Efficiency of Artificial Groundwater Recharge, Quantification Through Conceptual Modelling

The El Khairat wadi was dammed in order to improve the water resources management of El Khairat plain by increasing the surface water mobilization and using the stored reservoir water mainly for artificial groundwater recharge. Reservoir-type conceptual modelling was used to estimate the groundwater recharge over periods pre and post-dam construction. The comparison of the aquifer recharge in natural and artificialized regimes allowed to assess the artificial recharge efficiency. The mean groundwater recharge by the El Khairat wadi calculated over the period prior to the dam construction (1984–1997) is 10.5\(\times\)10⁶ m³/year, corresponding to a mean infiltration rate equaled to 17% of the annual rainfall. The median value is 5.6\(\times\)10⁶m³/year. After the dam construction, the annual recharge averaged over the period (2002–2015) is 2.8×10⁶ m³ corresponding to an infiltration rate varying between 40% and 80% of the released water. In spite the high infiltration rate, this average value is low in comparison with the natural recharge, due to the absence of regular artificial recharge campaigns. In post-dam construction, the artificial recharge rate slightly exceeded the renewable groundwater resources only in 3 years. The initial piezometric state observed in the late 1970s is not restored although the impact of artificial groundwater recharge operations is perceptible in piezometers situated in the close vicinity of the wadi. Regular recharge operations by releases with a flood discharge rate of around 75 l/s are recommended to ensure high yield of the artificial groundwater recharge and accordingly good management of groundwater resources.