GEOPHYSICAL EXPLORATION FOR GROUNDWATER POSSIBILITIES IN WADI EL- RAHBA, EASTERN DESERT, EGYPT

The concerned area has been geophysically studied applying the techniques of Vertical Electrical Sounding, Electrical Resistivity Imaging and refraction seismic. The aim of this study is to evaluate the groundwater conditions along the main channel of Wadi El Rahba. The geoelectrical resistivity survey includes 14 vertical electrical soundings and three 2-D resistivity imaging profiles. The subsurface succession downward consists of dry wadi deposits composed of gravel, sand, fine sediments and rock fragments as well as two water-bearing layers, the first layer is composed of wadi deposits and the second is composed of fractured basement rocks and the last formation is highly resistive layer massive basement rocks.
The results of interpretation revealed that downstream of wadi El-Rahba, two water bearing layers exist, an upper layer consisting of wadi deposits and an underlying layer consisting of fractured basement. Upstream of wadi the only water bearing layer is that of fractured basement. The results showed also that the basement reliefs as well as intersecting faults control the groundwater occurrences in the area. It was concluded that the promising parts of the area as to groundwater occurrences are those covered by VES station 1 to 3 and 8 to 12, where groundwater was detected at a depth of 40 –60m.