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Show bilities for its use to prevent flood damages might be found, but in all such cases the desirability of employing zoning restrictions should be thoroughly established on the basis of their economic feasibility as compared with alternative measures. 9. Conflict between Navigation Developments and Other Water Uses The Problem The extent to which navigation conflicts with other water uses, and resolution of such conflicts. The Situation Some reaches of the Sacramento and San Joaquin Rivers have been extensively used for navigation, and many improvements for this purpose have been authorized from time to time. A ship channel for oceangoing vessels has been constructed to Stock- ton. A similar channel to Sacramento is under construction. Most present navigation is within tidal waters and requires no extra water for operation. How- ever, an authorized shallow draft project on the Sacramento River above Sacramento involves the operation of Shasta Reservoir to provide a mini- mum flow of 5,000 cubic feet a second for navi- gation purposes, and in the Central Valley Project about 18 million dollars has been allocated to navi- gation. A considerable portion of the water re- quired in the Sacramento River for navigation can also be used to satisfy downstream requirements for irrigation and salinity repulsion. Comparatively little water is released exclusively for navigation. Nevertheless, such water as is released for this purpose results in some reduction in the supply available for irrigation and municipal use. In view of this conflict, and of the greater total benefits which would result from using this water for irri- gation, studies are now being made to determine if it is financially feasible for the irrigation and munic- ipal water supply components of the Central Valley Project to carry the portion of the cost presently allocated to navigation. However, navigation couJd be continued without water loss to irrigation if a slack water channel were provided. Federal water policy in the Western States has changed somewhat in recent years. It now recog- nizes domestic supplies and irrigation as higher uses than navigation. This policy was first stated in the Flood Control Act of 1944,16 and is in general conformance with California water law. One navigation project now under construction, the Sacramento Deep Water Ship Channel, may adversely affect salinity control in the Sacramento- San Joaquin Delta. Although the effect from the increased volume of the tidal prism caused by the new channel would be minor, studies have been undertaken to determine the advisability of com- pensating for the increased tidal prism by reclaim- ing inundated land in the delta region. Another problem associated with navigation is the additional cost of bridges across the channels. These bridges must either be high enough to permit river traffic to pass under them or must be provided with movable spans. The cost of modifying exist- ing bridges to provide for passage of boats is taken into account in comparing project costs and bene- fits and determining economic justification, but the increased cost of future bridges usually is not given full consideration. On the inland waterway above the junction of the San Joaquin and Sacramento Rivers, 41 bridges represent a total investment of over 17 million dollars, with about 4 million dollars of this necessary to obtain navigation clearance. Conclusions The conflict between navigation and other bene- ficial uses of water is secondary in the Central Val- ley. The conflicts which do arise can be resolved on the basis of determinations of relative benefits and costs, and in accordance with existing Federal and State water policies. Navigation, furthermore, is not entirely incompatible with maximum de- velopment of irrigation. Closer coordination with local highway agencies would be desirable in planning navigation improve- ments so that the increased cost of future crossings of navigable waterways may be taken into account to the maximum practicable extent. C. The Character of Development 1. Basic Data Essential to Future Plans The Problem The data essential for efficient planning, con- struction, and operation of water projects in the valley. 1 Act of December 22, 1944, § 1, 58 Stat. 887. 129 |