Investigation of groundwater potential using geological, hydrogeological and geophysical methods in Federal University of Technology, Minna, Bosso Campus, North Central, Nigeria

Abstract

Groundwater exploration and extraction in challenging hard rock formations with inherent heterogeneity is ad- dressed comprehensively in this study through geological, hydrogeological, and geophysical investigations. Hydrogeological studies assess existing borehole recharge rates and provide an overarching groundwater potential assessment. A 1D Vertical Electrical Sounding (VES) survey, employing the Schlumberger method, acquires sounding data analyzed with WINRESIST software to extract groundwater controlling parameters, revealing dis- tinct geoelectric layers and illuminating groundwater and aquifer system structural control. Geological mapping, employing detailed topographical data, revealed the prevalence of granitic rocks exhibiting quartz vein and joint intrusions, primarily oriented in the NE-SW direction. These geoelectric layers encompassed the topsoil, weath- ered/fractured granite, and fresh granite, each characterized by apparent resistivity values ranging from 14 Ωmto 572 Ωm, 10.0 Ωmto408Ωm, and 1468 Ωmto19,031Ωm, accompanied by varying thicknesses. Further insights were gained from isopach and resistivity maps at depths of 10 m and 30 m, identifying areas with low apparent resistivity values and substantial overburden. These findings pinpointed zones with potentially high groundwa- ter potential, particularly in the northeastern and southeastern regions. Additionally, the results from the weath- ered layer analysis aligned with the isopach and resistivity outcomes. Hydraulic conductivity measurements, falling within the range of 7.00 × 10–5 m/s to 4.31 × 10–4m/s,confirmed the subsurface materials' capacity to transmit water. Moisture content ranged from 12% to 20%, while infiltration rates varied from 2.675 × 10–4L/s to 1.259 × 10–5 L/s. Yield test results from three borehole locations yielded production rates ranging from 56.52 m3/day to 364.26 m3/day, although other boreholes returned indeterminate results. Based on the ground- water potential classification, 25% of the area demonstrated high potential, 45% moderate potential, and 30% low potential. Accordingly, the recommendation is to prioritize well or borehole drilling in high-potential areas to ensure optimal water supply management.