not exceeding 40 feet. They will irrigate from 3 to 5 acres per day, and if carefully handled from 50 to 100 acres in a season. The cost of operating these pumps, or the water rate, ranges between $3 and $5 per acre, while the first cost of the plant erected is about $1500, or from $15 to $30 per acre. 303. Pumping Engines. The writer is strongly in favor of the use of steam pumping engines in preference to centrifu- gal pumps or any of the peculiar patented varieties. The regular steam pumping engines, such as those made by Worth- ington; Knowes; Smith, Vaile & Co., and numerous others, cost little or no more than the varieties of pumps just men- tioned. Their maintenance cost is no higher, especially if compound or condensing engines are employed, while for large pumping plants they are much cheaper. Their operation re- quires more skilled labor than do the other pumps just men- tioned, but they are far less liable to get out of order, and the injuries can be more readily repaired. A high-pressure pump- ing engine which the writer saw in operation in Arizona was capable of irrigating 100 acres. This pump cost $1000 erected, and its running expense was about $5 per half second-foot of water raised. Its original cost was about $10 per acre irrigated, while the annual charge for running expenses amounted to about $5 per acre. A much better and more modern plant, operated near Tucson, Arizona, by Mr. A. Hartt, consists of two compound pumping engines, capable of irrigating 600 acres per day of 12 hours at a cost of $3 per day. The first cost of 324 PUMPING, TOOLS, AND MAINTENANCE. this plant laid down was $4200, while the well, which is 70 feet in depth through quicksand, cost $5000. Allowing the well to have been of average cost, the whole plant would have cost a little over $5000 equivalent to a charge of $8.50 per acre. The daily working expenses are about $3 for raising 5^- second-feet a height of 70 feet equivalent to an annual charge of about 70 cents per acre. The following is considered by the writer as a first-class pumping plant for the irrigation of about 1000 acres, where the water is to be pumped directly from a river or from an in- expensive well. This plant should consist of a duplicate set of the best of duplex compound pumping engines capable of rais- ing each about 1200 gallons per minute, with a suction height not greater than 15 feet, and a force height of 20 to 40 feet additional. In developing the irrigable lands from such a plant as this a boiler capable of serving both pumps should be purchased at first, but only one pump need be purchased until sufficient of the land is developed to necessitate the purchase of the other pump. Then only one pump will be required for the performance of the requisite service during much of the time, the other being a duplicate or relay pump in case of ac- cident. When, however, the entire property is to be irrigated,, both pumps will be called upon to do their highest duty. Such a pumping plant can be erected in nearly any portion of the West for about $5000, or at a charge of $10 per acre. The cost of maintenance and operation for this plant should not exceed 75 cents an acre, which is much lower than the ordi- nary water rates for gravity systems. 304. Irrigation Tools. There is little to say of the tools- required in the construction and management of irrigation works. The only tools here discussed will be such unusual mechanisms as special-shaped ploughs and scrapers. The tool- makers now manufacture hoes, spades and shovels, ploughs, and scrapers, of special designs for the making and control of ditches and furrows. Special ditching ploughs of unusual depth and reach are made as right and left ploughs, or some- times to throw dirt in both directions, having a V-shaped SCRAPERS. 325 shear, thus making a V-ditch at one operation. Ploughs of this kind are also arranged in gangs on sulkies. Corrugated ribbed rollers are employed where the surface of the country is even and level, and for such crops as grain and alfalfa. These consist essentially of a roller of the ordinary form, on the outer surface of which are iron rings or projec- tions of from 2 to 3 inches in height and of about the same width, placed from 4 to 8 inches apart. These projections are sometimes V-shaped. In running this roller over the surface of a well-harrowed field it leaves small furrows, down which the FIG. 99. BUCK SCRAPER. water runs, thus irrigating the crop much as if it were flooded. 