High Flow Outfalls for Juvenile Fish Bypasses: Preliminary Guidelines and Plans for Research and Implementation

Publication Date



adult, bypass, Columbia River, fish bypass, injuries, juvenile, juvenile fish bypass, mitigation, predation, Snake River, spillway, survival

Publication place

Portland, OR


U.S. Army Corps of Engineers


None supplied. From introduction: The overall goal of this part of the Columbia River Fish Mitigation Program is to develop high flow outfalls for juvenile fish bypasses at mainstem dams on the Columbia and Snake Rivers. To meet this goal, the objectives are to: (1) achieve survival rates as good or better than those at spillways, i.e. 98 to 100 percent; (2) minimize predation; (3) minimize stress and physical injury; (4) provide adequate recovery time (prior to encountering potential predation pressure); (5) not allow project operations to compromise the survival of fish using the outfall; and (6) not allow the high flow outfall to compromise the survival of other fish (adults and juveniles) passing the project. High flow outfall development will be sequential, from general to specific or qualitative to quantitative. It starts with general goals and objectives and progresses to specific performance measures at a given outfall site. This report largely concerns generic outfall characteristics.

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