Juvenile and Adult Fish Passage Improvements at The Dalles Dam, Columbia River

In recent years a steady decline in salmon populations has been reported in the Columbia River and its tributaries. Dams constructed to provide recreation, barge/tow access, power production, flood control, and many other regional benefits along the Columbia River system have been sited as one of the major contributors to the declining numbers of salmon. To address issues related to adult and juvenile fish passage at The Dalles Dam, a 1:80 scale physical model was constructed. The three dimensional undistorted physical model reproduces the dam features and the Columbia River for approximately 2.3 km (1.4 miles) upstream and 1.6 km (1.0 mile) downstream from the axis of the dam spillway. Spillway discharge is currently the primary method of fish bypass at The Dalles Dam. Until a permanent surface bypass collection facility or a juvenile bypass system is implemented, interim solutions can be utilized to improve fish passage survival rates. This paper discusses changes in dam operational procedures that were implemented at The Dalles Dam as a result of the physical model investigations.