Effets des éclusées hydroélectriques en rivière : diagnostic hydroécologique et aide à la gestion. Exemple de la Fontaulière (Ardèche)

CEMAGREF, Division Biologie des Ecosystèmes Aquatiques, Laboratoire d'Hydroécologie Quantitative, 3 bis, quai Chauveau, CP 220, 69336 Lyon Cedex 09

Abstract

Hydropower generation induces artificial fluctuations of flow and thus of hydrodynamic parameters in rivers, downstream of hydroelectric impoundments. On the Fontauliere river (Ardèche basin, France), the ecological effects of two different hydropeaking regimes were tested and compared to a reference upstream reach. Fish, invertebrate and epilithon communities were surveyed in these different reaches. The results enabled to classify the factors responsible for the observed effects. The base flow between peaks was the most important for the studied site. When it was too low, aquatic communities were destructured in comparison with the natural reach. These results enabled to suggest a current velocity threshold to respect in order to determine acceptable base flow for this type of stream. They also enabled to guide for the impact evaluation of hydropeaking sites. An ecological diagnosis should include the study of the structure and composition of the communities.