Beznau hydropower plant: new fish ascent works perfectly

20.11.2024 - The renovation of the fish ascent at the Beznau hydropower plant is a valuable contribution to biodiversity in the Aare and the large Central Plateau rivers. Detailed monitoring has shown that around 77,000 fish used the new fish ladder during the study period. In addition, almost all known fish species in Aargau were detected.  

The renovation of the fish ascent on the right bank at the Beznau hydraulic power plant (HKB) was carried out in accordance with the provisions of the Water Protection Act (GSchG) and the Federal Act on Fisheries (BGF). After the Klingnau power plant, the HKB is the second power plant on the Aare and one of the two gateways for ascending fish to the Aare, Reuss and Limmat. A well-functioning fish ascent facility is essential for connecting the High Rhine with the Aare and its tributaries.

Almost all species use the fish ascent

The renovated fish ascent has been in operation since 2019. Its effectiveness has now been analysed in a comprehensive monitoring programme using fish counts. The results are encouraging: during the 293-day census, around 77,000 fish used the new fish ascent. In addition, a total of 29 species were counted, meaning that almost the entire known species spectrum of the Aare in the canton of Aargau was recorded.

In addition to the fish count, the monitoring also included a detailed investigation into how well the fish find and pass the fish ascent. Fish were tagged using PIT (Passive Integrated Transponder) technology in order to investigate their migration behaviour. The results suggest that the lighting conditions in some basins can restrict the fish's ability to pass through in a species-specific manner. Based on these findings, Axpo further optimised the fish ascent in summer 2024 and improved the lighting conditions in eight of a total of 45 basins. With the new fish ascent at the HKB and the renovation of the fish ascent at the Klingnau power plant planned for 2028, Axpo expects that many more fish will find their way upstream into the large Mittelland rivers in the future.

The fish ascent at the HKB is around 175 metres long and consists of 45 interconnected basins. It has two entry points (for strong-swimming and weak-swimming fish species) and so-called lure current pumps, which guide the fish upstream.