Outline of the Ground Water Occurrences Beneath the Area Around Ain Zubida by Integration of Magnetic, Electrical Resistivity Sounding, and Seismic Refraction Methods

Ain Zubida lies in Wadi Numan east of Arafat, Makkah Al- Mukarramah, K.S.A. The study area is located between latitudes 21?17’-21?24’N and longitudes 40?00’-40?10’E. Wadi Numan discharges its water to the Red Sea. The area under investigation forms a part of the Arabian Shield of the Western Saudi Arabia. Accordingly, igneous and metamorphic rocks cover the study area. In the upstream of Wadi Numan, the escarpment is a conspicuous structural feature; besides, major and minor faults are dominant in Wadi Numan and adjacent areas. The aim of this study is to define the distribution of ground water around Ain Zubida, and to select suitable locations for drilling exploratory wells. Therefore, the integration among ground magnetic, resistivity and seismic refraction methods is used to obtain the most useful results. The ground magnetic survey conducted along eight profiles across Wadi Numan indicates that the depth of basement rocks in the area under investigation ranges between 25 and 121 m. The magnetic method was also used to define the main structural zones and the relatively thick sedimentary cover which affect the ground water distribution. The vertical electrical sounding survey was conducted at 62 sites. This survey led to classifying the alluvium covering the basement rocks, according to its resistivity values, into two layers. The upper layer has relatively high resistivity values and the lower has relatively low values. This latter is expected to be water-saturated. 22 T.A. Mokhtar, H.I. Hassanein and M.M. Alsaeed The seismic refraction method was used at three selected sites to emphasize the structures, layering and water saturation at those sites. The present study revealed the presence of a graben structure in Wadi Numan. This structure acts as a channel stream of water accumulation. Accordingly, this study suggests a number of suitable locations for exploratory drilling.