ReHydro’s main objective is to make hydropower more sustainable by retrofitting existing power plants with new technology. Part of that sustainability is the protection of biodiversity: one of our tasks is solely dedicated to the protection of the European eel. Once thriving in our rivers, this migratory species is now critically endangered. The eels begin their life cycle in the ocean, then make their way towards European freshwater rivers where they spend most of their lives before returning to the sea to spawn. Aside from predators, parasites and overfishing, hydropower facilities pose a risk to their health and survival as their journey often leads them through hydropower turbines.
To make their migration safer, ReHydro is working on the design of eel-friendly turbines that can significantly reduce eel mortality in large hydropower plants. These specially designed turbines will be optimized for a wide range of operating conditions and will retrofit existing Kaplan and bulb machines, starting with 15-meter head Kaplan turbines at our Belver demonstration site in Portugal.
A strategy has already been defined, supported by a detailed literature review conducted by our partners at GE Vernova with the support of EDP, EDF, CNR, and NINA, that pinpointed the laws and parameters most critical to eel survival. Based on our review, turbine design will be optimized to reduce collisions and mortality while not sacrificing its performances. A key part of this will involve model eels, designed to represent the average sizes of wild eels. These models will pass through model scaled turbine on GEV platform, with cameras recording their journey. A post-processing software will be adapted to detect any collisions with runner blade edges, and collect data on the turbine’s performance in relation to the model eels’ “survival”. Model testing at Belver will begin in spring 2026.
Once the design meets its safety targets at Belver, testing will expand to 20-25-meter head Kaplan and bulb turbines on-site at Bollène and Golfech in France.
Header image by the Freshwater and Marine Image Bank at the University of Washington.