Decision on the rehabilitation and draining of the retention basins of a small hydroelectric dam

Facts

Company X. has been operating a right to use the waters of the Wigger for hydroelectric power production since 1863. As part of flood protection works, the Cantonal Government of Lucerne authorized the complete renovation of the retention structure in 1988 and 1991, without setting a residual flow, but requiring the construction of a fish passage. In 2011, the Cantonal Government set a residual flow of 200 to 250 litres per second and regulated the procedures for draining the retention basin in order to protect the aquatic fauna and flora. Company X. challenged these latter provisions before the Cantonal Administrative Court and then before the Federal Tribunal.

Considerations

The Federal Tribunal considers that the contested provisions regarding the draining of the retention basin fall under Art. 40 of the Federal Act on the Protection of Waters (WPA), which specifically governs the dredging of retention basins to remove accumulated sediments in order to maintain the exploitable storage capacity. Although these drainages result in sudden flow variations, they are not subject to Art. 39a WPA on hydropeaking, which addresses flow variations related to the normal operation of the turbines.

To determine whether the ordered rehabilitation measures infringe on the substance of Company X.'s acquired rights,…