OCR Text |
Show 0 .90 0 .k2 1 .80 exclusive of Colorado River flow, for the period 191^ to 1965 is estimated as follows: Millions of Acre-Feet Subregion 1 (Lower Main Stem) Subregion 2 (Little Colorado) Subregion 3 (Gila) ____ Total Lower Colorado Region 3.12 Present Modified Water Supply To illustrate the sufficiency of regional water supply in 1965j an overall regional water balance was estimated by computing the remaining water supply in each subregion after all manmade depletions, evaporative losses, channel losses, system spills, and out-of-region diversions were subtracted. Figure 9 illustrates that from a broad regional point of view, the total 1965 water supply in the Region was nearly equal in amount to the total water requirements. The apparent water supply deficiencies in the Gila Subregion could have been almost satisfied, assuming the hypotheti- cal possibility of complete control and adequate facilities for redistri- bution of water from areas of surplus. It should be noted that for this condition to occur would require 100 percent utilization of regional run- off and 100 percent efficiency of water storage and transport facilities. Similar estimates, based on average annual depleted flows at the compact point for the 191*1-1965 and the 1922-1965 periods of record, show 1965 regional water deficiencies of 0.63 million acre-feet and 1.^0 million acre-feet, respectively. Ground Water It is estimated that 1,^30 million acre-feet of ground water are theoretically recoverable from depths of less than 1,200 feet in the Lower Colorado Region. Of this amount, about 1,150 million acre-feet are found in Arizona, 93 million acre-feet are in New Mexico, and 190 million acre-feet are in Nevada. The alluvial aquifers in the first 700 feet below ground surface contain approximately 990 million acre- feet. Because of location, cost of pumping, low yield rates, land subsidence problems, declining water levels, and increasing salinity of water at greater depths, it would be neither feasible nor practical to develop much of the 1,^30 million acre-feet. Efficient mining of these waters, as well as much of the ground water located nearer to the land surface, would require detailed well design, spacing, and installation of much deeper wells than currently 55 |