 Water level is controlled by a sluice in the north-western end of the lake where the lake empties into Lake Mälaren through a system of dikes and culverts.Polluted waste water was poured directly into the lake during the early 20th century which caused up to two third of the lake to be choked-up until the 1940s.It was subsequently one of the first lakes in Stockholm to be subject for various attempts to restorations.