Integrated Geophysical Techniques for Groundwater Exploration in Karlahi, Northeastern, Nigeria
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Karlahi is underlain by (3) lithological units and are clearly demarcated by topographic forms, and in most cases reflect the geology of the underlying rocks which are basically coarse grained granite, medium grained granite and banded gneiss. The study was aimed at delineating groundwater potential zones in Karlahi, Northeast Nigeria by integrating electromagnetic method (EM), vertical electrical sounding and borehole logging techniques. Ten (10) EM profiles of 200 m lengths were conducted at 20 m coil separation using EM 34 - 3 meter/device, perpendicular to tectonic structures of the area. The result revealed sandy clay and weathered basement with relatively low to high conductivity values. The locations with the highest conductivity values of vertical dipole with 30m penetration were used to conduct 30 Vertical Electrical Soundings (VES) using Schlumberger electrode configuration. The VES results revealed 4 layers, the first layer is sandy clay with thickness ranging from 0.812 to 5.92 m and resistivity values between 21.18 to 303.5 Ωm, the second layer a weathered basement with thicknesses from 12.51 to 27.86 m and resistivity values ranging from 10.15 to 1669.9 Ωm, the third layer a slightly weathered basement with thicknesses of 24.49 to 37.98 m and resistivity values ranging from 14.18 to 7063.4 Ωm. The fourth layer a fresh basement environment has resistivity values ranging from 342 to 9811 Ωm. Potential aquifer units in the area have been delineated into upper highly weathered and lower slightly weathered layers. The thickness of the highly weathered layers range from 9 to 18.41 m with an average of 13.7 m. While that of the slightly weathered range from 13 to 50 m with an average of 31.5 m. The highly weathered and slightly weathered basement aquifer units are unconfined and should be exploited for groundwater development. It is recommended that 35 to 50% of the total thickness of the highly weathered and slightly weathered formations should be screened in borehole projects for optimal borehole water yields and the borehole should be cased to the bottom.
Publication Info:
Author: Yusuf, S.N. , Ishaku, J.M. and Wakili, W.M. 2
Volume: 57
Issue: March
Published By: Journal of Mining and Geology, 2024-03-01