Electrical Resistivity Sounding for Groundwater Investigation around Enugu Metropolis and the Environs, Southeast Nigeria
- 1 Department of Geology, University of Nigeria, Nsukka, Enugu State, Nigeria
- 2 Department of Geology, University of Nigeria, Nsukka, Enugu State, Nigeria
- 3 NNPC, Lagos, Nigeria
Abstract
This report evaluates the use of electrical method and borehole data to investigate the subsurface to delineate the groundwater potential in Enugu metropolis and the environs, south-eastern Nigeria other than rely only on resistivity method w hich could lead to interpretation error. Integrating these 2 data sets is key in this study. The study area is located in the Anambra Basin and is underlain by Nkporo/Enugu Shale which is overlain by the Mamu Formation. It is bounded by Latitudes 6 ° 2 0'00 " N to 6 ° 30'00 " N and Longitudes 7 ° 25'00 " E to 7 ° 35'00 " E and covers surface area of about 342 m 2 . Thirty - one vertical electrical soundings (VES) were carried out across the area using the Schlumberger electrode array with current electrode separation from 2 to 500 m to identify the depths and resistivity values of the identified geo-electric layers. Through data analysis using WinResist software, the apparent resistivity, thicknesses and depths and the thicknesses of the aquifers were generated. The resistivity and depths were modelled to generate resistivity map and depth map. The resistivity of the aquiferous zone within the study area varie d from 20.55 - 427.8 ohm-m at depths of between 10.7 - 40.05 m. Depth to the water table appears to be shallow at the south western part of the map. The interpreted geo-electric layers show a sequence of lateritic top soil, shale, sand and shale. The frequency distribution of the VES curves generated shows the presence of 3 to 5 layers with HK type as the highest. Also, a 2D model was generated using the correlation of VES to VES data and borehole data to VES data to show the underlying stratigraphy beneath the study area as well as the direction of ground water flow. Result of the VES curve analysis reveal s that the sub-surface is underlain by three lithological layers namely: lateritic top soil, shale, sand and shales with NW direction of groundwater flow from the 2D model. Groundwater prospective zones can be seen along NW, SW and central parts of the study area which have low resistivity values.
- Bouwer, F.L. (1978) Groundwater Hydrology. Mac Graw Hill, New York, 149 p.
- Paranis, D.S. (1986) Principles of Applied Geophysics. 4th Edition, Chapman and Hall, New York, London.
- Telford, W.M., Geldart, L.P. and Sheriff R.E. (1991) Applied Geophysics. Cambridge University Press, USA, 860 p. https://doi.org/10.1017/CBO9781139167932
- Loke, M.H. (2011) Electrical Resistivity Surveys and Data Interpretation. In: Gupta, H., Ed., Encyclopedia of Solid Earth Geophysics, 2011 Edition, Springer, Dordrecht, 276-283. https://doi.org/10.1007/978-90-481-8702-7_46
- Nwajide, C.S. (2005) Anambra Basin of Nigeria: Synoptic Basin Analysis as a Basis for Evaluation of Its Hydrocarbon Prospectivity. In: Okogbue, C.O., Ed., Hydrocarbon Potentials of the Anambra Basin: Geology, Geochemistry and Geohistory Perspectives, Great AP Express Publisher Limited, Nsukka, 83-110.
- Sundararajan, N., Al-Garni, M.A., Ramabrahmam, G. and Yasala, S. (2007) A Real Spectral Analysis of the Deformation of a Homogenous Electric Field over a Thin bed—A Hartley Transform Approach. Geophysics Prospecting, 55, 901-910. https://doi.org/10.1111/j.1365-2478.2007.00650.x
- Massoud, U., Santos, F., Khalil, M., Taha, A. and Abbas, A.M. (2010) Estimation of Aquifer Hydraulic Parameters from Surface Geophysical Measurements: A Case Study of the Upper Cretaceous Aquifer at the Central Sinai, Egypt. Hydrogeology Journal, 18, 699-710. https://doi.org/10.1007/s10040-009-0551-y
- Ezeh, C.C. and Ugwu, G.Z. (2010) Geoelectrical Sounding for Estimating Groundwater Potential in Nsukka L.G.A. Enugu State, Nigeria. International Journal of Physical Sciences, 5, 415-420.
- Farid, A., Jadoon, K.Z., Akhter, G., Asim Iqbal, M. (2013) Hydrostratigraphy and Hydrogeology of the Western Part of Maira Area, Khyber Pakhtunkhwa, Pakistan: A Case Study by Using Electrical Resistivity. Environmental Monitoring and Assessment, 185, 2407-2422. https://doi.org/10.1007/s10661-012-2720-z
- Okonkwo, A. and Ezeh, C.C. (2013) Aquifer Hydraulics and Delineation of Groundwater Quality Zones Using Electrical Resistivity Method at Oduma and Environs in Enugu State, Southeastern Nigeria. International Research Journal of Geology and Mining, 3, 31-39.
- Fadele, S.I., Sule, P.O. and Dewu, B.B.M. (2013) The Use of Vertical Electrical Sounding (VES) for Groundwater Exploration around Nigerian College of Aviation Technology (NCAT), Zaria, Kaduna State, Nigeria. The Pacific Journal of Science and Technology, 13, 549-555.