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<br />. <br /> <br />Basin constitute less than lO percent of the average annual releases from <br /> <br />Lake Powell. Groundwater withdrawals exceed half a million acre- feet each . <br /> <br />to) year, and overdraft is occurring in some areas, particularly in southern <br />ClO <br /> <br />IA Nevada. <br />...... <br /> <br />. <br /> <br />The Little Colorado subregion consists of the drainage of the Little <br /> <br />Colorado River which rises on the north slopes of the White Mountains and <br /> <br />flows in a northwesterly direction to its cQnfluence with the main stem of the <br /> <br />. <br /> <br />Colorado River at a point about 178 miles downstream from Glen Canyon Dam. <br /> <br />The average annual undepleted watet' supply for the subregion is estimated <br /> <br />at about 420,000 acre- feet at the mouth of the Little Colorado River. Of <br /> <br />. <br /> <br />this quantity, about one-third (220 cfs) is contributed by Blue Springs which <br /> <br />are situated near the mouth of the river. The water from these springs, <br /> <br />. <br /> <br />however; contain large quantities of sodium chloride and thus is of a poor <br /> <br />quality. Groundwater storage in the subregion is great, but only minor <br /> <br />development has occurred because of low yields and generally poor quality. <br /> <br />. <br /> <br />At the present time groundwater withdrawals amount to approximately 75,000 <br /> <br />acre-feet annually, with about 20 percent of this water being used for industrial <br /> <br />. <br /> <br />purposes and the remainder for irrigation. <br /> <br />The Gila subregion consists primarily of the area drained by the Gila <br /> <br />River abovll Painted Rock Dam. The total area of the subregion is 57,600 square <br />. <br /> <br />miles, of which 4,000 square miles are in Mexico and an additional 4,000 <br /> <br />square miles consist of closed basins. The subregion extends from the <br /> <br />Continental Divide in west- central New Mexico to Yuma, Arizona, and <br /> <br />. <br /> <br />22 <br /> <br />. <br />