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Protecting the downstream migration of salmon smolts from hydroelectric power plants with inclined racks and optimized bypass water discharge

Tomanova, Sylvie and Courret, Dominique and Richard, Sylvain and Tedesco, Pablo A. and Mataix, Vincent and Frey, Aurélien and Lagarrigue, Thierry and Chatellier, Ludovic and Tétard, Stéphane Protecting the downstream migration of salmon smolts from hydroelectric power plants with inclined racks and optimized bypass water discharge. (2021) Journal of Environmental Management, 284. 112012. ISSN 0301-4797

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Official URL: https://doi.org/10.1016/j.jenvman.2021.112012


The sustained development of hydropower energy in the last century has caused important ecological impacts, promoting recent advances in efficient mitigation measures to be implemented in existing and future hydropower plants. Although upstream fish migration has been largely addressed with the development of fish-pass infrastructures, downstream passage solutions are often missing or inefficient, strengthening the need for their improvement and efficiency assessment. The efficiency of horizontally inclined (26°) low bar spacing racks associated to a bypass was assessed using salmon smolts radiotelemetry along three successive hydropower plants (HPP) in the Ariège River (southern France). In average, nearly 90% of the smolts were successfully protected by the racks and rapidly guided to the bypass, within few minutes in most cases. Furthermore, we detected a significant positive influence of the bypass discharge (Qbp% expressed as the proportion of concurrent HPP discharge) on the probability of successful bypass passage, reaching 85% of successful passage with a Qbp% of only 3%, and more than 92% when the Qbp% exceeded 5%. The probability of bypass passage without hesitation (e.g. passage within the first 5 min) also increased with Qbp%, and reached 90% with 5% of Qbp%. Passage without hesitation was especially detected on the site having larger bypass entrances and transversal currents, providing better guidance into the bypass. High-efficiency results of inclined racks yielded with reduced Qbp% confirmed their relevance to mitigate some of the HPP ecological impacts, re-establishing safe downstream salmon migration with lower impact on energy production than older less efficient solutions.

Item Type:Article
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Other partners > EDF (FRANCE)
Other partners > Ecole Nationale Supérieure de Mécanique et d'Aérotechnique - ENSMA (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Other partners > Université de Poitiers (FRANCE)
Other partners > Office français de la biodiversité - OFB (FRANCE)
Other partners > Etudes et COnseils en Gestion de l'Environnement Aquatique - ECOGEA (FRANCE)
Laboratory name:
European Union
Deposited On:04 Mar 2021 17:56

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