Alpiq Hydro Aare has created a new fish ladder at its run-of-river power plant in Flumenthal at the River Aare in the canton of Solothurn. The near-natural facility complies with state-of-the-art environmental standards as it enables fish to swim safely around the power plant and creates new biotopes. At peak times, around 20,000 fish per day are likely to use the fish pass.
Fishing expert Gabriel van der Veer from the canton of Solothurn expects that around 20,000 fish are likely to use the fish ladder every day at peak times. Whether perch, barb, grayling, trout, roach, pike or catfish, it will be possible to regularly measure which of the 30 or so native fish species for which the Aare is an important migration corridor swim through the fish ladder. Gabriel van der Veer refers to the separate counting pool in the facility, where the species, size and number of fish can be determined by the local fishing association during fish counts. The counting pool is most likely to fill up in August and September, when the fish migration reaches its peak every year. According to Gabriel van der Veer, fish often have to migrate for many kilometres because they are looking for food or to reach their spawning grounds: “The new fish ladder therefore significantly contributes to ensuring fish access here on the Aare near the Flumenthal power plant.”
According to the Federal Office for the Environment (FOEN), a total of 630 such projects are currently underway throughout Switzerland to make Swiss rivers more fish-friendly and improve the fish pass. The background to this is the revision of the Waters Protection Act of 2011. The aim is for all power plants in Switzerland to meet the requirements of the new Waters Protection Act by 2030.
Around CHF 20 million has been invested in the new fish ladder in Flumenthal. The entire costs have been covered by the federal government, which uses money from the national grid supplement fund (“Netzzuschlagsfonds”) for this purpose. The fund serves to promote renewable energies and is financed by the grid surcharge paid by all electricity consumers in Switzerland.
The water of the River Aare gently trickles through here, flowing over gravel banks and clearance cairns, passing tree trunks and rootstocks and giving the water flow a varied structure. Huge stones also rest on the banks of the stream. We are standing at the new fish ladder of the Flumenthal run-of-river power plant on the River Aare in the canton of Solothurn. Roland von Arx, Head of Hydropower Projects at Alpiq Hydro Aare, points to the upstream rock ramp that is part of the new facility and explains: “As a near-natural stream, our fish ladder is very well integrated into the existing landscape. It is not only used for fish migration but is also a biotope that provides valuable habitat for various small aquatic animals and proliferates aquatic fauna.”
As the operator, Alpiq Hydro Aare built the approximately 480-metre-long fish ladder at its run-of-river power plant in around two years of effective construction. According to Roland von Arx, the project proved to be technically challenging because the fish ladder had to be built around the existing infrastructure of the power plant. The end product was achieved thanks to careful planning and close cooperation with the federal government, the canton of Solothurn and environmental protection organisations. The modern fish ladder replaces the old fish ladder from 1970, which no longer meets modern requirements. The new fish ladder is also one of the largest newly created artificial bodies of water in the canton of Solothurn. On their way from the tail water to the supply canal, fish can safely bypass the power plants. The difference in height of around eight metres is largely overcome in a variety of natural basins. The animals are attracted by an artificial current and reach the entrance via a collecting channel, a vertical slot pass and a mouth structure. They then swim through the fish ladder.
Alpiq Hydro Aare AG is a wholly owned subsidiary of Alpiq. It owns and operates the three hydropower plants Flumenthal, Ruppoldingen and Gösgen at the Aare River in the canton of Solothurn. The Flumenthal hydropower plant was commissioned in 1970 with three horizontal bulb turbines and processes around 386 m3 of water per second at full capacity. The performance of the three machines amounts to 25 MW and the average annual production is around 146 million kWh of electricity, which corresponds to the annual electricity consumption of 32,450 households.
