The aim of this study is to quantify the sources of pollution in the Yagang River Basin. The 1-D hydrodynamic model and the 1-D water quality model are combined with the excessive pollutant flux analysis method to calculate pollution data of the Yagang area. The results showed the following. (1) Upstream pollution was the primary cause of water quality degradation for the Yagang Basin, exceeding the water quality standards. In addition, the pollution problem ranking of the entire basin was the following: the Yagang area (30.4%) > the Foshan area (23.2%) > the Baini River Basin (13.1%) > the Liuxi River Basin (0.6%). In addition, the rainy season had the greatest influence on pollution concentrations. (2) It was also concluded that if the boundary water quality could meet the inspection requirements (class IV water), the internal research area sewage collection rate would reach 60%, and the ammonia in the river discharge would reach 35.7%. This would allow the water quality reach standard class IV.
Pollutant flux in the different seasons have different results.
Different rivers contribute different pollutant flux.
Non-point source pollution from the upstream is the key reason to worse the water environment.