The Draix-Bléone observatory is located in the Alpes-de-Haute-Provence, near Digne-les-Bains, southeast of France. Eight catchments, from 0.0013 up to 34 km² are instrumented on the left (Draix site) and right (Galabre site) banks of the Bléone river. Both sites are mountainous (800 to 2,300 m) dominated by sedimentary rocks and in particular Jurassic black marls highly vulnerable to weathering (« black soils »).
The climate is mountainous-Mediterranean with an average rainfall of 800 mm/year, cold winters and intense summer storms.
Land use varies along a gradient from non-existent soils to a forest cover reconstituted from the end of the 19th century by the Restoration of Mountain Land (RTM) services. The gullies visible in the present landscape are evidence of the period of agricultural overexploitation that this region underwent before the RTM operations.
Starting year : 1983 then 2007 for Galabre and Bouinenc catchments
Location: Alpes-de-Haute-Provence, near Digne-les-bains, South-East of France
Keywords: Mediterranean mountain climate, marl, erosion, hydrology, geomorphology
The main objective of the Draix-Bléone observatory is to study and improve the understanding of hydrological and erosive processes in mountains. The scientific themes concern:
- Water flows and their pathways in the basins,
- Erosion processes and transport of fine and coarse sediments on the slopes of the surrounding landscape and riverbeds,
- The estimation of carbon stocks and fluxes in soils and rocks, organic and mineral,
- The dynamics of the vegetation and its interactions with geomorphological processes,
- The role of variability (spatial and temporal) of rainfall on hydrological and sedimentary processes.
Sites and measured variables
Instrumentation is distributed over eight basins: Roubine (0.013 km2), Moulin (0.09 km2), Francon (0.73 km2), Laval (0.86 km2), located on black marls and included in the medium-scale watershed of Bouinenc (22km²), then Brusquet (1.07 km², reforested), and finally the medium-scale watershed of Galabre (20 et 34 km²).
Each basin is equipped with a meteorological station, a hydrological station at the outlet, and soil sensors for the acquisition of high frequency data: meteorology, rainfall, hydrology (water temperatures, water height and flows), sediments (turbidity, concentration of suspended matter, volume of sediment deposited in the deposition beaches at each flood), hydrochemistry (electrical conductivity, major ions), as well as soil data (temperatures, soil moisture, piezometry). Spatial data surveys enables monitoring the evolution of vegetation and the topography of the slopes and in the riverbeds.
Partners and further information
The monitoring of the observatory is co-managed since 2008 by the INRAE research teams UR ETNA (Torential Erosion Snow and Avalanches, Grenoble), by UR « EM » (Ecosystèmes Montagnards, Grenoble) and by IGE (Institute of Environmental Geosciences, CNRS/Grenoble University). A scientific consortium “GIS” composed of nearly 20 research units gathers the different teams involved in the observatory and enables multidisciplinary exchanges. Collaborative projects also involve British and Swiss teams. The observatory has been labeled Service National d’Observation (SNO) since 2021.