The Okertalsperre is a dam near Altenau in the Harz in Lower Saxony Goslar and is operated by the Harzwasserwerke. Its water reservoir, also known as the Okerstausee, has an area of ​​2.25 square kilometers (km²) and a storage area of ​​47.4 million cubic meters (m³) of water through a maximum of 75 meters (m) high and 260 meters long Dammed dam is dammed. The pent-up water drives the turbine of the.