An ambitious scientific project, unprecedented in Europe
When the concession for the Vezins and Roche-Qui-Boit hydroelectric dams was not renewed, the French Ministry of the Environment decided that the dams would be removed in 2012. The goal was to restore ecological continuity between the terrestrial and marine habitats connected by the river basin. This decision came about as a result of the EU water framework directive (WFD) and the French Grenelle Environment Forum.
An interdisciplinary scientific program ongoing for 16 years (before and after dams dismantling) has been set up under INRA coordination. Researchers follow the ecologic restoration of the river in order to characterize physical, chemical and biological processes in place and to support upcoming societal changes. Scales of study vary from landscape to chemical element.
The aim of this program is to get a complete feedback and to bring real recommendations for managers concerning rivers restoration.
Ecologic continuity of aquatic ecosystems
Breaking ecologic continuum, dams are at the root of significant modifications of hydrologic regime, water temperature, biologic and biogeochemical flows. They also cause socioeconomic concerns because many of the hydroelectric dams built in the early 1910s and 1920s have aged, resulting in greater security risks and diminished economic returns. Across the globe, more and more dams are being removed, and projects are underway to restore the ecology of watercourses. It is necessary to gauge the success of these restoration efforts. Consequently, international research dedicated to this topic is on the rise.
To date, The Ushas been the most proactive in dismantling dams. However, few dam removal projects have been the object of scientific monitoring, and most of the dams concerned have been small (<15 m).
In France, three large dams have been removed to date (between 1996 and 1998 in Brittany—on the Léguer and the Loire). However, none of the operations were the object of scientific studies.
Ecologic restoration issues on the Sélune
The Sélune case study is unique in Europe regarding the height of the two dams (16 and 36m) located near the ocean and regarding their impact on the river (20 km is submerged, about 25% of the total length), in a water catchment dominated by agriculture (polyculture-breeding, mostly dairy farming). The scientific program coordinated by INRA and AFB must enable:
1. Analysis of ecologic restoration mechanisms of the river in this transforming territory.
2. To make of this experimental site a scientific standard.
3. To acquire feedback on the becoming of aging dams around the world.
Actions undertaken in the frame of this program are mainly funded by the Water agency in charge of this territory (Agence de l’Eau Seine-Normandie), the French Agency for Biodiversity (Agence Française pour la Biodiversité) and involved research institutes.