Abstract: Watershed involves a wide range of complexities in its water environment issues. Water environment assessment and driving force analysis are crucial aspects of watershed research. In this study, an assessment model, the WQI_min, for the water environment in the Xiangjiang River Basin is established by combining cluster analysis and principal component analysis (PCA) based on measured water quality indicators from 77 monitoring stations. The socio-economic driving factors of the basin are also analyzed using the Pearson linear correlation method. Results indicate that the WQI_min values in the Xiangjiang River Basin range from 95.2 to 70.0, with an overall rating of excellent-good. The water environment in non-flood season is superior to that in flood season. Areas such as Yongzhou and Xiaoshui exhibit the best water quality, while the Changsha-Zhuzhou-Xiangtan cluster and the city of Hengyang demonstrate poorer conditions. The main pollution factors include dissolved oxygen (DO), biochemical oxygen demand (BOD₅), chemical oxygen demand (COD_Mn), hexavalent chromium (Cr⁶⁺), and ammonia nitrogen (NH₃-N). Furthermore, the WQI_min values progressively decrease from upstream to downstream along the main stream, with the lowest value recorded in the Xiangtan area at 78.65, while the value in Changsha increases to 81.6. The driving factors impacting the water environment vary across different areas. Industrial pollution, agricultural pollution, and population factors influence the water environment in Changsha-Zhuzhou-Xiangtan region and Hengyang, whereas agricultural pollution affects Yongzhou, and industrial pollution influences Loudi and Chenzhou. The primary driving factors for the mainstream of Xiangjiang River include industrial pollution, agricultural pollution, and urban pollution in upstream cities.

Key words: water environment assessment, driving factors, WQI_min model, principal component analysis, Xiangjiang River Basin