Abstract: Small sized rivers in towns are facing the problems such as complex pollution sources, serious water pollution, and lack of hydrological monitoring data. It is thus of great significance to accurately analyze pollution source for watershed water pollution control. Based on water quality monitoring data of each monitoring section of the Fuxi River, a primary tributary of Tuojiang River from 2018 to 2020, we comprehensively evaluated water pollution using the Nemerow pollution index and analyzed pollution sources using the absolute principal component score-multiple linear regression model. Results showed that water quality of Fuxi River basin was mainly in moderate pollution level in 2018, while in mild-moderate pollution level in 2019 and 2020. Water quality of the basin was mainly in light to moderate pollution level in wet season and normal season, while in moderate pollution level in dry season. Water quality of the main stream was better than that of the tributaries. Agricultural-livestock and poultry breeding mixed sources, domestic-livestock and poultry breeding mixed sources, natural sources, and organic pollutant sources were main pollution sources in the basin. The agricultural-livestock and poultry breeding mixed sources contributed greatly to chemical oxygen demand (COD_Mn) and total phosphorus concentrations, with a contribution rate of 7.8% and 11.8%, respectively. As for ammonia and total nitrogen, the main pollution sources were domestic-livestock and poultry breeding mixed sources, with a contribution rate of 59.4% and 23.8%, respectively. For five-day biochemical oxygen demand, the main contributor was organic pollutants, with a contribution rate of 12.1%. The framework of watershed pollution analysis based on multivariate statistical technology proposed in this study can be used to quickly and accurately analyze the pollution sources and their contribution rates in river basins with hydrological data lacking and complex pollution sources, which provides a scientific basis for water environmental management in tributaries of Tuojiang River basin and a reference for the analysis of water pollution characteristics and pollution sources in other rivers with small towns similar to the tributaries of Tuojiang River basin.

Key words: source apportionment, Fuxi River, comprehensive evaluation of pollution, multiple linear regression.