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Preliminary Analysis: Wayne N. Aspinall Unit Operations and the Draft Endangered Fish Flow Recommendations for the Gunnison and Colorado Rivers Introduction and Background At the request of the Department of the Interior, Reclamation has prepared this report to analyze: (1) the effects of meeting desired hydro graph criteria (draft flow recommendations I for endangered fish) on the purposes and operations of the Wayne N. Aspinall Unit (Aspinall Unit), and (2) the Aspinall Unit's ability to meetthe flow recommendations. The report contains a brief review of background material; a description of the hydrology model, model runs analyzed, and hydrology results; preliminary analyses on the effects of the flow recommendations on Aspinall Unit purposes; a discussion of the relationship between flow recommendations and the National Park Service (NPS) reserved water right quantification application for the Black Canyon of the Gunnison National Park; and conclusions and recommendations. A similar report was prepared in October 2000 on the NPS reserved right proposal. Aspinall Unit operations affect or depend upon senior water rights, existing contractual obligations and other factors. The report does not attempt to assess impacts of the flow recommendations on private water supplies, water rights, and water diversion structures; nor on storage rights of Federal and State agencies such as the Forest Service, Bureau of Land Management, and Colorado Division of Wildlife. Other than the Redlands Diversion, historic senior diversions downstream of the Aspinall Unit are accounted for in the model assumptions. The Redlands senior right receives more water under the flow recommendation alternatives than under the baseline condition because of the recommended minimum base flow (750 cfs) requirement at the Whitewater gage. Reclamation will prepare an environmental impact statement (EIS) evaluating operational alternatives to help meet the flow recommendations prior to any decision on long-term operations. The Aspinall Unit, authorized by the Colorado River Storage Project Act (CRSP) of 1956, is located in Gunnison and Montrose Counties in western Colorado along a 40-mile reach of the Gunnison River just upstream from the Black Canyon of the Gunnison National Park. The Aspinall Unit consists of three dams and reservoirs-Blue Mesa, Morrow Point, and Crystal. The Aspinall Unit is operated by Reclamation, while recreation on the land and reservoirs is managed by the NPS as the Curecanti National Recreation Area. Western Area Power Administration (Western) markets electricity produced. Reclamation operates the reservoirs and powerplants to meet the following purposes: lFor purposes of this report flow recommendations when referenced means draft flow recommendations. 1