Identifying sources of groundwater recharge in the Merguellil basin (Tunisia) using isotopic methods : implication of dam reservoir water accounting

• Published in: Environmental geology (Berlin) 2005-11, Vol.49 (1), p.114-123
• Main Authors: DASSI, Lassaad, ZOUARI, Kamel, FAYE, Serigne
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Hydrogeology; Hydrology. Hydrogeology; Isotope geochemistry; Isotope geochemistry. Geochronology; Pollution, environment geology
• ISSN: 0943-0105; 1432-0495
• DOI: 10.1007/s00254-005-0069-0

Thirty-two groundwater samples collected from the Merguellil Wadi basin (central Tunisia) complemented by the Haouareb dam reservoir water samples have been isotopically analysed in order to investigate the implication of the reservoir water to recharging the aquifer, and also to infer the sources, relative ages and mixing processes in the aquifer system. Plots of the stable isotopes data against the local meteoric lines of Tunis-Carthage and Sfax indicate a strong implication of the dam water noticeable up to a distance of 6-7 km. A contribution as much as 80% of the pumped water has been evidenced using isotopic mass balance. In addition, poorly distinguished water clusters in the stable isotope plots, but clearly identified in the diagrams delta super(18)O versus super(3)H and super(3)H versus super(14)C, indicate various water types related to sources and timing of recharge. The isotopic signatures of the dam accounting water, the 'old' and 'native' recharged waters, have been evidenced in relation to their geographical distribution and also to their radiogenic isotopes ( super(3)H and super(14)C) contents. In the south-western part of the aquifer, mixing process occurs between the dam reservoir water and both the 'old' and 'native' water components.