Science et changements planétaires / Sécheresse
MENUPast and present groundwater recharge processes in the Kairouan plain aquifer (Central Tunisia) inferred from geochemical analyses Volume 20, issue 1, janvier-février-mars 2009
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- Key words: dam, hydrogeochemistry, isotopes, natural recharge, Tunisia
- DOI : 10.1684/sec.2009.0160
- Page(s) : 87-95
- Published in: 2009
The phreatic aquifer of the Kairouan plain (semiarid, central Tunisia, 3000 km 2) is made up of thick alluvial sedimentary formations of Plio-Quaternary origin. This aquifer represents a key resource for regional development and irrigated agriculture (e.g., watermelon, cereals). For the past few decades, over-exploitation of groundwater resources and building of dams located in the upstream part of the plain to prevent flash floods have led to dramatic changes in recharge processes and the water balance of the aquifer. Water chemistry and isotopic data ( 18O, 2H, 3H, 14C, 13C) confirm that groundwater recharge previously depended mainly on wadi floods. Chemical data suggests that water-rock interaction is the main process contributing to groundwater salinity. The isotopic approach reveals that a significant part of recent recharge comes from uncontrolled dam leakage (El Haouareb dam) or from surface water stored in dams and released during high stages (Sidi Saad dam).