Résumé
This study presents the first results from the multicriteria approach using geochemical and isotopic tools to understand the origin, geochemical evolution and renewability of deep groundwater in Wadi Guenniche basin, northeastern Tunisia. The study area is a coastal plain that plays an important regional socio-economic role, as the groundwater resources are the most important source for agricultural and drinking supply. Geochemical and isotopic (18O, 2H) data show that the water-rock interaction and cation-exchange process are the major geochemical mechanisms controlling hydrochemical evolution of groundwater. Isotope data (Oxygene-18, deuterium and tritium) point out recent recharge by atmospheric precipitations. Samples from deeper boreholes (300 m) characterized by low 18O and 3H contents suggest older recharge under different climatic conditions.