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Show PART VI STREAM MANAGEMENT Release Patterns Operating criteria have been developed to fit the needs and functions of the individual reservoirs based on full recognition of water rights priorities and other legal restraints affecting the availability of water for storage. Water, stored during the nonirri- gation season and during the snowmeIt-runoff period when water is surplus to needs, is released to supply specific uses in accordance with established demand patterns. Irrigation demands are usually first met by direct diversion of available natural streamflows. As the streamflows diminish in the late summer, storage water is released as needed to supplement the natural flows in meeting the irrigation demand. Reservoir releases for irrigation usually begin in July and end in September or October. Reservoirs operated to supply municipal and industrial water are operated to supplement natural streamflows available under direct flow rights in much the same way as for irri- gation. Reservoirs for fish and wildlife and recreation are maintained at full stage as nearly as possible. Operations for flood control are based on progressive runoff forecasts that predict the magnitude of the seasonal flood runoff. Using the forecasts as a guide, reservoirs being operated for flood control on a joint use basis are drawn down to provide the necessary storage space to control the predicted flood flows. The coordinated flood control and filling operation is designed with the objective of filling the reservoirs by the end of the high runoff season. Provisions for inviolate flood control capacity has not been found necessary in any of the region reservoirs. Constraints The water codes of the various states within the region, together with several legal documents of interstate and international signifi- cance, are commonly referred to as the "Law of the River." Discussions on the state water codes, compacts, and treaties are contained in Appendix III, "Legal and Institutional Environments." Main Stem River Regulation A further modification is being effected by the main stem regulatory facilities of the Colorado River Storage Project. In the process of Main Stem regulation, evaporation from these reservoirs becomes an additional depletion, the magnitude of which is dependent upon the fluctuation of the regulatory facilities as they store and release water to meet the Colorado River Compact obligations. 25 |
