Comparative Analysis of 1D, 2D, and 3D Resistivity Inversion for Mapping Basement Aquifers in Niger State

This study conducts a systematic comparative analysis of one-dimensional, two-dimensional, and three-dimensional electrical resistivity inversion approaches for mapping basement aquifer targets in Niger State, North Central Nigeria, addressing the practical question of which level of modelling complexity provides the best return on investment for hydrogeological surveys in crystalline basement terrain. One-dimensional VES inversion is the standard tool for groundwater exploration in Nigeria due to its simplicity and low cost, but its inability to account for lateral heterogeneity creates interpretation errors in geologically complex terrain. Two-dimensional ERT inversion provides a more complete representation but requires more field time and processing expertise. Three-dimensional resistivity inversion provides the most complete model but is rarely applied due to cost and computational requirements. This study acquires co-located VES, 2D ERT, and 3D resistivity datasets at six test sites in Minna, Suleja, and Paikoro districts with contrasting basement geological complexity, selected from prior geological mapping. Sites are drilled after geophysical survey for validation. All three inversion approaches are applied to each site and results compared for accuracy of aquifer delineation, borehole yield prediction, and depth to competent basement estimation. Findings reveal that 2D ERT produces a 24 percent improvement in borehole yield prediction accuracy over 1D VES at sites with confirmed lateral heterogeneity, with most accuracy gains in structurally complex zones. Three-dimensional inversion improves over 2D primarily in areas near known fault intersections. Cost-benefit analysis shows 2D ERT provides the best value-to-accuracy ratio for routine groundwater surveys. The study provides decision guidance for inversion method selection in Nigerian groundwater exploration surveys.

Keywords: resistivity inversion, 1D versus 2D versus 3D, basement aquifer, Niger State, comparative analysis.