Development and evaluation of an empirical equation for the screening effect of bar racks

Abstract

Passage through hydropower plants can cause severe injuries for downstream migrating fish. Bar racks and bypass systems can help to protect fish from turbine-induced mortality if they are designed correctly following guidelines. Currently, it is not possible to assess how effective bar racks are that do not meet design criteria for fish protection. We introduced the screening effect as a performance parameter for bar racks and developed an equation for determining the screening effect of bar racks for silver eels based on an empirical approach. We compared the equation for eels with the results of behavioural laboratory studies with European eels (Anguilla anguilla), roach (Rutilus rutilus) and Atlantic salmon smolts (Salmo salar). We showed that the equation is not applicable for roach and Atlantic salmon smolts. Using univariate statistics, we identified a significant influence of the bar rack spacing on the screening effect for eels for the guidance system with (Kruskal-Wallis test, p = 0.002) and without a bypass (Kruskal-Wallis test, p = 0.0220) and for salmon without a bypass (Kruskal-Wallis test, p = 0.001) for a significance level of 0.05. The screening effect was significantly different between the fish species tested for a bar rack without bypass and 20 mm bar rack spacing (Kruskal-Wallis test, p = 0.003) and 40 mm (Kruskal-Wallis test, p < 0.001) as well as a bar rack with a bypass and either 40 mm bar rack spacing (Kruskal-Wallis test, p = 0.014) or 60 mm (Kruskal-Wallis test, p = 0.001). The results can help to perform biological evaluations and plan retrofitting measures of non-optimal bar racks.

Keywords:

• Downstream migration
• fish protection
• bar racks
• eels
• behavioural laboratory studies

Acknowledgements

Special thanks to Theresa Lachmann, Madeleine Geldmacher, Christopher Ulrichs, Fabian Fester, Nils Hoffmann, Kathrin Henning and Jennifer Heermann for assistance in the lab and to Pia Bünis for assistance in researching. Review from Claus Till Schneider (innogy SE) strengthened the content of this manuscript. Equation for determining screening effect for eels at bar racks is part of the dissertation thesis by Elena-Maria Klopries, which has been published prior to this article (Klopries, 2018).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The research project Orientation and sounding behaviour of fish in front of screens at hydro power intakes (acronym OVeR) was financed by innogy SE and financially supported by the District Council of Cologne and the Ministry for Environment, Agriculture, Conservation and Consumer Protection of the State of North Rhine-Westphalia (MULNV) within the programme Living Waters in North Rhine-Westphalia. Fish obtained in this study were obtained from eel protection initiative Rhineland -Palatinate / innogy SE, a river in North Rhine-Westphalia and a Swedish salmon breeding facility.