Groundwater Recharge Assessment Using WetSpass: Case Study of the Sidi Marzoug-Sbiba Aquifer (Tunisia)

Abstract

The rainfall infiltration process depends on several factors related to climatic and hydrological conditions, land use and hydrogeological characteristics. These factors vary at spatial and temporal scales. The objectives of this work is to assess the groundwater recharge of the Sidi Marzoug-Sbiba aquifer using WetSpass, locate the favorable zones of natural recharge, and help water managers for selecting areas of possible artificial recharge following the global changes that can undergo the region. WetSpass calculates evapotranspiration, runoff and recharge. The Sidi Marzoug-Sbiba aquifer is located in the Center of Tunisia. It is formed by three juxtaposed reservoirs contained respectively in limestone, sandstone and coarse and fine sand. The study is carried out for an average state over the period 1980–1985 including wet and dry seasons. The results showed that the maximum recharge is 165 mm during the wet season, whereas it is reduced to 90 mm for the dry season. The mean annual recharge flux is calculated to 14.8 MCM/year, representing 28% of the average annual rainfall inflow. The most favorable areas to recharge are located upstream, at the level of the limestone outcrops and downstream at the level of the sandy formations. The assessment of the recharge and the identification of the favorable areas to natural recharge represent a fundamental guideline for water managers in order to consider a possible artificial recharge project. Other criteria such as global changes should also be considered before the final decision.