Geophysical Exploration for Groundwater in Crystalline Rocks, El Obeid Area, North Kordofan, Sudan

Abstract

The study area lies between latitudes 13° 22’ and 13° 05’ North and longitudes 30° 20’ and 30° 12’ East. The geology of the study area comprises the superficial deposits of Qoz sand, sands of different grain size, sandy clay, clay and silt overlie the Basement complex rocks. The Basement complex rocks consist of gneiss, quartzite, schist, granite and pegmatite. This type of geological formation is recognized as a poor aquifer for occurrence and accumulation of groundwater. Only in certain circumstances water may exist; that is in the presence of geological structures like fractures, joints, cracks faults.... Etc. The water quantity depends on resistivity of rainfall and infiltration in the study area. - In the current study geophysical techniques (electromagnetic and resistivity) were conducted to investigate the groundwater occurrence in the area. Ten electromagnetic profiles of total length 11.5 km, were conducted in the study area. The measurement reflects considerable fracturing, faults and cracks trending in North-South direction parallel to the streams or Wadis channel. ' Seven horizontal electrical resistivity profiles of total length 4.3 Km were carried out in the study area to locate anomaly sites and to verify the measurement done by electromagnetic profiles. These resistivity measurements insure the viability of locating sites by using the electromagnetic methods by giving better results in delineation of Basement rock structures. \ Finally fifteen vertical electrical soundings were applied in the study area in the center of the anomaly that shown by conduction of electromagnetic and electric resistivity profiles. These VES results confirm the result depicted by electromagnetic and electric resistivity profiles and, show depth to fresh Basement rock more than 54 meter in Kurbage locality, 77 — 135 m in El Sunut locality and 69 — 75 m in Jebel Kordofan locality which is a best locality compared to other two localities ( Kurbage and Elsunut ) in term of water quantity, quality and depth to water.