Comprehensive ecological risk assessment for semi-arid basin based on conceptual model of risk response and improved TOPSIS model-a case study of Wei River Basin, China.

Comprehensive ecological risk assessment is of great significance for the restoration of watershed ecosystem health, and the appropriate and effective assessment method is the premise of ecological risk assessment. In this study, the conceptual model of risk response was developed by identification of ecological risk sources, stressors, endpoints and the corresponding response mechanism as well as the improved TOPSIS model based on Canberra distance and the combinatorial weighting method based on AHP and Critic were combined for the assessment. According to the three aspects of agriculture, industrial and urbanization, the occurrence mechanism of comprehensive ecological risk of rivers in semi-arid areas was analyzed. Furthermore, twenty-four indexes were selected to establish the index system and the Wei River Basin was taken as an example to verify the model. The results of comprehensive ecological risk assessment and stressor analysis showed that the deterioration of water quality (enrichment of heavy metals) and the decrease of benthos integrity were the two main risk factors for the increase of comprehensive ecological risk in Wei River Basin. And the regulation of ecological risk for the Wei River Basin is improvement of water quality and biotic integrity.