Abstract: Taking the Erhai Lake Basin as the research object, an indicator system was constructed from two dimensions of natural environment and anthropogenic pressure environment. The cloud model and comprehensive index model were used to study the spatio-temporal evolution characteristics of ecological risk in Erhai Lake Basin from 2002 to 2022 by combining qualitative analysis and quantitative analysis. The results indicated that the ecological risk levels in the Erhai Lake Basin presented a distribution pattern of “lower in the north and higher in the south, higher in the west and lower in the east”. High-risk areas were mainly distributed in regions surrounding the Erhai Lake waters, such as Xiaguan Town and Fengyi Town. From 2002 to 2012, due to the development of urbanization and the interference of human activities, the ecological environment deteriorated, which led to a rise in ecological risk levels. After 2015, the Yunnan Provincial Government implemented a series of policies to advance the protection and management of Erhai Lake and the transformational development of the basin, which significantly improved both the ecological condition and quality of the Erhai Lake Basin. Overall, from 2002 to 2022, most areas of the Erhai Lake Basin were currently at an extremely low risk level. Specifically, the risk levels of human agglomeration areas in the southwestern part of the water area exhibited a trend of first increasing and then decreasing.

Key words: ecological risk, cloud model, entropy method, spatio-temporal evolution, Erhai Lake Basin