Author(s): Andris Wyss; Thomas Dubach; Ismail Albayrak; Luiz G. M. Silva

Linked Author(s): Luiz G Martins da Silva, Ismail Albayrak

Keywords: upstream fish migration; fish pass; field measurements

Abstract: River fragmentation by hydropower plants (HPP) can block or delay fish migration. Fish passages have been used to restore river connectivity and maintain fish movements. The design of upstream fish passages has been consolidated in the literature, resulting in the existence of many well-established guidelines. However, the efficiency of fish passages has to be assessed by monitoring programmes that, ideally, include quantification of hydraulic features and fish movements. In this study, the hydraulic and biological performance of a fish passage at the HPP Schiffmühle, Switzerland, was assessed. The HPP Schiffmühle is located in the Limmat River. The fish passage combines nature-like and vertical slot passages with two entrances. Fish movements within the fish passage were quantified using Passive Integrated Transponder (PIT) tags. Hydraulic measurements focused on quantifying the flow fields in the tailrace, around the fish passage entrances, and within selected pools to assess the attraction flow and the hydraulic conditions within the fish passage. The results showed that fish passage efficiency varied between 62% to 81% for different fish species and most fish species passed within a relatively short time of 1-2 hours in the median. However, passage times of about 15 hours (median) were also recorded for some species. This longer passage time is partly explained by frequent individual movements within pools of the fish passage.

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

Year: 2024