Wayne N. Aspinall Unit: Briefing on Reservoir Operations

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Previous biological opinions on two other Reclamation projects in the Colorado River Basin, the Dallas Creek and Dolores Projects, depend on operations of the Aspinall Unit to offset their depletion impacts. The RIP studies and biological opinion for the Aspinall Unit will help clarify how these previous commitments will be met for endangered fish. As part of the RIP activities specific to the Gunnison River Basin, in 1996 Reclamation constructed the Redlands Fish Passageway around a private irrigation diversion dam. The passageway is located approximately 2 miles upstream from the Gunnison's confluence with the Colorado River. This recovery action included negotiation of a short-term agreement to provide water from the Unit to operate the passageway. Operation and use of the passageway is being monitored to verify native fish movement to historical habitat that had been blocked for over 70 years. Non - native fish using the passageway are sorted from native fish to prevent competing non - natives from entering Gunnison River habitat. The experiment appears to have succeeded in opening the 50 miles of critical habitat on the Gunnison. By October 2002, 52 endangered Colorado pikeminnow and 5 razorback suckers, along with thousands of other native fish, had migrated up the ladder during their summer spawning season. The biological opinion on the operation of the Unit will prescribe changes needed to help establish self - sustaining populations of endangered fishes in both the Gunnison and Colorado rivers. Changes will most likely call for operating the Unit to provide higher spring/early summer releases, followed by lower releases the remainder of the year. Operations since 1992 have shown that a more natural hydrograph can be provided while meeting Unit purposes. There is a potential for conflict with Unit purposes in the future, however, dependent on the final flow recommendations for endangered fish. Black Canyon Reserved Water Right The Colorado Water Court has granted a yet to be quantified reserved water right to the United States for the National Park. The reserved right dates to the Black Canyon of the Gunnison National Monument's (now National Park) designation in 1933, and thus would be senior to the Aspinall Unit's water rights and many other public and private storage and diversion rights in the basin. Quantification of this right will remove some of the unknowns concerning how this water right and Aspinall Unit operations interrelate. The National Park Service has conducted studies in the Black Canyon on vegetation, stream organisms, recreation access, and stream morphology to provide data for quantifying the reserved right. Operation of the Aspinall Unit was coordinated to supply flows needed for these studies. The National Park Service believes a more natural hydrograph, with higher spring flows and lower base flows, would best protect National Park resources. 7