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The impact of geologic setting on the groundwater occurrence in the Eocene limestone of El Minia-East Nile-Egypt, using geoelectrical technique

Ahmed N. El Sayed

The investigated area is a part of the Nile Valley and the surrounding Eocene limestone plateau of central Egypt. It is defined by Latitudes 28º 15′ - 28º 33’ N and Longitudes 30º 45- 31º 00′ E, and has a surface area of about 790 Km2(Figure 1). The geoelectrical resistivity measurements within the present study have been carried out, using the Schlumberger array, to identify the resistivities and thicknesses of the different subsurface layers and to determine their groundwater occurrences. For that reason, 29 Schlumberger Vertical Electrical Soundings were conducted with a maximum half current electrode spacing of 700 m. Results from the quantitative interpretation of the sounding data indicate that the land area is generally underlain by four main geoelectrical units. The main characteristics of these geoelectrical units, as well as the main geologicalfeatures of the constructed geoelectrical cross sections have been interpreted for determining the groundwater occurrences. Based on the results obtained, three water-bearing layers were detected in the investigated area. The Quaternary deposits, which represented by Pleistocene Neonile sediments of sands and gravels with clay and shale lenses (A3) act as the first aquifer. The second one (C4) corresponds to water-bearing limestone of Samalut Formation, which leads to the second aquifer, that represents a wide distribution in the investigated area. The third one (D) corresponds to water-bearing limestone of El-Minia Formation, which leads to the third aquifer and represents a wide distribution in the investigated area. In order to make the geophysical results more useful for the decision maker, two priority maps for groundwater exploitation in the investigated area have been presented for each of El-Minia and Samalut aquifers. According to the priority maps, it can be concluded that, the priority of groundwater occurrences and its exploitations in the study area are generally increasing toward the southern parts, especially at Wadi El Saririia area, where El-Minia aquifer occupies the first category and at Wadi El Sheikh Hasan, where the two main aquifers of Samalut and El-Minia faces are well represented.