Recharge and paleorecharge of the deep groundwater aquifer system in the Zeroud Basin (Kairouan plain, Central Tunisia)

The multilayered aquifer of Zeroud basin is characterized by the hydrodynamic complexity due to natural (geology) and anthropogenic (management) features. Stable and radioactive isotope data have been used to investigate the origin of the groundwater and its recharge area and to understand the deep groundwater system within the southern Kairouan sedimentary basin. Most of the stable isotopic data indicate that most deep groundwater samples derived either from meteoric water or from the Zeroud River, and were not affected by any significant degree of evaporation during recharge. Current tritium concentration in the groundwater is very low. However, it proved useful in the qualitative identification of modern recharge and mixing of recent and old groundwater. Radiocarbon-deduced ages range from more than 30,000 years to modern. A modern recharge characterizes the deep aquifer upstream of the basin. The groundwater with ages range from more than 30,000 years and depleted of heavy isotopes are found in the deeper aquifer (aquifer B), downstream of the basin, and could be inherited from paleorecharge. (C) 2011 Elsevier Ltd and INQUA. All rights reserved.