The Integrated Groundwater Health Risk (IGHR) Decision-Support Model: Integrating Hydrogeological, Environmental, and Knowledge, Attitude and Practice Indicators for Groundwater Health Risk Prediction in Abeokuta, Nigeria

Abstract:

Groundwater contamination from petroleum filling station (PFS) activities poses an increasing environmental and public health challenge in rapidly urbanizing regions where groundwater constitutes a major source of domestic water supply. Existing groundwater risk assessment approaches primarily focus on hydrogeological vulnerability or water quality and often overlook the influence of community behavioural factors on human exposure. This study developed and evaluated an Integrated Groundwater Health Risk (IGHR) Decision-Support Model that combines hydrogeological, environmental, and Knowledge Attitude Practice (KAP) indicators to predict groundwater-related health risks in Abeokuta Urban, Ogun State, Nigeria. A mixed-methods approach was adopted, comprising hydrogeological assessment, groundwater quality analysis, household surveys, Geographic Information System (GIS)-based spatial analysis, and statistical modelling, to sample a total of 187 geo-referenced groundwater sources surrounding 19 PFS transects alongside 374 household respondents spatially linked at a 2:1 sampling ratio. Significant spatial variability was observed across physicochemical parameters (pH, EC, TDS, BOD, COD, Cl⁻, NO₃⁻; p < 0.001). Heavy metals (Pb, Cd, Cr, Ni, As, V, Ba) differed significantly across vulnerability classes (p < 0.001), with Lead (29.4%) and Cadmium (33.2%) frequently exceeding WHO drinking water guidelines. Household surveys revealed moderate knowledge (41.9%) and positive attitudes (56.1%) but poor protective practices (37.4%), with regression analysis confirming that attitudinal disposition and education significantly drive water protection practices (R² = 0.285, p < 0.001). The IGHR Decision-Support Model integrated the normalized sub-indices using a weighted additive structure: IGHRI = 0.20(HVRIN) + 0.30(WQIN) + 0.35(HMIN) + 0.15(1 - KAPIN). Using site-wide sub-index mean values HVRIN (0.233), WQIN (0.366), HMIN (0.482), and KAPIN (0.438), the composite index yielded an overall score of 0.4094. The Heavy Metal Index represented the largest weighted contributor (0.1687) to the composite score. Based on equal-interval threshold boundaries (0.401–0.600), the study area is categorized as Moderate Risk, indicating a need for continuous water quality surveillance and targeted community risk communication. Spatial hotspot analysis identified elevated risks down-gradient of PFSs where hydrogeological vulnerability, heavy metal accumulation, and behavioral deficits converged. Model validation against USEPA Non-Carcinogenic Hazard Index scores demonstrated strong spatial predictive accuracy (ROC-AUC = 0.824, p < 0.001). Conclusively, the IGHR model offers a practical spatial decision-support tool for groundwater protection and public health management in petroleum-impacted urban environments.