The Hornberg Basin (German: Hornbergbecken) is the upper reservoir of the Wehr power station, whose lower reservoir is impounded by the Wehra Dam. It lies near Herrischried (Hornberg) and near the town of Wehr in the county of Waldshut in Baden-Württemberg on the dome of the Langer Eck, the highest hill in the Hotzenwald. It was opened in 1975, is only used to generate pumped-storage power and is operated by the Schluchseewerk.
An addition to the existing Hornberg Basin was planned as part of building the Atdorf Power Station, but the effort was cancelled in 2017 by the local operating company EnBW.[1] With a length of almost one kilometre and storage capacity of 9 million m3 it would have been considerably larger than the present Hornberg Basin.