Assessment of Intrinsic Aquifer Vulnerability Using GODTP Framework at Igbesa-Lusada, Southwestern Nigeria

Abstract

Groundwater serves as a critical source of potable water in many parts of Nigeria, yet increasing waste generation and inadequate disposal practices continue to threaten its quality. This study applies a modified GODT, which is GODTP vulnerability assessment framework to evaluate the susceptibility of aquifers to contamination in a rapidly urbanizing area – Igbesa-Lusada of southwestern Nigeria. The framework integrates five parameters: Groundwater occurrence (G), Overlying strata characteristics (O), Depth to water table (D), Topography (T), and Protective capacity (P) derived from longitudinal conductance. Hydrogeophysical data from vertical electrical soundings (VES), topographic (elevations), and geological mapping were used to compute the GODTP index and classify the terrain into vulnerability zones. The introduction of the “P” parameter, representing aquifer protective capacity, improved framework sensitivity by capturing the influence of clay-rich or lateritic layers that attenuate contaminant migration. The GODTP results for the Igbesa-Lusada Road (Dump Corridor) indicate high vulnerability, with ~70% of VES stations in both the high and moderate. Frequency analysis further confirms that about 68.57% of the area exhibits low protective capacity, while only 8.57% shows high protection. These findings demonstrate that dumpsite activities significantly increase aquifer vulnerability in the study area, provide a spatially explicit evaluation of aquifer susceptibility, offering a practical tool for groundwater management and land-use planning in the region and highlight the importance of monitoring and remediation planning in this critical zone.