Résumé
Karstic hydrosystems are highly nonlinear and heterogeneous but they represent one of the main water resources in the Mediterranean area. Neither local measurements in boreholes nor analysis at the spring can take into account the variability of the water storage. Since 10 years, ground-based gravity measurements (absolute FG5 and relative CG5) allow the monitoring of the water storage in heterogeneous hydrosystems at intermediate scale between boreholes (local scale) and spring (global scale). Since three years, a geophysical observatory has been setup in the Mediterranean area (on the Durzon karstic basin in the south of France). Water level in boreholes and rainfall from rain gauges are classical hydrological observations. They are completed by evapotranspiration measurements from a flux tower and continuous gravity measurements from the GWR iGrav#002 superconducting gravimeter. The main objective of this study is to model the whole data sets with explicit numerical models. Hydrus-1D software allows explicit modeling of water storage and 1D-flow in variably saturated media. With a stochastic sampling, we find the underground parameters (porosity, permeability) that reproduce the most the different observations (gravity, water level, evapotranspiration and rainfall). From the results of the modeling, we discuss the size of the area observed by each type of measurements. Furthermore, water storage and transfer variability may be inferred from the synergy of local (boreholes) and more integrative (gravity) measurements. This study shows the potential of gravity measurements at aquifer scale.