Influence of Urban Sprawl on Water Quality Parameters in River Rupingazi in Embu Municipality, Kenya

Urban sprawl refers to the uncontrolled or unplanned expansion of urban areas into the surrounding areas. It typically results to inefficient land use and environmental degradation as the urban areas spread outward beyond their planned boundaries. This study aimed to determine the influence of urban sprawl on water quality parameters of water along the Rupingazi River in Embu Municipality, Kenya. A sample of thirty water–soil samples were collected along the river in ten sampling points. Parameters such as temperature and pH were measured in-situ while other parameters were analyzed in the laboratory using standard water testing procedures. These included: Lead, Phosphates, Nitrates, TSL, TDS, Dissolved Oxygen, Turbidity and Electrical Conductivity. Ten key water quality parameters were tested. Mann-Whitney U test results showed that all parameters were statistically significant (< 0.001) between the municipality and catchment areas. Findings revealed that urban sprawl had markedly degraded water quality. Most parameters were higher in the urbanized municipality: lead increased from 0.00378 mg/L to 0.02296 mg/L (above WHO limits), phosphates from 1.8535 mg/L to 5.612 mg/L, nitrates from 0.3663 mg/L to 2.970 mg/L, and TSL from 40.8 mg/L to 250.4 mg/L. Electrical conductivity and turbidity also rose sharply, while DO declined from 10.53 mg/L to 4.94 mg/L, falling below NEMA standards. Pollution Index (PI) values similarly increased, with the Average Pollution Index (API) rising from 3.05 in the catchment to 12.98 in the municipality. The analysis revealed that water quality was significantly degraded in the urban municipality compared to the catchment area due to increased concentrations of pollutants such as lead, phosphates, nitrates, turbidity, and total suspended load, which are associated with urban runoff, waste disposal, and land-use changes caused by urban sprawl. The study recommended for stricter urban land use policies by the county government of Embu to curb the menace.