305. Scrapers. The most useful implement for the ditch and canal maker is the scraper, of which there are many forms and with most of which engineers are familiar. Two forms of scrapers which have peculiar advantages in ditch-making over the ordinary road scraper are the Fresno and Buck scrap- ers. The latter is especially useful in sandy soil with a low lift and short haul, and cheaper work has been done with it than with any other implement. A common form of Buck scraper consists of a working or frond board with an effective length of about 9 feet and a height of 22 inches. This board rests hori- .zontally on edge on the ground, and consists of two planks each 326 PUMPING, TOOLS, AND MAINTENANQE. 2 inches in thickness, below which is fastened an iron cutting edge which reaches 7 inches lower (Fig. 99). At either end of the scraper is a cam-shaped roller 4 inches in height, on which the scraper is turned over. This board is fastened at the back to a tailboard 3 feet 9 inches in length, on which the driver stands, and is drawn forward by from two to four horses, the scraper being dumped by the driver merely stepping off the tailboard, the forward pull upsetting it. This implement han- dles a load of from I to i cubic yards, while its average daily capacity is about 130 cubic yards. For two horses a scraper of this form is rarely made over 6 feet in length, and the angle of the faceboard to the ground is about 28 degrees, and is regu- lated by the attachment to the tailboard. The Fresno scraper is most satisfactory in handling tough earth too heavy to be handled by a Buck scraper, and which would even give trouble to a road scraper. This implement is usually drawn by four horses and handles about 100 cubic yards a day, each load averaging a third of a cubic yard. 306. Excavating Machines. One of the most popular ditching machines now employed in the West is the New Era ditcher and excavator, which consists of a series of gang-ploughs suspended on wheels. An endless belt or elevator is attached to the truck above these ploughs in such manner that it catches the dirt turned up by them and deposits it on the banks of the canal (Fig. 100). This machine requires from eight to twelve horses and three men to operate it, its maximum lift being about 10 feet, while each plough makes a furrow 12 inches wide and 6 inches deep. These machines have attained an average capacity of 100 cubic yards per linear mile and handle about 1000 cubic yards in a day's run. They are of use not only in excavating and building canals, but also in building low earth embankments for storage reservoirs. The most elaborate apparatus yet employed in canal con- struction is the great canal excavator built by the San Fran- cisco Bridge Company. This machine consists of abridge truss supported on wheels running on rails on either bank of the canal. This deck truss has on it a track on which the engine-house EXCAVATING MACHINES, 327 arid machinery travel back and forth across the canal, and the excavator consists of a dredging arm carrying an endless chain of buckets. The material brought up by these is deposited on one of two endless belt-carriers running on booms which dump it on either spillbank. The engineer can cause the excavator to move across the canal on the truss bridge, or can raise or lower the excavating arm carrying the buckets, causing these to move forward and perform their work. There are twenty- FiG. 100. NEW ERA EXCAVATOR. six of these buckets, each having a capacity of cubic yard, and the apparatus will excavate 3000 cubic yards a day in hard- pan. This machine has been found cheapest and most effec- tive in material so hard that a pick will hardly penetrate it, and especially in excavating under water where scrapers cannot be used. In earth it has excavated from 4000 to 5000 cubic yards a day, at an average cost of 7 cents per cubic yard. Dredges of various forms are employed on the larger canals to remove silt which may be deposited in them, and to repair and straighten banks which have been cut down or eroded by the action of the water. Such dredges are usually employed on scows or flatboats, and are operated by small steam engines, 328 PUMPING, TOOLS, AND MAINTENANCE. being similar in design and in construction to the ordinary dredges employed in river and harbor work, and in like opera- tions. 307. Maintenance and Supervision of Canal Works. Careful attention should be paid to the proper maintenance and the making of all needful repairs on the lines of canals, reservoirs, and other irrigation works. The expenditure of an exceeding small amount of time or money in repairing an in- jury to canal banks or other works may, if done in time, prevent great destruction of life and property consequent on an injury to the canal system. In order that these repairs may be intel- ligently made, and that damage to the canal property may be discovered in time, a suitable system of supervision must be inaugurated upon the completion of construction. Such a system should include an engineer, a superintendent, and patrolmen. 