Monitoring the river's health

The disappearance of the reservoirs behind the dams (lakes) led to the creation of a new free-flowing water ecosystem. To understand its evolution, three communities are being studied: photosynthetic biofilms, benthic macroinvertebrates and macrophytes (aquatic plants). These communities are called bioindicators.

Bioindicators are species or ecological communities that are sensitive to environmental conditions and respond rapidly to changes in these conditions. Bioindicators can be used to establish indices of a system's health status, and are traditionally used to measure the health of aquatic ecosystems in accordance with European directives:

• IBD Index (Diatom Biological Index) for photosynthetic biofilms,
• I2M2 Index (Multi-metric Invertebrate Index) for benthic macroinvertebrates,
• IBMR Index (River Macrophytic Biological Index) for macrophytes.

Photosynthetic biofilms are composed mainly of benthic diatoms, organisms at the base of the food chain. Their presence and specific richness is therefore essential for the stability of ecosystems. Benthic macro-invertebrates (insects, crustaceans, molluscs, worms) form an important link in the food chain. Monitoring these communities allows for a rapid visualisation of environmental conditions changes. Macrophytes are a group of aquatic plants. They are at the base of the food chain and can provide a habitat for many other species.

By monitoring these three bioindicators, it is possible to observe the restoration process in the valley in a complementary way.