Quantitative Evaluation Of Connectivity Of River Network Systems In The Plain With Multiple Dams In Langfang City

River network water system is the carrier of water cycle and water resource formation in the basin.River network connection is an important foundation for regional water security,water ecology,water resources,water environment,and water culture.It is to meet the requirements of regional water resources allocation,water storage,flood prevention and disaster reduction,Important conditions for ecological protection,restoration and landscape enhancement.This study analyzes the characteristics of the river network and water system of Langfang City by sorting out the current situation of the natural geography,water resources and river network system of Langfang City in the plain area with multiple dams.Comprehensive analysis of the domestic and international applications of quantitative evaluation technology for river and lake connectivity in modern water networks,based on graph theory and complex network theory,a quantitative evaluation technology for river network connectivity in plain areas with multiple dams is proposed.propose a technical method for optimizing the connectivity and layout of regional river networks.Thereby providing technical support for improving regional water resources allocation,water storage and flood prevention and disaster reduction,ecological protection and restoration,and landscape enhancement needs.Taking Langfang as an example,this paper makes a quantitative evaluation of the connectivity of the river network water system in Langfang,and optimizes the connectivity layout scheme of Langfang.The main research contents and results are as follows:(1)Based on field research and related data combing,the natural geography,water resources,river network and water conservancy projects in the plain area with multiple dams—Langfang City are analyzed,and the characteristics of the river network in Langfang City are summarized.The uneven distribution of surface water resources in the river network system of Langfang City,the fragmentation of the river network structure,the difference in the scale and function of the river channel,According to the characteristics of the river network in Langfang City,it provides a theoretical basis for the optimization of the border weight indicators in the quantitative evaluation technology of the connectivity of the multi-dam plain river network.Based on the weighted adjacency matrix of the shortest path of the river network,the connectivity of the river network with multiple dams is quantitatively evaluated.(2)A quantitative evaluation method for the connectivity of the plain river network with multiple dams is proposed.Taking the main river as the skeleton,the ditches and the gates and dams in the river network as the connected objects,the social attributes of the river and the impact of water conservancy projects are considered.Based on graph theory,select the scale and function of the river channel,the capacity of sluices and dams,and the length of the river section as the edge weights.Through the weighted adjacency matrix of the shortest path of the river network,the connectivity of the river network with multiple dams is measured.Quantitative evaluation.The connection status of the river network under three scenarios in Langfang City is calculated.Scenario 1:Connecting all water systems in the study area;Scenario 2:Current river network system in the study area,that is,a river network without water transfer and flood control requirements;Scenario 3:Excluding siltated rivers in Langfang City and forming a river network with unobstructed rivers Water system composition.In the scenario,the connectivity of the river network in each region of Langfang City is north>central>south.In the second scenario,there is no connectivity among the regional river networks.In the third scenario,the connectivity of the river network in each region of Langfang is north>central>south.(3)An optimization evaluation method for the connection layout of the river network system in the plain with multiple dams is proposed,and the connection layout of the river network system in Langfang City is optimized.Through the process of "determining the importance of nodes and channels in the river network--setting the connectivity layout scheme of river network water system--quantitative evaluation of connectivity degree of river network water system in each scheme--comparing and optimizing the connectivity layout of river network water system",the final evaluation process of optimizing the connectivity layout of river network water system is achieved.The final selection of the layout of the river network and water system in the northern,central and southern parts of Langfang City:Option 10(0.1264),Option 13(0.0723),Option 10(0.0388).Therefore,option ten,option thirteen,and option ten are selected as the recommended schemes for the connectivity of the river network in the north,middle and south of Langfang City.