308. Sources of Impairment of Irrigation Works. These are : 1. Erosion of the canal banks by water. 2. Filling of the canal channel or reservoir from deposition of sediment. 3. Erosion of the outer banks due to storm and flood waters. 4. Damage from cattle, horses, and trespassers destroying the banks, channel, and dams by walking over them. 5. Injury or destruction to the headworks, regulators, es- capes, or wasteways by floods. 6. Incendiarism. 7. Decay in timbers forming structures. 8. Destruction of earth banks due to burrowing by gophers. 9. Injury from growth of weeds or water plants choking the channel, and thus diminishing its discharge. The first and second causes of impairment may be dimin- ished by the use of intelligent engineering skill in the alignment and construction of the canals, and by the vigilance of patrols in discovering indications of erosion and rectifying them. If the amount of sediment deposited is large, it will have to be INSPECTION. 329 removed by dredges or scrapers, and such changes will have to be made in the headworks or slope of the canal or by the in- sertion of flushing escapes as to rectify them. Little injury should be caused the outer banks of the canal by storm waters if the canal is properly aligned and ample provisions made for the passage of drainage channels. Injury due to rain falling on the banks may be reduced to a minimum by the encourage- ment of the growth of grass and trees. Damage to the canal from the fifth and seventh causes may be provided against in the construction by building the structure of some permanent material as masonry or iron, and during operation by proper supervision and repairs* of the weakened part. Much damage may result from the burrowing of gophers and moles. This can only be prevented by careful supervision, the discovery of the holes, and the destruction of the pests. The discharge of a canal may be considerably re- duced by the growth of aquatic plants and willow along the banks. This is to be prevented only by pulling up or mowing the brush or by destroying it by fire when the canal is empty. 309. Inspection. In order that the supervision and inspec- tion of works may be properly performed, the canal line should be divided into a number of sections, each of which should be patrolled by a ditch rider, while the whole should be in charge of a superintendent. Where the line is long, telephone com- munication should be had from each section to the main office of the engineer and superintendent. In addition to this piles of lumber or other building material should be placed at each bridge, escape, or other work on a canal, and by this means any damage inflicted to the property by whatever cause may be immediately repaired by the patrol, or he may telephone to headquarters for further assistance and proper advice. The length of a division of the patrol should be regulated by the number of irrigation outlets and the character of the works, and they should be of such length that every portion can be visited daily. 330 PUMPING, TOOLS, AND MAINTENANCE. 310. Works of Reference. Pumping Machinery and Water Pipes. BUTLER, W. P. Irrigation Manual. Huronite Printing Company, Huron, S. D., 1892. COLLYER, F. Pumps and Pumping Machinery. E. & F. N. Spon, London. CULLEN, WILLIAM. A Practical Treatise on the Construction of Water Wheels. E. & F. N. Spon, London. FANNING, J. T. Water Supply Engineering. D. Van Nostrand & Co., New York, 1890. HUGHES, SAMUEL. Water Supply of Cities and Towns. Crosby, Lock- wood & Co., London, 1882. MAHAN, F. A. Water Wheels. E. & F. N. Spon, New York. RONNA, A. Les Irrigations. Firmin-Didot et Cie, Paris. TROWBRIDGE, W. P. Turbine Water Wheels. D. Van Nostrand & Co., New York. WOLFF, A. R. The Windmill as a Prime Mover. John Wiley & Sons, New York. WEISBACH, P. J., and DuBois, A. JAY. Hydraulics and Hydraulic Motors. John Wiley & Sons, New York, 1889. INDEX. PACK Absorption 19 Amount of, ine Rservoirs and Canals 20 Acre-foot 38 Duty of Water per 42 Agra Canal, Iron Aqueduct 135 Scouring Sluices 188 Alessandro Hydrant 214 Alignment of Canals, Obstacles to 74 and Survey of Canals 73 Alkali 32 Causes of 32 Prevention of 33 Reference Works on 43 Soil, Chemical Treatment and Leaching of 34 Allen, C. P , 201 Appleton Weir 128 Application of Water, Methods of 204 Aprons to Weirs 117 Aqueducts and Flumes 172 Iron 177 " Agra Canal 188 " Bear River Canal, Utah 178 " Henares Canal, Spain 179 Masonry 181 Nadrai, over Kali Nadi on Lower Ganges Canal, India 181 Solani River, Ganges Canal, India 77, 81 Areal Duty of Water 42 Arizona Canal, Fall on 162 Plan of Headworks 143 Regulator Gates 148 Arizona Weir ill 331 33 2 INDEX. PAGE Arrangement of Canal Head 145 Artesian Wells 29 Sources of 28 Ashlar Masonry 267 Ashti Dam 231, 305 Atmospheric Pressure 46 Automatic Shutters and Gates 386 Sluice Gates 136 " Soane Weir 138 " Shutters, Mahanuddy Weir 137 Available Annual Flow of Streams 27 Baker, Ira O 255 Banks of Canals, Side Slopes and Top Widths of 91 Bari Doab Canal, Drainage Diversion 169 Rapids 169 Bear River Weir 112 Canal, Cross-section in Rock , . . . 