Sea Water Intrusion: A Case study, Gargub port, Egypt

The study area is located at the western coastal zone of the Mediterranean Sea, Egypt between Wadi Abu Emera and Abu- Hesha. It has a general slope towards the sea which occupies coastal plain, piedmont plain and southern tableland. The general stratigraphic succession consists of Middle Miocene to Quaternary deposits. The groundwater aquifers consist of marine limestone and clay intercalations of Miocene age. The objective of this research is to study the effect of sea water intrusion on groundwater quality, using geo-electrical techniques including the vertical electrical resistivity soundings (VES) and the time domain electromagnetic methods (TEM). Ten Schlumberger VES with a current electrodes distance of as high as 600m and twenty TEM soundings with a single loop of 200*200 meters were carried out during this study. Processing and interpretation of the field data concluded that the geo-electrical succession of the area consists of three layers of which the bottom layer is the water bearing formation. Also, the resistivity values decrease seriously with depth and towards the Mediterranean Sea because of the sea water intrusion. This intrusion occurs along faults and fractures of limestone formation which act as conduits to bring the sea water inland. However, the southern part of the study area is suitable for drilling shallow wells as the resistivity decreases to as low as 3000 ppm. Some precautions should be considered to maintain the safe yield of these wells.