The Möhne Reservoir is an artificial lake created by a dam that was built between 1908 and 1913 to help control floods, regulate water levels on the Ruhr river downstream, and generate hydropower. Today, the lake is also a tourist attraction. The lake is formed by the damming of two rivers, Möhne and Heve, and with its four basins stores as much as 135 million cubic meters of water.
The dam was destroyed by British bombers (“The Dambusters”) during Operation Chastise on the night of 16–17 May 1943, together with the Edersee dam in northern Hesse.
Though the Organisation Todt quickly repaired the dams with forced labourers commanded over from the construction of the Atlantic Wall, the impact of the raid on German industry in the Ruhr valley and indeed on the civil population was significant. In the Möhne and Ruhr valleys, 11 factories were totally destroyed, 114 seriously damaged, 25 road and rail bridges were destroyed and throughout the region power, water and gas supplies were seriously disrupted. Industry production was back at normal level by September, however.