Use of Environmental Isotopes and Hydrochemistry to Characterize Coastal Aquifers in Semi-arid Region. Case Study of Wadi Guenniche Deep Aquifer (NE Tunisia)

Abstract

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 (18 O,2 H) data show that the water-rock interaction and cation-exchange process are the major geochem-ical 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 low18 O and3 H contents suggest older recharge under different climatic conditions.