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.

Meteorological observations from weather stations interpolated on a 25x25 km grid, on a daily basis from 1979 to the last calendar year completed, for France. Meteorological observations are freely accessible via OGC SensorThings Standard service : https://frost.geosas.fr/agri4cast/v1.0/ Observed properties : - maximum air temperature (°C), - minimum air temperature (°C), - mean air temperature (°C), - mean daily wind speed at 10m (m/s), - vapour pressure (hPa), - sum of precipitation (mm/day), - potential evapotranspiration from a crop canopy (mm/day), - total global radiation (KJ/m2/day), More informations on Agri4cast Resources Portal : https://agri4cast.jrc.ec.europa.eu/DataPortal/Index.aspx

The re-establishment of the river continuum on the Sélune after the dams have been levelled will enable colonization of the upper reaches of the basin, which were previously inaccessible to eels. Before the dams were levelled, two main tributaries were used by amphihaline fish for reproduction, in addition to the main river: the Beuvron and the Oir. The eel population of the Sélune was monitored in the pre-flushing phase by abundance index campaigns carried out in 2013, 2015, 2019 on a network of stations covering the entire Sélune hydrographic network. Since 2021, this network of stations has evolved to monitor changes in the part of the watershed accessible following the dismantling of the 2 dams. These data enable us to estimate changes in eel abundance along the Sélune and its tributaries, as well as their size structure before and after the removal of the dams. The inventory is carried out in early September, every other year between 2013 and 2019, then every year since, using an electric fishing device and dip nets. Thirty thirty-second fishing stations are set up. A fishing station comprises approximately 100 meters of river. All eels caught are anaesthetized and biometric measurements are taken (weight, length, horizontal and vertical eye diameter, determination of yellow or silver stage). All eels are released directly at the fishing site. Two different protocols were implemented: the Eel Abundance Index (Pottier and Chapon, 2022) at 23 stations and exhaustion fishing at eight other stations (IAA01 to IAA08) on the Oir River and some of its tributaries, according to an internal protocol. This layer provides station abundances by fishing session.

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. 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 specific composition and cover, at 8 stations in the main course located upstream, downstream and in the neolotic zones of the macrophyte communities. The monitoring frequency consists of one annual campaign for stations outside reservoirs (S0, S1 and S5) and two annual campaigns (spring/autumn) for neolotic stations (S2, S3.4, S4.1 and S6). The protocol used is the sampling protocol for macrophytes and bryophytes in accordance with standard NF T90-395 (October 2003), which defines the IBMR. The taxa are sampled for laboratory identification. This layer shows the location of the study sectors used for macrophyte monitoring, as well as the campaigns carried out and the mesology identified during these different campaigns.

Geodetic markers were installed along the main course of the Sélune. Physically marked out in the field, these markers have been located with a high-precision GPS (planimetric and z-precisions are given in the table). Please note that these markers may move slightly with the wetting/drying cycles of mainly clay soils, and their coordinates may be updated if necessary. Geodetic markers can be used as reference points to define a device or a new study area.

The opening of the dams should impact the functioning of Atlantic salmon populations migrating up the Sélune River and its tributaries. 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 before 2021 and every year since then. Field campaigns comply with the fishing protocol developed by INRAE and OFB. The aim of this method is to estimate the abundance of juvenile Atlantic salmon (Salmo salar) at a station (or sector). This protocol targets juveniles of the year (aged 0+) whose abundance reflects the renewal of generations within the population (or recruitment) and survival after the embryonic development phases under gravel and the first months of life in the open environment. Field campaigns are carried out by INRAE and the Manche d'Ille-et-Vilaine Federation for Fishing and the Protection of the Aquatic Environment (FDAPPMA50 and FDAAPPMA35). This dataset provides individual biometric data on Atlantic salmon caught during PAS fishing sessions in the Sélune watershed, by station and by fishing session.

The opening of the dams should impact the functioning of Atlantic salmon populations migrating up the Sélune and its tributaries. Restoring the river's ecological continuity will alter population flows by allowing Atlantic salmon to migrate further upstream and downstream of the dams. The Atlantic salmon population is monitored at a network of stations covering the entire Sélune basin using an abundance index, which was carried out every two years before 2021 and annually since then. Field campaigns comply with the fishing protocol developed by INRAE and OFB. The aim of this method is to estimate the abundance of juvenile Atlantic salmon (Salmo salar) at a station (or sector). This protocol targets juveniles of the year (aged 0+) whose abundance reflects the renewal of generations within the population (or recruitment) and survival after the embryonic development phases under gravel and the first months of life in the open environment. Field campaigns are carried out by INRAE and the Manche d'Ille-et-Vilaine Federation for Fishing and the Protection of the Aquatic Environment (FDAPPMA50 and FDAPPMA35). This dataset provides the locations of these study sectors for IAS fishing sessions in the Sélune watershed by fishing session.

The study of riparian vegetation is based on the observation of natural plant communities spontaneously colonizing newly exposed areas following the erasure of the Vezins and La-Roche-Qui-Boit dams. The vegetation monitoring system includes two complementary approaches: i) a vegetation sampling method based on floristic surveys (composition & structure) carried out within a series of quadrats positioned along a transect ii) a monitoring of the vegetation units (UV) observed within the valley This sheet specifically concerns the monitoring of vegetation units (UV) observed within the valley, only for data from the Sélune Observatory (2021-2026). The monitoring system for Vegetation Units is based on the identification of vegetation distributed along the transect at each station in the main stream. It aims to obtain a representative view of diversity and the organization of plant formations and communities. This monitoring consists of identifying the discontinuities in terms of composition and structure of the various vegetation types that develop within the neo-valley along the transect that descends to the bank, and to report their influence. (distance in metres from the reference point at the edge of the old dam). These data can be used to establish a pro rata of the different plant formations encountered along the transect. Although this value is thus really valid only at the transect of each station, this information can potentially constitute an approximation of the heterogeneity and distribution of vegetation at the valley scale. This layer gives, for each riparian vegetation monitoring station and each campaign from 2021 to 2026, the following information: – Campaign information (id, code, date, campaign), – Station information (code, name, protocol applied, number of quadrats, code for the associated Sélune reference point and, as a result: location on the watershed, distance to sea, distance to source and water course) – Information on the transect by campaign (number and length, X, Y, LON coordinates, LAT of reference points "NGF" and end point "rive") – Information regarding the Vegetation Units (VU) identified by campaign (number, description: code, start position, end position, EUNIS3 characteristics, 4) – Origin of the data ("Observatoire Sélune," "Hors Observatoire Sélune," "Projet Séripage," or "Projet Restaure") – “Point” geometry (default) corresponding to the transect reference point – Line (alternative) geometry of the associated transect for each campaign. The study of riparian vegetation in exposed areas is based on the observation of natural plant communities colonizing newly exposed mudflats, at different time scales (intra- and interannual variations) and at nested spatial scales. The botanical inventory is carried out according to the Braun-Blanquet method. The sampling protocol is stratified in order to maximize the recorded diversity. For each study area, a transect perpendicular to the riverbed is established, where strips parallel to the watercourse are marked on the ground according to the exposure rate. This layer indicates the location of these study areas, the layout of transects and information regarding vegetation units recorded between 2021 and 2026.