94 " Fall 163 " Iron Aqueduct .... 178 " Regulator Gates 151 Bear Valley Dam 264, 266, 298, 314 Beetaloo Dam 268, 287 Beresford, J. S 19, 20, 194 Betwa Canal, Drainage Diversion 169 Dam 268, 291, 304 Bhatgur Dam 281, 304, 307 Bifurcation, Del Norte Canal, Col 199 Big Drop, Grand River Canal, Col 167 Borings on Canal Locations 76 Bowlder and Brush Weirs 98 Bowman Dam 245 Brush and Bowlder Weirs 98 Buchanan Dam 266 Buck Scraper 325 Calloway Canal, Cross-section 92 " Distributary Heads 198 '" Escapes 156 " Regulator. 146 Weir 103 Canal Alignment, Ganges Canal as an Example , 76 Obstacles to 74 Turlock Canal as an Example 79 Canal Cross-sections, Form of. 89 Rock 93 Canal Grades for given Velocities 87 INDEX. 333 PACK. Canal Head, Arrangement of 145 Locations, Borings on 76 Trial Pits on 76 Survey, Permanent Marks on = 76 System, Parts of 69 Water, Measurement of 61 " Methods of Measurement of 62 Works, Maintenance and Supervision of 328 Work, Sidehill > 74 Canals and Canal Works, Works of Reference 215 Curvature on 75 Deltaic 69. Dimensions and Cost of some Perennial. * 70- Efficiency of 194 Inspection of 329 Inundation 68 Limiting Velocity on 86. Navigation and Irrigation 67 Perennial 68 Prevention of Sedimentation in 35 and Reservoirs, Amount of Absorption in 20 Slope and Cross-section of 85, 88 Survey and Alignment of 73 Carpenter, L. G 59 Castlewood Dam 247 Causes of Alkali 32 Cavour Canal, Inverted Siphon under River Sesia 190 Centers of Pressure of Water 46 Central Irrigation District, Inverted Siphon 186 Centrifugal Pumps 322 Check-Levees, Flooding by 206 Chemical and Physical Properties of Water 44 Treatment of Alkali Soil 34 Chezy's Formula of Flow 50- Chutes of Wood 167 Cippoletti's Formula of Flow over Weirs 59 Closed and Open Weirs 99 Coefficient C for Kutter's Formula, Table of 50 of Friction in Masonry 252 Colorado Current Meter 53 River Dam, Texas 297 Wooden Pipe 202: Composite Gravel and Rock Weir 115 Concrete 269 Construction of Crib Weirs 115. 334 INDEX. PACK Construction of Embankment. ..,..... 331 in Flowing Streams 274 of Flumes 175 of Masonry Dam, Details of 271 Contracts and Specifications 275 Core Walls, Masonry 227, 229 Oost and Dimension of Storage Reservoirs 221 Perennial Canals 68 -Cost of Irrigation 3 Crib Dams 244 Foundations for Masonry Weirs 123 and Pile Foundations for Masonry Weirs 122 and Rock Weirs , in Weirs, Construction of 115 Cribwork, Underground 316 Cross-section of Bear River Canal in Rock 94 Galloway Canal 92 Canals 85, 88 Canals, Form of 89 Canals in Rock 93 Canal with Sub-grade 92 Turlock Canal in Rock .... 93 Croton Dam, New, at Cornell's, N. Y 268, 282, 304 Croton Weir or Dam 1 23 Crushing, Stability against, in Masonry Dams 254 Current Meters 53 Colorado 53 Haskell 54 Rating the 55 Use of 55 Curved Dam, Design of 265 Masonry Dam 261 Curvature on Canals 75 .Dam, Ashti 232, 305 Bear Valley 264, 266, 298, 314 Beetaloo 268, 287 Betwa 268, 291, 304 Bhatgur 281, 304, 307 Bowman 245 Buchanan 266 Castlewood 247 Colorado River 297 Croton, N. Y 125 Design of Curved 265 Earth with Masonry Retaining Wall 238 INDEX. 335 PACK Dam, Ekruk 239 English 246 Folsom 295, 304, 310 Furens 277 Geelong 268 Gran Cheurfas 278 Gros Bois 256 Idaho 242, 305 Kabra 239 Loose-Rock with Masonry Retaining Walls 246 New Croton, Cornell's, N. Y 268, 282, 304 Pecos 241, 305 Periar 268, 269, 285, 305 Profile of 260 Profile Type for Masonry 259, 261, 263 Quaker Bridge 256 San Fernando 274 San Mateo 268, 269, 287, 315 Sweetwater 264, 289, 314 Tansa 279, 304 Turlock f ., .295, 304 Verdon 256 Vir 268 Vyrn wy 289, 304, 3 1 5 Walnut Grove 244 Zola 264, 266, 298 Dams, Crib 245 Curved Masonry 261 Details of Construction of Masonry 271 Dimensions of Earth 225 Diversion 131 Earth k 224 Earth and Loose-Rock 240 Examples of Masonry 276 Foundations of 267 Foundations of Earth . . 226 Inlet ; for Drainage , 170 Limiting Pressures in Masonry 255 Loose-Rock 243 Material of Masonry 267 Puddle Walls and Faces of Earth 230 Rock-filled 244 Springs in Foundations of 229 Stability against Crushing 254 Stability of Gravity 249 336 INDEX. Dams, Stability of, against Overturning 256 Stability against Sliding 251 Submerged ... 273 Theory of Masonry . . 