OCR Text |
Show (75 maf in successive 10-year periods )to insure more power generation and financial support for the Upper Basin development, the net depletion at Lee Ferry by Upper Basin development would be less than the amounts indicated above. These depletions are less than the 7.5 maf apportioned to the Upper Basin which, in turn, are less than the ultimate total requirements of the Upper Basin." "All studies disclose without exception that any increase in the use on the lower river must now be made from water apportioned to the Upper Basin, but now unused by it. Actually, at present the aggregate demand on Lake Mead is close to 9 maf per year. It is apparent that even present uses on the lower river are dependent upon significant amounts of water released from Lake Powell in excess of those required by the Colorado River Compact. "As the Upper Basin develops there will arrive a time when its water will no longer be available for further uses on the lower river. The question is when will that time arrive. To forecast this, studies have been made using various assumed rates of depletion in the Upper Basin and various assumed rates of releases from Lake Powell. All of the studies indicate that substantial shortages, amounting to more than 1.0 maf per year before the end of the present century, will exist in the supplies required to meet total uses of 7.5 maf by Arizona, California and Nevada and to meet a delivery of 1.5 maf of water per year to Mexico. The period would be extended somewhat if Lake Mead were depleted to absolute dead storage, during long periods of drawdown. "A period of low water supply in the Colorado River Basin, such as existed from 1930 to 1964, will occur again at some time, or one which might be more severe could occur. Under such conditions, minimum releases from Lake Powell would be necessary. Simple arithmetic indicates that there will not be enough water on the lower river to sustain a delivery of 7.5 maf for the states of Arizona, California and Nevada, and to take care of the Mexican burden, as shown by the following analysis: Lower River Requirements: 1. Beneficial consumptive use by Arizona, California and Nevada 7.500 maf 2. Mexican Treaty Deliveries 1.500 3. Reservoir Evaporation 0.730 4. Losses below Hoover Dam 0.810 Total Requirements 10.540 maf 32 |