Fish mortality at hydropower plants

Hydropower plants adversely affect the ecosystem of the water body: they act as barriers and prevent the natural migration of fish and other aquatic organisms. In order to prevent these adverse effects in compliance with the legal provisions, mortality risks of relevance for conservation must be distinguished from less important individual losses or those that are negligible from a planning viewpoint. Some population biology and nature conservation criteria and parameters have already been "operationalised" in the Mortality Threat Index of Bernotat & Dierschke (2015) for a number of species groups in accordance with a unified evaluation approach.

The aim of the project is first to carry out this conservation operationalisation in a similar way for the German native fish species. It will also provide indications of how to evaluate individual losses or mortality risks for specific types of projects. In addition, a comparison will be made of the technologies available on the market (e.g. Kaplan, Francis and other turbines; vertical/horizontal screens). Technical measures for fish protection and downstream fish movements (e.g. vertical/horizontal screens, bypass systems, attractant flow turbines) will be evaluated in terms of their effectiveness for different fish species or populations, and site-specific risks included in the evaluation.

The project will provide an assessment of how individual losses compared across species can be evaluated from a nature conservation standpoint so as to improve the assessment of hydraulic engineering projects in terms of the anticipated mortality. This information is primarily of relevance for processing the legal approval of nature conservation interests.

Data research, an assessment of the literature and expert questionnaire to compile the data set will be evaluated and best practice examples demonstrated.

Results

The new working aid for the assessment of the conflict intensity of hydropower plants presents a differentiated and manageable methodology for the technical and legal assessment of hydropower plants. With the methodology each plant and each constellation can and must be considered on a site-specific basis in order to be able to evaluate the massive impacts of this type of project on the water morphology and fish populations in a sufficiently differentiated and valid manner.