The installation of HPPs and dams may cause a number of problems for the fish fauna. These include: blocking or delaying upstream and downstream fish migrations, damage or mortality to fish when passing through turbines or over spillways and mortality due to predation by fish or birds at the outlets and in the retention area upstream of the dam. As a result population can decline. European Water Framework Directive and Swiss Water Protection Act (WPA) and the Swiss Federal Fishery Law (BGF) demand restoration of water bodies and elimination of negative impacts of HPPs as to river connectivity for the fish fauna. These requirements represents challenges to Hydropower Plant (HPP) operators and local authorities alike due to the current lack of design standards for downstream fish protection and guidance technologies.
In the scope of FIThydro project, VAW of ETH Zurich conducts two laboratory investigations developing Fish Guiding Structures (FGS) based on physical model investigations and live-fish tests.
Illustration of Modified Curved-bar Rack system (MCR) for protection and guidance of downstream migrating fish (VAW)
 
One PhD student, Julian Meister, investigates various aspects of the FGSs with horizontal bars (Horizontal Bar Rack, HBR) for smaller hydropower plants (HPPs) (design discharge QD < 100 m3/s), while another PhD student, Claudia Beck, focuses on the newly developed Modified Curved-bar Rack (MCR) for medium to large HPPs (QD > 100 m3/s).
Photo of Horizontal Bar Rack (HBR) for protection and guidance of downstream migrating fish (VAW)
 
The first results from the latter study show that the new curved bar shapes (MCR) reduce the head loss by more than a factor of 4 compared to the previously developed Modified angled Bar Racks (MBR). Given the highly reduced head losses, MCRs present a huge potential over MBRs for fish protection and guidance facilities at medium to large HPPs, minimizing negative economic impacts. MCRs and HBRs will be tested with live-fish in the laboratory flume in autumn 2018 and spring 2019.
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Ismail Albayrak, Robert Boes, Helge Fuchs, Claudia Beck and Julian Meister  (VAW, ETH Zurich)