Risk Assessment and Delineation of Point and Nonpoint Source of Surface Water Pollution on Bishenyi Sub-Catchment in Kamonyi District
DOI:
https://doi.org/10.53819/81018102t2616Abstract
This study assessed water pollution risks in the Bishenyi Sub-Catchment, Kamonyi District, Rwanda, using Geographic Information Systems (GIS) and field-based assessments to identify pollution sources and examine relationships between land use and water quality. Five water samples, representing agricultural, commercial, industrial, residential, and forestry areas, were analyzed for pH, temperature, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), turbidity, and conductivity. Results indicated substantial organic pollution in industrial and commercial areas, with BOD concentrations of 220.3 mg/L and 61.8 mg/L, respectively, and COD concentrations of 550.8 mg/L and 154.5 mg/L. These elevated values suggest significant contamination from untreated effluents and waste discharges. Agricultural areas recorded the highest reported turbidity of 115 NTU and a COD concentration of 37.8 mg/L, likely associated with sediment and agrochemical runoff. Residential areas exhibited increased conductivity of 322 µS/cm, indicating potential domestic wastewater influence. Conversely, forestry areas showed comparatively lower pollution, with TSS of 16.7 mg/L and turbidity of 18.7 NTU, highlighting the protective role of forest cover. GIS-based hydrological modeling identified industrial, agricultural, and residential areas as major pollution contributors and revealed downstream vulnerability through flow accumulation analysis. The findings demonstrate that land-use practices influence water quality and emphasize the need for improved wastewater management, pollution-source control, sustainable land-use planning, and forest-buffer conservation to reduce point and non-point pollution risks.
Keywords: Bishenyi Sub-Catchment, GIS, Risk assessment, Water pollution, Water quality. Top of Form
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