Juvenile Salmonid Guidance at the Bonneville Dam Second Powerhouse, Columbia River, 1983–1989

Abstract

Studies of fish guidance with submersible traveling screens (STS) were conducted at the Bonneville Dam second powerhouse, Columbia River, during the 1983-1989 seaward migrations of yearling (age-1) and subyearling (age-0) salmonids Oncorhynchus spp. In 1983, the initial measurements of fish guidance levels were less than 25% for yearling and subyearling chinook O. tshawytscha and coho O. kisutch salmon and approximately 33% for steelhead O. mykiss, compared with expected levels greater than 70% for all species. Modifications based upon hydraulic models and field research were made to the trashracks, STSs, and face of the powerhouse. With these modifications, yearling chinook and coho salmon guidance levels greater than 75% were sometimes attained, but maximum steelhead guidance was less than 70%. Guidance of subyearling chinook salmon during the spring migration was as high as 60% but during the summer migration remained below 30%. Even with major modifications to the second powerhouse, fish guidance was lower than levels obtained at many other hydroelectric projects on the Columbia River.