The Marana Golo wellfield supplies drinking water from the Golo alluvial aquifer to over 23,000 people south of Bastia (Corsica, France). Wells in the catchment area tap the aquifer at shallow depths, 5 km far from the Mediterranean coastline. This productive aquifer is largely sustained by the Golo river. Annual production volumes average 2.6 million m3. In Autumn 2017, under drought conditions, a conductivity peak of up to 900 µS/cm was measured in the eastern part of the wellfield by one of the autonomous and remote controlled geophysical monitoring tools (SMD@pattented by imaGeau presented at SWIM2018). This phenomenon could be a precursor of saltwater intrusion progressing near the wellfield. In this context, the acquisition of multi-disciplinary & multi-scale (both temporal and spatial) data on • geology of the reservoir (geophysical prospecting by ERT; Well logging), • Physical parameters of groundwater (multi-depth electrical conductivity via automation and long-term monitoring SMD, real time water level), • Physical parameter of surface water- the Golo river (topology, real time level, electrical conductivity campaigns from the mouth to the wellfield) have enabled the construction and calibration of a variable-density groundwater model taking into account the interaction between surface water and groundwater. The simulations generated by the hydrogeological model allow us to determine the origin of high chloride content episodes in the wellfield. The results show that salinity peaks in groundwater, and notably the 2017 event, are due to chloride originating from the Golo river through marine inflows and tide propagation; groundwater-river exchange being enhanced by pumping. The simulations also allow the definition of a threshold level for the Golo river (-6 cm NGF at the front of the wellfield) for which saltwater would reach the meander located in the middle of the wellfield if the river mouth is open (climate change simulation to 2070). This would impact groundwater over the wellfield with salinity levels exceeding 4g/l.