Urbanization impact on groundwater quality of selected rural and urban areas in Ondo State, Nigeria using Water Quality Index

Abstract Groundwater is the primary source of water in Ondo state, Nigeria, the study area for the research. However, there has been a rising concern in recent times with regard to the contamination of this important water source as a result of urbanization. This study quantified 13 physicochemical parameters (Turbidity, Conductivity, pH, Mg 2+ Hardness, Ca 2+ Hardness, Total hardness, Alkalinity, Chloride, Nitrate, Sulphate, Phosphate, Total Dissolved Solids (TDS) and Total Suspended Solids (TSS)) in ten groundwater samples collected from dug wells in urban and rural study areas and compared them with the WHO drinking water standards. The comparison reveals that 30.8% of the parameters had levels above the World Health Organisation (WHO) standard limits in the study areas, while 69.2% were within the recommended limits. Water Quality Index (WQI) computations were also carried out which revealed that 60% of samples from the urban study area were of good quality and 40% were poor, while in the rural, 80% of the samples were good and the remaining 20% were poor. Based on the statistical and WQI results, groundwater in the urban study area is generally of lower quality than that of the rural. Possible factors influencing this include surface sealing, seepage of domestic and industrial effluents into aquifers and over-exploitation of groundwater, which characterize urbanized areas. The study thus recommends regular monitoring of groundwater quality, integration of effective systems for safe sewage disposal and strategic city planning of urbanized zones to maximize runoffs for groundwater recharge to improve groundwater quality.