Groundwater vulnerability to pollution in terms of the source is usually complex and ubiquitous. Hence, the application of conventional water quality assessment techniques cannot provide an equitable and holistic assessment of the water quality. Using conventional water quality indexing usually involves the apportionment of each parameter weight based on expert judgments and practical experience, which is usually subjective and associated with bias. To overcome this limitation, this study has integrated the information entropy theory, pollution index of groundwater (PIG), and overall index of pollution (OIP) to generate a composite drinking water zonation map of the entire study area. Additionally, a visual assessment of the groundwater aquifer hydraulic characteristics and patterns of contaminant flow has been generated using GIS-based spatiotemporal modeling. Physicochemical analysis revealed that groundwater is fresh, slightly acidic to alkaline, attributed to high buffering from rainfall and dissolution of carbonate rocks. Among the heavy metals, As, Zn, Mn, Cd, and Pb, showed elevated concentrations in groundwater above the drinking water standards of the World Health Organization (WHO) and Standards Organization of Nigeria. Information entropy theory, OIP, and PIG revealed that 45.83%, 95.84%, and 100% respectively, of the groundwater samples, are unsuitable for drinking; with the water quality deteriorating toward the western, eastern, and southern directions. Multivariate statistical analysis revealed that the source of pollution is mostly from anthropogenic activities and to a lesser extent geogenic processes. The groundwater flow map revealed that the flow pattern is fracture-controlled; with the flow pattern trending from the north-eastern direction toward the south-western direction. It is therefore recommended that drinking water wells and boreholes be prohibited from being drilled within the western and southern parts of the area, until remedial measures are put in place to curb the spread of contaminants.
