Draix-Bléone observatory

Draix-Bléone observatory

Scientific context

The Draix-Bléone observatory is located in the Alpes-de-Haute-Provence, near Digne-les-Bains, South East of France. Eight catchments with a surface of 0,0013 up to 34 km² are instrumented on the left (Draix site) and right banks of the Bléone river (Galabre site). Both are in a mountainous context (800 to 2300 m) dominated by sedimentary rocks and in particular Jurassic black marls highly vulnerable to erosion (« black soils »). The climate is of the mountainous-Mediterranean type 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 recreated from the end of the 19th century by the services of Restauration of Mountain Land after this region had suffered of an agricultural over-exploitation. The visible gullies in the current landscape are evidence of this period of soil destruction.


Starting year : 1983 then 2007 for Galabre and Bouinenc catchments

Localisation: Alpes-de-Haute-Provence, near Digne-les-bains, South-East of France

Keywords: Mediterranean mountain climate, marl, erosion, hydrology, geomorphology

Database: https://bdoh.irstea.fr/DRAIX/

Web site : https://www.osug.fr/missions/observation/ocean-atmosphere-surfaces-continentales/draix-bleone/

PIs : Caroline Le Boutellier et Cédric Legoût

Scientific questions

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 developed concern:

  • Water flows and their pathways in the basins;
  • Erosion processes and transport of fine and coarse sediments on the slopes and riverbeds;
  • The estimation of carbon stocks and fluxes in soils and rocks, in organic or mineral form;
  • The dynamic of the vegetation and its interactions with geomorphologic processes;
  • Finally, the role played by the spatial and temporal variability 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 (22km²), Brusquet (1,07 km², reforested), as well as 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 allowing the acquisition of high frequency meteorological , rainfall, hydrological (water temperatures, water height and liquid flows), sedimentary (turbidity, concentration of suspended matter, volume of sediment deposited in the deposition beaches at each flood), hydrochemical (electric conductivity), as well as soil data (temperatures and soil moisture, piezometry). Spatial data monitoring allowing to follow the evolution of vegetation and the topography on 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, UR « EM » – Ecosystèmes Montagnards, Grenoble, and by « IGE » – Institute of Environmental Geosciences (CNRS/Grenoble University), Grenoble. A scientific consortium “GIS” composed of nearly 20 research units gathers the different teams involved in the observatory and enables pluridisciplinary exchanges. Collaborative projects also involve British and Swiss teams. The observatory has been labeled Service national d’observation (SNO) since 2021.