<^;^k lis: S',v '.jfe.' ■'■ .>N^ ■.('■•: I V,,"' piiii; ■iiii* sii Class Book, .^32. REPORT Massachusetts State Forester Reservoir Commission city of fall river, With Recommendations for the Protection and Maintenance OF THE Watershed of North Watuppa Pond. F. W. RANE, State Forester. H. O. COOK, Assistant in Charge. December, 1908. BOSTON: WEIGHT & POTTEE FEINTING CO., STATE PEINTEES, 18 Post Office Square. 1909. REPORT Massachusetts State Forester, Reservoir Commission y^f CITY OF fall river, With Recommendations for the Protection and Maintenance OF THE Watershed of North Watuppa Poj^d. F. W. RANE, State Forester. H. O. cook, Assistant in Charge. December, 1908. BOSTON: WRIGHT & POTTER PRINTING CO., STATE PRINTERS, 18 Post Office Square. 1909. Preface At the invitation of the Reservoir Commission of the City of Fall River, — a Board created for the purpose of protecting the purity of the city's v^ater supply, — the State Forester's department has made an examination of the watershed of the North Watuppa Pond, located in the city of Fall River and the town of Westport, and here- with presents the results of said examination, with such recommenda- tions as to it seem wise. Acknowledgments. To INIr. H. O. Cook, M.F., my assistant in charge, is due the credit of carrying out and completing this work; and to His Honor Mayor John F. Coughlin, City Water Commissioner Wm. Sullivan and City Engineer Philip D. Borden of the Reservoir Commission we are greatly indebted for their interest and many courtesies. F. W. RANE, State Forester.' State House, Boston, Mass. By Transfer JAN 13 1912 Pakt I. Influence of Forests on Water Supplies. Although this is a subject of great importance to this country, and one much discussed of late, it has never been carefully studied. Even European foresters, who have investigated this subject for many years, have not as yet established their final conclusions covering the whole field. That a relation does exist is indisputable, for forest destruction always produces a change in the character of the stream flow. Influence of Forests on Rainfall. Rainfall is caused by the cooling of moisture-laden air to below the dew point. Forests shade the ground, making it cooler and conse- quently keeping the air above it at a lower temperature than that of the surrounding air. It is reasonable to suppose that rain might fall over a forested area when it would not if that area were cleared. On the western prairies this is a popular conviction, but observations made in Europe have yielded conflicting results, and no definite con- clusion can be drawn from them. Influence upon the Dlsposal of Rainfall. It is after the rain has reached the earth that the forest exerts its most potent influence. Rainfall escapes in four ways from the ground upon which it falls: by evaporation, transpiration, surface run-off and seepage run-off. Evaporation. The rapidity with which moisture evaporates depends on its ex- posure to the sun and wind. A thick forest cover shades the ground from the direct rays of the sun, thus preventing too rapid evaporation. Experiment has shown that from the surface of a small pond, situated in the open, three to four times as much evaporation took place as from a similar sheet of water in the forest. Experiments made on the surface soil in California gave practically the same results. From 1,000 square centimeters of bare ground 5,730 grams of water were evaporated in the months of July and August; while from ground under a heavy mulch of leaves on the forest floor it was but 1,150 grams. In the thick spruce woods of INIaine one will often find snow on the ground in June, whereas in the open it disappeared bet* ore the first of May. Evaporation is profoundly affected by wind. Observations of the United States AVeather Bureau indicate that with a wind velocity of 5 miles an hour, other conditions" being equal, the rate of evaporation is 2.2 times that of a calm; at 10 miles an hour, 3.8; at 20 miles, 5.7; and so on. It will be readily seen that, by the check in the velocity of the wind that a forest cover causes, the amount of water lost in this way is greatly reduced. Not only is the force of the wind broken within the woodland, but it is retarded for a considerable