Application of the two dimensional geoelectric imaging technique to explore shallow groundwater in wadi El Gerafi basin, Eastern Central Sinai – Egypt

Abstract

Wadi El Gerafi has an important strategic situation in central Sinai, where it is the only entrance to Egypt from the northeastern borders. Also, El Kuntilla village, which lies at the downstream portion of this wadi, has many Bedouins settlements. These settlements are suffering from the shortage in water supplies besides the drying weather without any floods through the last decade. Accordingly, exploring of the groundwater of Bedouins is considered as a national target, which prevents the migration and helps to establish new settlements in this area. To achieve the main objectives of the present study, 72 km land magnetic profile and 26 2-D resistivity imaging profiles were carried out along the main channel of Wadi El Gerafi and its tributaries. The interpretation of these field works aim to determine depth to the basement rocks, thickness of the sedimentary section, subsurface geological structures, subsurface layering, vertical and horizontal variations in the resistivity, and test the groundwater occurrences in the Quaternary deposits and the shallow fractured limestone layers as well as to locate the best sites to drill new water wells. Based on the results of these works, depth to the basement rocks was found to be increased from the south (upstream portion) to the north (downstream portion) along the main stream of Wadi El Gerafi; it varies from 408.9 to 1,823.3 m below the ground surface. Also, this study revealed that the groundwater can be exploited from the Quaternary deposits and the fractured limestone layers at shallow depths. Three sites were recommended to drill new groundwater wells. Two of them were chosen for drilling, the first one is drilled to test the groundwater occurrence in the Quaternary deposits, and it is located at El Kuntilla village. While the other is drilled to test the groundwater occurrence in the fractured limestone layers and it is located at about 5 km to the south from El Kuntilla village. The data obtained from the drilling of these wells exhibited a good match with the data obtained from the interpreted 2-D resistivity models. The water salinities of these wells are suitable for all purposes, and they are considered as additional important sources for drinking water in this area.