A geophysical survey has been carried out on a watershed (10km²) in north Benin for contributing to a parameterization of hydrological modelling. For delineating rock and soils units we used Electromagnetic (EM) conductivity mapping. For estimating thickness of regolith we used resistivity methods. For characterising aquifers we used Magnetic Resonance Sounding method (MRS) implemented according to main geoelectrical units. We discriminated 5 MRS hydrogeological units: fresh rock with very low water content, low density fractured rock, clayey aquifer, sandy aquifers and fractured rock, high density fractured rock. A clear complementarity between resistivity and MRS methods is shown: MRS has advantage to discriminate low from high density fractured rock and solid rock with identical resistivity signature. Resistivity discriminates sandy aquifers from fractured rock with identical MRS parameters, and provides useful information for MRS inversion. Before integrating MRS parameters into hydrogeological model, identified units should be calibrated in boreholes with pumping tests. For the future, a detailed parameterization of hydrological model could be proposed using MRS results and EM map interpreted with geomorphological data. Keywords : MR Sounding, resistivity methods, hydrology, Benin


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