Study On Health Assessment Of Urban River Based On GIS

The accelerated development of urbanization has promoted the development of social economy,but also brought the problems of water shortage,water pollution and damage to water ecosystem.More than half of China's cities are facing water shortage,eutrophication and water pollution.For a long time,the focus of the public and the government is mainly on the physical and chemical indicators of water bodies.However,with the advancement of regional urbanization,rivers are facing a series of environmental and ecological problems,such as ecosystem decline,connectivity decline,function decline,water environment habitat degradation,aquatic organisms sharp decline,etc.,so it is an inevitable trend to combine the current situation of rivers with the concept of ecosystem health.The research on river health assessment started late in China.This study systematically combed the connotation,methods,application status and development trend of river health assessment at home and abroad.In view of the level of urban development and the current situation of rivers in China,based on the full consideration of the four factors of river structure,water body status,aquatic biological community and social function,the flow was studied and constructed Index system of three spatial scales: region,riverbank and habitat.In this study,AHP is used to determine the weight of indicators,and a fuzzy comprehensive evaluation model of river health is built based on the principle of maximum fuzzy membership degree.Taking the main river channels of Wangyu River West Bank basin in Wuxi as the research object,a comprehensive evaluation study on river health and regulation effect is carried out,and the evaluation results are visualized by the powerful spatial data processing ability of GIS It provides a scientific basis for river regulation and long-term management.From January 2018 to October 2019,in the empirical study on the river health evaluation of the West Bank of Wangyu River in Wuxi City,the overall river health status of Liangxi district is at or below the basic health level.During the research period,the sections in very unhealthy and unhealthy grades have a significant downward trend,while the sections in basic health and above have an upward trend,which shows that the river regulation effect in Liangxi district is obvious,and the river health status has been significantly improved.The health status of the whole river in Xinwu district is in the basic health and health level,and the overall health status is better than that in Liangxi district.During the study period,the sections in very unhealthy or below state and in basic healthy or above state showed fluctuation state with time,and there was a certain change rule with seasons.The overall health condition of summer and autumn was better than that of spring and winter.The overall river health in Xishan District is at or above the basic health level.The overall health of Xishan river is better than that of Liangxi and Xinwu.During the study period,the sections in very unhealthy and unhealthy grades have a slight downward trend,while the sections in basic health and above have a slight upward trend,and the river health status has a certain improvement on the basis of maintaining the original health status.More than 55% of the results in the whole watershed are in the basic health and health level,and the health status is good.During the study period,the number of sections in the unhealthy and very unhealthy grades decreased significantly,while the number of sections in the healthy grades increased significantly,but the number of sections in the very healthy grades was always small.From the perspective of spatial distribution,the areas with the most unfavorable river health status are concentrated in Liangxi District,the northwest of Xishan District and the north of Xinwu district.Land use types and riparian conditions have a significant impact on river water quality,the abundance of aquatic organisms and the quality of aquatic habitat,while the water quantity,water quality,biological community and habitat quality of the river also have an inseparable relationship.Based on the above conclusions,suggestions for urban river regulation and long-term management are put forward:(1)At the same time of ensuring the water quantity and quality of the river,the maintenance and restoration of the river bed,shoreline,sediment and the ecosystem of the whole river basin should be taken into consideration;(2)Avoid the reconstruction of the original riverbank by large-scale urban construction and pay attention to the ecological restoration and the whole reconstruction of the old community;(3)In the daily maintenance stage,strengthen the management of the river in the spring and winter dry season,Clear management responsibility,improve the governance system;(4)Increase the promotion of water conservancy information construction and the use of advanced geographic information technology for river real-time monitoring and management.