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<br />2372 <br /> <br />OTHER PROBLEMS AND NEEDS <br /> <br />The most important aspect of water management on the <br />Reservation is the adequacy of the supply to irrigate as much land as <br />may be justified economically. In recent years Colorado River diver- <br />sions have been near the entitlement for the Arizona portion, while <br />the amount of land irrigated has been less than three-fourths of the <br />total certified. In order to irrigate the 99,375 acres certified as irri- <br />gable in Arizona, it will be necessary to operate the distribution <br />system more efficiently and to improve onfarm water use efficiency. <br />Agricultural Development <br />The Tribal Council plans to expand irrigated acreage in the <br />future, but no definite schedule is presently contemplated for the <br />entire amount. Growth will depend on a number of factors, including <br />the profitability of agriculture, the availability of funds to construct <br />additional laterals and drains, and the increasing cost of land prepar- <br />ation as the more suitable land is gradually used up. As discussed <br />above, the projection assumed for this report is the attainment of <br />93,046 acres on the flood plain by 1994. Development of the acreage <br />on the mesa will probably occur by 1985. <br />With each improvement in water use efficiency more land can be <br />irrigated. Table 3 shows the acreages that can be irrigated with <br />various improvements, and compares those conditions to 1974 con- <br />ditions. With improvements in efficiency the 99,375 "decree acres" in <br />Arizona can be irrigated with river water. <br />The highest onfarm efficiency and system efficiency shown are <br />estimated to be reasonably attainable, but will require major improve- <br />ments to the irrigation system and greater onfarm water use effi- <br />ciency . Methods of achieving them are discussed in the following <br />sections of this chapter. <br />The Colorado River diversion of 640,000 acre-feet shown on the <br />table is used as a target for estimating. It is based on the Supreme <br />Court allocation, and contains an allowance for future municipal and <br />industrial use on the Reservation, and a cushion of 20,000 acre-feet <br />as a safety factor against overdiversion. The estimates are based on <br /> <br />23 <br />