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

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Operation of the Aspinall Unit as proposed under Alternatives A and B would result in decreased Blue Mesa storage levels, particularly over a dry period such as occurred between the fall of 1988 to the spring of 1991. However, in all but very dry conditions (for example, in 1977), Alternatives A and B would meet or exceed supplies to existing users as compared to historic conditions while providing desired fish flows below Redlands. In very dry years, such as 1977, water supply shortages would be shared by both fish and water users. All alternatives for the interim agreement would be implemented under Colorado water law, would not interfere with the purposes of the Aspinall Unit, and would help meet purposes of the Recovery Program -- to recover the endangered fish while allowing water use and development to continue under the "Law of the River." River Flows, Water Rights and Water Uses -- Review of past hydrologic records indicates that flows of at least 300 cfs are in the river below the Redlands Diversion Dam during July through October in most years already. However, in certain below average runoff years, special releases would need to be made because flows would be too low to meet the needs of both the fish and the senior water rights. Under the originally proposed Alternative C, such senior water rights could request a call on the river. This would cause upstream junior diversions (for example in the Upper Gunnison Basin or along the North Fork of the Gunnison) to be reduced or shut down to increase the supply to the Redlands Diversion. While such calls have occurred during dry years under existing conditions, they would occur more frequently with the interim flow agreement as presented in Alternative C. One purpose of Alternatives A and B is to see that junior water users are better protected from such calls. To show the effects of the agreement .alternatives on river flows, water rights, and river administration, data from Appendix E was used for 4 representative water years: wet (1985), normal (1987), dry (1990), and very dry (1977). The monthly information is shown to allow comparison among all the alternatives: No Action and Alternatives A, B, and C. Data for No Action represents the baseline against which anticipated conditions under the interim agreement alternatives are compared. Alternatives A and B are shown together because the water supply requirements are the same for both alternatives. Tables 1 through 3 show monthly average Gunnison river flows for the representative years at three locations on the river near Whitewater, _ below Redlands, and below the Gunnison Tunnel. Table 1 shows that average monthly flows near Whitewater are nearly the same for all alternatives during wet, normal, and very dry years, but they change in a dry year such as 1990. When flows of at least 1,095 cfs occur at Whitewater, the needs of both the fish and water users are met (750 cfs for the Redlands Diversion, 45 cfs for the absolute water rights between Redlands and Whitewater, and 300 cfs for endangered fish). Figure 3 illustrates the 1990 information from Table 1 in a bar graph format. The graph shows flows were often less than 1,095 cfs in the winter and summer months for No Action and Alternative C. Figure 3 shows that Alternative C does not provide sufficient flow for both fish and water users under dry year (for example, 1990) conditions. Shortages to water users would occur during 20