Vertical Electrical Sounding (VES) Resistivity Survey Technique to Explore Groundwater

A geoelectrical survey using the electrical resistivity method was carried out to investigate the sub-surface layering and evaluation of the aquifer characteristics. Applying the Schlumberger array, a total of 596 vertical electrical soundings were conducted along 26 profiles. Quantitative and qualitative Interpretations of data were carried out. Overall, isoapparent resistivity maps, the geoelectrical pseudosections analysis and the established geoelectric sections reveal the presence of the following geoelectric layers: (a) A superficial layer characterized by electric resistivity values ranging from 3 to 800 Ωm with a thickness of less than 15 m. (b) A second layer (dry alluvium layer) is thicker than the surface layer with electric resistivity values less than 100 Ωm. (c) A third layer that corresponds to the aquifer is characterized by electric resistivity values of less than 10 Ωm and depth values of less than 30 m in most locations. The maximum depth of this layer is 60 m that lies in northwest and southeast of area. (d) A fourth layer (bedrock layer), characterized by two electric resistivity values ranges. In most parts of the area, it is more than 60 Ωm, corresponds probably to Slate. In other area, it is less than 60 ohm-m, corresponds probably to Shale. From the quantitative interpretation of VES curves, the boundary of aquifer was determined. Finally, zones with high yield potential in the aquifer were determined. Southeastern and northwestern parts of the aquifer were the best parts for choosing the drilling sites and future development.

Direct current resistivity method is a common tool for surveying water in arid areas. It is well known that this method can be successfully employed for ground water investigations, where a good electrical resistivity contrast exists between the saturated and unsaturated layers. The vertical electrical sounding with Schlumberger array as a low-cost technique and veritable tool in groundwater exploration is more suitable for hydrogeological survey of sedimentary basin. This method is regularly used to solve a wide variety of groundwater problems. Some recent studies include: determination of zones with high yield potential in an aquifer, determination of the boundary between saline and fresh water zones , delineation groundwater contamination, exploration of geothermal reservoirs, groundwater exploration in hard rock, estimation of aquifer specific yield and estimation of hydraulic conductivity and transmissivty of aquifer