Achen Lake

Lake Achen (German: Achensee) is a lake in Austria, north of Jenbach in Tyrol. Lake Achen is also called "Fjord of the Alps" and "Tyrolean Sea". The largest lake within the federal state, its maximum depth is 133 metres (436 ft). Together with the Achen Valley, it parts the Karwendel mountain range in the west from the Brandenberg Alps in the east.

Water quality is near that of drinking water, with sight up to ten metres (33 ft) below the surface. An alpine lake, water temperature is accordingly low, rarely above 20 °C (68 °F). Its size and wind conditions make it suitable for windsurfing.

Eben am Achensee, Achenkirch, and Pertisau are municipalities on the lake.

The city of Innsbruck bought the lake in 1919 from the St. Georgenberg-Fiecht Abbey, who had received it from the rulers of Schlitters around 1120.

Due to various texts and illustrations in the hunting and fishing manuscripts of Emperor Maximilian, Lake Achensee was famous already at the beginning of the 15th century.

Since 1924, the lake is managed by the Tiroler Wasserkraft AG (TIWAG), which was founded for this purpose.

Originally, its only outflow was the Achenbach, feeding the Isar. Since 1927, when a power plant in Jenbach was finished, it primarily feeds the Inn, at a level difference of 380 m below. Eight pelton wheels at 500 RPM produce a total of 96 MW.

In winter, the level of the lake is lowered by up to 6 meters; accordingly the size of the lake keeps changing. At maximum level, the reservoir can store 66 million m³ of water.