Can turbulent eddies save fish from turbines?

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Researchers seek to use turbulent eddies in the river to safely guide salmon and eels past hydropower plants. 

— Some say that this is a completely crazy idea, says project leader Ana Silva, who is a researcher at the Norwegian Institute for Nature Research. 

The project was born after a meeting where experts on turbines, fish, hydrology and hydropower started talking about the how fish are influenced by vortices in the water, and that vortices can be created and manipulated by different objects. 

— Many of the large power plants have no solutions get fish down the river and into the sea, and the solutions that exist are large, expensive and do not guarantee that the fish survive, she says. 

The researchers therefore aim to find a completely new solution. 

How to make fish-friendly eddies? 

Fish can detect turbulent movements in the water via sensory systems along their entire body and change their swimming behavior.  

— Accordingly, in FishPath we will utilize these abilities to develop turbulent eddies based guiding structures for salmon, trout and eel, says Silva. 

— We are so happy to team up with some of the leading international experts on fish biology and behavior, hydrology, fluid mechanics and engineering, and that we can pool our different resources and fields expertise to come up with a completely new solution for fish migration, she says. 

NINA-researcher Ana Silva leads FishPath, where the goal is to save fish from hydropower turbines without having to reduce the production of renewable energy.

The researchers first need to further explore the shapes and behavior of eddies created by different objects in the flow and how the fish species respond to the different types of eddies. 

— We will test objects like cylinders and hydrofoils and see what type of eddies they create. The behavior of the eddies will be studied by data modelling and experiments in a small flume.  

The responses of fish to different turbulent eddies will be explored in a series of fish flume experiments.  

Next, we need to align the objects that produce the desired eddies to create fish paths that we expect that   fish will follow, also explored by modelling and experiments, Silva says. 

— Next, we need to align the objects that produce the desired eddies to create fish paths that we expect that fish will follow, also explored by modelling and experiments, Silva says. 

Salmon smolts are only about 10-15 cm and 14 grams when they start their big swim down the river towards the sea. Many get sucked into the turbines when they follow the current into the hydropower plant, but the researchers aim to use the currents to guide them past.

Will make practical guidelines 

Once the candidate guiding systems have been developed their ability to guide fish will be tested, first in a  small laboratory flume, next in a larger flume and finally the most promising in a full-scale  at the Mandal  river  in Norway, with a medium hydropower intake.  

Results will be compiled in a practical guideline for eddy based guiding system, where we will also explore how the knowledge on turbulence and fish can be used in mitigation of other migration challenges, for instance upstream migration. 

— We are also very happy to see that the project has attracted several industry and management partners, that not only contribute financially but have dedicated representatives with years of experience on the topic of migration solutions from several river systems. This also ensures that developed solutions can be rapidly implemented, says co-manager in the project, Torbjørn Forseth.  

Read more on the project webside


Ana Silva, project leader FishPath

Torbjørn Forseth, co-manager FishPath

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