Water in karst hydrosystems unsaturated zone; MRS evidences within an integrated hydrogeophysical approach

International audienceKarst unsaturated zone (UZ) is recognized to play a key role in karst hydrosystems recharge and contaminant attenuation processes. Its characteristics are identified as an important factor for karst groundwater vulnerability assessment and resource management. A large scale hydrogeophysical experiment was undertaken over the last 4 years combining several surface-based geophysical methods and measuring techniques in a unique experimental site within the Fontaine de Vaucluse (FDV) hydrosystem in southern France. The aim was to apprehend the UZ structure and functioning of typical urgonian karstified mediterranean limestone. Geological structure is being well recognized by electrical, electromagnetic and seismic measurements. Magnetic Resonance Sounding (MRS) results clearly identify water presence and evidence seasonal variations within the karst UZ. Due to these results a conceptual hydrogeological model is proposed. On May–June 2014 a drilling campaign is being programmed and a cross-validation of the MRS results is also planned