Importance of a high resolution lithological and geometrical knowledge for Mediterranean coast sedimentary aquifers management. Application to the Roussillon basin, South of France

International audienceA good understanding of coastal aquifers is particularly important for their management and preservation,as well as for specific implementations (artificial recharge). A detailed knowledge of the lithology andgeometry of the aquitards and aquicludes is as important as that of the aquifers, particularly for seawaterencroachment dynamics. A new methodology, based on reservoir geology, is used to contribute to highresolutionlithological and geometrical knowledge of coastal sedimentary aquifers. The proposedmethodology is being applied on the Roussillon Basin, located along the southernmost part of the FrenchMediterranean coast, near the Spanish border. This basin covers an area of 700 km2 and comprises twoPliocene aquifers whose characteristics are linked to the Messinian event, and is overlain by the Quaternaryaquifer whose geometry is linked to eustatic variations. All these aquifers consist of alluvial and coastaldeposits. A detailed lithology and geometry model of this basin has been made mainly on the basis ofreservoir geology methods: (i) on-shore, through genetic stratigraphy and (ii) off-shore, through seismicstratigraphy. A detailed mapping of the elevation of the top and base of the aquifers andaquitards/aquicludes is thus available and will be used in a hydrogeological finite difference model. Thismodel will be used for various applications such as aquifer management, location of the outflow areas ofthe aquifers and sensitivity analysis on geometry (on-shore-off-shore)