Popular local recreation area in Hagen and the surrounding area

Lake Hengstey is located near Hagen below the mouth of the Lenne into the Ruhr. When it was commissioned, the mixture of the acidic and iron-rich Lenne water with the alkaline Ruhr water resulted in increased sludge precipitation and thus an intensive cleaning effect. Even though the ultra-modern wastewater treatment plants of the Ruhrverband are the main means of ensuring water quality today, the reservoirs cannot be dispensed with as a fine purification stage for the rainwater discharged and as a bed load trap for the river gravel from the Lenne.

In addition, since its commissioning, Lake Hengstey has served as a lower reservoir for the Herdecke pumped storage power station (Koepchenwerk) built by RWE. The water level in the Hengsteysee can fluctuate by up to 70 centimetres due to the pumped storage operation. The sediments of around 400,000 cubic metres deposited up to that point were removed from Lake Hengstey in 1988/89 using the dredging method.