In the present study, nine hydropower plants with different innovative and conventional hydropower plant technologies were assessed over a period of 10 years regarding their direct effects on passing fish (e.g. mortality and injuries) and their effects on the habitat and the aquatic community composition. The results of the project clearly demonstrate that the downstream passage of fish via hydropower plants can cause considerable fish damage, regardless of the hydropower plant technology. The installed fine screens with bar spacing of less than or equal to 20 mm could not efficiently prevent a large proportion of the naturally downstream moving fish from passing through the turbines. The identification of turbine technologies with a lower fish injury risk and more effective bypass strategies into hazard-free corridors is therefore of great importance for successful fish protection at hydropower plants. For fish protection and downstream bypass systems, the design, the dimensioning and their spatial location to the hydropower plant are decisive for their functionality and efficiency. In addition, knowledge of the river-specific, daily and seasonal fish downstream movement patterns is of great importance for an ecologically less harmful management of hydropower plants. In addition to installing a less harmful turbine technology, a higher level of fish protection can also be achieved through optimised operational management.
At each of the sites investigated in this project, the results on the ecological effects of the hydropower plants showed that the river continuum is severely disrupted by the hydropower plant or the associated transverse structure. Contrary to the promises made by the developers of these innovative concepts, the installation of the various types of innovative hydropower plants has not improved the habitat conditions for rheophilic species. Conversely, retrofitting existing weirs in conjunction with an increase in the damming target has significantly increased the effects of the interruption of the river continuum and further deteriorated the habitat conditions for rheophilic species in the areas upstream of the hydropower plants.
The results of the investigations show that many of the current assumptions regarding the expected ecological improvements through the installation of innovative hydropower plants do not hold true and that, under certain site-specific conditions and operation modes, even greater ecological damage can occur than when operating conventional hydropower plants. The study provides important information on which hydropower plant types and operation modes under which site-specific conditions enable a reduction in fish damage and negative impacts on habitats, which can lead to significant ecological improvements, particularly when retrofitting existing hydropower plants.
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In the present study, nine hydropower plants with different innovative and conventional hydropower plant technologies were assessed over a period of 10 years regarding their direct effects on passing fish (e.g. mortality and injuries) and their effects on the habitat and the aquatic community composition. The results of the project clearly demonstrate that the downstream passage of fish via hydropower plants can cause considerable fish damage, regardless of the hydropower plant technology. The i...
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