REVEALING THE SUBSURFACE: AN INTEGRATED GEOPHYSICAL AND GEOLOGICAL INVESTIGATION OF HYDROGEOLOGICAL SYSTEMS, GEOLOGICAL FORMATIONS, AND ENVIRONMENTAL PROCESSES FOR ENHANCED RESOURCE CHARACTERIZATION AND MANAGEMENT

Abstract

The Bojude–Gadam area of Kwami Local Government Area, Gombe State, northeastern Nigeria, was investigated to characterize the subsurface and assess groundwater potential using geological mapping and ten vertical electrical soundings (VES) acquired with a Schlumberger array. The VES data were interpreted by one-dimensional geoelectrical inversion and checked using least-squares and smoothness-constrained (Occam) inversion. Dar-Zarrouk parameters were calculated directly from the inverted resistivity and thickness values, with transverse resistance ranging from 195.87 to 195,629.32 Ω·m². The interpreted subsurface comprises sandy, clayey and sandstone units, with medium-grained sandstone, sandstone and locally silty/shaly sand identified as the principal inferred aquifer-bearing materials. Aquifer-bearing intervals occur at shallow to intermediate depths, generally from about 7 to 64 m depending on station and layer assignment. VES 7 has the largest transverse resistance and represents the most favourable geoelectrical target, whereas VES 5, VES 2 and VES 8 show lower transverse resistance and require greater lithological and hydrogeological caution. The VES fitting errors range from 3.6 to 9.6%. The previously reported hydraulic-conductivity and transmissivity estimates were not retained as validated quantitative results because the supplied manuscript did not document the empirical equations and constants required to reproduce them. Spatial interpolation is therefore treated as exploratory because only ten spatial observations are available. The results identify promising groundwater targets but do not establish sustainable groundwater abundance; pumping tests, borehole logging, water-quality data and seasonal monitoring are required for independent confirmation.