Sohlstabilisierung, Gewässerökologie und Wasserkraft: Die Sanierungsvariante E1+ „Mehr Fluss“ an der Unteren Salzach

Progressive global warming requires a reduction of greenhouse gas emissions. In this context, hydropower plays a central role in renewable energy generation, particularly in Austria. Hydropower plants offer a number of advantages, including high energy efficiency, low CO₂-equivalent emissions and high energy return factors. At the same time, however, large parts of Austria’s rivers are affected by anthropogenic influences such as hydropower plants, both in terms of water ecology and morphology.

An example of this is the Lower Salzach on the border between Austria and Germany. As a result of the straightening and bank reinforcement, the river has suffered a significant loss of structural diversity and is in the process of deepening, also due to bedload retention in the catchment area and upper reaches. The focus of the river restoration here is to achieve long-term stabilization of the riverbed and to implement ecological improvements according to the model of a self-dynamic pre-alpine gravel river. An integrative concept for combining renaturation measures with climate-neutral energy production is particularly promising for such a heavily anthropogenically influenced river section, where river engineering adjustments are necessary anyway. The restoration variant E1+ “Mehr Fluss” represents such an integrative concept for the Lower Salzach that combines the requisite riverbed stabilization and improvement of the river ecology with renewable energy use. In addition to the stabilization of the riverbed by means of a resolved asymmetrical ramp, initial measures for a self-dynamic widening of the tailwater are planned. The head resulting from the ramp will be used for energy generation by a river flow power plant. This is designed in such a way that the potentially negative effects of conventional river power plants, such as disruptions to biological continuity, sediment retention or loss of the river’s character, can be avoided as far as possible.

The concept can thus contribute to climate protection and simultaneously improve ecology of the watercourse and overall ecology, while stabilizing and raising the bed of the Lower Salzach in a sustainable manner.