Preparation for Fish Passage and Survival Compliance Testing at Bonneville Dam, Columbia River

The 2008 Biological Opinion and Columbia Basin Fish Accords require the U.S. Army Corps of Engineers (USACE) to meet juvenile fish passage and survival performance standards at eight Federal dams on the Snake and lower Columbia rivers.  Testing at Bonneville Dam (BON) requires deployment of cabled Juvenile Salmonid Acoustic Telemetry System (JSATS) hydrophones at two elevations on each of 44 main piers at two powerhouses (B1 and B2) and the spillway.  In addition, the study design requires deployment of arrays of autonomous JSATS hydrophones (nodes) in the forebay, tailrace, and three tailwater cross sections >70 km downstream.  The USACE took a staged approach to fully monitor BON to learn ways to maximize effectiveness and fish-passage survival.  In 2006, the USACE funded a study of dam-passage and reach survival that relied solely on JSATS autonomous nodes deployed above and below the three lower river dams.  This study provided detailed information on passage survival and factors affecting detection efficiencies of detection arrays.  From 2006 through 2010, average detection probabilities of detection arrays have ranged from 68% to 94% and generally increased over time as site selection and deployment strategies improved.  In 2007, the USACE funded a BON spillway-passage survival study that provided information about effects of passage distributions on survival and valuable lessons on how to better deploy hydrophones in a noisy environment (i.e. increase signal-to-noise ratios).  Percent detection of tagged fish more than doubled between spring and summer  and was about 80% in late summer  as a result of baffling the downstream side of hydrophones and improving the detector/decoder software.  In 2008, passage and survival studies were extended to include B2 and the spillway, and the B2 study was repeated again in 2009 to provide a second evaluation of effects of a 700-ft behavioral guidance device in the forebay.  Between 2008 and 2010, there were improvements in hydrophones (omnidirectional with -180 dB sensitivity), detection and decoding efficiency and range, and timekeeping accuracy (<± 10 µs through the decoder).  In 2010, all three dam structures were wired for monitoring.  Independent double arrays of dam hydrophones achieved 100% efficiency for every route, and detection probabilities for the first two survival arrays averaged 81% and 94%, respectively.  Plans for 2011 compliance testing include further tuning of the detector and a 40% increase in node densities at the first survival array in the tailwater to increase efficiency to >90%.