Empirical Assessment of the Relationship Between Urban Expansion and Groundwater Contamination in Awka, Anambra State

Urban expansion generates multifaceted groundwater contamination risks through increases in impervious surface area, unsewered wastewater disposal, solid waste leachate, and industrial chemical use, yet the empirical relationship between urban growth and groundwater quality has not been systematically examined for Anambra State's rapidly growing capital city. This study empirically assesses the relationship between urban expansion patterns and groundwater contamination in Awka using a spatial panel data approach. Urban built-up area extent was mapped at five-year intervals from 2005 to 2025 using Landsat imagery, and expansion rates were computed at the ward level. Groundwater quality data from 48 monitored boreholes were compiled from Anambra State Water Corporation records, and field sampling was conducted in 2024 to update bacteriological and physicochemical parameters. Spatial regression models test the association between borehole proximity to newly urbanised areas, waste dump sites, fuel stations, and septic system density, and groundwater contamination indicators. Results indicate that boreholes within 200 metres of areas urbanised after 2010 show a 3.6 times higher probability of coliform contamination compared to boreholes in pre-2005 urbanised areas, suggesting inadequate sanitation infrastructure accompanies rapid urban growth. Nitrate contamination hotspots spatially correlate with high-density residential areas without sewer connections, consistent with septic system leachate as the dominant nitrogen source. Fuel station proximity is associated with elevated benzene and hydrocarbon indicator concentrations in 14 percent of nearby boreholes. Recommendations address mandatory sanitation impact assessments for new urban subdivisions, groundwater protection zones around municipal supply boreholes, and regular contamination monitoring. Keywords: urban expansion, groundwater contamination, Awka, spatial analysis, water quality.