The Biggesee or Bigge Reservoir (German: Biggetalsperre) is a reservoir in Germany. It lies in the southern part of the Sauerland between Olpe and Attendorn.
The lake serves to regulate the rivers Ruhr and Lenne as well as providing water for the Ruhrgebiet. It is fed from the Bigge, a tributary of the Lenne.
The lake serves primarily to store water for the Ruhrgebiet so as to maintain the same level of water in the Ruhr. The lake can deliver, via the rivers Bigge and Lenne, up to 40% of all the water supplied by all the reservoirs in the river system of the Ruhr combined. A hydroelectric power station produces around 24 million kWh electricity annually. The power of the three large and one small Francis turbines amounts to 17.52 MW. The owner of the lake is the Ruhrverband.
Along with the Listertalsperre, the Biggestausee forms a large reservoir system. The formerly self-standing Listertalsperre joins immediately on to the Biggesee.
In middle of the Biggesee itself is the circa 30 ha (74 acres) Gilberginsel which, together with the neighboring lakeshore area, forms a nature reserve.
