Abstract:

The upper reaches of the Minjiang river are key barriers of ecological safety in the upper reaches of the Yangtze river. Since the Wenchuan earthquake in 2008, the underground rock masses, surface matrix, and aboveground ecology were severely damaged. To investigate the status of ecological and geological safety in the upper reaches of the Minjiang river before and after the earthquake, we selected 16 evaluation indicators from the two dimensions of “geological environment-ecological environment”. We also evaluated the ecological and geological environment safety of the upper reaches of the Minjiang river basin in 1995, 2001, 2009, and 2020 based on the AHP-PCA entropy-combination weight method, and furthermore analyzed its evolution trend. The results indicate that the overall ecological and geological environments in the upper reaches of the Minjiang river basin are generally safe. Specifically, the ecological and geological environments are relatively safer in the central and eastern regions of the basin, while the relatively less safe or unsafe regions are mainly distributed in the western and northern high mountain areas and deep valley areas. This presents a general pattern of high safety in the central and eastern regions and low safety in the western and northern regions. From 1995 to 2020, the overall ecological and geological environment safety in the upper reaches of the Minjiang river showed a trend of decreasing at the beginning and then gradually increasing. The ecological and geological environment safety in the northern and deep valley areas of the watershed fluctuates greatly, showing an increasing-decreasing-increasing trend and unstable ecological and geological environments. The overall safety of the ecological and geological environments in the southwest is reduced after the earthquake. Although the reduced area gradually decreases, the overall ecological and geological environments continue deteriorating. The overall safety of the ecological and geological environments in the central part of the basin is generally increasing and the area is gradually increa-sing. The results of this study provide theoretical basis for the ecological protection and restoration in the upper reaches of the Minjiang river.

Key words: ecological and geological environment safety, analytic hierarchy process, principal component analysis, minimum information entropy, upper reaches of the Minjiang river