Hydrogeophysical investigation and estimation of groundwater potentials of the Lower Palaeozoic to Precambrian crystalli
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ORIGINAL PAPER
Hydrogeophysical investigation and estimation of groundwater potentials of the Lower Palaeozoic to Precambrian crystalline basement rocks in Keffi area, north-central Nigeria, using resistivity methods G. K. Anudu & B. I. Essien & S. E. Obrike
Received: 30 June 2012 / Accepted: 21 November 2012 # Saudi Society for Geosciences 2012
Abstract The use of resistivity sounding and two-dimensional (2-D) resistivity imaging was investigated with the aim of delineating and estimating the groundwater potential in Keffi area. Rock types identified are mainly gneisses and granites. Twenty-five resistivity soundings employing the Schlumberger electrode array were conducted across the area. Resistivity sounding data obtained were interpreted using partial curve matching approach and 1-D inversion algorithm, RESIST version 1.0. The 2-D resistivity imaging was also carried out along two traverses using dipole–dipole array, and the data obtained were subjected to finite element method modeling using DIPRO inversion algorithm to produce a two-dimensional subsurface geological model. Interpretation of results showed three to four geoelectrical layers. Layer thickness values were generally less than 2 m for collapsed zone, and ranged from 5 to 30 m for weathered bedrock (saprolite). Two major aquifer units, namely weathered bedrock (saprolite) aquifer and fractured bedrock (saprock) aquifer, have been delineated with the latter usually occurring beneath the former in most areas. G. K. Anudu : B. I. Essien : S. E. Obrike Department of Geology and Mining, Nasarawa State University, PMB 1022, Keffi, Nasarawa State, Nigeria G. K. Anudu (*) Department of Geology and Petroleum Geology, Kings College, University of Aberdeen, Meston Building AB24 3UE, Aberdeen, Scotland, UK e-mail: [email protected] G. K. Anudu e-mail: [email protected] S. E. Obrike School of Civil Engineering and Geosciences, Newcastle University, NE1 7RU, Newcastle upon Tyne, UK
Aquifer potentials in the area were estimated using simple schemes that involved the use of three geoelectrical parameters, namely: depth to fresh bedrock, weathered bedrock (saprolite) resistivity and fractured bedrock (saprock) resistivity. The assessment delineated the area into prospective high, medium and low groundwater potential zones. Keywords Keffi . Resistivity sounding . 2-D resistivity imaging . Aquifer . Groundwater potential
Introduction Keffi has witnessed an upsurge in infrastructural development as well as in human population because of its proximity to Abuja, the federal capital of Nigeria. The demand for potable water for domestic, agricultural and industrial uses has grown astronomically over the years. At present, the Nasarawa State Water Corporation supplies pipe-borne water to the area from the Mada Dam located a few kilometers away. The water supply has been grossly inadequate, and therefore, majority of the populace and establishments depend on groundwater abstracted from hand-dug wells and boreholes. Availability of groundwater in Lower P
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