Other Authors: Ana T. Silva¹, Karl Øystein Gjelland¹, Henrik Baktoft²
Other Authors Affilliations:

¹Norwegian institute for Nature Research, Trondheim, Norway

²Danish Technical University

While fine mesh trash racks constitute a safe barrier for downstream migrating smolts, such racks can be expensive and technically difficult to retrofit at hydropower intakes. Alternatively, a combination of attraction and repulsion measures can successfully pass fish by the intake and into safe corridors. At the Laudal hydropower plant in Norway, Atlantic salmon smolts were tagged with conventional radio tags during the migration period in four different years. Based on recordings of the migration route, a statistical model could be developed to predict how flow diversion could attract fish into a bypass channel. Additionally strobe lights in front of the intake had repulsing effect during night. In order to create favorable flow diversion at the intake, manipulation of mountainous reservoirs were modeled and the economic cost related to flood spill and flow changes were calculated. Finally, 20 receiving stations were used to collect accurate 3D recordings from 100 smolts with surgically implanted acoustic tags during one migration season. An advanced computational fluid dynamics model was calibrated and applied at the intake to describe the hydraulics at different flow conditions and relate the physical variables to fish movement recordings. The results can be used to generate general rules for safe bypassing of salmon smolts at intakes.