The Réal Collobrier experimental catchment is a reference site for the knowledge of hydrology in a Mediterranean forest environment. The Real Collobrier is a tributary of the Réal Martin and sub-basin of the Gapeau, located on the Mediterranean coast in the commune of Collobrières (Var department), at the western end of the Maures mountain range, 20 km north-east of Toulon (France). It is made up of a set of gauged sub-basins, nested or contiguous, from 1.5 to 70 km². It is underlain by metamorphic rocks (gneiss, schists, phyllades) with mostly clay-sand soils of varying thickness. It has Mediterranean vegetation (chestnut groves, cork and holm oaks, maquis) and vineyards in the lower valleys. The climate is of the humid Mediterranean type with a very marked drought and high intensity rainfall events (average annual rainfall of 750 mm to 1200 mm and record flows of 15 m³/s in the small Rimbaud basin (1.5 km²) and 175 m³/s in the Pont de Fer basin (70 km²) at the basin outlet).
Starting year: hydrometeorological data since 1967
Localisation: commune of Collobrières, at the western end of the Maures mountain range, 20 km north-east of Toulon
Keywords: mediterranean climate, schist, mediterranean forest, flash floods, rainfall
PI: Patrick ARNAUD
Created in 1966 on the initiative of the Ministry of Agriculture, the initial objective of this observatory was to improve knowledge of hydrological phenomena specific to Mediterranean regions. The scientific objectives focus on the study of the Mediterranean climatic environment with several strong components:
- Flash floods;
- The availability of water resources;
- Vegetation-water cycle interactions;
- Spatial and temporal knowledge of hydrometeorological processes.
These interdisciplinary research topics involve hydrology, soil physics, geomorphology, hydrogeology, hydrobiology, biochemistry and remote sensing.
Sites and measured variables
Since 1967, the observatory has been equipped with instrumentation for measuring hydrological and meteorological parameters on different spatial and temporal scales. The collection of meteorological variables includes rainfall (15 rainfall stations over 100 km²), as well as a climatological station for the measurement of temperature, humidity, radiation, wind direction and speed. Water flow measurements at the outlet are carried out by 7 flow monitoring stations (1.5 to 70 km²), since 1967. More recently, water temperatures are measured at the 7 hydrometric stations and 2 multi-parameter probes measure pH, Redox, turbidity and conductivity continuously since 2016. A sampler for chemical analysis of water (anions, cations) has also been installed. Soil moisture probes are installed at 3 sites (6 probes in total). Two sub-basins, Rimbaud (gneiss, maquis) and Vaubarnier (schistose soil and fairly deep soils) show very marked differences in behaviour during flood periods. The Rimbaud basin, where almost 85% of the vegetation was destroyed by a fire in 1990, has become a privileged site for the study of changes in hydrological behaviour caused by the modification of the vegetation.
As a benchmark site for hydroclimatology since 1967, the Real Collobrier catchment gathers more than 50 years of observation data allowing an analysis of climatic trends, showing an increase in the duration and severity of low water periods.
Partners and further information
The site is managed by INRAE.