Conceptual and Numerical Hydrogeological Modeling of the Shallow Aquifer of Sidi Bouzid: Discussion of the Different Hypothesis

Abstract

The Sidi Bouzid region is one of the main centers of agricultural production in Tunisia, based on groundwater. Therefore, a numerical regional hydrogeological model of the shallow aquifer of Sidi Bouzid was developed to estimate the regional impact of current and future groundwater use. A numerical flow model using a finite difference method and the Processing Modflow code version 5.3 was built for the steady state in the year 1989 and the transient conditions for the period 1989–2015. The developed numerical model was used to estimate the regional impact of current and future groundwater use. The addressed aspects, based on many hypotheses, consisted of natural recharge estimation, quantification of water budget, as well as the assessment of the impacts of overexploitation on the decrease of groundwater levels. A sensitivity analysis was also conducted in order to identify the most sensitive parameters in determining the aquifer behavior. The model parameters calibration was performed under steady-state flow conditions, and the simulations of groundwater flow were then performed under the stress conditions for the period 1989–2015. The simulations’ results showed a high decline of the piezometric levels from 1989 to 2015 that can be related to the weak and irregularity of precipitation in the study region as well as the groundwater overexploitation. This work has shown that the study area is now in a situation of water stress. It suffers from overexploitation conditions throughout the whole study area. Consequently, the Sidi Bouzid aquifer requires urgent action through good management, which consists of implementing a priority control plan for the pumping system. In the meantime, measures must be taken to reach an integrated management plan for the Sidi Bouzid aquifer.