Ödseen

The Große Ödsee is a forested mountain lake in the Salzkammergut, near Grünau im Almtal in Upper Austria. It lies in the Hetzau valley, a side valley of the Almtal, with peaks of the Totengebirge such as the Großer Priel nearby. The lake is reached by a six-kilometre road from the Almtal to the Almtalerhaus, open from early summer until mid-September. Two small lakes stand close together, the Große Ödsee and the Kleine Ödsee, both popular for swimming in warm summers. Steep wooded limestone or moraine shores surround the water, with gravel and sand banks at some points. The lake covers about eight hectares and reaches a depth of twenty-two metres. In the south two deep basins drop below twenty metres, separated by a shallow section only three and a half metres deep. Three small springs feed the lake, but most water comes from underground sources. The outflow also disappears underground into the Straneggbach, and water stays in the lake for about 174 days. Levels can vary by more than a metre, rising in winter and falling in summer when surrounding moraine material holds back inflows and draws water out. The Ödseen formed during the Würm glacial period when a glacier from the Priel group pushed into the Hetzau valley. Moraine ridges above the lakes show the ice’s former extent. Five lakes once filled the valley, but only these two survived because moraines shielded them from the Straneggbach’s sediments. The lake remains largely unpolluted, with clear summer water and few nutrients. It supports populations of brown trout, brook trout and lake trout, and is protected as a nature reserve covering over eight hectares.