Delineation of Groundwater Aquifers using an Electrical Resistivity Survey in the Dordab Region, Red Sea State, Eastern Sudan
Adam, Ammar; Kaka, SanLinn
We have carried out a resistivity survey in the Dordab region of Red Sea State in eastern Sudan. The survey aims at delineating and characterizing groundwater aquifers and efficiently determines the best sites for water well locations. The region is characterized by a complex subsurface geology and hence complex groundwater aquifers in term of distribution and quality of the existing aquifers. Delineating existing aquifers is, in fact, vital to solving the water supply, as the region's arid desert climate with an average annual precipitation of 150 mm contributes very little to the state-wide water supply. A total of thirteen vertical electrical soundings and three horizontal profiles were acquired using both Schlumberger and Wenner configurations at five different locations. The locations of the survey were selected to represent the diversity of groundwater aquifers, and hydrological settings in the Dordab region. All relevant data including surface geology to understand the different rock types, structural (i.e., fracture orientation, thickness) and hydrological parameters (i.e., static water table from existing water wells) were also acquired and integrated for delineating and characterizing aquifers. The results show that apparent resistivity values change significantly in the study area, with a systematic increase in the apparent resistivity values (30.9 to 3667 ohm.m) towards the east as well as several smaller high-resistivity regions on the north-western periphery. Low resistivity values define the fractured basement aquifer which has a north-south trending fracture system in the region. In generally, alluvial aquifers in the study area are characterized by lateral discontinuity and quality changes due to facies changes. We identified three types of aquifers in the study area, namely an alluvial sandy aquifer, an alluvial shaly aquifer, and a fractured basement aquifer with varying depth from 10 to 20 meters. This correlates well with the static water table level from existing water wells in the study area. We determined a number of sites for water well locations which were subsequently verified by drilling successful wells. Integrating geological, structural, and hydrological and geophysical data has proven to be a cost-effective way to delineate the aquifers. Thus we recommend similar integrated studies in other regions to provide a short-term solution to address the water shortage across eastern Sudan.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013