Interaction between groundwater and surface water through El Haouareb dam (Kairouan plain, Central Tunisia)

The alluvial aquifer of the Kairouan Plain is the most important aquifer in the semi-arid central Tunisia to provide the main water supply for agricultural and human needs. In f 989, the construction of the El Haouareb dam over a karstic sill completely changed the aquifer recharge process. Prior to the dam construction, recharge came from the infiltration of the Merguellil wadi floods in the plain and from the Ain el Beidha groundwater flow close to the dam site. Presently, recharge still comes from the Ain el Beidha aquifer but also from the dam reservoir through karstic fissures. A detailed isotopic survey (18O, 2H, 3H, 13C, 14C) completed the hydrodynamic analysis. The new recharge pattern is identified and the progress of water infiltrated after 1989 is visible. Ratios of Ain el Beidha and darn waters in the karst or in the plain aquifer vary with time. A first water budget is proposed for the period 1998-2000. (author)