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1 CHAPTER III AFFECTED ENVIRONMENT Though each State has different water laws, all Western States adhere to the doctrine of appropriation. A water right is acquired by the taking of water from the natural streams and the application of the water to a beneficial use. The order of such taking creates a preference which, together with the continued right of use, constitutes the water right. In the past, water rights were acquired through diversions for consumptive uses such as irrigation. Only recently are some States beginning to accept the concept of allowing water rights to be established for instream flows. Preservation of instream flows to avoid jeopardy to species under Section 7 of the Endangered Species Act could affect the ability of water developers to use their State-created water rights. This potential for conflict between Federal and State law was of sufficient concern as to be one of the reasons for developing the Recovery Implementation Program. 3. Water Ouality The principal water quality issue in the Upper Basin is control of salinity. The Colorado River Basin Salinity Control Act of 1974 established maximum allowable concentrations of dissolved solids in the Colorado River as it enters Mexico. Irrigation return flows, natural discharges of saline water, coal mining operations, and reservoir storage can all contribute to dissolved solids concentrations. The Service has identified water temperature as a potential problem in some river reaches, such as below reservoirs and in areas with irrigation diversions and return flows. Temperature changes in these areas may affect Colorado squawfish reproduction. This potential problem is being studied by the Service and Reclamation under a research and monitoring agreement. 4. Channel Maintenance The endangered fishes adapted to a riverbed with areas of silt, sand, gravel, and cobble. Gravel and cobble bed parts of the channel, especially riffles, are essential for spawning. Sand and silt bed parts of the channel, especially backwaters, are utilized extensively by larval and juvenile fishes. Aggregation that results in an all sand bed channel or degradation that results in an all gravel bed channel would eliminate essential habitat for the endangered fish. Scouring flows prepare river beds for spawning by removing sand and silt and may be requested to maintain the present character of the streambed in areas of concern. Little information exists on scouring and subsequent flows required to transport sediments. Flow requirements for these purposes have not yet been established, but current thinking is that these flows may resemble historic peak flow patterns, though they will likely be ' of lesser magnitude and shorter duration. Since reservoir storage projects remove peak flows, they may adversely affect channel flushing requirements. III-5