| Summary: | Abstract 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 sucessfully pass fish by the intake and into a safe corridor. At the Laudal powerplant in Norway, Atlantic salmon smolts were tagged with conventional radio tags during the migration period in four different years. A statistical model could be developed to predict how flow diversion could attract fish into a bypass channel and strobe light in front of the intake had repulsing effect during night. In order to create favorable flow diversion at the intake, manipulation of mountanious reservoirs were modelled and the economic cost related to flood spill and flow changes were calculated. Finally, 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 accurate recordings from stateof-the-art three dimensional radio tags surgically implanted in smolts. The results can be used to generate general rules for safe bypassing of salmon smolts at intakes.
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