Considering the Haihe River Basin as an example, the DPeRS model was used to analyze the spatial distribution characteristics and pollution sources of the diffuse pollution by remote sensing pixel scale. Combined with the evaluation standard of surface water quality, a potential risk grading method for diffuse pollution was constructed to assess the potential risk of diffuse pollution in Haihe River Basin. The results showed that, in 2016, the diffuse discharge loads of total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH4+-N), and chemical oxygen demand (COD) were 429.2, 25.7, 288.3, and 1017.0 kg ·km-2, respectively, with the amount of river entry being 2.5×104 ton, 1597.2 ton, 1.7×104 ton, and 6.6×104 ton in Haihe River Basin, respectively. Farmland runoff is the most important source of diffuse pollution of TN, TP and NH4+-N in the Haihe River Basin. For COD index, urban life is the primary type of pollution, followed by livestock. The diffuse pollution is relatively severe in the central and southern areas of Haihe River Basin, and this area is also a high-risk concentrated distribution area of diffuse pollution in the basin. The distribution of high-risk areas of nitrogen-phosphorus diffuse pollution are relatively concentrated, and the chemical oxygen demand is relatively scattered. More than 36% of the Haihe River Basin has a nitrogen-phosphorus diffuse pollution risk, and 2.94% of the area has a chemical oxygen demand diffuse pollution risk.
Keywords: DPeRS model; Haihe River Basin; diffuse pollution; remote sensing; risk assessment.