Temporary turbine and reservoir level management to improve downstream migration of juvenile salmon through a hydropower complex

Stéphane Tétard (1, 2) , Romain Roy (2) , Nils Teichert (3) , Jocelyn Rancon (4) , Dominique Courret (5)

1 TBI-ICEO - ICEO - Ingénierie et du Criblage d’Enzymes Originales
2 EDF R&D LNHE - Laboratoire National d’Hydraulique et Environnement
3 BOREA - Biologie des Organismes et Ecosystèmes Aquatiques
4 CNSS - Conservatoire National du Saumon Sauvage
5 IMFT - Institut de mécanique des fluides de Toulouse

Developing management rules to improve downstream migration of salmon smolts in large hydropower plants is essential to limit mortality and migration delay. A 2-year telemetry study was conducted to assess the efficiency of temporary measures to enhance the safety and speed of juvenile salmon passage through the Poutès dam (Allier River, France). 124 smolts were tracked through the reservoir and downstream of the dam, during implementation of turbine modulation and/or shutdown during night and reservoir level lowering. Level lowering significantly reduced median residence time from 3.4 days to 4.4 hours. However, even with high spill during turbine modulation, the risk of smolt being drawn toward the turbines was increased at low reservoir level due to the site’s configuration, greater proximity to the surface and weak repulsive effect of the rack. Moreover, results revealed that a substantial proportion of smolts can migrate during daytime and twilight during floods, even at the beginning of the migration period. Thus targeted turbine shutdown has a good potential to protect smolts, but implementation requires studies taking account of site specificities and a flexible approach.

Mots clés: Atlantic salmon; Downstream migration; Migratory delay; Operational management; Turbine shutdown

Domaines: Biodiversité et Ecologie; Ingénierie de l'environnement; Ecosystèmes; Mécanique des fluides [physics.class-ph]

Stéphane Tétard, Romain Roy, Nils Teichert, Jocelyn Rancon, Dominique Courret. Temporary turbine and reservoir level management to improve downstream migration of juvenile salmon through a hydropower complex. Knowledge and Management of Aquatic Ecosystems, 2021, 422 (4), pp.0. ⟨10.1051/kmae/2021004⟩. ⟨hal-03181067⟩