Integrated Hydrogeophysical Study for the Delineation of Mio–Plio–Quaternary Aquifers in the Central Part of the Sousse Governorate (Tunisian Sahel)

Abstract

The Sousse governorate (Tunisian Sahel) is an important socio-economic pole with a strong need for water. Intense drought during the last years has harmed the governorate’s activities. Therefore, groundwater exploitation is increasingly becoming necessary for ensuring sustainable development. It takes in-depth knowledge of aquifers to create an appropriate exploitation plan. In this context, the present study aimed for precise delineation of Mio–Plio–Quaternary aquifers in the central part of the Sousse governorate by thoroughly reconstructing their geometry and understanding their functioning. To reach this goal, a rich database, including 142 water boreholes and 123 vertical electrical soundings (VES), was used. Water borehole data containing lithological columns and their corresponding well logs as well as hydrodynamic and hydrochemical measurements were exploited. Second, VES data were interpreted and geoelectrical cross sections are accordingly established. Two aquifer formations showing variable arrangement were differentiated from well log analysis and correlation: AI and AII, which are Quaternary and Mio–Pliocene in age, respectively. Aquifer AI is absent at the Kalaa Kebira anticline, while on either side of this structure, both formations are present with deepening of aquifer AII. The established piezometric map exhibits groundwater flow toward the north and south of the Kalaa Kebira anticline. In the same directions, water salinity values increase gradually from 1 to 5 g/l. The geoelectrical cross sections highlighted that tectonic deformations control the water reservoirs arrangement and the groundwater circulation. Cross-comparison of the deduced information regarding the aquifers geometry, hydrodynamics, and water quality brings new elements to the hydrogeological scheme in the central part of the Sousse governorate. The Mio–Plio–Quaternary deposits encompass two multilayered aquifers, which are the Balaoum–Sidi Bou Ali aquifer to the north and the Oued Laya aquifer to the south. These aquifers are juxtaposed with a groundwater divide at the Kalaa Kebira anticline. The present study will guide groundwater exploitation in the Sousse governorate and thereby support sustainable development in the Tunisian Sahel. More broadly, it constitutes a model of hydrogeophysical application for better groundwater management in other arid regions.