A novel comprehensive model of set pair analysis with extenics for river health evaluation and prediction of semi-arid basin- A case study of Wei River Basin, China

The accelerated development of urbanization in semi-arid areas is easy to cause varying degrees of disturbance to its fragile aquatic ecosystem. To find a general method for assessing the health status in semi-arid basins in China, and to provide theoretical basis for river health management and sustainable development, this study is that health evaluation index system is established in the Wei River Basin, covering a huge semi-arid area, and analyzed the biological structure of plankton obtained by field sampling and identified in laboratory, chemical conditions including dissolved oxygen, water temperature, ammonia nitrogen, pH, chlorophyll and other water physical and chemical factors determined by field instruments and sediment heavy metals analyzed in laboratory, physical habitat scored on site and social factors including water resource utilization rate and water consumption per 10,000 yuan of GDP collected in local water resource bulletin. Based on the idea of game theory, an improved coupling model of set pair analysis with extenics is established to assess and predict health. The results show that Wei River System and Jing River System are healthy, Beiluo River System is sub-healthy, and the whole Wei River Basin is also healthy; most of the cross-sections have a tendency to change to a bad level. Compared with simple weighting, set pair analysis and variable fuzzy set methods based on the corresponding sampling data and the weight in this paper, the coupling model can explain the transition and its trend between levels, reflect the certainty and uncertainty, and get more accurate results. It is suggested that daily monitoring and management should be strengthened in most sections to improve their health. And improve the development level of ecological function and social service function, give priority to the development of downstream water resources economy. (C)2021 Elsevier B.V. All rights reserved.