Author(s): Ismail Albayrak; Mohammadreza Maddahi; Maximilian Kastinger; Alfredo Scherngell; Roland Sutter; Robert M. Boes
Linked Author(s): Robert Boes, Ismail Albayrak
Keywords: Upstream fish migration multi-structure vertical slot fishway hydraulic performance effect of turbine operation attraction flow
Abstract: In this study, we investigated the hydraulics of the fishway at the low-head run-of-river hydropower plant (HPP) Dietikon located on the Limmat River in Switzerland. The focus is on the effect of HPP operation on the attraction flow at the fishway entrances. The fishway consists of 35 pools, designed as a multi-structure vertical slot pass with alternating slot sides. Three velocity measurement campaigns were conducted using an Acoustic Doppler Current Profiler in 2021 and 2022 during low flows with either the left or right turbine in operation, and high flows with both turbines operating at full load. Results show that when only the left turbine operates, high flow velocities occur along the fishway entrances, creating a migration corridor. In contrast, operation of the right turbine creates a recirculation zone near the fishway entrances, potentially misdirecting upstream-migrating fish and, hence causing some delay. Under full-load operation, two high velocity zones are observed – one in the middle and one on the left side of the tailrace channel – potentially creating two migration corridors. The middle flow may attract fish to the central pillar of the turbine outlets while the left-side flow attracts fish to the fishway entrances. Preliminary results from the ongoing fish monitoring campaign suggest that the fishway’s hydraulic design is effective under all three turbine operation conditions, given that about 300,000 fish successfully used the fishway during the nine-month monitoring period.
Year: 2025