Safe and efficient two-way migration for salmonids and European eel past hydropower structures

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2015

End date

12/31/2019

Budget

1,672,800 EUR

Fundings

Abstract

Many of the 500 fishways in Norway enable salmon and sea trout to pass waterfalls and hydropower dams, whereas malfunctioning fishways often hinder migration of inland fish species. Aiding fish past upstream barriers is of limited value if the return migration of adults and their offspring is not secured. Fish may enter hydropower turbines and be injured or killed. The hydropower industry in Norway is facing new legislations demanding better solutions for two-way migration of fish, particularly for the strongly declining European eel. Most migration solutions depends on spill of water and thus reduced hydropower production, whereas society aims for increased renewable energy production. We thus need good solutions for both fish and hydropower. SafePass has been a major boost for the scientific approach to migration challenges in Norway. New cost effective solutions has been developed based on international cooperation, basic research and tests of different measures. Detailed studies of fish behaviour and hydraulic conditions has been central. Fish migration tracks of unique quality has been provided in front of HP intakes in Norway for salmon smolt in two rivers, for salmon kelts in one river, smolt and kelts of trout in one inland river, and finally tracks of downstream migrating eels in a Swedish river. The tracks have been linked to detailed hydraulic data to explain behaviour. A migration model for salmon smolt has been developed, and work is ongoing for other species. The models allow simulation based test of different measures, a time- and cost effective approach compared to traditional trial and error. Fine-meshed racs are best practice solutions to prevent fish from entering turbines and we have experimentally tested different designs for head-loss and fish repulsion efficiency. Because such racks are expensive and technically challenging in large HP systems, recent focus has been on floating guiding racks. After initial studies on swimming abilities of trout and grayling, we used accumulated knowledge to retrofit a poorly functioning fishway in the River Glomma. The improvements in passage success were striking, and the design is a template for similar retrofitting elsewhere. Existing and accumulated knowledge has been published as best practice reports, and are already in use to develop migration solutions.