Assessment groundwater occurrences using VES/TEM techniques at North Galala plateau, NW Gulf of Suez, Egypt

Abstract

Water resources assessment is important for urbanization and industrial projects in remote areas. As the area is far from the Nile and characterized by rarity of rainfall, the main source of freshwater is groundwater. Vertical Electrical Sounding (VES) and Time Domain Electromagnetic (TEM) methods are chosen. To overcome the ambiguity, TEM station no.1 was conducted close to a borehole. The information from the borehole includes lithology and producing aquifer zones. The processing started with the inversion of VES data then use the models obtained as the primary model for TEM inversion. The last models from VES and TEM were further used to construct 3 geoelectrical profiles and 8 contour maps illustrating subsurface water-bearing aquifers electric resistivity. From the results, two aquifers are found divided by a highly conductive clay unit. The shallow one is consisting of coarse sand with silt. It displays moderate to low resistivity, depth ranging from 6 m to 33 m underground surface and a thickness of 15–35m. On the other hand, the deep one shows low resistivity values that may show brackish to fresh water with depths to the upper surface ranges from 58m to 118m and thickness distribution of 26–80m. In general, the groundwater flow is expected to be from southwest to northeast towards Suez Gulf as indicated by the elevation trending of the aquifers. According to the resistivity distribution, the direction of seawater intrusion is the northeast in the directions of Suez Gulf.