ANALYSIS OF POTENTIAL IMPACTS TO RESIDENT FISH FROM COLUMBIA RIVER SYSTEM OPERATION ALTERNATIVES

The US Army Corps of Engineers, the US Bureau of Reclamation, and the Bonneville Power Administration initiated the Columbia River System Op eration Review (SOR) in 1990. The SOR will assist agencies in comparin g the benefits and risks to Columbia River uses and natural resources from alternative strategies for using Columbia River water. Focusing o n 14 federal dams within the basin, the agencies are attempting to imp rove on the efficient and coordinated use of the Columbia River system . An initial screening of all potential strategies of reservoir operat ion was necessary to reduce the number of possibilities to a limited s et for detailed analysis. To that end, the Resident Fish Work Group of the SOR developed spreadsheet models capable of assessing the impacts of different management strategies on resident fish at six storage re servoirs. The models include biological, physical, and hydrological re lationships important to resident fish specific to each reservoir. Alt ernatives that kept the reservoirs near full pool and held stable duri ng the growing season resulted in positive benefits to resident fish a t all locations modeled. Conversely, alternatives designed to improve anadromous fish survival with increased instream flow generally had a negative impact on the resident fish in the reservoirs modeled. The mo dels developed for resident fish in the screening analysis phase of th e SOR were useful in assessing the relative impact to resident fish fr om a large number of alternatives. The Screening analysis demonstrated that future analytical efforts must consider trade-offs among river u ses/resource groups, among reservoirs throughout the basin, and among resident fish species within a reservoir.