VERBUND Innkraftwerke is progressing construction of a new fish pass at the Rosenheim hydropower plant on the Inn River in Bavaria, Germany, as part of a project to restore ecological connectivity along the river.
Construction was scheduled to begin on 29 June 2026 following site establishment from 22 June. The project involves building an approximately 2.2km bypass channel on the left bank of the Inn between the bridge on Miesbacher Straße and the Happinger Ausee.
The channel is designed to replicate natural river conditions and will allow fish and other aquatic species to bypass the hydropower plant while overcoming a height difference of 8.3m.
According to VERBUND, the project will make the Bavarian section of the Inn passable for fish and other aquatic species from 2027 for the first time since the power plants were constructed more than 100 years ago.
The meandering bypass will incorporate varying flow rates and water depths, together with gravel beds, sediment bars, felled trees and other features intended to provide shelter and spawning habitat.
The channel will be 2215m long and range from 8.6m to 34m wide around local island structures. Water depths will vary from a minimum of 0.4m to approximately 1.2m.
A basic flow of around 1.5m³/sec will be supplemented by variable flows of up to 4m³/sec to replicate the dynamic conditions of a natural floodplain stream. Temporary flushing flows of up to 6m³/sec will also be possible to flush spawning grounds and promote sediment movement.
Other design elements include gravel rapids, rootstocks, shallow-water zones, nesting areas, stone piles and sediment bars to provide habitat for fish, birds and reptiles.
The Inn Cycle Path along the reservoir dam has been diverted during construction, with traffic restrictions scheduled to remain in place until 31 August 2027.
Main construction work is scheduled for completion in June 2027, followed by final recultivation and remaining works in autumn 2027.
