Selune Observatory

Selune Observatory

Selune Observatory

The Selune Observatory carries out environmental monitoring to characterise the biological and environmental dynamics of the Selune before, during and after dam removal operations.

Objectives of the Selune observatory

The construction of a dam hinders the circulation of water, sediment and aquatic and riparian organisms, thereby significantly altering ecosystems. Conversely, its removal should restore their natural functioning by re-establishing ecological continuity between the source, the estuary and the ocean.

To monitor the restoration of continuity on the Selune, our scientific teams have set up an environmental data observatory: The Selune observatory. This will enable us to measure the dynamics involved in restoring water, sediment, chemical and biological fluxes.

The Selune observatory reports on the dynamics of various environmental parameters linked to:


Abiotic conditions

Our teams are characterising the hydrological, fine and coarse sediment and chemical fluxes along the Selune river. The aim is to measure and understand how these fluxess and their dynamics are affected by the presence of the dams (2014-2017 period), the emptying works (since 2017), the removal of the dams (2019-2022) and the restoration of continuity (from 2022).



Aquatic, riparian and terrestrial biocenoses

The aim is to characterise the demography and expansion of migratory fish populations, estuarine communities, invasive species such as crayfish and riparian vegetation (vegetation on the banks). This will allow identifying changes in the ecological status of the watercourse, based in particular on bio-indicator species such as communities of benthic macro-invertebrates, photosynthetic biofilms and macrophytes.


To learn more about the observatory's monitoring activities, see the articles at the bottom of the page.

Organisation of the Selune observatory

The Sélune Observatory is the result of a collective effort. Scientists from various research institutes (INRAE, CNRS, MNHN, Ifremer, Institut Agro Rennes) are working together to carry out the monitoring.

The environmental monitoring is managed by :

  • The mixed research unit SAS, for abiotic conditions
  • The experimental unit U3E, for aquatic riparian and terrestrial biocenoses

Where can I get data from the observatory?

Data from the Sélune observatory are made available through SISélune, the scientific program's information system. Find out more about SISélune...

In this rubric

Will the flow and turbidity of the Selune change with the removal of the dams? How will sediment continuity and habitat quality change?
How is sediment transported in the Sélune? How is the morphology of the river changing?
How is the ecological status of the river changing following the removal of the dams?
What kind of vegetation is colonising the river banks and the new riverbanks that were previously submerged under the reservoirs?
What migratory fish will recolonise the upper reaches of the Sélune, which have been inaccessible until now? Where will they go, and how quickly will this recolonisation take place?
What is the potential for migratory fish to colonise the Selune?
How many European eels leave the Selune river after spending several years in the catchment?
How is the signal crayfish colonising the Selune catchment? How will the dispersal of this species be affected by the removal of the dams?
What changes have been observed in the ecological functioning of the little Bay of Mont Saint-Michel following the removal of the dams?
What landscapes of yesterday and tomorrow?

Modification date: 08 September 2023 | Publication date : 31 July 2023 | Redactor : Selune Team