Les barrages sont à l’origine de modifications significatives du régime hydrologique, de la température de l’eau et des flux biologiques et biogéochimiques. C’est le cas des barrages de Vezins et de la Roche qui Boit, présents sur le cours principal de la Sélune, et d’autres plus petits obstacles qui fragmentent le bassin versant de la Sélune. Cette couche représente les barrages hydroélectriques de la Sélune, avec les batiments associés, en lien avec la production électrique. La géométrie de ces polygones est issue de plusieurs sources : BD Topo, OpenStreetMap (de 2019), complétée par photointerprétation. Des informations extraites du livre « Quand les rivières reprennent leur cours – Notes sur l’effacement de barrages et de seuils, sur la Sélune et ailleurs » ont été ajoutées pour décrire l'état (en service ou arasé), la nature et les caractérisques physiques de ces barrages.

Microbial communities play a major role in the functioning of ecosystems: they are at the base of the food chain (primary production) and participate in the degradation of organic matter. These communities are also known to respond rapidly to environmental changes. Like macro-invertebrates, they can be used as ecological indicators. Benthic diatoms are the main photosynthetic organisms in this biological community. The relative abundance of the different species is used to calculate an environmental quality index (EQI). Major differences in communities between the upstream and downstream zones were observed when the dams were in place. These differences will change once the dams are removed. As part of the Sélune observatory, pilot stations have been set up along the main course of the Sélune, distributed from upstream to downstream of the hydroelectric dams. Three stations are located in the former reservoirs of the dams, while the other two, known as the reference stations, are outside the area of influence of the former dams (one downstream and the other upstream). At these stations, aquatic biocenoses (including benthic macroinvertebrates, biofilms, macrophytes, etc.) are monitored. Since September 2014, the stations are ideally sampled every month from April to October (7 annual surveys) using artificial substrates (glass slides placed in the water). In addition to the diatom survey (floristic list, IBD calculation), the chlorophyll-a concentration is measured. During each campaign, an INRAe experimental sampling protocol is implemented. This protocol involves the immersion (1 month) of glass slides, in situ measurement of chlorophyll-a concentration via BentoTorch and then collection of the biofilm on these glass slides. The biofilm is conditioned in (1) 99.9% ethanol for determination of IBDs and floristic lists (outsourced service, based on standard NF T90-354) and (2) mineral water for measurement of chlorophyll-a concentration using a spectrometer. Taxon identification is based on version v17 of the TAXREF reference. The dataset is currently under embargo.

The removal of the dams on the Sélune River is the subject of a scientific program launched in 2012, in which environmental parameters are monitored in order to provide real feedback on this restoration operation. In 2019, a data observatory was set up to collect and process these parameters (biotic and abiotic). The data acquired from 2012 and at least until 2027 will be centralized through an information system (IS) called SISelune. SISelune aims to assist scientists associated with the Sélune program and make the data accessible to all. This layer shows the study area, based on hydrographic sub-basins for the continental part and the transitional water body for the Bay of Mont St-Michel.

The hydrographic sections, which make up the waterways, were extracted from the Topage database covering the study area.

In partnership with ANR Reppaval, the Syndicat Mixte du bassin de la Sélune has begun implementing a photographic observatory of the landscapes of the Sélune basin. This is a photographic itinerary consisting of viewpoints spread across the entire territory, where photographs will be taken regularly. The aim is to monitor changes in the landscape, particularly in relation to the Sélune restoration project. The layer shows the location of the sites on the photographic itinerary that are directly affected by the Sélune restoration work: lakes and dams.

Major hydrological basins and their sub-basins. This dataset divides the African continent according to its hydrological characteristics. The dataset consists of the following information:- numerical code and name of the major basin (MAJ_BAS and MAJ_NAME); - area of the major basin in square km (MAJ_AREA); - numerical code and name of the sub-basin (SUB_BAS and SUB_NAME); - area of the sub-basin in square km (SUB_AREA); - numerical code of the sub-basin towards which the sub-basin flows (TO_SUBBAS) (the codes -888 and -999 have been assigned respectively to internal sub-basins and to sub-basins draining into the sea)

Benthic macro-invertebrates (insects, crustaceans, molluscs, worms) form an important link in the food chain. As part of the Sélune observatory, pilot stations have been set up along the main course of the Sélune, distributed from upstream to downstream of the hydroelectric dams. Three stations are located in the former reservoirs of the dams, while the other two, known as the reference stations, are outside the area of influence of the former dams (one downstream and the other upstream). At these stations, the aquatic biocenoses (including benthic macroinvertebrates, biofilms, macrophytes, etc.) are monitored. The parameters monitored are the taxonomic composition of the communities at 5 stations in the main river, located upstream, downstream and in the new lotic habitats. The sampling frequency involves two annual sampling campaigns (spring and autumn). The protocols implemented are the installation of 4 artificial substrates (SUBART) per station and a survey after 1 month of immersion as well as 12 Surber samples per station, in accordance with standard NF T 90-333 (2016), allowing the calculation of the I2M2 in accordance with standard NF T 90-388 (2020) and Mondy et al. 2012, 2012. This layer shows the location of the study sectors used to monitor benthic macroinvertebrates and the campaigns carried out. This monitoring was finalised with the latest field acquisitions in 2025.

The opening of the dams will have a significant impact on trout populations in the Sélune. Restoring the river's ecological continuity will alter population flows by allowing amphihaline sea trout to migrate further upstream and native trout to move downstream and upstream of the dams. The trout population is monitored at a network of stations covering the entire Sélune basin using an abundance index, which is carried out every two years. The field campaigns comply with the Vigitruite® fishing protocol, developed by INRA and intended for use throughout France. This abundance index, relative to the area of favorable habitats in the watercourse, makes it possible to assess the quantity of young trout present in the river, resulting from natural reproduction in previous years. This table provides individual data on trout caught according to the year of study.