Résumé
The geochemistry and isotopic composition (18O, 2H) of groundwater from the alluvial phreatic aquifer in the Wady Guenniche basin (NE of Tunisia), were investigated in order to reveal the origin of the water salinity. The major geochemical processes in the aquifer are evaporite mineral dissolution and mineral exchange with clays. The salinization of groundwater would be a limiting factor in their use for irrigation. The stable isotopic composition of water indicates a groundwater recharge in current climate condition and the point closest to the sea indicates the possible beginning of a seawater intrusion as a result of the intensive exploitation of resources. The tritium data confirm a recent recharge younger than 1950.