Water quality change in Nanchong section of Jialing River Basin based on multivariate statistical analysis

To better understand the temporal and spatial variation characteristics of water quality of the Jialing River and its main influencing factors, this work adopted the methods of cluster analysis and discriminant analysis of multivariate statistical analysis and collected the monitoring data of five main sections (Liduzhen, Xiaodukou, Wencheng, Shaxi, Caihongqiao) of the Nanchong section of the Jialing River from 2011 to 2019. The results showed that the overall water quality of Jialing River Basin is clearly demarcated before and after 2017. pH, dissolved oxygen, chemical oxygen demand permanganate index, and ammonia nitrogen (NH3-N) are the main influencing factors that distinguish the water quality in different periods. After 2017, the water quality of the Langzhong section of the Jialing River is generally in good condition, and the content of reducing pollutants and nitrogen-containing pollutants in the water body is showing a downward trend. Taking 2015 as the boundary, the main water quality influencing factors of Xichong River after 2015 (Caihongqiao monitoring point), a tributary of Jialing River, are pH and NH3-N. However, the current trend of water pollution in the Nanchong section of the Jialing River still exists. According to the water quality analysis results of the Nanchong section of the Jialing River Basin (Xiaodukou and Liduzhen monitoring points), the concentration of NH3-N in the water body increased after 2017, indicating that the Nanchong section of the Jialing River will be more affected by nitrogen pollutants after 2017.