Natural and artificial recharge investigation in the Zeroud Basin, Central Tunisia: impact of Sidi Saad Dam storage

Hydrochemical and isotopic data of waters from the Z,roud aquifer have been used to potentially provide a means for locating occurrences and to trace movements of a variety of natural and anthropogenic recharge waters in the Z,roud Basin, Central Tunisia. Geochemical data have been measured during the dam water release, from May to September 2005, with a sampling time step of 15 days. An implication of dam water has been demonstrated that is noticeable up along the main flow path to a distance of 10 km far from the injection site. Environmental isotopes H-2, O-18 and H-3 of water molecule were studied to investigate the effect of dam water on the hydrological system, and an isotope balance was established to compute the contribution of water storage component in groundwater. Based on isotopic mass balance, we assess that an average of 13% of total groundwater in the upper aquifer came from dam water storage. Three distinctive recharge waters in the aquifer can be determined. Water from local rainfall (pre-dam Z,roud River) that infiltrated into the boundaries of the Draa Affane Mountain was easily distinguished from the water influenced by anthropogenic recharge located in the Z,roud right rivulet. Distinguishable isotopic signatures of native wadi Z,roud recharge due to recent lineal recharge through the riverbed were also identified.