Geology and Geophysical Investigation of Groundwater Potential around Boh and Environs, Gongola Arm of the Northern Benue Trough Northeastern Nigeria

Abstract

Groundwater exploration within crystalline basement and sedimentary terrains requires 
the integration of geological and geophysical investigations to accurately delineate aquifer 
systems and identify viable groundwater targets. This study employed detailed geological 
mapping and Vertical Electrical Sounding (VES) to evaluate the groundwater potential of 
Boh and its environs within the Upper Benue Trough, northeastern Nigeria. Thirteen VES 
stations were established using the Schlumberger electrode configuration with a maximum 
current electrode half-spacing (AB/2) of 100 m. The acquired resistivity data were 
interpreted using WinResist Version 1.0 software to determine subsurface resistivity 
distributions and layer thicknesses. The geoelectrical interpretation revealed three major 
subsurface units. The uppermost unit comprises lateritic/topsoil materials characterized 
by resistivity values ranging from 13.7 to 147.7 Ωm. Beneath this layer occurs a 
weathered/fractured basement and saturated sandstone horizon, interpreted as the 
principal aquifer unit, with resistivity values varying between 29.3 and 915.1 Ωm. The 
deepest unit corresponds to the fresh basement complex, exhibiting relatively high 
resistivity values ranging from 242 to 2359 Ωm. Variations in resistivity and thickness 
indicate considerable heterogeneity in subsurface hydrogeological conditions across the 
study area. Aquifer evaluation identified VES locations 1, 7, 9, 11, 12, and 13 as the most 
promising borehole sites due to the occurrence of relatively thick aquiferous zones with 
resistive to moderately conductive characteristics favorable for groundwater storage and 
transmission. Overall, the groundwater potential of the area is classified as low to 
moderate, largely constrained by limited aquifer thickness and poor fracture connectivity. 
The study highlights the importance of careful borehole siting and recommends the 
integration of complementary geophysical methods to enhance fracture characterization 
and support sustainable groundwater development.