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Show 25 percent more than the estimated annual amount of water available. The areas adjoining the basin and within reach of its diverted water include the east slope of the Rocky Mountains in Wyoming, Colorado, and New Mex- ico, the Great Basin in Utah, the coastal plain, and the Imperial Valley of California. These areas represent the largest centers of population, agricul- ture, and industry in these States. They contain the processors and main markets for the raw ma- terials produced within the basin. The States are recognizing the need for water in these areas in planning their future economy. The main diversion projects are the Denver municipal water supply; the Colorado-Big Thomp- son Project in Colorado, designed to divert approxi- mately 300,000 acre-feet annually; the Strawberry Project in Utah, diverting about 70,000 acre-feet annually; the metropolitan aqueduct of Los An- geles, capable of diverting 550,000 acre-feet an- nually; and the diversion to the Imperial Valley of California. During the past 10 years, a maximum annual diversion of 2.85 million acre-feet was made to the Imperial Valley. In addition there are num- erous small out-of-basin diversion projects operat- ing at the Rocky Mountain Divide in Colorado, and the Wasatch Divide in Utah. Some of the larger potential out-of-basin diver- sion projects now under consideration include: (1) the Gunnison-Arkansas Project of Colorado, with an initial diversion of about 60,000 acre-feet an- nually, and increasing to an ultimate diversion of about 500,000 acre-feet annually; (2) the Central Utah Project, with an initial diversion of 150,000 acre-feet annually, and increasing to about 700,000 acre-feet annually; (3) the Blue River-South Platte Project of Colorado, with diversion of about 500,000 acre-feet annually; and (4) the San Juan-Chama Diversion Project of New Mexico, with about 300,- 000 acre-feet annually sought for diversion. Diversion problems are of particular concern to Colorado. Before it received a definite allotment of Colorado River water, Colorado was confronted with deciding upon competitive in- and out-of-basin uses of single water supplies. In connection with the establishment of one of her major out-of-basin diversion projects, that State announced a policy of protecting not only present users within the basin but also potential users. Its diversion projects thus require certain protective measures such as ex- changes and replacement reservoirs, where in-basin uses are directly affected. Through a steering committee, the State is assisting the Federal agen- cies in planning of projects for the use of Colorado River water. In this manner, the respective rights of the in- and out-of-basin interests are brought to proper attention. A steering committee also is being set up to con- sider similar problems in New Mexico where there is a desire to distribute appropriately its share be- tween in- and out-of-basin interests. Utah, where relatively small opportunities exist for new projects within the natural basin, has in- dicated a desire to use the majority of its allotment outside the basin, but with due allowance for use in most areas of the natural basin. Possibilities of exporting water in Wyoming are under study. They appear remote and offer no particular problem at this time. Arizona lies completely within the natural limits of the basin and is not confronted with this par- ticular problem. Nevada is so situated topographically that she is not susceptible to export of Colorado River water from the basin. On the other hand a great proportion of Cali- fornia's use of Colorado River water is and will be accomplished through importation. Because of differing interpretations of compact provisions as between California and Arizona, the exact amount of this potential exportation is not known. (See Problem A-l.) One other unanswered question concerning the diversions relates to their effect on the quality of water in the lower river. Most of the diversions are of relatively clear water from the headwater areas. The diluting effect that this water has had on the water of the lower basin may be significant. Removal of sizeable amounts of mountain water from the Colorado system, together with increasing return flows from irrigation, may possibly leave the remaining water with toxic amounts of alkali at some locations. This may well influence the life of the irrigated areas in the lower basin, and their economy. Conclusions Within the framework of present legal limita- tions, use of Colorado River Basin water through out-of-basin diversions offers problems mainly of State and local consequence. This may mean, although it is not yet proven, that the most efficient use is being made of the river and its tributaries through these diversions, particularly from the point of view of comprehensive multiple-purpose development. 445 |