distance to the leeward. In general, the retardation is felt over 20 feet of hori- zontal distance for every foot in the height of the trees. Thus a stand of trees 50 feet in height all around North Watuppa Pond would materially reduce the evaporation caused by the wind over a water surface of 1.4 square mile, or about one-half the total area of the pond. Transpiration. Vegetation in the process of growth uses up a large amount of water, which is gathered from the soil by the roots and is then transpired to the air through the leaves. Only a small portion of it remains in the structure of the plant. From a lengthy series of experiments, Risler came to the conclusion that a forest takes up less than one-half as much water as an ordinary agricultural crop. We infer from this that a soil covered with grass or other herbaceous growth loses more moisture from this cause than one covered by a forest. Different species of trees take up varying amounts of water. For deciduous species the average amount during one season is 470 pounds of water for every pound of leaf matter; but in the case of coniferous trees it is but 43 pounds, or one-tenth as much. In one or two other respects a broad-leaf wood has slight advantages over the evergreen one as a conserver of moisture; but this matter of transpiration points to the latter as the most efficient protector of water supplies. Evaporation and transpiration represent actual losses of water. Just how great this loss is, will appear from the following table, taken from the excellent report of the Reservoir Commission for 1902. We are indebted to Mr. Safford's work for a great deal of careful informa- tion used directly and indirectly in this report. This table shows the precipitation on the watershed of North Watuppa Pond, compared with the amount of water which found its way into the pond, for the different months of the years 1899 to 1902. On the average, nearly 50 per cent, of the total rainfall was lost. Although there were un- doubtedly other factors of waste, the larger part of the loss must have come from evaporation and transpiration. A minus sign indicates that the evaporation from the water surface was greater than the total amount coming into the pond; consequently, the amount collected was a minus quantity. On H a < m ^ — a w H S o w H ^ H n- • OJ ilj 10 CO t^ CO 00 •* OS ■y" CO CO o> lO 05 w t^ CO (N CO IM t^ 1 O o o « ^ IB.S 4) s d •* r^ 00 d d d I. t< -ws t^ 00 CO CO 1 in m "CL, o 1 1 PM^ o 1 o £|1 ^ M CO 05 Tl" m ■* CO ^ 00 •* 05 00 M IM ■n 10 CO 00 CD CI cc CD o CO ■* 00 M< (M CO •* CO a> 1 w rH d ■* t^ 10 t— « d d d d d •* in 31-1 T 1 (M a: " 1 1 B Pre- on on Pond shed es). 00 in in C^l CO t^ C) Tf CO 05 10 00 00 CD I^ t^ ■* t^ eragi itati irth : ater Inch (M 03 00 CO CO ■* in '^ '^ CO IM 1 (M CO 00 00 r-t CO (N (M CO M 00 d in 1 1 ^•i^^^ . k 1:1 al 05 CO CO ■* 05 ^ 00 ^ _, CO CO « 05 05 c^ t^ C^l 00 CO CD c^ " " 00 05 d 00 10 CO t^ ■* CO 00 CO •* 1 ^ -* l>- t^ 10 (M CO CO ■ (M CO (N in ^ C5 CO in in o> 1 1 |-8 ^ M d d d d d d c-\ 3>-H 1 T a: " 1 1 rage Pre- tation on th Pond itershed nches). '*< t^ -* 00 in CD t~ in h- , >> j3 C 4) "s s OS 3 2 0. < >, a c 3 3 M < s 0. a > s 1 > < Distribution of the Run-off. There are two kinds of run-off, surface and seepage. The first is on the whole harmful, while the latter is beneficial. On cleared land the soil becomes baked and hardened by the sun, so that when the rain falls on it the water runs over the surface to the nearest stream. If the rain is heavy or the slope steep, the soil is washed and the brooks become filled with sediment and impurities. The forest, on the other hand, is provided with a floor of vegetable material, decayed leaves and branches, called humus, anywhere from 2 inches to 2 feet in the thickness. This humus has great absorbing powers, and acts as a huge sponge, converting the surface drainage into a seepage run-off. Ebermayer estimates that the water-storing capacity of humus is considerably more than its own weight ; while Henry, from laboratory experiments, "Revue des Eaux et Forets," makes it four times its own weight. The interlocked roots of the trees prevent any washing of the soil. By converting a surface run-off into a seepage run-off, water which comes in the