Teufelsteich, Reservoir in Harz District, Germany

Teufelsteich is a reservoir in the Harz District fed by several small streams that spreads across roughly 20 hectares in an elongated, narrow form. The dam was rebuilt in the 1980s and stands nearly 18 meters high, with the water behind it capable of holding up to 785,000 cubic meters.

Teufelsteich was built at the end of the 17th century to supply surrounding mines with water and to power machinery through water force. In the 20th century mining declined in importance, and since 1947 the reservoir has primarily served as the region's drinking water supply.

The Teufelsteich was built in 1697 as a Kunstteich, a pond supplying water power to Harz mines, and was raised in 1837/38 for silver mining. Its water came from the Teufelsgrundbach and Siebengrundbach, and from 1903/04 the Siebengründer Graben linked it to the Lower Harz Pond and Ditch System. Since 1947 it has served drinking water supply.

The dam, rebuilt in 1985, stands about 30 m below the site of the old embankment; its structure of shale with a clay core, plus spillway, bottom outlet, valve house and pump station, can be seen from outside. The reservoir lies near Harzgerode in the Siebengrund, fed by the Teufelsgrundbach and Siebengrundbach. Since 1947 it has supplied drinking water, so the water itself is not open to visitors.

The 1985 rebuild placed the new dam 30 metres downstream of the old one, which was then demolished; the clay-cored structure raised storage by 203,000 cubic metres. Botanists recorded the first Pannonian vetch in the inner Harz here in 1999, on fallow ground northeast of the pond.