WSP12515 - Laserfiche WebLink

Home Browse Search

OOJ3~~5 Draft - Do Not Cite 1 August 2003 EVALUATING THE EFFECTS OF ASPINALL UNIT RELEASE STRATEGIES ON ENDANGERED FISH HABITAT IN THE LOWER GUNNISON RIVER prepared by Kirk E. LaGory, David Tomasko, and John W. Hayse Environmental Assessment Division Argonne National Laboratory Argonne, TIlinois 1 INTRODUCTION The U.S. Fish and Wildlife Service (FWS) recently developed flow recommendations for endangered fishes (Colorado pikeminnow Ptychocheilus lucius, humpback chub Gila cypha, bonytail Gila elegans, and razorback sucker Xyrauchen texanus) that identify critical flows to be achieved in the lower Gunnison and upper Colorado Rivers in Colorado (McAda 2003). Although flow recommendations can be achieved in a variety of ways including changes in diversion rates and release patterns from a number of flow regulation structures, it is likely that the Aspinall Unit (Crystal, Morrow Point, and Blue Mesa Dams) located in the upper Gunnison River, will be called on to provide a majority of the flows needed to meet recommendations because it is the largest regulation structure in this portion of the Upper Colorado River Basin. The evaluation presented in this report is intended to determine if and to what extent the use of water at risk of spill1 from the Aspinall Unit could meet FWS flow recommendations. Use of this excess water exclusively to meet the flow recommendations would reduce the impact of the flow recommendations on power and water users and, thus, the effectiveness of using water at risk of spill is of interest. 1 Spilled water is defmed as exce~ water that can not be stored in the Aspinall Unit reseIVoirs because of limited storage capacity relative to inflow and that is greater than the flow-through capacity of the power plants. Spilled water would be released either through bypass structures or spillways.