Winznau weir: new fish ladder

Atel Hydro AG has built a new, naturalistic fish ladder bypassing the weir on the river Aare at Winznau. A similar watercourse at Ruppoldingen power station inspired the design. With this CHF 1.8 million project, Atel Hydro is contributing further to improving our river ecosystems.

Fish bypass weir via naturalistic watercourse

The new fish ladder makes it possible for fish and other aquatic life to get past the 5.5 metre high weir via a naturalistic watercourse. It took some 10 months to build the 150-metre long channel on the right bank of the river Aare, with its 36 mini-weirs made from stone blocks placed in the water’s path. Around 700 litres of water a second bubble along the course, which has been designed to be as natural as possible. Counting facilities are in place for periodically checking the ladder’s popularity with fish on their way upstream.

This new construction replaces the old fish ladder, a concrete staircase-like structure dating back to 1917. An investigation of fish migratory patterns revealed that it was being little used. Atel Hydro made a commitment to the Swiss cantons of Solothurn and Aargau to replace the old fish ladder at Winznau as part of modernisation work at Gösgen power station between 1996 and 2000.

Aare-Tessin Ltd. for Electricity Corporate Communications