Geo-electrical and hydrochemical characterization of unconfined aquifers in the Niger Delta: implications for groundwater management and SDG achievement

Abstract

ABSTRACT The Niger Delta in southern Nigeria faces growing groundwater stress due to industrial expansion and land-use changes. Understanding aquifer behaviour and water quality is critical for sustainable management in this vulnerable region. This study aims to evaluate the geo-electrical and hydrochemical characteristics of unconfined aquifers to support sustainable groundwater use in line with SDG 6 (Clean Water and Sanitation). Water samples from eight boreholes were analysed for pH, conductivity, major ions, and heavy metals. Vertical electrical sounding (VES) and pump tests assessed subsurface resistivity, transmissivity, and aquifer thickness. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to identify pollution sources and water quality trends. Groundwater showed strong acidity (pH 3.2–4.6), elevated conductivity (up to 940 μS/cm), and chloride (6.08–85.08 mg/L). Lead and mercury exceeded WHO limits. VES revealed resistivity of 97–722 Ωm and transmissivity of 0.92–30.33 m2/day. WQI classified BH 1–5 as ‘Good’ and BH 6–8 as ‘Poor’. Contamination likely stems from industrial effluents and agricultural runoff. Aquifer variability suggests the need for localized interventions. This integrated hydrochemical–geophysical approach offers a robust framework for groundwater monitoring and informed management in complex deltaic systems.