Lake Zurich (47.34N, 8.54E) is located at the border between the midland and the prealpine region of Switzerland. Two ridges that protect the lake from direct exposure to the dominant west winds enclose Lake Zurich. Its width varies between 2.5 and 0.5 km. In Rapperswil, Lake Zurich is separated by a dam from Lake Obersee the outflow of which is the main inflow to Lake Zurich with an average discharge of ~76 m3/s. The only outflow is the river Limmat which leaves the lake in Zurich with an average discharge of ∼90 m3/s. Lake Zurich has a surface of 65 km2, a volume of 3.3 km3 and an average residence time of ~420 days. The deepest location is 137 m depth (Omlin et al., 2001).