Résumé
Sur le Rhône, les réservoirs sont des habitats artificiels résultant de l’aménagement hydroélectrique du 20ème siècle. Ces habitats abritent aujourd’hui une biodiversité typique et permettent de nombreux usages et services. Cependant, ils peuvent aussi avoir un rôle de piège pour les sédiments fins, qui se déposent à l’amont du barrage, réduisent le volume de la retenue, et peuvent causer une menace pour les populations et les biens publics en périodes de crue. Le relargage de sédiments fins par des vidanges constitue une opération courante de gestion, mais de telles opérations peuvent avoir des impacts écologiques importants. Suite à la vidange de la retenue de Verbois de 2012, les concessionnaires suisses et français des ouvrages ont élaboré une stratégie concertée et durable de gestion sédimentaire. La mise en œuvre de ces nouvelles mesures est accompagnée d’un suivi piscicole. Ce suivi vise à acquérir des connaissances sur les peuplements des réservoirs pour lesquels aucune méthodologie d’échantillonnage standardisée n’existe. Il est attendu de ce suivi qu’il 1) donne une image fiable de la biodiversité piscicole dans les réservoirs, 2) permette une estimation de la biomasse et de ses variations saisonnières, 3) soit suffisamment sensible pour estimer les impacts des opérations de gestion sédimentaire. Ce poster présente la méthodologie de suivi ainsi que les premiers résultats.
On the Rhône River, reservoirs are artificial habitats resulting from the hydroelectric planning of the 20th century. These habitats now shelter a typical biodiversity and support many water uses and services. However, they can also act as a trap for fine sediment which deposit upstream the dam, reduce water volume, impede energy production, and can originate safety concerns during floods. Releases of fine sediment by drawdown flushing are common management operations, but they can have substantial ecological impacts. Following the Verbois reservoir flushing of 2012, the Swiss and French dam concessionaires elaborated a coordinated and sustainable sediment management strategy. The implementation of these new management measures is accompanied by an ecological monitoring, especially for fish. This monitoring aims at gaining insights into the fish assemblages of reservoirs for which no standard sampling methodology exists. It is expected to 1) provide a reliable picture of the fish biodiversity in the reservoirs; 2) allow the estimation of fish biomass, and of its seasonal variations; 3) be sensitive enough to assess impacts of sediment management operations. In this poster, the fish monitoring methodology is presented, as well as the first results.
On the Rhône River, reservoirs are artificial habitats resulting from the hydroelectric planning of the 20th century. These habitats now shelter a typical biodiversity and support many water uses and services. However, they can also act as a trap for fine sediment which deposit upstream the dam, reduce water volume, impede energy production, and can originate safety concerns during floods. Releases of fine sediment by drawdown flushing are common management operations, but they can have substantial ecological impacts. Following the Verbois reservoir flushing of 2012, the Swiss and French dam concessionaires elaborated a coordinated and sustainable sediment management strategy. The implementation of these new management measures is accompanied by an ecological monitoring, especially for fish. This monitoring aims at gaining insights into the fish assemblages of reservoirs for which no standard sampling methodology exists. It is expected to 1) provide a reliable picture of the fish biodiversity in the reservoirs; 2) allow the estimation of fish biomass, and of its seasonal variations; 3) be sensitive enough to assess impacts of sediment management operations. In this poster, the fish monitoring methodology is presented, as well as the first results.