Application des outils chimiques et isotopiques à l'étude de la relation hydrodynamique entre les aquifères profonds de Sfax et de la Djeffara de Gabès Nord (Sud-Est tunisien)

Abstract

The study of the coastal basins of Sfax and Djeffara in northern Gabes, based on the interpretation of hydrochemical (major elements) and isotopic (18O, 2H and 14C) data, has allowed us to understand the hydrodynamic functioning of the Miocene aquifer. Indeed, the geochemical data highlight the presence of two different groundwater types: (Na-Cl) in the Sfax basin and (Cl/SO4-Ca/Na) to (Na-Cl) in the northern Gabes basin. This difference between groundwater types underlines the variability of the origins of groundwater mineralization. The use of isotopic tools showed a relatively old water, with the exception of some local recent recharge inferred by the rainwater infiltration through Zemlet Beida Mountain in the upstream part of the northern Gabes basin. This is also confirmed by the high 14C contents of groundwater in this region. Consequently, it is noted that the transition from south to north along the coast is marked by a big lateral variation of lithology and thickness of the waterbearing formation, underlining the independence of the coastal aquifers of Sfax and Djeffara in the absence of any significant flow exchange between the two basins. © 2012 Copyright 2012 IAHS Press.