Fish pass of Birsfelden Hydroelectric Plant

Fish ladders have to ensure unblocked upstream migration for a variety of fish. Fish orientate their migration according to the current, therefore the access into a fish ladder has to be close to the main current, i.e., near the turbine’s tailrace at power stations. On larger bodies of water, an extra small hydro power plant is built next to the fish ladder, discharging a lot of water into the lowest basin of the fish ladder. A strong current from the fish ladder attracts fish, while only the water flowing through the fish ladder is lost for electricity gain. Two types of technical construction are prevalent: Given enough space, brook like diversion channels are built. With little space, vertical slot fish passages are used. Concrete basins with varying water levels, differences ranging between 15-30 cm, are built in a row, connected by vertical slots.

Different sources, including Der Lachs – ein Fisch kehrt zurück. Mertens et al. 2011, Haupt-Verlag, Bern.