Development of a Deepwater Reservoir Passage System for Juvenile Salmonids at the Baker River Hydroelectric Project, Northwest Washington

Abstract – Facilities for downstream passage of juvenile salmonids past the two dams of Puget Sound Energy’s Baker River Hydroelectric Project have undergone almost 60 years of evolution, beginning with the original collectors (known as “gulpers”), and culminating with two new floating surface collectors (FSCs). The first FSC began operation spring 2008, and was followed by three record outmigrations and an increase in collection performance of nearly 35%. The second FSC, now under construction and scheduled to begin operation spring 2013, will replace the original “gulper” at the Lower Baker reservoir. The FSC uses a conventional vee-screen contained within a floating channel, with flow induced by pumps. The 1000-cfs pumping capacity of the new facility is over seven times that of the original collectors, and is approximately 20 percent of plant turbine capacity. Computational fluid dynamic and physical hydraulic models were used in the design development, as was information from radio- and acoustic-telemetry fish tracking studies. The system consists of an exclusionary ¼-inch mesh guide net spanning the forebay, a net transition structure which provides a gradual transition from the vertical guide net to the FSC primary screen bay, and the FSC. Design concepts for the FSC reflect over 25 years of biological evaluations and improvements. These improvements contributed to the reversal of the steep decline of sockeye salmon, Oncorhynchus nerka, which in 1985 numbered 99 returning adults.