Madbachtalsperre, reservoir in Germany

The Madbachtalsperre is a reservoir on the Flamersheim cadastral area of Euskirchen, a few hundred metres from the Rheinbach hamlet of Queckenberg. Its dam was begun in the late 1930s to supply process water to the Euskirchen cloth industry but was left unfinished in 1940 because of the war, so the reservoir holds just under 70,000 m³ instead of the planned 300,000 m³. The lake is up to 9.10 m deep.

The dam was built between 1938 and 1940 to provide water for industry and farming in the surrounding area. Plans to expand the structure were later abandoned as industrial activity in the region declined after the war.

The name comes from the Madbach stream that feeds the reservoir, which lies on Euskirchen territory a few hundred metres from the Rheinbach hamlet of Queckenberg. Fishing is permitted in the water, which reaches up to 9.10 m deep, while swimming and other water sports are banned; signs at the lake explain the rules. Textile-free sunbathing is tolerated on the shore.

The area around the reservoir can be reached by simple paths and tracks that follow the valley floor, making it accessible on foot. Visiting in dry weather is advisable, as the paths near the dam can become slippery after rain.

The reservoir is monitored only manually, without automated gauges. During the July 2021 Eifel heavy rain, the dam was overtopped in the night to 15 July; two scour holes of about 50 m² each formed on the air side, plus smaller areas by the tunnel entrance at the dam foot, without endangering stability.