Author(s): Tobias Ruesch; Robert Boes; Ismail Albayrak

Linked Author(s): Ismail Albayrak, Robert Boes

Keywords: Downstream fish passage; Fish guidance system; Curved Bar Rack; Bypass system; Operation; Recommendations

Abstract: The present study deals with the development, construction, operation, and success-control of the downstream fish passage system for the pilot hydropower plant (HPP) Herrentöbeli on the Thur River in Switzerland. This system is called foiledshape Curved-Bar Rack – Bypass System (f-CBR-BS) and functions as mechanical behavioural fish guidance system. In the project's initial phase, a rack angle of 37° to the flow direction and a clear bar spacing of 25 mm were selected and tested with the target fish species of brown trout in the laboratory. Results revealed improved fish guidance efficiency with a 25 mm compared to 50 mm. The existing headrace channel underwent a complete redesign to accommodate the rack. Subsequently, numerical modelling and simulations were conducted to optimize the flow field for fish guidance efficiency and operational effectiveness. Additionally, an adjustable BS and a 60 cm high bottom overlay were developed for the f-CBR. The final f-CBR-BS design, including the headrace channel was constructed and commissioned in 2022. Since then, success control studies, including hydraulic and fish monitoring have been performed and are still ongoing. Initial findings from camera monitoring within the BS indicated effective guidance for fish species with weaker swimming abilities across various life stages. Hydraulic results match with numerical simulations, confirming favourable fish guidance conditions and corroborating the fish monitoring results. Despite this, several operational challenges were experienced, and hence various adjustments were made to the project to ensure economic operation.

DOI: https://doi.org/10.3929/ethz-b-000675921

Year: 2024