Delineation of the fresh/salt water zones at a coastal Mediterranean area, West of Alexandria using electrical resistivity investigation

The present investigation aims to map the shallow Pleistocene aquifer and to demonstrate the impact of the human activities as well as the salt water intrusion phenomena on this aquifer Using the Schlumberger symmetrical co-linear configuration. Thirty five vertical electrical soundings were measured at the Agami area located to the west of Alexandria City, in the northern Mediterranean coastal area. The maximum current electrode distance was 200m giving maximum depth of penetration of about 60m. The investigation revealed that the resistivity of the fresh water-bearing layer is greater in summer than in the winter season. The depth to the fresh water-bearing layer is less in summer than in the winter season. This indicates that the infiltration of the sewagewater from the septic tanks plays a considerable role in such situation. The resistivity of the mixed water-bearing layer is greater in winter than in summer, due to the subsurface flow of the rainwater from the southern direction directly into this layer. Thus the depth of this layer is greater in summer than in winter season. Resistivity of the salt water-bearing layer is less in winter than in summer, due to the high salt-water intrusion rate in winter from the dynamics of the sea activity. Rising of the groundwater in the fresh water-bearing layer results from the hubhazard accumulation of waste disposal. This phenomenon will cause damage in the soil and then serious environmental problem in the shallow subsurface, which in turn will lead to damage the building foundations in this area.