Schwarzenbachtalsperre

Here the Schwarzenbach stream is dammed into a lake two kilometres long – the largest in the northern and central Black Forest, 66 hectares of water at 668 metres above sea level, between the Schwarzwaldhochstraße ridge road and the Murg valley. It is held by a concrete gravity dam: 400 metres long, 65.3 metres high, 285,000 cubic metres of material, and 14.4 million cubic metres of water behind it.

It was built between 1922 and 1926, with up to 2,000 workers, and it is still regarded as a pioneering feat of German dam building. The wall is a listed monument.

What the lake does for the power grid

The reservoir is the upper basin of the Rudolf-Fettweis plant, named after the engineer who led its expansion in the 1920s. EnBW is converting it into a full pumped-storage power station by the end of 2027: the machinery and an additional store will sit in caverns inside the mountain, and the compensating basin down in Forbach will become the lower reservoir. The lake up here stays what it has been for a hundred years.

Around the lake

A shoreline path leads around the reservoir in 6.5 kilometres – along the water on the northern side, through the forest on the southern one. Boards along the way explain how the dam was built and how it works; the starting point is the car park opposite the dam. From May to September there are pedal boats and electric boats for hire; people also swim, fish and windsurf here.

What a visit in 2026 means

From early April to October 2026 the lake lies dry – for the fourth time in a hundred years, after 1935, 1952 and 1997. During that time EnBW is renewing the closing mechanisms in the dam wall and building new shoreline structures in the empty basin that will later give fish shelter. After that it will be filled again and restocked. Until then parts of the shoreline path and the dam crest are closed at times, and nobody may enter the basin: the muddy ground will not carry you.

What is nearby

The Black Forest National Park begins at the southern shore, and the Herrenwieser See lies a walk further on. Down the valley it is about ten kilometres to Forbach, where the longest free-standing covered wooden bridge in Europe crosses the Murg.