Assessment of Rainfall-Runoff and Nonpoint Source Pollution Loads in the Sakumo Catchment Using Gis and Qnspect

Land use and land cover (LULC) transformations significantly impact ecosystem hydrological characteristics. This study analysed the Sakumo catchment from 1990 to 2020 to assess changes in runoff volume and nonpoint source (NPS) pollutant loads. Using remote sensing, GIS products, and the QNSPECT (QGIS Plugin for Nonpoint Source Pollution and Erosion Comparison Tool) hydrologic model, we quantified and spatially analysed rainfall-runoff and pollutant loads. Our results revealed increasing trends in runoff (110.3 mm/year) and pollutant loads (total nitrogen: 0.22 kg/year; total phosphorus: 0.34 kg/year), attributed to population growth (1, 475 ppl/km²) and urbanization-induced LULC changes (Development: 44.7%). GIS outputs identified the sources of these increments. This research addresses critical gaps in understanding Ghanaian wetlands by estimating runoff magnitudes, identifying spatial pollution sources, and assessing catchment-scale impacts on wetland functions. The study's findings align with historical water quality trends in the Sakumo Ramsar Site, and our runoff estimates demonstrate satisfactory agreement with global runoff model products. This study provides a practical approach for stakeholders in data-deficient regions to investigate hydrological and environmental changes, guiding informed decision-making.