Combined geophysical approach as a tool to identify spatial groundwater aquifer distribution in structurally complex area. Case study of Kasserine aquifer system (central Tunisia)

Abstract

Many countries are facing water resource scarcity. The Kasserine region in central Tunisia, is characterized with semi-arid climate and it is one of the most affected areas by drought in the country. Groundwater constitutes the main resource for drinking and irrigation water in Kasserine region. The groundwater aquifer levels are very structured, in this geologically complex zone, and their geometry needs to be well characterized. The present study aims to identify the geometry and the distribution of Campanian to Quaternary main aquifers in the Kasserine hydrogeological basin.

In this study, we adopted a combined geophysical approach; we analyzed and interpreted gravity and seismic existent data in addition to acquiring conventional vertical electrical soundings. The gravity data analysis and mapping revealed that the study area is structured in numerous geological blocks. It highlighted the existence of two major negative gravity anomalies associated with the Megdoudech basin and the Kasserine graben. The gravity maps illustrated the role of the NW-SE Kasserine major Fault in the block structuring. The seismic reflection sections have emphasized the same structuring of the basins. They have exposed the fault network responsible for the compartmentalization of geological structures and which plays an important role in the hydrodynamics of the aquifer system in the region. The geoelectrical investigation highlighted the existence of three aquifer units: the sandy to sandy-clay levels of the Plio-Quaternary in the Kasserine graben, the sandstones of the middle Miocene with an average resistivity of 75 Ω m profiled at different depths, and the Campanian limestones with high resistivities in the Kasserine plateau.

This combined approach is proven to be very useful to understand groundwater distribution in such geologically complex zones. The results will help the decision makers to ensure the safe management of groundwater resources especially in semi-arid and arid regions.