Final Environmental Assesment and Finding of No Significant Impact Gunnision River Activities June 1995

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August and from November through April. Fish flows would be reduced before water user supplies were reduced from November through June under Alternative C (Table 2). Under Alternatives A and B, Aspinall Unit releases would be provided to meet the needs of both fish and water users on a year round basis. River flow changes below Redlands Diversion Dam as a result of the alternatives are shown in Table 2. The alternatives are aimed at ensuring that flows of at least 300 cfs are available to the fish. There is no change in flows below Redlands Diversion Dam during wet and normal years. However, differences occur during the dry (1990) and very dry years (1977). In the dry year, Alternatives A and B succeed in providing at least 300 cfs year - round. This is not the case for Alternative C, when average monthly flows are allowed to drop to zero in the winter months. In the extreme drought year conditions, water supply shortages would be shared by both fish and water users under Alternatives A and B, as represented by the 200 cfs flow shown in July through September of 1977. In this example, supplies to fish were reduced by 100 cfs and supplies to water users were reduced by 200 cfs. Effects of the alternatives on flows through the Black Canyon of the Gunnison National Monument and Gunnison Gorge are also a concern. Table 3 compares the average monthly flows as measured below the Gunnison Tunnel, which is near the upstream boundary of the Monument. The data reflects how the Aspinall Unit is currently operated to provide a flow of at least a 300 cfs below the Gunnison Tunnel diversion. In wet, normal, and very dry years, flows are nearly the same for all alternatives. Changes occur only under the 1990 dry year conditions. In this example, flows increase during the winter months and in August under Alternatives A and B compared to No Action and Alternative C. The increases are caused by extra releases to meet the downstream needs for water users and /or endangered fish on a year -round basis. As indicated previously, there are several water projects being considered for development in the Gunnison Basin. The water rights for these projects would not be affected by the proposals. Concerns were expressed in public meetings that the fish passageway or interim water agreement could lead to establishment of a more stable population of endangered fish species in the Gunnison River, and this would make construction of the Dominguez Project more difficult. The goal of the proposed actions is to establish a larger self - sustaining population of the endangered fish in the Gunnison River. The proposed location of the Dominguez Project is in a reach already designated as critical habitat for the endangered fish and already occupied by the fish. Thus, protection for the fish exists on the river and will exist whether or not the fish passageway and interim agreement are completed. Recovery of the fish and their removal from the endangered species list is an advantage to future water development. Reservoir Storage Levels -- Since the interim agreement alternatives would draw from storage in Blue Mesa reserved for endangered fish, there is a concern that their implementation would cause reservoir storage content and associated water surface levels to drop. Table 4 compares end -of -month content data for Blue Mesa Reservoir for the representative water years. It shows that content does not change for all alternatives during wet and normal years, therefore the 22