Geophysical Approach to Delineate Groundwater Potentials in the Northwestern Part of Wadi Dara, Eastern Desert, Egypt

Abstract

he applied geophysical investigations attempt to locate the waterbearing layer(s) that are regarded as the most important elements for the development objectives, which are developed northwest of Wadi Dara, east of the Gulf of Suez. To investigate the condition of groundwater potentials, twenty-five Transients Electromagnetic [TEM] soundings and six twodimensional Electrical Resistivity Imaging [2D-ERI] lines were conducted. The results of the two geophysical methods detected four main geoelectrical layers (Quaternary alluvium deposits [A], layer of dry sand, gravel and shale [B], waterbearing layer/s [C], and basement rocks [D]). Two aquifers were identified during this study. The first aquifer [sublayer C1] corresponds to sandstone, shale, and limestone deposits of the Middle Miocene age. It has low resistivity values ranging from 3 Ωm to 9 Ωm and is restricted to the east direction. This sublayer had a thickness of about 50 m. The second aquifer [sublayer C2] corresponds to Lower Cretaceous sandstone, which has resistivity values ranging from 13 Ωm to 106 Ωm. It was observed that subsurface geological structures have a significant effect on groundwater occurrences throughout the study area. As a result, the generated geoelectrical cross sections show an apparent connectivity between the two aquifers. Because of variability in resistivity values and thicknesses, the groundwater potential varies throughout the studied area. The western portions of the study areas have priority for drilling productive wells into the lower Cretaceous sandstone aquifer, and then the eastern portions offer groundwater from deposits of sandstone, shale, and limestone of the Middle Miocene age.