RESTORATION OF LAKE SEMPACH, SWITZERLAND

Surface: 14.4 km²; volume: 0.68 km³; max. depth: 87 m; mean residence time: 20 y.

Lake Sempach was highly eutrophic due to pollution, especially by intensive agri-culture.

TANYTARSUS System, designed by Jungo Engineering Ltd., was installed in 1984 as an internal lake restoration measure. Successful use of TANYTARSUS System is illustrated by the two basic parameters, oxygen and phosphor.

After the first season the restoration already led to excellent oxygen levels. Previously the net dissolved oxygen at the lowest point was at minus 15 mg/l. The total phosphor content decreased while the phosphor input was still rising. A goal in lake restoration was attained in 2003 when the total phosphor concentration reached the 30 mg/l mark (see fig.).