Groundwater behavior in a hydrologically-modified watershed by a Managed Aquifer Recharge system (Wadi Khairat, NE of Tunisia)

In addition to their agricultural role, Tunisian hill dams provide important water volumes for Managed Aquifer Recharge (MAR) through water release in wadis such as the cases of Wadi Khairat in Sousse prefecture, Sahel of Tunisia. The aim of this study is to evaluate the Tunisian experience in MAR throughout assessing the efficiency of water release from hill dams for the artificial recharge of the shallow stressed aquifers. Frequent field observations were conducted between 2013 and 2015, and during them, physical and geochemical parameters of stream, dam and well waters were measured. MAR efficiency is firstly assessed based on WTF method. Furthermore, based on the geochemical and isotopic data, an End Member Mixing Analysis (EMMA) model was used to calculate the contribution of released dam water in aquifer recharge. Results show that dam water release is playing an important role in aquifer recharge and its contribution exceeds 70% in some locations. Recharge amount is clearly depending on the released volume, climatic conditions and wadi lithology and morphology. The present MAR method is more efficient in Wadi underlying aquifer. This concept is strongly encouraged to be applied in stressed aquifers where an excess of surface water might exist during rainy periods in order to guarantee the sustainability of these resources.