Mapping of seawater/freshwater interface at the northwestern coast of Egypt by 2-D resistivity imaging and transient electromagnetic soundings

Abstract

The phenomenon of seawater intrusion is a very common and widespread environmental problem present in the majority of Egyptian coastal aquifers and showed its negative effects on all crops up on the coasts. This work was conducted at Ras El Hekma Gulf, which is about 70 km east of Matrouh city and occupies the northwestern Mediterranean coastal zone between latitudes 31 o 06` and 31 o 15` N and longitudes 27 o 40` and 27 o 54`E. Groundwater is the sole source for water supplies in the study area due to its remoteness from surface water channels. Therefore, it is vitally important to maintain this available resource to sustain our domestic and agricultural developments in this promising area. This paper refers to the investigation of seawater intrusion into the coastal aquifers at the study area using electrical resistivity tomography (ERT) and transient electromagnetic (TEM) soundings. In this concern, DC resistivity and TEM data have been measured along lines parallel and perpendicular to the Mediterranean coast line. Integrated interpretation of these data sets has effectively succeeded in identification of the subsurface litho-stratigraphic succession and revealed that the groundwater occurrences have been affected by the seawater invasion at different depth levels with variable extents.