Journal of American Science
2010;6(10)
Estimating the Groundwater Storage from the Electrical Resistivity Measurements in Wadi El-Natrun Area, Western Desert, Egypt
Abdallah Ibrahim Ammar Research Institute for Groundwater, National Water Research Center, El-Kanater El-Khairiya, Cairo, Egypt. Abdallah_ammar_708@hotmail.com Abstract: Forty-three vertical electrical sounding stations (VESes) were measured in Wadi El-Natrun area, northern western desert. The analysis of the given well log data was used to estimate the groundwater storage. These VESes were interpreted to determine the subsurface layers and the true resistivities, lithologies and thicknesses variations of such layers. The result of this geoelectrical analysis is the subdivision of the shallow section into five geoelectric layers throughout the study area, except in some parts, where the surface layer disappeared; and the fifth layer is not reached. These layers varied in their resistivities from very low to high values. However, the groundwater is generally contained in the second layer of the unconfined Nile Delta aquifer (Quaternary period), in the third and fourth layers of the confined and semi-confined Wadi El-Natrun aquifer (Pliocene period), then in the fifth layer of the Moghra aquifer (Lower Miocene period). Also, the effective zones of the second, third and fourth layers were separated from the electrical interpretations. However, the variation in the net and effective thickness of each layer was calculated and represented in maps. The well log data of the resistivity, SP and gamma-ray logs were used for evaluating the rock units encountered in fifteen wells. The results of these data arrive at determining the shale and non-shale contents, water saturation and the effective zones as petrophysical parameters to the second, third and fourth layers. However, the variation in the water saturation percentages, net thickness and effective thickness was represented in maps. Then, the statistical analysis from the true resistivity that derived from the geoelectric analysis, and water saturation that deduced from the well log analysis, was carried out, only to the third layer. At the end, a comparison between the net and effective thickness values from the electric and well log interpretations was made, and then by applying the resulted mathematical equations, the groundwater amounts were calculated to the three layers. The results of these calculations showed that, the third layer as high groundwater content, then the fourth layer, but the second layer contains the least amounts. Therefore, the electrical resistivity measurements can be used for estimating the groundwater amounts in case of availability the geological information and the well log data are not available. [Journal of American Science 2010;6(10):492-502]. (ISSN: 1545-1003). Keywords: Vertical Electrical Sounding Stations (VESes); Geoelectrical; Groundwater Storage; Western Desert 1. Introduction The study area lies in the northeastern corner of the Western Desert, to the west of the Nile Delta. It is bounded by longitudes 30o 03` 19`` and 30o 37` 6.3`` E and latitudes 30o 13` 51`` and 30o 36` 13`` N, or stretched between kilometer 78 to kilometer 136 at the Cairo-Alexandria Desert Road from Cairo city toward the northwestern direction. Wadi El-Natrun depression extends parallel to Cairo-Alexandria Desert Road and it is located about 86km North West of Cairo city (Fig.1). The surface and subsurface geologic information of the study area are available and contained in the works of Said (1962), Shata et al. (1962), El-Fayoumy (1964), El-Shazly et al. (1975 and 1978) and others. I) Geomorphology The study area, having low relief, occupies a portion of the initial Nile Delta basin and it is western fringes. In this area, there are several geomorphic units. These units are the young alluvial plain occupies

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