RESERVOIR DRAWDOWN - CASE-STUDY IN FLOW CHANGES TO POTENTIALLY IMPROVE FISHERIES

Salmon populations in the Columbia River Basin have declined, and seve ral species are now protected under the Endangered Species Act. Many f actors have contributed to the decline, including overharvest, loss of habitat, degradation of water quality, and construction of dams. Many measures have been implemented to reduce the impact of the darns, but additional measures are being considered. Lowering water-surface elev ations behind four lower Snake River dams has been proposed as a measu re to improve juvenile salmonid survival. The Corps of Engineers has d etermined preliminary costs, schedules, and required modifications for several drawdown alternatives. Initial estimates of the ability of th is type of operation to improve salmonid survival are controversial.