Integrated Modeling of Water Table Depth Using Controlled-Source Electromagnetic Sounding (ADMT-200S) and SRTM-Derived Terrain Data: A Case Study of Ile-Ife, Southwestern Nigeria

This study investigated the integrated modeling of water table depth in the Ile-Ife region of Southwestern Nigeria, addressing the critical need for precise groundwater mapping in a rapidly urbanizing environment characterized by water scarcity and reliance on costly private boreholes. The research employed a synergistic approach combining Controlled- Source Electromagnetic Sounding (ADMT-200S) for subsurface resistivity, Shuttle Radar Topographic Mission (SRTM) data for terrain analysis, and interpolated borehole records. Methodologies included Ordinary Kriging interpolation of 20 borehole depths to generate a continuous water table surface, followed by GIS-based overlay analysis to integrate ADMT- 200S resistivity maps (identifying fracture zones and low-resistivity regions, typically <30 ohm-m, indicative of water presence) with SRTM-derived elevation data. Key findings revealed significant spatial variability in water table depths across the study area. Higher elevations generally corresponded to deeper water tables, as demonstrated by the comparison of modeled depths with SRTM topography. Observed depths ranged from 80m to 100m in high overburden areas, for instance, Ede road (20m overburden, 100m depth) and Olugbodo (15m overburden, 80m depth). The integrated model successfully classified high groundwater potential areas where low resistivity overlapped with shallower interpolated depths. This research provides crucial, localized insights into the complex interplay of surface terrain and subsurface hydrogeology, enhancing the predictive accuracy for borehole siting. The findings underscore the potential for such integrated approaches to inform sustainable land and water management practices in Ile-Ife and similar regions to ensure long-term water security.