As a result of intensive and ongoing discussions in the German Participatory Forum on Fish Protection and Downstream Migration, a mutual understanding was reached in 2014, up to which screen size a functioning mechanical fish protection and bypass system including the necessary cleaning technology can be realised:
"With vertical screens (up to approx. 30 m³/s per screen) and horizontal screens (up to approx. 50 m³/s per screen) there is currently a state of knowledge and technology with which functional, mechanical fish protection and bypass systems, including the necessary cleaning technology, can be realised for fish larger than 10 cm." (Source: Empfehlungen und Ergebnisse des Forums Fischschutz & Fischabstieg 2015)
The objective of the research underlying this Fact Sheet 04 was to verify whether the statement of the German Participatory Forum on Fish Protection and Downstream Migration is confirmed in the actual operation of existing fish screens. The key messages of Fact Sheet 04 are:
- The statement of the German Forum on Fish Protection & Downstream Migration that the current state of knowledge and technology allows functional fish protection screens at hydropower sites (up to approx. 50 m³/s discharge per screen) to be realised, is confirmed. They can be operated to protect fish larger than 10 cm and include the necessary cleaning technology.
- The use of screen cleaners with tooth- or brush-like elements can avoid problems with permanent congestions of fish protection screens with small bar spacing.
- Planning, design, and technical implementation of fish protection screens and screen cleaning are of major importance for the functionality of the hydropower site.
The Fact Sheet is based on data from the Atlas Fischschutz & Fischabstieg, on information provided by DWA Working Group 7.1 Fish Protection and Fishways, which has been revised and updated, and on the kind support of the operators of the Willstätt, Unkelmühle, Kemnade and Öblitz hydropower plants.
The Fact Sheet "Technical functionality of large fish protection screens confirmed in practice" is available for download.