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Hamed Y.,Gabes University | Hamed Y.,Energy and Environmental Laboratory L3E ENIS | Demdoum A.,University of Mentouri Constantine | Al-Gamal S.A.,University of Engineering and Technology | And 3 more authors.
Quaternary International | Year: 2012

The Continental Intercalaire (C.I.) aquifer is one of the two aquifer members that constitutes the North-Western Sahara Aquifer System (NWSAS) shared by Algeria, Tunisia and Libya extending over an area of more than one million km2. The Continental Intercalaire (C.I.) aquifer is one of the largest confined-to semi confined aquifers in the world, comparable in scale to the Nubian Sandstone Aquifer System (NSAS) shared by Egypt, Sudan, Libya, and Chad, as well as the Great Artesian Basin of Australia, and covers some 600,000 km2 with a potential reservoir thickness of between 120 and 1000 m. The aquifer is mostly unconfined, unlike the eastern part. Its depth increases from north to south and from west to east. It has a shape of a depression that disappears further south where it becomes confined. TDS increases southward along the recognized flow path (0.7 ≤ TDS ≤ 8.7 g/l). Major elements increase with the increase of TDS. The radiocarbon activities of the groundwater are very low, varying between 0.27 and 70.3% modern carbon. The confined part of the reservoir shows depleted stable isotopes data and low 14C content, reflecting the absence of modern water at the discharge zone. The combined evidence shows that the recharge coincides with cooler, humid periods during the Late Pleistocene, which existed across the whole of Saharan Africa. © 2012 Elsevier Ltd and INQUA.

Hamed Y.,Gabes University | Hamed Y.,Energy and Environmental Laboratory L3E ENIS
Journal of African Earth Sciences | Year: 2013

The hydro-geochemical and isotopic data of groundwater of the aquifer of the El Kef area, North-Western Tunisia, were examined to determine the main factors controlling the groundwater chemistry and salinity as well as its hydro-geochemical evolution. This study area has a complex geological structure which is mainly controlled by halokinesis movements and inherited structures. Groundwater occurs in different water bearing formations belonging to Upper Cretaceous, Paleogene (Eocene) and Mio-Plio-Quaternary (MPQ). Different geochemical interpretation methods were used to identify the geochemical characteristics. Groundwater of the MPQ aquifer has the highest salinity values (0.3-7.0gl-1) in the study area due to the impact of agricultural activities. Piper diagram showed that Cl- and SO42- are the dominant anions, where as Na+ is the most dominant cation, where it is sometimes replaced by Ca2+ and/or Mg2+ in the hydro-chemical facies of the groundwater. Dissolution of carbonate and sulfate minerals in the aquifer matrices and recharge areas as well as cation exchange are shown to modify the concentration of ions in groundwater. The groundwaters are depleted in 2H and 18O and displayed an isotopic signature close to that of meteoric water with d-excess values indicating present-day precipitation over the region and reflect the contribution of vapor masses from Mediterranean and Atlantic origins. The isotopic features suggest that most of the groundwater at the study area result from mixing between recent recharge and an older component recharged under climatic conditions cooler than at present. © 2013 Elsevier Ltd.

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