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Summary The model results show that flow recommendations can partially be met; however, none of the model runs completely meet the desired flows. Sufficient time has not been available to review the factors that determine this; however, operational criteria entered in the model and existing physical outlet capacities at all three darns playa significant part. One example is the winter elevation target at Blue Mesa designed to reduce icing problems. This often prevents lowering releases to save water for a spring peak. This operational criteria is very important in preventing upstream ice flooding in Gunnison County. Another factor is criteria for Blue Mesa Reservoir that protect downstream areas from flooding. Difficulty in matching duration and peak of downstream tributary flows is also important. Impacts on Aspinall Unit purposes such as hydropower, downstream flood protection, recreation, and fish and wildlife would occur under the flow recommendations and are summarized below. It must be noted that these impacts result from model runs that only partially meet the flow recommendations; in most cases, fully meeting the recommendations could increase impacts. Hydropower - Impacts to hydropower generation at the Aspinall Unit were analyzed for the four model runs and indicate an annual energy losses averaging 7,000-11,000megawatt hours. Ooeration and Maintenance - Costs and scheduling of operation and maintenance activities would increase due to more frequent use of bypass valves, spillway gates, spillways, and stilling basins. Additional costs for modifications would be incurred in order to ensure this equipment and these structures meet engineering requirements. This higher and more frequent use would also result in periods of time where river flows would be interrupted in order to adequately inspect and maintain the structures. Fish and Wildlife - At Blue Mesa Reservoir, any change in the reservoir operation can affect loss offish through reservoir outlets, the thermal regime of the recservoir, and the overall reservoir productivity. It appears summer reservoir levels would decrease by an average of 5 feet (and over 30 feet in some dry years) under the flow recommendations, having a negative, but unquantified, effect on reservoir fisheries. In the Gunnison River below Crystal Dam, May peaks, with appropriate ramping, should not be detrimental to the trout fishery. Base flows recommended may benefit the trout fishery by providing desirable flows through most of the season. Endangered Species - \\illile not meeting flow recommendations fully, the model runs would improve habitat conditions for endangered fish in the Gunnison River and downstream in the Colorado River. Other threatened or endangered species are not expected to be significantly impacted. Recreation - As stated earlier, throughout most of the recreation season, elevations at Blue Mesa reservoir would be reduced by an average of 5 feet, with significantly higher drawdowns in dry years. Generally, higher reservoir levels are more desirable for recreation, aesthetics, and fish production. Flooding - Under the flow recommendation model runs, flooding due to icing upstream of the Aspinall Unit was not affected since the end of December target elevation was set as an operational parameter. The potential for flooding in Delta and other downstream areas would increase. 16