248 D'Arcy's Formula of Flow 49 Del Norte Canal Distributing Heads 199 Regular Gates 149 Screw Regulator Gate 151 Deltaic Canals 69 Diagram of Discharges of Western Rivers 26 Dickens, Col. C. H. t Formula for Runoff 23 Discharge Diagram for Western Rivers 26 over Rectangular Weirs, Table of 60 of Streams 51 " " Mean 27 " " in Seasons of Minimum Rainfall 25 of Waste Weirs 303 of Western Rivers 26 Ditches, Private 196 Diversion Line 72 Weirs 97 Divisors, Water 65 Distributary Channels in Earth 198 Heads, Calloway Canal, Cal 198 Del Norte Canal, Col 199, " of Masonry 201 of Wood 1-98 Pipes of Iron, Steel, or Wood 201 Distributaries, Design of 193 Dimensions of 197 Location of 191 Object and Types of 191 Distribution of Rainfall in Detail 6 Water, Rotation in .... 203 Drainage. 34 Crossing at Level 1 70 Cuts 169 Diversion, Bari Doab Canal, India 169 " Betwa Canal, India 170 Inlet Dams for. ... 1 70 Works 169, Dredges 327 Duty of Water . . 38 per Acre-foot 42 Linear and Areal 4.2 INDEX. * 337 PAGE Duty of Water, Measurement of 40 Reference Works on , 43 per Second-foot 40 Table of 41 Dyas, Col. J. H 160 Earth Dams, Construction of 231 Dimensions of 224, or Embankments 225 Foundations of 225 with Masonry Retaining Wall 237 Puddle Walls and Faces 230 Earth, Distributary Channels in rgS Evaporation from i& Earth Embankment, Homogeneous 227, 233, Slope and Paving of 235 Earth and Loose-Rock Dams 240 Earthwork, Shrinkage of 93, English Dam 246. Effect of Evaporation on Water Storage 18 Efficiency of a Canal 194 Egypt, Area irrigated in I Ekruk Dam 239- Elevators 319 Embankment, Construction of 231 Earth Dams , 224 Homogeneous 227, 233 Material 234 with Masonry Retaining Wall 237 Slope and Paving of 235 Engines, Pumping 323 Escapes 154 Bear River Canal, Utah 156 Galloway Canal, Cal 156 Heads, Design of 156 Highline Canal, Col 156 Idaho Canal 156 Location and Characteristics of 155 Turlock Canal, Cal 1 57 Evaporating Pan 14 Evaporation, Amount of 15 Effect of, on Water Storage 18 from Earth 18 Measurement of 13 Percolation and Runoff, Works of Reference 27 Phenomena 13 338 INDEX. PAGE Evaporation, from Snow and Ice 17 Table of Depth of 16, 17 Evaporometer, Piche 15 Excavating Machines 326 Excavator, New Era 326 Faces, Puddle of Earth Dams 230 Factors Affecting Flow of Water 48 Fall of Wood, Simple Vertical .... 162 Wooden, with Water-cushion 165 on Arizona Canal 163 Bear River Canal, Utah 165 Fresno Canal 165 Turlock Canal, California 165 Falls of Masonry 167 and Rapids 160 Retarding Velocity of Approach to, by contracting Channel above. . 161 by Flashboards 160 by Gratings 161 Falling Water, Scouring Effect of 1 16 Fanning, J. T 23, 25 Fertilizing Effects of Sediment. 36 Flashboard or Open-Frame Weirs roi Regulators of Wood 146 Flood Discharges of Streams 25 Flooding by Check-Levees 206 and Furrow Irrigation Combined 210 of Sidehill Meadows 205 by Squares 207 by Terraces 208 Flynn, P. J 161 Flow, Annual, of Available Streams 27 in Open Channels, Formulas of 49 of Water, Units of Measure of 38 Flume, Highline Canal, Col 173 on Pecos Canal, N. M 177 San Diego, Cal 173, 175 Trestles 177 Flumes and Aqueducts 172 Construction of 175 Rating 64 Sidehill 173 Folsom Canal, Hydraulic Lifting Gate 153 " Sand Gates 157 Dam 295, 304, 310 Foote, A. D. 62 INDEX. * 339 PACK Foote's Water Meter 63 Foundations of Dams, Springs in 228 Earth Dams 226 Masonry Core and Puddle Wall 227 " Dams 267 France, Area irrigated in i Francis, J. B 58, 254 Francis Formulas of Flow over Weirs 58 Fresno Canal, Fall on 165 Friction, Coefficient of, in Masonry 262 Furens Dam 277 Furrow and Flooding combined 210 Irrigation 209 Furrows, Irrigation by Small 211 Ganges Canal, as an Example of Canal Alignment 76 Headworks and Plan of 141 Ranipur Superpassage 77, 183 Regulator Gates 147 Rutmoo Level Crossing 77, 172 Solani Aqueduct 77, 181 'Gate Towers 312 Examples of 314 Gates, Automatic Weir 306 Gauge Heights, Weir 61 Gauging Rainfall 1 1 Stations 54 Station, Rating the 56 Stream Velocities 52 Gearing, Regulator Gates raised by 148 Geelong Dam 268 Geology of Reservoir Site 220 Gila River Valley, Precipitation in 6 Grade for given Velocities on Canals 87 Gran Cheurfas Dam 278 Grand River Canal, Big Drop 167 Gratings to Retard Velocity of Approach to Falls 161 Gravity Dams, Stability of 249 Gravity and Lift Irrigation 66 Gravel and Rock Weirs, Composite 115 Greaves, Charles iS Gros Bois Dam 256 Hartt, A 323 Haskell, Current Meter 54 Headworks of Arizona Canal, Plan of 142 Arrangement of 145 340 INDEX. PAGE Head works, Character of 96 Ganges Canal, India 141 Idaho Canal, Plan of 143. Location of 72, 95 Height of Waves 236- Henares Canal Iron Aqueduct, Spain 179, Weir, Spain 127 Highline Canal, Bench Flume 173, Escapes 156. Scouring Sluices 134 Holyoke Weir 113 Homogeneous Embankment 227, 233 Huffer Pumps. 