season of excess rainfall is kept in the ground to feed the springs during the time when rainfall is deficient. It is not generally considered that this region has a distinct rainy season, but there is a period in the year when more than the average amount of rain falls. The following table shows the average monthly rainfall for the region to be 3.96 inches; for the four months December to March inclusive it is 4.24 inches, and during the months from June to September it averages 3.50 inches a month, — a loss of about 17 per cent, from the winter average. Average Monthly Rainfall (Inches). Fall River Fall River Water Works Providence, New Bedford, Water Works Average for Average Average Months. for 1899, Twenty-nine for Seventy for Seventy "Old Gauge." \ears, "Old Gauge." Years. Years. January, ..... 5.84 4.91 4.08 4.08 February, 4.11 4.41 3.80 3.71 March, 7.44 5.19 4.17 4.29 April, 2.92 4 2'' 3.72 3.95 May, 1.82 3.91 3.80 4.02 June, 4.46 3.02 3.17 3.05 July, 3.37 3.64 3.32 3.31 August, . 1.85 4.29 4.13 4.02 September, 7.90 3.41 3.26 3.39 October, . 2.39 4.68 3.73 3.98 November, 2.44 5.36 4.16 4.29 December, 1.45 4.02 3.91 4.24 Totals, 45.99 51.06 45.25 46.33 10 The excess amount of rainfall comes at a time when the least amount of water is being used by the citizens of Fall River. The ^following table gives the monthly and average daily consumption, as indicated by the gauges at the water works, for the year 1901. The increase in the summer consumption is at times nearly 50 per cent. This and other causes, such as increased evaporation, makes a loss in the water stored in the pond during the warm months. Consumption for 1901. Months. Total Con- sumption of Water from Water Works Report (U. S. Gals.). Gain in Water stored in North Pond during Month , (U. S. Gals.). Loss in Water stored in North Pond during Month (U. S. Gals.). Consumption of Water, Averasre Daily for Month, from Water Works Report (U. S. Gals.). January, .... 97,758,000 24,136,000 - 3,121,000 February, . 90,661,000 - 90,967,000 3,238,000 March, 99.353,000 701,128,000 - 3,205,000 .4pril, 95,435,000 827,254,000 - 3,181,000 May, 105,380,000 87.696.000 - 3,399,000 June, 112,160,000 - 137,196,000 3,739,000 July, 126,741,000 - 408,037.000 4,088,000 August, 121,262,000 - 390,986,000 3,912,000 September, 122,440,000 - 325,630,000 4,081,000 October, . 122,095,000 - 219,712,000 3,939,000 November, 112,680.000 99,263,000 3,756,000 December, . 114,875,000 633,152,000 - 3,706,000 Totals, 1,320,840,000 2,273,366,000 1,671,791,000 - Average, - - 3.619,000 If a dam could be constructed at the "Narrows" which would hold all the excess of water that would accumulate in the winter months, the regulation of the run-off by the forest cover would not hold such an important place in this report. But because of riparian rights held by the Reservoir Company, which controls the. water power for the mills on the Quequechan River, the city is obliged to let the water flow freely from North Pond into South Pond until the level of the former is 40 inches below full pond, after which they can shut the flowage down to 5,000,000 gallons a day. In other words, it is im- possible for the city to lay up a store of water in North Pond against the time of need; they can only husband it when the time of need arrives. The rainfall must be .stored in the earth, and to bring this about, the watershed of the pond must have a forest cover. 11 Purifying Influence of Forests on Water. We could not find that any investigations on this subject have ever been made. It seems reasonable to suppose that forests do exert some influence in this direction, because water is purified by percolating through the earth, so that a seepage run-oft' should yield a better supply of water than a run-off from the surface. In a table taken from Mr. Saft'ord's report, which gives the results of analyses made by the State Board of Health on samples of water from the pond and from its various feeders, we find that the water in the pond is considerably the purer. As only about 50 per cent, of the water supply of the pond comes through the brooks or by direct precipitation, the remainder must be fed to it by springs in the bottom of the pond. 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