Effects of turbine operations and a prototype rotating vertical barrier screen on fish condition at McNary Dam, 2006

This study was initiated to evaluate the condition ofjuvenile salmonids during passage through the fish bypass and collection system at McNary Dam, with an emphasis on identifying guidance structures and turbine operations that may adversely affect fish condition. Earlier studies at the dam indicated that juvenile salmonid survival may not have differed while passing through turbines over a range of discharges. However, the more turbulent conditions associated with higher discharges, together with debris accumulations on contemporary vertical barrier screens, may require structural modifications to protect collected fish during their time in the gatewells. A prototype rotating vertical barrier screen was installed in gatewell 4A during 2005 to address these issues. Also, earlier tests at McNary Dam in 2004, indicated that an increase in descaling during higher turbine discharges may not have been solely related to gatewell conditions. Contract no. W68SBV20655422