Hydrogeophysical Studies of Central Kwara State Basement Complex of Nigeria

The quest to meet the required groundwater need of citizens of Nigeria, especially Central Kwara State for both domestic and industrial application in the face of scarce water resources, occasioned by incessant borehole failure/low yield, has prompted researches for viable source of water. In this study, an integrated geophysical approach involving ground magnetic, Very Low Frequency Electromagnetic (VLF-EM) and Vertical Electrical Sounding (VES) has been employed to establish geologic features associated with groundwater occurrence in four (4) local government area of Central Kwara State. Twenty VLF-EM profiles, fifteen magnetic profiles and seventy-three VES were conducted in W-E orientation across the geologic strike within settlements in the area, with traverse length 500 to 3000 m and spread 200 to 650 m (AB). The ABEM Wadi VLF-EM and SAS 4000 terrameter equipments, and total field intensity magnetometer G19T were used to measure conductive/resistive variation and magnetic susceptibility of various lithologic units. The results from VES were used to determine the second order parameters such as total traverse resistance (T), longitudinal conductance (S) and coefficient of anisotropy (λ) while the product of coefficient of anisotropy and total traverse resistance were employed to determine the yield index The yield index ranged between 1to 3000 G.W.I with range of 32 to 350, 350 to 450, 450 to 850, 850 to 1750 and 1750 to 3000 and above representing dry/abortive, extremely low yield, low yield, medium yield and high yield respectively. From the results, it is concluded that the north-eastern and the central region of the area has the highest prospect while part of the north western, north central and the south eastern part has medium prospect and the rest of the area has prospect for low yield except for the south western end. Part of the south western and the middle part of the north eastern part has lean or least prospect for groundwater.