Low Stress Fish Passage: An Innovative Approach For Medium-Head Dams

There remains a need for non-labor intensive, safe, and effective upstream and downstream transport of fish at medium and high head dams and hydroelectric projects. The proposed Obermeyer system combines pneumatically operated gates for diverting fish into a lifting (and lowering) system with a variable speed reversible pump-turbine that hydraulically transports a floating cage of submerged fish through an auxiliary penstock between a tailwater fish trap and the upper reservoir. Fish are not subjected to high velocity flows, harmful pressure changes, or turbine transit. The pumping energy required for upstream transport is almost completely recovered while draining the auxiliary penstock which may be used for downstream as well as upstream fish passage. Energy use may be further cut in half by using two auxiliary penstocks. The pump-turbine associated with the fish passage system may be used for additional and efficient hydropower generation during non-fish passage seasons.