CONTRIBUTION OF ISOTOPIC INDICATORS TO THE ASSESSMENT OF GROUNDWATER MIXTURE BETWEEN CONTINENTAL INTERCALAIRE AND DJEFFARA AQUIFERS (SOUTH-EASTERN TUNISIA)

摘要

The Continental Intercalaire and the Djeffara aquifers are the most important groundwater resources in Southern Tunisia. Previous hydrogeologic and isotopic studies ( 18O, 2H, 3H, 14C) allow to defi ne the main hydrodynamic and hydrochemical characteristics for each aquifer. The Continental Intercalaire aquifer, which has important water reserves contains very old groundwater with low 14C activities and very depleted values of stable isotopes ( 18O, 2H). This is why this aquifer is considered as fossil and contains non renewable resources. Compared to the Continental Intercalaire aquifer, Djeffara aquifer has more scattered stable isotopes values which confi rms that there are different water origins. Near to the El Hamma faults, isotopic contents of Djeffara aquifer are very similar to the isotopic signature of the Continental Intercalaire, indicating mixing fl ows between the two systems and showing that the recharge of Djeffara of Gabes is partially ensured by the discharge of the old water of the Continental Intercalaire through faults.