Hydrogeophysical Survey of Ungwan Kwara and Its Environs, Kokona LGA of Nasarawa State. North Central Nigeria (Part of Jema'a Sheet 188SE)

The study area Ungwan Kwara and its Environs lies within the Basement Corrjplex of the North-central Nigeria, the study area is situated between longitudes 008° 06'13.30 E to 008°09 0.00‘E and latitudes 09°02' 46.70‘N to 09°05' 32.50'N. It is located in areas of high relief, where runoff is high and infiltration rate is low, the occurrence of groundwater in this terrain is localized and confined to the weathered and fractured zones. Hence a detailed pre-drilling geophysical investigation becomes inevitable. Vertical Electrical Sounding Technique was used in locating weathered and fractured zones as source of groundwater development in the study area. A total of eight vertical electrical sounding locations were probed using Abem Terrameter SAS 3000C with a maximum cable spread of AB/2 = 70m and MN/2 = 5m. The data obtained from the field were interpreted using 1X1D software for qualitative analysis. The layer resistivities, thicknesses, depth to basement were gotten and the groundwater potential was deduced, it revealed four to five geoelectric layers, consisting of top soil (laterite, sand and clay), sandy clay, highly weathered basement, partially weathered/fractured basement and fresh basement rock. The type of curve that defines the study area is the A, H and KH type, with depth to groundwater from 30m to 60m. Pieziometric map, Depth to basement map, Iso-resistivity map, Basement resistivity map and Overburden resistivity map were produced from the modeled data using Surfer 7 software to deduced qualitative result.