Integrated GIS-AHP and Hydrogeophysical Approaches for Groundwater Potential Mapping in Akure Metropolis, Ondo State, Nigeria

Abstract

Groundwater remains the principal source of potable water for domestic, agricultural, and industrial activities in many parts of Nigeria. However, increasing population growth, urban expansion, and climate variability have intensified pressure on groundwater resources, necessitating accurate assessment of groundwater potential zones for sustainable water resource management. This study integrated Remote Sensing (RS), Geographic Information Systems (GIS), the Analytical Hierarchy Process (AHP), and Vertical Electrical Sounding (VES) techniques to delineate groundwater potential zones in Akure Metropolis, Ondo State, southwestern Nigeria. Eight groundwater conditioning factors comprising geology, lineament density, land use/land cover, drainage density, soil, rainfall, slope, and elevation were selected and weighted using the AHP multi-criteria decision-making approach. The thematic layers were integrated through weighted overlay analysis to generate a groundwater potential map. Furthermore, forty-one (41) Vertical Electrical Sounding (VES) stations were conducted across the study area to characterize subsurface hydrogeological conditions using parameters such as overburden thickness, aquifer thickness, aquifer resistivity, bedrock relief, hydraulic conductivity, transmissivity, transverse resistance, and longitudinal conductance. The VES-derived groundwater potential map was subsequently integrated with the GIS-AHP model to improve prediction reliability and reduce uncertainty associated with surface-based analyses.The integration resulted in the classification of the study area into five groundwater potential zones: very low, low, moderate, high, and very high. Moderate potential zones covered the largest area—52.08%, high-26.36%, low-18.78%, very high-1.66% and the very low-1.12%. Areas with high to very high groundwater potential were predominantly concentrated in the northeastern and eastern parts of the study area, particularly around Ogbese and Ita-Ogbolu, where favourable geological formations, high lineament density, and enhanced aquifer characteristics occur. Conversely, low to very low groundwater potential zones were mainly located in the southwestern parts of the study area where unfavourable hydrogeological conditions prevail.The integration of GIS-AHP and hydrogeophysical data demonstrated strong spatial agreement between predicted groundwater potential zones and subsurface aquifer characteristics obtained from VES interpretation. The study highlights the effectiveness of integrating geospatial and hydrogeophysical techniques for groundwater exploration, borehole siting, and sustainable groundwater resource management in crystalline basement terrains.