Fischwanderhilfe Kraftwerk Egglfing-Obernberg

Carried out as part of the EU-funded LIFE project "Riverscape Lower Inn"
https://www.life-riverscape-lower-inn.eu/de

FOR GREATER BIODIVERSITY
VERBUND is constructing a 5.8-kilometer-long bypass channel at the Egglfing-Obernberg Inn power plant by 2027
5.8 km in length by 2027 at the Egglfing-Obernberg Inn power plant. Preparations began as early as fall 2024. In the future, fish will be able to
swim past the power plant, and new habitats for endangered species will be created

A near-natural aquatic habitat

To allow fish to swim past the power plant, a bypass channel with natural flow dynamics is being built. It extends from the upstream section to the downstream section of the river, downstream of the power plant. The Malchinger Bach will also be integrated into the new channel.
Downstream from the confluence of the bypass channel, the Inn riverbank will be restored to its natural state.
The fish migration aid is more than just a migration corridor: with fords, gravel banks formed by the current, shallow-water zones, deadwood, and coves, a structurally rich waterway is created that offers an attractive habitat for numerous Inn fish and other aquatic organisms.

Shallow gravel banks serve as spawning grounds and resting places for young fish, while deeper zones provide space for large Inn fish such as the huchen.
Alongside the bypass channel, new habitats are emerging for gravel-nesting bird species, amphibians, reptiles, insects, and typical floodplain plants. The bypass channel also improves the water supply to the adjacent floodplain and enhances its ecological value.

Fish migration and the ecological development of the bypass channel and its surroundings are documented through monitoring, and the results are published.

In the Lower Inn European Reserve, the LIFE project contributes to the implementation of the Fauna-Flora-Habitat Directive and the Birds Directive, as well as the European Union’s Water Framework Directive.

Technology and Specifications

Construction work will be carried out in the most environmentally and climate-friendly manner possible: Excavated material will be reused on-site to create new gravel habitats—thereby minimizing transportation distances and vehicle emissions.

The fish passage will allow 4 to 10 cubic meters of water to flow through per second. During the spawning season for most fish in the Inn—from spring through summer—the flow rate increases; in fall and winter, it decreases again. Water is diverted from the Inn into the fish passage via the intake structure; a controlled supplementary intake structure enables the seasonal increase in flow.

Over a total length of 5.8 kilometers, the water first flows over a ramp and, after joining the Malchinger Bach, through the floodplain forest. Between the power plant and the road bridge, the bypass channel rejoins the Inn.
A gravel island is being created at the confluence, and downstream, the banks of the Inn are being renaturalized with a variety of structures over a length of 1.7 kilometers.