Analysis Of Flow Regime And Ecological Regulation Of Urban Rive

A near natural flow regime is a basic element for river restoration of ecological health.However,with the development of human society,the flow regime of both natural rivers and urban rivers has been disturbed to varying degrees.Different from the problems of natural rivers,such as the runoff reduction due to rough development and over development,urban rivers are over protected and over utilized due to their special geographical location,which leads to the homogenization of runoff process,the simplification of runoff components,the sharp rise and fall of flood process and the acceptance of urban reclaimed water.In order to solve these problems,the thread of this paper is to identify the disturbance factors and to regulate the disturbance process(ecological regulation).Based on this,CA-Markov model and copula function are used to analyze the alteration of urban river hydrological process,and then an identification framework of flow regime from the whole to the flow classification and then to consider the index distribution law,analyzes the flow regime before and after the abrupt change,and identifies the disturbance components and indicators.For the identified disturbance components and indicators,this paper builds their own ecological regulation model through the combination of dynamic programming and hydrological model,Bayesian network and multivariate joint probability distribution,etc.Water quality is also included in the regulation range of runoff process,forming a scheduling scheme.These methods are applied in Xiaoqing River Basin of Jinan City,the results show that:the proposed method identifies the disturbance factors of urban river flow regime,and carries out reasonable and effective ecological regulation of the disturbance factors,so as to provide technical support for similar river ecological governance.The main research results are as follows:(1)According to the alteration of river flow regime,the concept of FDC evenness is put forward by combining the flow duration curve(FDC)and eco-index to evaluate the overall alteration river flow regime.Then,the alteration of flow regime of each flow component is deconstructed by environment flow components(EFCs),and the correlation between the overall and the flow classification alteration is analyzed.The components with violent disturbance are identified as high flow,small flood and low flow components.The Maximum entropy principle is used to analyzed the distribution law of flow regime indexes,and the alteration of each index is evaluated in combination with OWA operator and Shannon's Diversity Index.According to the analysis of flow regime,the ecological flow thresholds of different flow components are calculated.(2)For the medium and small floods,this paper clarifies the definition and scope,and proposes the concept of the river ecological flow threshold during flooding.With the ecological flow threshold during river flooding as a constraint and the minimum difference between the main river flooding and the ecological flow as the goal,an ecological regulation model for medium and small flood in urban rivers was constructed.The combination of typical precipitation situations in each sub-basin forms the final simulation scenarios.Combined the MIKE 11 HD-NAM model and dynamic programming,these typical simulation scenarios are simulated to obtain the regulation process of each control gate and then form a regulation scheme of medium and small flood.(3)For the flow process regulation,the conception of "total volume control,discharge process allocation" was proposed.The flow process regulation refers to the ecological regulation of flow processes except for medium-small flood and major flood components,and according to the characteristics of regulation,a combination of water transfer and emission reduction is adopted to restore urban river flow regime.Based on the near natural flow regime of the Xiaoqing River in the historical period,the severe disturbed index were regulated on a monthly scale to realize the monthly allocation of total water transfer.Using the multi-dimensional joint probability distribution and the Bayesian network based on the mechanism model,the joint probability distribution of water quality and water quality before and after emission reduction was calculated and analyzed,and the trade-off between water quality improvement and water transfer was found,providing a theoretical basis for successive regulation.Based on this,a water quality model was constructed,and the water replenishment sequence,water replenishment interval,and water replenishment flow were verified by orthogonal experiments,and successive ecological water replenishment schemes with better results were screened out,and the monthly allocation of total water transfer was realized Based on process scheduling.