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Show taken into account there should be no serious diffi- culty in resolving them. 4. Conflicts between Upstream and Downstream Interests The Problem Resolution of conflicts between upstream and downstream water users. The Situation This problem relates principally to the use of the water resources for domestic and irrigation pur- poses, but also is concerned with the use of water for waste disposal. In the Central Valley, the principal issue of the conflict has been expressed in terms of reserving water for beneficial use in the areas on which it originates, the so-called counties of origin. The California water code states a policy that a water- shed or area in which water originates should not be deprived of the prior right to all of the water reasonably required for beneficial purposes in that area. In effect this code also says that these up- stream areas are entitled to an adequate water sup- ply in conformity with the State Water Plan. The accepted principle is that only surplus water can be exported. However, in many cases these areas of origin lie above the most economical reservoir sites, which are generally at the foothill line and which are used before more expensive upstream sites. Irrigation development on the valley floor has been more rapid than in the foothill and moun- tain areas for this reason, but upstream develop- ment also has been retarded because rainfall is greater and the land is sloping. This foothill area, especially in the Mother Lode country on the west slope of the central Sierras, is particularly concerned. Here highly valuable de- ciduous froiits and vegetables can be grown in a cooler climate than is found in the valley. Al- though the Bureau of Reclamation estimated some 350,000 acres in the foothills, of which about 200,000 axres are currently irrigated, the State estimated an ultimate irrigation of some 1.6 million acres requiring over 2.5 million acre-feet of water. The State estimate was made "without test of economic ^feasibility." Presently irrigated lands in the foothill area obtain water through old placer mining di-tches. Future irrigation there will be more costly because new ditches will be needed and reservoirs required to provide hold-over storage. The recent congressional authorization of the Engle Act11 tied the upstream Sly Park develop- ment to the Folsom Project, and added both units to the Central Valley Project. The Sly Park unit would provide a municipal water supply and irri- gation water supply for about 7,350 acres in the foothills east of Folsom. Because the cost of this unit exceeds the repayment ability of the water users,12 it is proposed to repay part of the cost of the Sly Park unit from Central Valley Project power revenues. Another illustration is presented in the case of the proposed transfer of water from the Sacramento River Basin to the San Joaquin River Basin under the initial Central Valley Project. Such a transfer was proposed on the basis that the available water supply in the Sacramento Valley exceeds its ultimate requirements, leaving a surplus for the San Joaquin Valley. It was contemplated that Shasta Reservoir would be used partly to meet the needs of the Sac- ramento Valley but principally for the San Joaquin Valley, and that additional reservoirs would be constructed later to meet the full Sacramento Valley demands. However, recent irrigation development in the Sacramento Valley has been more rapid than was anticipated, and water users in this locality now are of the view that their present full demands should be met from Shasta and other reservoirs before any water is exported. The proposed im- portation of water from streams outside the basin, such as the Trinity, Klamath, and Eel Rivers, in- volves problems of the same type. Conclusions Procedures for estimating the ultimate beneficial needs of an area and allowing for such ultimate use in determining the amount of water available for export to other areas seem logical. However, such estimates necessarily have limited accuracy and must be accompanied by sound judgment, tak- ing into account local conditions. Moreover, the opportunities for economical use of a limited water supply in either upstream or downstream areas should be weighed carefully in preparing plans for comprehensive use of water resources in the Central Valley. State and other local interests appropriately can take an active part in these determinations, in view "Act of October 14, 1949, § 2, 63 Stat. 852. 12 Project benefits, however, are estimated by the Bureau of Reclamation to exceed project costs. 124 |