Evaluation on risk of non-point source pollution in Dayanghe watershed based on GIS

Four indices which include surface runoff, soil erosion, agricultural nutrient loss, human and animal feces were selected and method to evaluate risk of non-point source pollution in watershed was constructed based on GIS. As a case, non-point source pollution in Dayanghe was evaluated. Results showed that very high risk area of non-point source pollution accounted for 3.41% area of the watershed, mainly located in farmland with steep slope along upper valley of the watershed. High risk area of non-point source pollution was located in farmland and human settlement placecs, accounted for 16.40% area of the watershed. Areas with low risk of non-point source pollution was riverbeds, shrub and grassland in eastern and western hilly with steep slope. Areas with lower risk of non-point source pollution located in middle of the watershed and accounted for 60.55% area. GIS-based risk evaluation system of non-point source pollution can reflect real map of pollution in the Dayanghe watershed and give implication for protection plan.