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Show 5. Rehabilitation of Existing Irrigated Areas versus New Developments The Problem The choice between using water supplies for new lands or providing additional water to old lands with deficient supply. The Situation The choice between providing water for new lands and adding to the deficient supply of old lands in the Colorado Basin is one which must be made within the limitations of water allocation. It therefore is a choice to be made within the amounts of water to which they are entitled and the boundaries of the several States. Where choices must be made between alterna- tives in approximately the same natural environ- ment, it usually is assumed that the use of water as a supplement to an existing irrigation supply pro- duces returns and benefits exceeding those attain- able under the use of the same water on new lands. This is true for several reasons. Among them are: (1) Ordinarily, as long as the optimum applica- tion for the given land type is not exceeded as in- crements of additional water are applied, each suc- ceeding increment yields increasing crop value. The fanner can, then, pay more for supplemental water; with greater repayment ability available, the maximum use of this resource more nearly can be attained. (2) Supplemental water is superimposed upon an existing supply which may have been developed at low cost. The irrigator can pay so much addi- tionally for supplemental water as will bring his total watetr cost up to his payment ability. Again, the greater the repayment ability applicable to sup- plemental water, the more nearly maximum use of the water zresource is attained. (3) The use of water for new lands brings in costs not incident to its use as a supplemental supply. New land must be cleared, leveled, and processed before it can be watered; the farmstead must be built; roacls and utilities must be extended to the area; schools and the usual community facilities must be provided. The costs of these must be met out of th& productive capacities of the land and water. (4) There is less venture risk in providing sup- plemental water. The productive capacity of the lands under irrigation has been established through use, and the individual farmer has an equity in his farm and in his base water supply which makes him a more responsible contractor for water. On the other hand, in some instances providing supplemental water will require extraordinary measures, and the justification of those measures must be examined. An example of the examina- tion of those extraordinary measures is the report of the Bureau of Reclamation on the proposed Cen- tral Arizona Project.33 This project area lies in south central Arizona. Because of a year-round growing season and pro- ductive soils, a profitable irrigated agriculture could be sustained here. Essentially all of the irrigated lands are dependent in some degree upon pumped water. Some 428,000 acres now are irrigated from surface streams and pumping, and some 138,000 acres by pumped water exclusively. Some 106,000 acres irrigated in the past have been abandoned for lack of water. Expansion of the irrigated area, and parallel development of the urban areas, have resulted in full use of available surface waters, and have led to pumping from the ground water at the rate of 1.1 million acre-feet annually during 1940-44. The safe yield of the ground water basin is estimated to be 695,000 acre-feet. (See Problem A-3.) As the ground water level is lowered, pumping costs rise, irrigation becomes less profitable, values decrease, and eventually there is abandon- ment. Because the ground water basin is available to all of the irrigated lands, the shrinking process cannot be localized. Its effects can be seen in the abnormal amount of land being fallowed so that the individual farmer may concentrate his available water on the remainder of his farm. The Bureau of Reclamation proposes works designed to conserve to the maximum extent local surface waters, and others which would serve to import water from the Colorado River. Of the latter the major elements are pumping plants near Parker Dam capable of pumping 1,800 second- feet through 985 feet of lift into an aqueduct 241 miles long leading to the Phoenix area; and a dam and power plant at the Bridge Canyon site on the Colorado River to produce pumping and commer- cial energy. If Arizona's claims to Colorado River water were upheld, full water supply could thereby be brought to about 640,000 of the 672,000 acres **H. Doc. 136, 81st Gong., 1st sess., Central Arizona Project, March 22, 1949. 412 |
