Assessing groundwater quality and pollution hotspots using simple fuzzy classification in a rapidly urbanizing region

In the absence of centralised water supply infrastructure, groundwater serves as the primary source of water for domestic, agricultural, and industrial use in Ekiti State, Nigeria. However, its quality is increasingly threatened by anthropogenic pollution. This study evaluated the quality of groundwater in selected areas of Ekiti State, identified pollution levels and potential hotspots. It addresses the critical gap in regional groundwater quality assessment by applying a simple fuzzy classification (SFC) model to 22 groundwater samples collected from four local government areas. Twenty Physicochemical and heavy metal parameters were analysed and compared with regulatory guidelines (WHO, USEPA and the Nigerian Standard for drinking water quality). Findings revealed widespread contamination, with elevated turbidity, chlorine, manganese, and iron levels, e.g., Fe and Mn levels reached 2.1, and 0.55 mg/L against a 0.3, and 0.05 mg/L limit, respectively, posing health risks. The fuzzy model classified water from all sampling points as having membership functions of more than 90 % in pristine category (C 1 ). Presence of about 38, 30 and 27 % membership functions in contaminated (C 2 ), polluted (C 3 ) and extremely polluted (C 4 ) categories in sampling points 5, 20, and 7, respectively calls for concern, indicating localised contamination. The study highlights the urgent need for continuous groundwater quality monitoring, the implementation of pollution control strategies, and targeted water treatment interventions to ensure the safe and sustainable use of groundwater resources in Ekiti State. • Groundwater is the main water source in Ekiti State but is under pollution threat. • 22 groundwater samples analyzed for key physico-chemical and metal parameters. • Fuzzy classification grouped samples from pristine (C 1 ) to extremely polluted (C 4 ). • Pollution hotspots linked to industrial and agricultural land use activities. • Results call for groundwater monitoring and urgent pollution control measures.