Ahmed N El Sayed, Mostafa SM Barseem, Hosny M Ezz El Deen and Hesham A Ezz El Din
The agriculture investments on both sides of the Cairo-Alexandria desert road are suffering from the increase in salinity of the groundwater and effect on the sustainable development. The present study was applied to delineate the reasons and solutions for this problem. This study concentrates on the area lies at south-west El Khtatbah city of Cairo-Alexandria desert way as a model. The investigated area is a part of the old alluvial plain which is characterized by a rolling surface sloping to the north and northeast. It contains sedimentary rocks belonging to Miocene, Pliocene, and the Quaternary times which are the most outcropping sediments. The water-bearing formation belongs to the Pleistocene, Lower Miocene (Moghra formation) and Oligocene aquifers. The last two aquifers are separated by the Oligocene basalt sheet. To achieve the aim of the study, a total of 12 Vertical Electrical Soundings (VES) in free wells and one 2D imaging with a roll along technique were carried out in the area of study. Also, the available data of 13 drilled wells were used that comprised lithological description, the thickness of the successive layers, water sample, and depth to water. The quantitative interpretation of the field curves revealed that the geoelectrical succession is formed of four main layers(A, B, C & D).The third geoelectrical layer (C) corresponding to saturated layer and divided into three zones (C1, C2 & C3) according to resistivity values. The first zone (C1) composed of clayey sand with resistivity values ranging from 15 to 26 Ohm.m and their thickness vary from 14 to 38 m. The second zone has relatively high resistivity value due to less clay content with sand. The resistivity value of this zone ranging from 21 and 40 Ohm.m and thickness varies from 20 to 40 m. The last geoelectrical zone does not extend all over the subsurface of the area due to faults with resistivity values ranging from 31 m to 54 Ohm.m. The high resistivity value is due to coarse sand but this zone end by clay content as well data. The thickness of this zones ranging from 16 to 50 m. The result of the roll along two-dimensional resistivity imaging profile refers to the heterogeneous character of the upper surface due to different degrees of clay contents that increase north western side of the investigated area.The three detected zones reflect three geoelectrical layers with different thickness due to the effect of two faults (F1 & F2) which throw northern trend detected that effect on the subsurface succession. The results of the analyzed samples were interpreted based on major ions and environmental stable isotopes determinations. Chemical analyses data revealed that most of the collected ground water samples from the Miocene aquifer are of fresh water type. Stable isotopic data (δ18O and δD); showed that there is no contribution from rains to the groundwater. While mixing with the adjacent Pleistocene as well as the underlying Oligocene groundwater is confirmed.
