The assessment of aquifer potentials and aquifer vulnerability of southern Paiko, north central Nigeria, using geoelectric method
Vertical electrical sounding (VES) was carried out in southern Paiko, north central Nigeria, using Abem Terrameter model SAS 4000. The study area which is about 100km square, falls within the basement complex region of Nigeria with an elevation of 304m above sea level. The study was carried out with a view of determining the subsurface layer parameters (resistivities, depths and thicknesses) that were employed in delineating groundwater potential and sites for structural development of the area. A total of six transverses with ten VES stations along each traverse, having separation of 50m apart, were investigated. It has a maximum current electrode separation (AB/2) of 100m. Three to four distinct geoelectric layers were observed namely; Top layer, weathered layer, fractured layer, and fresh basement layer. Top layer has resistivity, depth and thickness range of 194-4582Ωm, 0.5-47.9m and 0.5-47.9m respectively. Second layer has a range of: resistivity, 11-8475.2Ωm; depth, 1.33-59.6m and thickness, 0.13-55.7m. Third layer has a range of: resistivity, 42.0-9730.9Ωm; the depth and thickness are not defined in some part of the area, while the fourth layer has a resistivity range of 50.2-9145.7Ωm, its depth and thickness are not defined. Eighteen VES stations were delineated as groundwater potentials of the area, having third and fourth layer resistivities ranging from 98Ωm to 309Ωm. Depths range found were from 12.50m to 25.70m and thickness varying between 6.94m and 23.98m. The southeastern and northwestern part of the study area having good aquifer at depths ranging from 21.00m to 26.70m, thickness varying between 18.75m and 55.7m are good sites for location of viable boreholes for potable water. Also the southeast and northwestern parts of the area were delineated for structural development having depths to bedrock varying between 0.63m and 3.99m. Most part of the study area have weak protective capacity, hence are prone to contamination.
KEYWORDS: Vertical electrical sounding, groundwater potentials, Southern Paiko, protective capacity, structural development sites, depths to bedrock