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Switzerland – a land of nature-like bypass channels


Some fish such as salmon need access to freshwater but obstacles such as dams and hydropower plants can act as barriers and prevent them migrating and spawning.

However, rivers in Switzerland, which are all regulated, have benefitted from some innovative solutions to reduce the impact of hydropower plants and dams on fish. To solve this challenge, bypass channels or fishways have been built at almost at every dam and weir.

Left photo: Rheinfelden fish pass facility. Middle photo: a rock cascade pass. Right photo: a vertical slot pass (photos by Sini Olin, SYKE).


Rheinfelden is one of Switzerland’s many nature-like bypass channels. Located on the River Rhine, it is the largest fish pass facility of its type in Central Europe. It stands out with its three fish ways, a vertical slot pass, bypassing river course and a rock cascade pass.

The environmental aspects have been taken into consideration by providing constant discharge of 10 m3/s to the bypassing river course as an environmental flow. Additional discharge up to 25 m3/s can be provided via the regulated gates, in order to provide a dynamic flow regime. Discharge of 10 m3/s is also provided to the main channel as a landscape flow – purely for landscape reasons.

Even though this bypass channel has been in operation for only a short period of time, its environmental benefits are already evident. It has been estimated that the amount of fish in the by-pass channel is up to 30 000, many times more than most bypass channels.

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