323 Humphreys and Abbott 49 Hydrant, Alessandro 214 Hydraulic Lifting Regulator Gate, Folsom Canal, Cal 153 Hydraulics, Works of Reference on 65 Ice, Evaporation from 17 Idaho Canal Dam 240, 30 j Escapes 156- Plan of Headworks 143 Rapids on Phyllis Branch 169. Rolling Regulator Gates 151 Sliding Regulator Gates , 149, 151 Impairment of Irrigation Works, Sources of 328 India, Precipitation in .... 5 Inlet Dams for Drainage 170- Inspection of Canals 329 Interior Slope and Paving of Embankment 235 Inundation Canals 68 Inverted Siphons.... 185, 189 of Masonry 189 Investment, Value of Irrigation as an 2 Iron Aqueducts 177 Iron, Steel, and Wooden Distributary Pipes 201 Irrigation, Cost and Returns of , 3 Extent of I, 3 by Flooding and Furrows combined 210 by Furrows 209 Harmful Effects of 32 Lift and Gravity 66 and Navigation Canals , 67 Period 39 Pumping or Lift 318 Relation of Rainfall to INDEX. 341 PAGE Irrigation, by Small Furows 21 i Subsurface 212 Table of Extent and Cost of 3 Tools 324 Works, Classes of 66 " Control of I " Sources of Impairment of , . 328 Italy, Area irrigated in I Precipitation in 5 Kabra Dam 239 Kao Torrent Siphon Aqueduct on Soane Canal, India 189 Krantz, J. B 249 Kmter's Formula of Flow 49 Land, Percentage of Waste 42 and Water Supply, Relation between 72 and Water Supply, Relation, to Reservoir Site 216 Lawrence Weir 131 Laying Sub-irrigating Pipes, Method of 213 Leaching of Alkali Soil 34 Level Crossings of Drainage 170 Rutmoo 77, 172 Turlock Canal, Cal. 171 Lever, Wooden Regulator Gate raised by 146 Lift and Gravity Irrigation 66 Irrigation or Pumping 318 Limiting Pressures in Masonry Dams 255 Linear Duty of Water 42 Little Kukuna Weir 1 16 Location and Characteristics of Escapes 155 of Distributaries 191 of Headworks 72, 95 Survey, and Alignment of Canals 73 Loose-Rock and Earth Dams 240 Dams 242 " with Masonry Retaining Walls 246 Lower Ganges Canal, Nadrai Aqueduct, India * J 8i Machines, Excavating 326 Mahanuddy Sluice Shutters 137 Maintenance of Canal Works 328 Material of Embankment 234 Masonry Aqueducts 181 Ashlar 267 Coefficient of Friction in 252 Cores. 227, 229 " Foundation of 226 34 2 INDEX. PAGE: Masonry Dams, Curved 261 " Details of Construction 271 " Examples of 276 ' ' Foundations of 267 " Limiting Pressures in 255 " Material of 267 " Profile Type for 259,261,263 " Theory of 248 Distributary Head 201 Falls 167 Rapids 169 Retaining Wall, Embankment with 237 Weirs 121 " Founded on Piles 122 " Founded on Piles and Cribs 123 " Founded on Wells 126. " Open Indian Type 104 Material of Masonry Dams 267 Mean Discharge of Streams 27 Mean and Surface Velocities 52 Meadows, Sidehill Flooding of 205 Measure, Units of, for Water Duty and Flow 38- Measurement of Canal Water 61 Evaporation 131 Water Du ty 40- Measures of Water, Table of Units of ; 39 Measuring Stream Velocities 52 Sub-irrigation Waters 214 Weirs 57 Meiers, Current , 53 Miner's Inch . . 38 Molesworth, Guilford L 259 Profile Type for Masonry Dam 259 Monte Vista Canal Scouring Sluices 1 35 Weir 101 Mot 318 Motion of Water 46 Nadrai Aqueduct, Lower Ganges Canal, India 181 Navigation and Irrigation Canals 67 Newark Weir 1 29- New Croton Dam, Cornell's, N. Y 268, 282, 304 New Era Excavator ..." 3 26> Norwich Water Power Co.'s Weir 122 Nye Pumps 323 Object and Ty pes of Distributaries iQt INDEX. 345- PAGE Obstacles to Alignment of Canals ... 74 Ogee-shaped Weirs 118 Open Channels, Formulas of Flow in 49 and Closed Weirs 99 Frame or Flashboard Weirs 101 Iron Frame W T eirs, French 109 Masonry Weirs, India Type 104 Outlet Sluices 310 Examples of 314 Overturning, Stability of Dams against 256 Paecottah , . 318 Parts of a Canal System 69 Paving of Embankment 236 Pecos Canal Flume 177 Dam 239, 305 Valley, Precipitation in 6 Pelletreau, M 264 Pequannotk Weir 129 Percentage of Waste Land .... 42 Percolation, Amount of 18 Prevention of 20 Runoff and Evaporation, Works of Reference 27 Perennial Canals 68, 70 Periar Dam 268, 269, 285, 305 Permanent Marks on Canal Surveys 76 Persian Wheel 318 Phoenix, Precipitation at 8 Physical and Chemical Properties of Water 44 Piche Evaporometer 15 Pile Foundations for Masonry Weirs 122 Weirs. 99 Pipes, Iron and Steel and Wooden Distributary 201 Method of Laying Sub-irrigation 213 Sub-irrigation ' 213, Precipitation by River Basins, Table of 9, States, Table of 10 Pressure, Atmospheric 46 Limiting, in Masonry Dams 255 of Water 45 Private Watercourses 196 Profile of Dam 260 Type for Masonry Dam 259, 261, 263 Puddle Trench 231 Walls 227, 230 and Faces 230 344 INDEX. Puddle Walls, Foundations of 226 Pumping Engines 323 or Lift Irrigation 317 Pumps, Centrifugal 322 Huffer and Nye 323 Steam , , 321 Quaker Bridge Dam 256 Rainfall, 6 Discharge of Streams in Seasons of Minimum 25 Distribution in Detail , 6 Gauging n Relation of, to Irrigation 5 on River Basins 9 Statistics, General 6 Statistics by States 9 Works of Reference on 12 Great - 7 Ranipur Superpassage 77, 183 Rapids, Bari Doab Canal, India 169 and Falls 160 Masonry 169 Phyllis Branch, Idaho Canal 169 Wooden , . . . 