Study On The Connectivity And Regulation Of The Middle And Lower Reaches Of The Yellow River Under Urban Development

River and lake systems are the main carriers of water resources,which are drastically changed under the combined effects of climate change and human activities.As an important attribute of river and lake systems,river-lake system connectivity has become an important water management strategy in China in the new era of rapid urban development.In order to promote ecological environmental protection and highquality development,a series of river-lake system connectivity projects have been implemented in the Yellow River basin to accelerate the construction of regional water networks,so it is important to conduct research on river-lake system connectivity and its regulation in the Yellow River basin for the construction of ecological civilization in the new era.This paper takes Luoyang city in the middle and lower reaches of the Yellow River basin as the study area,evaluates the connectivity of urban "naturalartificial" river network based on the analysis of the evolution of water system in the context of urbanization development,and discusses and analyzes the regulation and control strategies of water system connectivity in Luoyang city,in order to provide scientific basis for the ecological security of rivers and lakes in the Yellow River basin and the sustainable development of ecological environment.The main contents and results of the study are as follows The main research contents and results are as follows:(1)Urban development process and its impact on river network water system.Taking the period of 2005-2020 as the study period,land use data,population data and economic development data are selected to measure the urbanization process;the evolution pattern of water system structure is explored from three aspects:quantitative characteristics,structural characteristics and connectivity characteristics;correlation analysis is made between urbanization-related indicators and water system structurerelated indicators.The results show that:the construction land area increased,the arable land and water area decreased,the comprehensive index of land use degree increased,the urbanization rate of population increased,the city’s GDP increased by 361%,and the proportion of non-agricultural output value increased year by year;the density of river network and water surface rate decreased,the rivers tended to be simpler and more trunked,and the connectivity of water system increased;the development of the city was significantly correlated with the changes in the number,structure and connectivity of river network water system.(2)Evaluation of the connectivity of river networks and water systems.A comprehensive connectivity evaluation model coupled with linkage number and graph theory was created to evaluate the river network composed of major rivers and water system connectivity projects in Luoyang City by selecting natural morphology.hydraulic function,ecological function indicators and combining the overall structure,and deriving the connectivity rating value of each river section in Luoyang City and the importance ranking of water system connectivity projects.It also reflects that the overall river network connectivity in Luoyang City still needs to be improved.(3)River and lake water system connectivity regulation.Using the monthly minimum ecological flow meter algorithm and the monthly frequency calculation method to estimate the minimum ecological water demand and the appropriate ecological water demand of the rivers in Luoyang City at a total of 54,366,652,000 m3 and 153,877,500 m3,respectively,and to propose an ecological water replenishment scheme jointly supplied by water supply,water diversion and recycled water;The Minimum Cumulative Resistance model(MCR)and gravity model were used to extract 29 potential ecological connectivity corridors with a total length of about 1294.69 km,and suggestions were made to increase the planning of water system connectivity projects in the southwestern part of Luoyang City to optimize the ecological connectivity pattern;Suggestions are made for the management and restoration of water system connectivity in Luoyang City in terms of both engineering and non-engineering measures.