Science et changements planétaires / Sécheresse


Contribution of hydrochemistry to the characterization and assessment of the water resources of a multilayered aquiferous system in an arid region (Maknassy basin, central Tunisia) Volume 20, issue 2, avril-mai-juin 2009


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Laboratoire des ressources minérales et environnement Département de géologie Faculté des sciences de Tunis 2092 Tunis El-Manar Tunisie

Assessment of the water resources of an aquiferous system requires the knowledge of geometric and hydrodynamic features. Hydrochemistry, a method of prospecting in hydrogeology, makes aquiferous characterization possible. The Maknassy basin aquiferous system survey, founded on hydrochemistry, proves that phreatic aquifer water is sulphated. Deep aquifer waters are a mixture of sulphate, chloride, Na and Mg. An identical hydrochemical signature suggests intercommunication between the aquiferous levels of the upper cretaceous reservoir and the phreatic aquifer. A variety of mineralization processes are known. The effect of the gypseous dissolution crust is substantial for the phreatic aquifer water. Major ion anomalies for the waters of different aquiferous levels is observed from upstream to downstream. This mineralization variability depends on the aquiferous reservoirs’ lithological characteristics, exchange reactions and the time during which the water remains in place.