167 Rating 64 Current Meter 55 Flumes 64 Gauging Station 56 Rectangular Measuring Weir 57 Pile Weirs 99 Reference Works : Alkali, Sedimentation, and Duty of Water 43 Artesian Wells 31 Canals and Canal Works 215 Evaporation, Percolation, and Runoff 27 Hydraulics 65 on Rainfall 121 Storage Works 300 Regimen of Western Rivers 25 Regulator Gates, Arizona Canal 148 Bear River Canal, Utah 151 Del Norte Canal, Col 149 Del Norte Screw 151 Folsom Canal, Hydraulic Lifting 153 Ganges Canal, India 147 Lifted by Travelling Winch 148 Raised by Gearing or Screw 148 INDEX, 345 PAGE Kegulator Gates Rolling, Idaho Canal 151 Sliding, Idaho Canal 149 Soane Canal, India 147 of Wood lifted by Lever 146 of Wood lifted by Windlass 147 Regulators, Callovvay Canal, Cal 146 Classification of 143 Form of 144 Relation of Weirs to 139 Wooden Flashboard 146 Reinold, E. K 307 Reservoir Site, Character of 218 Geology of 220 Relation of, to Land and Water Supply 2iO Topography and Survey of 218 Reservoir, Vir, India 309 Reservoirs and Canals, Amount of Absorption in 20 Cost and Dimensions of some Storage 221 Prevention of Sedimentation in 35 Retaining Wall of Masonry, Embankment with * . . . 237 to Loose-Rock Dam 246 Retarding Velocity of Approach by Contracting Channel above Fall 161 Flashboards on Fall Crest 160 Gratings on Fall Crest 161 Returns of Irrigation 3 Rio Grande River, Precipitation in 6 River Basins, Rainfall on g Rivers, Western, Discharge of 26 Regimen of 25 Rock and Crib Weirs 1 1 1 Cross-section of Canals 93 Foundations for Masonry Weirs ... 126 and Gravel Weirs, Composite , 115 Rock-filled Dams 242 Rollerway and Ogee-shaped Weirs 118 Rolling Regulator Gates, Idaho Canal 151 Rotation in Water Distribution 202 Runoff 22 Examples of 24 Formulas of 22 Percolation and Evaporation, Works of Reference 27 Variability of 22 Russell, T 15 Rutmoo, Level Crossing 77, 172 Ry ves, Col., Formula for Runoff 23 INDEX. Sacramento Valley, Precipitation in 7 San Diego Flume 173, 175. Weir. 127 San Fernando Dam 274 San Joaquin Valley, Precipitation in 7 San Mateo Dam 268, 269, 289, 315 Sand Gates 157 Second-foot 38 Duty of Water per 40 Sediment, Amount of 35 Fertilizing Effects of 36 Sedimentation, Prevention of, in Reservoirs and Canals 35. Reference Works on 43 Seepage Water , . 21 Service Period 39, Sesia Siphon on Cavour Canal, Italy 190 Scouring Effect of Falling Water 116 Scouring Sluices , 133 Agra Canal, India 135 Examples of 135 Highline Canal, Col 1 34 Monte Vista Canal, Col 135 Scrapers 325 Scraper, Buck 325 Screw Regulator Gate, Del Norte Canal, Col 151 Screw, Regulator Gate raised by 145 Shutters, Automatic Weir 306 Shrinkage of Earthwork 93 Side Slopes of Canal Banks 91 Sidehill Canal Work 74 " Turlock Canal 81 Flumes 173: Sidhnai Weir , 107 Silt 35 Sirhind Canal, Siphon under Hurron Torrent .... 190 Siphon-Aqueduct on Soane Canal under Kao Torrent 189 Siphon, Stony Creek; on Central Irrigatiou District Canal, Cal 186 under Hurron Torrent on Sirhind Canal, India 1 90 Inverted, under River Sesia on Cavour Canal, Italy 190 Siphons, Inverted 185, 189 Masonry Inverted 189 Sliding Regulator Gates, Idaho Canal 151 Stability against, in Masonry Dams 251 Slope of Canals 85 Embankment 236- INDEX. 347 J'AGtt Slope , Excessive 1 59 Sluice Gates, Automatic 136, 138 Shutters, Mahanuddy Automatic 137 Sluices, Outlet 310 Scouring 133. Snow, Evaporation from 17 Soane Automatic Sluice Gates 138 Canal, Regulator Gates 148 " Siphon-Aqueduct under Kao Torrent 189 Weir 106 Soil, Depth of Water Required to Soak 41 Solani Aqueduct, Ganges Canal, India 77, 181 Sources of Earth Waters 28 Springs and Artesian Wells 281 Supply 67 Specifications and Contracts ." 275 Springs in Foundations of Dams. 225 Sources of 28 Squares, Flooding by 207 Stability against Crushing in Masonry Dams 254 against Sliding in Masonry Dams 251 of Dams against Overturning , 256 Gravity Dams 249 Steam Pump *2i Steel, Iron and Wooden Distributary Pipes 201 Storage Reservoirs, Cost and Dimensions of some 221 of Water, Effect of Evaporation on , 18 Works, Classes of 216 4 ' Works of Reference on 300 Stream Velocities, Measuring or Gauging 52 Streams, Available Annual Flow of 27 Construction in Flowing 274 Discharge of; and Velocities of Flow of 51 Flood Discharges of ." 25 Mean Discharge of 27 Sub-canals 30 Sub-grade to Canal Cross-section . . 