Electrical Resistivity Tomography (ERT) Applied to the assessment of Karst Carbonate Aquifers structure: Case Study from Zaghouan-Bent Saidan (NE Tunisia)

Abstract

<p>Abstract:</p><p>Karst aquifers belong to the fractured aquifer family. The Zaghouan region located in NE of Tunisia (North Africa) is characterized by a high degree of karstification due to the climate impact and the development of fracture network. Survey using electrical resistivity tomography (ERT) is deployed to provide a cost-effective characterization of the subsurface karst environments. A total of three ERT profiles with a length of 300 meters were evaluated in Zaghouan region.</p><p>The area represents an anticline of Jurassic limestone rocks, which is overlain by a thin clay layer. In this study, an ERT survey was conducted to examine the spatial distribution and shape of underground cavities in the karst area of Jebel Bent Saidan. In this study, geological, hydrogeological and electrical resistivity tomography (ERT) methods were applied to determine the geometry of the karst aquifer in the Zaghouan area (NE Tunisia). The area is characterized by fractured and karstic limestone aquifer of Jurassic. Three resistivity profiles were carried out along the study area (Jebel Bent Saidan). The correct resistivity data was interpreted using ZONDRes 2D software.  The results of the interpreted geo-electrical sections showed that the resistivity of the carbonate aquifer ranges from 350 to over 4000 Ωm. The thickness of the aquifer varies between 15 and 30 meters, while its depth from the surface is between 10 and 40 meters. The ERT not only provided accurate near-surface information, but was also very useful in establishing the geometry of the aquifer. It was also very useful in establishing the 3D geometry and position of several potential karst cavities and conduits. The results show the presence of two large isolated cavities at different depths. The low resistivity of karst cavities in the Jurassic carbonate of Jebel Bent Saidane was explained by the saturation of groundwater. The ERT imaging technique using to identify and characterize the discontinuities, faults and water investigation of the fractured and karstified limestone aquifers in the Bent Saidan Mounts. The conducted research demonstrated that the ERT method was an effective tool for imaging the subsurface in the karst terrain.</p><p><strong>Keywords:</strong> Bent Saidan (NE Tunisia), karst aquifers, electrical resistivity tomography (ERT), cavities.</p><p> </p>