2D geo-electrical imaging for groundwater exploration in Shika, along Zaria-Funtua Road north of Ahmadu Bello University main campus, Samaru, Zaria

Abstract

A two dimensional (2D) geoelectrical tomography of Ahmadu Bello University Teaching Hospital Premises was carried out with the aim of identifying a suitable location for siting a borehole. This was sequel to the fact that a borehole drilled without proper geophysical investigation in the quarters for resident doctors did not produce water. State-of-the-art equipment was employed and 2D surveying proved a powerful geological mapping tool, for use in hydrogeological mapping including engineering and environmental applications. The 2D inversion results of the survey were correlated with the lithology information obtained from the boreholes in Jama’a village, and the hostels and the residential quarters of ABUTH. The stratigraphic structure of the study area is very complex and is a product of volcanic and magmatic activities of various ages. Based on the geo-electrical images obtained in the study area, three distinct layers were revealed, the overburden with an average thickness of about 16 m – 26 m. The overburden is immediately underlain by the weathered basement, 5 m – 14 m thick which consists of disintegrated schistose rock materials, sand and gravel. This layer has a relatively low resistivity due to the presence of water and clay, which reduces the permeability, so this layer is thus regarded as the aquifer. The fresh basement rock was encountered at a variable depth of between 21 m and >30 m with resistivity 1223 Ωm up to 11918 Ωm. These results agree with the borehole logs. The complete set of borehole logs used in this research were obtained from the original hydro-geologic assessment report of the groundwater research department of the National Water Resources Institute (NWRI), Mando, Kaduna; Kaduna State, Nigeria.

Keywords: Tomography, Inversion, Lithology, Geo-electrical, Aquifer, Borehole