Quantitative traceability study on the water quality driving forces across cities in the Xiang River Basin

Based on the monthly monitoring data of 16 water quality monitoring stations in the Xiang River Basin from 1990 to 2020, the Mann–Kendall test was used to analyze dissolved oxygen, 5-day biochemical oxygen demand, permanganate index, total phosphorus, ammonia nitrogen, cadmium, arsenic, and hexavalent chromium. The changing trend of nine indicators, including the stepwise regression method, was used to determine the cross city driving force of each water quality index, and the contribution rate (weight) of each driving force was obtained by principal component analysis. The research results show that (1) agriculture in Yongzhou is the main driving force, and its contribution rate is 67.2%; (2) urbanization has a greater impact on the driving process of the water environment in the Xiang River Basin, and its contribution rate is as follows: Changsha (83%) > Hengyang (80.7%) > Pingxiang (63.7%) > Chenzhou (60.9%) > Xiangtan (57.4%) > Zhuzhou (50%) > Loudi (48.5%); (3) the urbanization of Zhuzhou City and Loudi City's urban sewage discharge not only has an impact on the city's water environment, but also drives the water environment in the downstream Xiangtan area. The research results can provide a basis and reference for the study of water environmental governance in the basin.