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

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.

Prosjektet har levert resultater med direkte effekter for både forvaltningspraksis og for industrien. Vi har etablert mønsterpraksis for opp- og nedvandringsløsninger i regulerte elver som benyttes i forvaltning og industri. Mønsterpraksis for nedvandringsløsninger er allerede implementer i ett vassdrag og er tatt inn i prosjekteringen i et annet. Arbeidet med alternative løsninger der mønsterpraksis er teknisk eller økonomisk utfordrende fortsetter i HydroCen, men allerede nå er det flere løsninger som er under sluttføring. Vi har utviklet metodikk for modellmessig utprøving av tiltak, noe som gir betydelige innsparinger i utviklingen av lokale tiltak. Prosjektet har i samsvar med ambisjonene bidratt til et betydelig kunnskapsløft innen forskningen, samt i forvaltning og kraftindustrien.

This project will provide vital knowledge for safe and efficient solutions for two-way passage of salmon, trout, grayling and eel past hydropower structures, applicable for the hydropower industry and water resources management. The project aims at developing migration measures that obtain maximum environmental effects at minimum power production loss. This will be obtained initially by compiling and validating international knowledge from a range of sources. Further, we will fill important knowledge gaps on downstream migration of the target species in combined behavioural and hydraulic experiments in selected river systems. We will also focus on the need and design for retrofitting inland fishways for upstream migration. The project has a strong international focus, to ensure effective knowledge transfer from internationally leading research groups. Results and findings will be published in peer-reviewed journals but also compiled in a Handbook for two-way fish migration design, directly applicable for the hydropower industry, consultants and water management. The project will thus provide a new foundation for cost effective migration solutions in existing hydropower facilities (e.g. to comply with the Water Framework Directive), during upcoming revisions of hydropower licenses, and in new hydropower projects in Norway and abroad.