Glattalpsee

Glattalpsee is a reservoir on the Glattalp plateau, above Bisisthal, in the municipality of Muotathal, Canton of Schwyz, Switzerland. The lake's water is used by the Sahli powerplant in Bisisthal to produce electricity.

Geography

The surface area is. The lake is located at an altitude of. Although the lake lies within the canton of Schwyz, it is considered to be part of the Glarus Alps. Its tributaries are the Glattalpseebach, Vorderer Läckibach and Hinterer Läckibach.
The natural lake has no surface outflow. A part of the water seeps through the karst lake bed, while the rest of is used by the Sahli powerplant. Almost half the water that could be used by the powerplant is lost to seepage. In order to increase productivity, it is planned to partially seal the lake bed.
Because of the leaking lake bed, the Glattalpsee dries out during winter months and only refills, once the snow starts melting in spring.
Starting at the summit station Glattalp of the gondola lift running between Sahli and the Glattalp plateau, there is a roughly long hiking trail along the lake's shores with the SAC hut Glattalphütte and the restaurant Berggasthaus along the trail. This loop has minimal elevation gain.
On February 7, 1991 a temperature of was registered, the lowest ever in Switzerland.