Through the construction of modern fish passes, diversion watercourses and bypasses, we expand fluvial habitats and restore the ability for aquatic life to pass power plants. The comprehensive formation of habitat by VERBUND also makes it possible to (re-)create habitats for many species.
The Braunau-Simbach power plant is a run-of-river power plant on the Inn and located in the municipalities of Ranshofen (Upper Austria) and Kirchdorf am Inn (Bavaria). The power plant was built between 1951 and 1954. Today, four vertical Kaplan turbines generate an average of about 550 GWh of electricity annually.
To enable aquatic life to pass the structure, a new dynamically fed bypass watercourse is being constructed from the headwaters of the power plant to the tailwaters, which restores continuity on the one hand and additionally creates new watercourse habitat for the long term. The large natural bypass river was created from a study of alternatives and is designed according to German and Austria guidelines in such a way that the entire fish fauna (species and life stages) can overcome the 12.1 m dam of the power plant.
In addition to restoring the link between various sections of the Inn, the generous layout of the bypass creates new fluvial habitats and thus partially compensates for the loss of rheophilic (flowing) habitats, which are absent in the central storage area. It also serves as a countermeasure for eliminating the lack of reproduction areas and juvenile fish habitats for the rheophilic fish fauna. In addition to the fish fauna, gravel-breeding birds also benefit from the newly created gravel banks.
The large near-natural bypass river has a total length of 3.1 km and a width of between 5 and 8 m. It is additionally designed with a range of depths, which offer several different types of habitat. The flow rate varies seasonally between 2 and 8 m³/s and represents the natural drainage of a large tributary of the Inn. The high hydrological dynamic results in a constant reshaping of the riverbed and the banks, offering loose gravel habitats for spawning fish and gravel-breeding birds.
The construction works are designed to be gentle on the environment and the climate, as the soil excavated on the construction site (a total of 110,000 m³) is being used to create new habitats or restore existing ones. Thus transport routes and vehicle emissions are minimised, which is good for the climate, the residents in the surrounding towns and the animal life in the area.
The Egglfing-Obernberg hydropower plant is a run-of-river power plant on the Inn in the municipalities of Bad Füssing (Bavaria) and Obernberg (Upper Austria). It was put into operation in 1944.
It is ensured that all fish fauna (species and life stages) can overcome the 10.6 m-high dam of the power plant. To this end, an approximately 5.8 km-long and 15 to 20 m-wide, dynamically fed bypass watercourse is being created in the course of the existing Malchinger Bach river, which runs on the orographic left bank of the Inn and empties into the Inn below the power plant.
It is designed with a range of depths, which offer several different types of habitat. The flow rate varies seasonally between 4 and 40 m³/s and thus mimics the natural flow rate of a large tributary of the Inn. The high hydrological dynamic results in a constant reshaping of the riverbed and the banks, offering loose gravel habitats for spawning fish and gravel-breeding birds.
In total, the bypass watercourse overcomes a height difference of around 10.6 metres and can be divided into 2 sections. The connecting channel with a length of 1.7 km creates the link between the headwaters (dam water level) and the low-lying floodplain level. The floodplain channel continues at the level of the floodplain in the original valley gradient of the Inn to the point at which it empties into the tailwaters of the power plant.
Lost river structures should be recreated around a total of three power plants in the project area. The floodplains play a special role in this – as habitats for typical flora and fauna.
Embankments in the area of the power plants are not just side effects of hydropower. They are also habitats of special quality – assuming appropriate care is taken. The opportunity to develop species-rich meadows and drygrass areas of European importance should be taken at a total of four power plants.
