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CHAPTER IV (2) Impact Findings ENVIRONMENTAL CONSEQUENCES [Note: Biological, recreational, electrical generation, social, and cultural impacts resulting from altered hydrological regimes are discussed in Sections IV.B through L.] Reclamation will offset the impacts of the Ruedi Round II/Green Mountain water sales on endangered fishes by releasing 10,000 acre-feet of water to improve habitat conditions in the Palisade reach of the Colorado River. If released entirely from Ruedi Reservoir, there will be a gain of 81 cfs in Fryingpan River flows in August and September in most years. When these releases are combined with water sales releases, flows in the Fryingpan River will increase by 159 cfs and 157 cfs in August and September, respectively, as compared to the presales flows. [Note: Fryingpan River flows would be less if Green Mountain Reservoir releases are made.] These changes are based on monthly averages for the period 1952 to 1982. For Flaming Gorge, the late July-September constrained releases will reduce the peak releases (4,300 cfs down to 2,600 cfs) of the daily fluctuation, and the low releases (800 cfs) will not change in either magnitude or duration. Attenuation of peak flows will result in a minimum flow of about about 1,000 cfs through Dinosaur National Monument above the Yampa confluence during a normal peaking operation. At the confluence, an additional 200 to 800 cfs is contributed by the Yampa River during August and September. Higher flows could be released from Flaming Gorge in the months not critical for endangered fish survival. Further downstream at Green River, Utah, the releases from Flaming Gorge will have an even smaller effect. Since the construction of the dam, flows in the Green River at Green River, Utah, have averaged 238,000 and 196,000 acre-feet during August and September, respectively. Historically, releases from the dam have comprised about 70 percent of these volumes. With the constrained releases, a decrease of about 20 percent can be expected in monthly volumes in average years. In a dry year, such as 1977 or 1981, there will be no impact because releases will be constrained by Reclamation to maintain water in Flaming Gorge to ensure that compact requirements in future years can be met. During wet years such as 1983 and 1984, the relative decrease in Green River flows due to the constrained releases will be minimal due to the high volume of water entering the Green River below Flaming Gorge Dam from other rivers. Flow variations at Green River, Utah, due to Flaming Gorge power operations are not expected to be significant because flow peaks are attenuated as downstream distance increases. Aspinall Unit interim releases will be made to ensure no less than 2,000 cfs at Stateline (a U.S. Geological Survey gage IV-A-5