92 Sub-irrigation Pipes 212 " Method of Laying 213 Waters, Measurement of - 214 Submerged Dams 273 Sub-supply Tunnels 30 Sub-surface Irrigation 212 Water Sources 28 Suddenness of Great Storms 8 34$ INDEX. Superpassages 1 8 r Superpassage on Ganges Canal over Ranipur Torrent 77, 183 of Iron, Agra Canal, India 183 Supervision of Canal Works 328 Supply, Sources of 67 Supplying Capacity of Wells 30 Surface and Mean Velocities 52 Survey and Alignment of Canals 73 Topography of Reservoir Site 218 Sweetwater Dam 264, 289, 314 Table, Coefficient C for Kutter's Formula 50 Coefficients of Friction in Masonry 252 Cost and Dimensions of some Storage Reservoirs 221 Depth of Evaporation 16, 17 Dimensions and Cost of some Perennial Canals 79 Discharge over Rectangular Weirs 60 Duty of Water 41 Extent and Cost of Irrigation 3 Precipitation by River Basins 9 Precipitation by States 10 Units of Measure for Water 39 Wegman n's Practical Profile Type 262 Tansa Dam 279, 304 Terraces, Flooding by 208 Theory of Masonry Dams 248 Tools, Irrigation 325 Topography and Survey of Reservoir Site 218 Top Width of Canal Banks 91 Towers, Gate 312 Trapezoidal Weirs 59 Trench, Puddle, in Earth Dams : 231 Trestles, Flume 177 Trial Pits on Canal Locations 76 Tunnels for Sub-supply 301 Turlock Canal 82, 84 Underground 317 Turlock Canal, Cross-section in Rock 93 Escapes 157 as an Example of Canal Adjustment 79 Fall 165 Level Crossings j 72 Sidehill Works 81 Tunnels 82, 84 Turlock Dam 295, 304 Undergreund Cribwork or Tunnels 316 INDEX. 349 PAGE Undersluices 309 Examples of 309 United States, Area irrigated in I Units of Measure for Water Duty and Flow 38 Valve Chambers 312 Variability of Runoff 22 Velocity of Approach, Retarding by Contracting Channel above Fall 161 Flashboards on Fall Crest 160 Gratings on Crest of Fall 161 Velocity, Limiting, on Canals 86 Velocities on Canals for given Grades 87 of Flow 51 " " Formula for 48 ' Streams, Measuring or Gauging 52 Surface and Mean 52 Verdon Dam 256 Vertical Fall of Wood 162 Vir Dam 268 Reservoir 309 Weir 129 Vischer, Hubert 265 Vyrnwy Dam 291, 304, 315 Wagoner, Luther 265 Walls, Puddle 229 in Earth Dams 230 Walnut Grove Dam 244 Waste Land, Percentage of 42 Waste Weirs, Discharge of 303 Shapes of 305 Wastevvays 301 Character and Design of 302 Classes of . . . 304 Examples of 305 Water, Centers of Pressure of, 46 Chemical and Physical Properties of 44 Courses, Private = 196 Depth of, required to Soak Soil 41 Distribution, Rotation in 203 Divisors 65 Duty of 38 ' ' Linear and Areal 42 " Reference Works on .... 43. ' ' Units of Measure for 38 Excessive Use of 35 Water, Factors affecting Flow of ' 4& 350 INDEX. Water, Measurement of Sub-irrigation 214 Meter, Foote's 63 Methods of Applying 204 Motion of 46 Pressure of 45 Scouring Effect of Falling. 116 Seepage 21 Sources of 28 Sources, Other Sub-surface 30 Storage, Effect of Evaporation on 18 Supply and Land, Relation between 72 " " " " of Reservoir Site to 217 Weight of 44 Water-cushions , 119 Water-cushion on Wooden Fall 165 Water-logging 33 Prevention of 33 Water-wheels 320 Wave Heights and Fetch 237 Weeds 37 Wegmann, Edward, Jr 257 Profile Type for Masonry Dam 263 Weight of Water 44 Wells, Artesian 29 " Reference Works 3 as Foundations for Masonry Weirs 1 26 Supplying Capacity of 30 "Weir at Appleton, Miss 127 Aprons , 117 Arizona Canal in Bear River Canal 112 Galloway Canal 103 'Composite, of Gravel and Rock 115 'Conditions of using Rectangular 58 Croton. 125 Formulas, Francis 58 Gates and Shutters, Automatic 306 Gauge Heights 61 Jienares, Spain 127 ,at Holyoke, Mass 113 .-Little Kukuna 116 Merrimac at Lawrence, Mass 131 Monte Vista Canal 101 of Norwich Water Power Co., Conn 122 .across the Pequaunock- River at Newark 129 INDEX. 351 PACK Weir San Diego, Cal 127 Sidhnai Canal 107 Soane Canal 106 at Vir, India 129 Weirs of Brush and Bowlders 98 Classes of 98 Construction of Crib 115 Crib and Rock in Diversion 97 Flashboard or Open-Frame 101 Masonry 121 founded on Cribs 123 " Piles 122 " " and Cribs 123 " Wells 126 Open Indian Type 104 Measuring. 57 Open and Closed 99 Open Iron Frame, French 109 Pile 99 Relation of, to Regulators 139 founded on Rock 126 with Rollerway or Ogee Shapes 118 Table of Discharge over Rectangular 60 Trapezoidal 59 Wheel, Persian 318 Windlass, Wooden Regulator. Gate raised by 146 Windmills 319 Winch, Regulator Gate lifted by Travelling 147 Works on Canals, Maintenance and Supervision of 328 Works of Reference, Alkali, Sedimentation and Duty of Water. 43 Artesian Wells 31 Canal and Canal Works 215 Evaporation, Percolation, and Runoff 27 Hydraulics 65 Precipitation 12 Pumping 330 Storage Works . , 300 Wooden Distributary Heads 198 Fall with Water-cushion 165 Flashboard Regulators. 146 Rapids or Chutes 167 Regulator Gate lifted by Lever 146 " " Windlass 146 Zola Dam 264, 266, 298 UNIVERSITY OF CALIFORNIA LIBRARY THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW UNIVERSITY OF CALIFORNIA LIBRARY \ & .X