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Show be continued under each procedure considered. The decision would then have been made whether or not the stored ground water should be pumped in excess of natural replenishment for a limited period pending the supplementing of these under- ground waters from more remote surface supplies. The present problem raises several questions: What to do to obtain supplemental water, or how to provide substitute gainful activities if it is not practicable to get enough water to continue irri- gation? Bad as it is, the present situation has at least served to emphasize the importance of ob- taining the hydrologic facts at the start, or before the start of such undertakings. The Central Valley program in California is also, in considerable measure, the result of efforts to correct over-development of ground water. Here, however, sufficient supplemental water was available to provide a solution-provided the supplemental stores of water do not open the way to expansion of use beyond the safe yield of avail- able water supplies. The program is designed to replenish the de- pleted ground water supply of the southern San Joaquin Valley indirectly through the use of surface water from the wetter northern part of the Central Valley, including the Sacramento River. W aters from the San Joaquin River, now used farther north, will be diverted to use for irrigation, thus conserving ground water in the southern part of the valley for use during dry cycles of years when sufficient surface-stored water may not be available. This water will in turn be replaced with water from the Sacramento River in the northern part of the Central Valley. The underground reservoirs of the northern or Sacramento part of the Central Valley will like- wise be used to store floodwater for later use. Thus, the underground reservoirs will be drawn down in dry cycles of years, and be refilled in wet ones through primary use of surface storages. By such coordination of use of surface and ground water stora_ge, there will be no shortage of water in dry seasons. Waste of water in wet seasons and years will be minimized and flood waters will be better contzrolled. This great project will provide an example of what can be done where the water of a major basin is regarded as a unit and plans are devised for its effective management. Many problems remain to be solved. These problems result mainly from existing irrigation works and compli- cated water rights situations. Lack of knowledge of geologic and hydrologic facts, or of the physi- cal means of securing effective coordination of surface and ground water storage and regulation, is a factor. The purpose of the Central Arizona project is to solve a similar problem of overdevelopment of combined ground and surface waters in the Salt River Valley of Arizona. Here the problem over which there is legal interstate controversy is rendered more difficult by the need to get the necessary Colorado River water through a 1,000- foot pump lift to lands now being irrigated by an overdraft on ground water reservoirs which in turn are being recharged in part by waters already used for irrigation. We Need More Facts Our need for useful water increases daily. Our basic information as to past and present water uses and as to future requirements is woe- fully inadequate. According to the Geological Survey: 5 At a time when use of water is increasing rapidly and is approaching feasible limits of de- velopment in area after area, and when there is growing national awareness of the true impor- tance of water in our economy, we must admit that we do not even know how much we use, to say nothing of how much we have that can be used. The Geological Survey's estimate6 of ground water use is for 1945, indicating a total of 20 billion gallons a day, including 10 billion for irri- gation, 5 billion for industrial use (exclusive of water from municipal systems), 3 billion for municipal systems, and 2 billion gallons a day for rural use exclusive of irrigation. 5 Id., p. 83. 6 W. F. Guyton, of the Geological Survey, in a paper presented to Geological Society of Washington, D. C, January 8, 1947, p. 84. 120 |
