Health Evaluation In The Lower Reach Of Minjiang River Based On Segmentation-Synthesis Method And Combined Evaluation Model

With the development of society and economy,the impact of human activities on rivers has intensified,and the ecological environment of rivers around the world has suffered different degrees of damage.Therefore,river health assessment has become an important research hotspot.The construction of river health evaluation index system,the selection of spatial scale and the evaluation methods are the key and difficult points in the process of river health evaluation.Based on this,this study has carried out three aspects of research:(1)Guided by domestic and foreign research reviews on river health,taking the lower reaches of the Minjiang River as the research area,based on river morphology,hydrology,water quality,biological and social service functions In five aspects,use model simulations and image data to construct a set of health evaluation index systems applicable to the tidal estuary of the river that flows into the sea;(2)Aim at the problem that there are large differences in the evaluation indicators in different river sections,and the lack of hydrological stations leads to insufficient data,a segmented-comprehensive evaluation method is proposed,and applying a two-dimensional non-constant hydrodynamic water quality model to assist the river channel and provide Partial evaluation index value;(3)Apply four commonly used river health evaluation models,that is,gray correlation(Grey Relational Analysis(GRA),Set Pair Analysis(SPA),Fuzzy Comprehensive Evaluation(FCE),Fuzzy Matter Element(FME))After the health evaluation of each river segment,the concept of drift degree was introduced to build a combined river health evaluation model.Segmentation evaluation result,the overall health status of the river in order to achieve healthy long river segments-Integrated Comprehensive Evaluation Method.Taking the lower reaches of Minjiang River as an example,the research results show that:(1)Based on the entropy perspective,a river health assessment index system constructed from 12 indicators in five aspects of river morphology,hydrology,water quality,biological and social service functions,is reasonably characterized.The characteristics of the river health in the study area were studied;(2)The simulation of the two-dimensional non-constant hydrodynamic water quality model of the lower reaches of the Minjiang River and the comprehensive analysis with the results of the existing water function zoning,the lower reaches of the Minjiang River were divided into the mouth of the water mouth ～ Diversion mouth,diversion mouth ～ Hongshan Bridge(Northport),Hongshan Bridge ～ Confluence mouth(Northport),Diversion mouth ～ Confluence mouth(Southport)and Confluence mouth-Minjiang Estuary 5 river sections;(3)Based on the same set of evaluation index system There are some differences in the results obtained by different evaluation models;the combined evaluation model results are that the health level of the Hongshan Bridge ～ Confluence(North Port)and Confluence-Minjiangkou sections are normal,the other river sections are sub-healthy,and the lower reaches of the Minjiang River are overall The condition is average.(4)The proposed channel segmentation of the integrated two-dimensional non-constant hydrodynamic water quality model of the river and the comprehensive tidal river health assessment method can not only reveal the spatial differences in river health in different sections of the long river,but also reflect the overall channel Health status and evaluation results are more reasonable.(5)The river health combination evaluation model based on the concept of drift degree,which can solve the problem of inconsistent evaluation results of different models,and also lays the foundation for the segmentation and comprehensive realization of river channels.