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- regulate flow of the Colorado River - store water for beneficial consumptive purposes - allow the Upper Basin states to use the apportionment made to and among them through the Colorado River Compact and the Upper Colorado River Basin Compact - provide for the reclamation of arid and semiarid lands - p~ovide for flood control - provide for fish and wildlife enhancement and public recreation - generate hydropower Previous biological opinions on the Dolores and Dallas Creek Projects depend on operations of the Aspinall Unit to offset their depletion impacts to the Colorado River of up to 148,000 acre- feet. A forthcoming biological opinion and EIS for the Aspinall Unit will clarify how this previous commitment will be met for endangered fish. The draft flow recommendation report prepared by the Upper Colorado River Endangered Fish Recovery Program (Recovery Program) contains recommendations on minimum spring peak flows, minimum base flows, and minimum fish passage flows in the last 3 miles of the Gunnison River. These flow recommendations are designed to provide flow patterns beneficial for the life stages of endangered fish and their habitat. Peak flow and base flow recommendations are set for and measured at the USGS gage, Gunnison River near Grand Junction, Colorado (Whitewater gage). This location is 80 miles downstream from Crystal Dam-the furthest downstream of the Aspinall Unit dams-and significant tributaries such as the North Fork of the Gunnison and the Uncompahgre rivers enter the Gunnison between Crystal and the Whitewater gage. Flows for endangered fish passage are measured downstream of the Redlands Diversion Dam (See Frontispiece Map). Hydrology Modeling RiverWare Model RiverWare is a software modeling tool developed by CADSWES (University of Colorado) for the Bureau of Reclamation and the Tennessee Valley Authority for operation and planning studies of river basins and river systems. A daily planning model of the Gunnison River was developed using RiverWare modeling software. The model includes the Gunnison River Basin from Blue Mesa Reservoir to just upstream of the Colorado River confluence. The modeling period runs from January 1975 through December 2000. A description of the model is included in Attachment A. Fish and Wildlife Service (FWS) Input The Recovery Program has issued draft f10w recommendations to recover endangered fish in the Gunnison River. These recommendations are undergoing review; final recommendations may differ from those considered in this report. The lower 57 miles of the Gunnison River downstream from the Uncompahgre River confluence have been designated as critical habitat for 2