Analysis of the trend change in water quality and its influencing factors in Changsha section of the Xiangjiang River

Based on the measured water quality data of national control stations in Changsha city of Xiangjiang River from 2016 to 2019, the principal component analysis method was used to evaluate the water quality at each section. The annual trends in concentrations of ammonia nitrogen and total phosphorus were analysed and the influencing factors were explored. The results show that the water quality of the tributaries of the Xiangjiang River was worse than that of the main stream. The average score of the principal component of Shengli section is the highest, which is 4.412. This suggests that the water quality is poor, where the main pollution sources are domestic sewage and agricultural discharge. From 2016 to 2019, the concentrations of ammonia nitrogen and total phosphorus in each tributary showed a downward trend. The variations of the water quality in each year were mainly affected by rainfall, e.g., the water quality concentration in the dry season was higher than that in the flood season.