Original Papers
Vol. 15 No. 1 (2026)
https://doi.org/10.7343/as-2026-928

An integrated geophysical and hydrogeological approach to aquifer vulnerability mapping: a case study from Ishielu, Ebonyi State

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Published: 31 March 2026
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Vertical Electrical Sounding, Aquifer Vulnerability Index, groundwater quality, physicochemical analyses, susceptibility

Authors

Johnson C. Ibuot
johnson.ibuot@unn.edu.ng
Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria.
Stella J. Obidike
Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria.
Daniel N. Obiora
Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria.
Chidiebere O. Obasi
Department of Physics and Astronomy, University of Nigeria, Nsukka, Nigeria.

This study aims to appraise the vulnerability of aquifers in Ishielu Local Government Area, Ebonyi State, Nigeria, using an integrated approach that combines geoelectrical, hydraulic, and physicochemical analyses. The objective is to evaluate the extent of groundwater susceptibility to contamination and identify areas requiring protection. A total of 22 Vertical Electrical Soundings (VES) delineated four geoelectric layers, with dominating HA-type curves (28.6%). The third layer, identified as the aquifer unit, showed electrical resistivity values between 2.5 and 100.1 Ωm and thicknesses ranging from 14 to 121.1 m. Estimated hydraulic parameters indicated moderate porosity (28.5-32.5%) and hydraulic conductivity (0.16-0.18 m/day), suggesting a moderate potential for contaminant transport. The Aquifer Vulnerability Index (AVI) was used to quantify the vulnerability of the subsurface and yielded Log C values between 1.04 and 1.89, classifying all sampled locations as highly vulnerable particularly in the northern and eastern zones. This is likely due to shallower water tables, thinner protective overburden, and more permeable lithologies in these areas. Hydrochemical analyses revealed elevated pH (8.9-9.9), high electrical conductivity (513-2130 μS/cm), and iron concentrations (0.1223-0.9782 mg/L) exceeding WHO standards in several boreholes. Piper diagram interpretation identified the dominant water type as Ca-Cl, indicating both geogenic and anthropogenic influences on groundwater chemistry. The study suggests that aquifers in the area are highly vulnerable and recommends land-use control and continuous groundwater quality monitoring to safeguard public health.

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An integrated geophysical and hydrogeological approach to aquifer vulnerability mapping: a case study from Ishielu, Ebonyi State. (2026). Acque Sotterranee - Italian Journal of Groundwater, 15(1). https://doi.org/10.7343/as-2026-928
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