Technical failure kills hundreds of fish at Rupperswil power plant
Wednesday 5th August 2026 on 18:30 in
Switzerland
Hundreds or possibly thousands of fish died in the Aare near Rupperswil between July 30 and 31 after a technical failure at the Rupperswil-Auenstein run-of-river power plant, SRF reported. The incident caused the water level to fall by 2.5 metres, leaving a fish passage completely dry for several hours.
The Swiss Fisheries Federation said fish, crayfish and insects died after the water drained rapidly. The local fishing association has filed a complaint.
The affected passage had recently been renaturalised. It includes a 770-metre stream designed to connect the existing fish passage with a side channel of the Aare. Images released by the fisheries federation showed the stream and side channel dry the morning after the incident.
Staff restored the water flow after discovering the failure the following morning, but the fish could no longer be rescued. Officials from the canton of Aargau were also present and considered an emergency fish rescue, according to Alexander Roschi, a spokesperson for the Swiss Fisheries Federation. “Unfortunately, it was already too late,” he said.
A passer-by discovered the dead fish and alerted police. The exact number could not be determined because the dry streambeds were flooded with large amounts of water after the failure was detected. Based on photographs, the fisheries federation estimated that hundreds to thousands of fish had died.
SBB said it had quickly informed the responsible authorities after discovering the incident. “We deeply regret what happened. It was a technical failure,” spokesperson Sabrina Schellenberg told SRF. The cause of the failure remains unclear.
The power plant operates automatically, as do many run-of-river power plants in Switzerland. The national fisheries federation criticised the lack of staff on site and said similar incidents occurred repeatedly across the country.
A comparable incident occurred on July 28 in the Albula river, where thousands of fish died after a sudden drop in water levels below the Sils im Domleschg power plant.