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Show XII-34 UPDATING THE HOOVER DAM DOCUMENTS full or nearly so when the Central Arizona project initially diverts water. By drawing on reservoir storage, the basic water demands of the basin under most circumstances could be met at least through the year 1995. However, by the year 2000 reservoir storage could be sorely depleted or exhausted, depending upon actual hydrologic conditions and the growth of upper basin water demands. After that date, serious water shortages could be common except in periods of high runoff conditions. The basic keys to the extent and timing of future Colorado River water shortages are the runoff patterns and rates of growth of upper basin water demands after the Central Arizona project is completed. In coping with the problem of potential future shortages, attention first should be directed to maximizing the yield and optimizing the use of the natural water supply of the Colorado River Basin consistent with environmental considerations. This can best be accomplished through a total water management program that includes such activities as coordinated operation of all major basin structures, conjunctive use of surface and ground-water supplies, increased irrigation efficiency, water salvage, and wastewater reclamation and reuse. Potential savings by these means could increase present supplies of the Colorado River by as much as 300,000 acre-feet annually. It is evident that a total water management program can only delay and not prevent water shortages from occurring eventually. When such shortages do occur, there appear to be two alternative courses open. The first would be to accept the limitation in water supply and pattern the economic and social future of the basin to that limitation. Such a situation could arise either from the desire of basin residents to restrict water-dependent developments or through the impracticality of augmentation for physical, economic, environmental, national policy, or other reasons. Under this option, there would still be choices of controlling the future economy of the basin through the transfer of irrigation water to other uses such as energy resource development, municipal and industrial, and recreation. The second option would be to augment the flows of the Colorado River thus increasing its water supply and permitting continued growth of water-dependent development. Study has been given as part of the Westwide endeavor to means by which the river could be augmented including weather modification, desalting of seawater, and desalting of geothermal brines. Importation of water from resource regions outside the seven basin States was not considered in the Westwide Study because of restrictions on import studies contained in the Colorado River Basin Project Act. Although physically possible, importation of water to the Colorado River from other basins in the seven basin States does not appear practical. Weather modification, from both a technical and economic viewpoint, appears to be a viable means of augmenting Colorado River runoff by from 0.9 to 1.3 million acre-feet annually. Social, legal, and environmental problems, however, remain to be resolved. Desalting of geothermal brines, although costly, may have augmentation potential. A decision point has not yet been reached on either its technical or economic feasibility. Desalting of seawater at this time appears to be too expensive to merit serious consideration as a source of large-scale augmentation. To assist in resolving the water supply problems of the Colorado River Basin: 1. The total water management concept for the entire Colorado River Basin should continue to be broadened and perfected. 2. There should be an acceleration of programs of assistance to water users which would bring about the adoption of water management methods and practices to improve the efficiency of water use. 3. In conjunction with the States and other interested parties, a wide range of future water demand 44 |
