Analysis On The Change Of Water System Connectivity In Daqing River Basin From 1980 To 2017

The river system is the carrier of water resources.The unobstructed river system plays a key role in ensuring the safety of hydrological storage,habitat safety and improving the water and soil environment.It is an important condition for maintaining the river ecosystem.In recent years,due to the extensive economic development model and the over-exploitation of water conservancy projects,the layout and connectivity of the rivers and lakes have undergone significant changes,resulting in serious flooding in some river basins and serious deterioration of the water ecological environment.problem.Therefore,the study of the interannual variation of the connectivity patterns and functions of rivers and lakes is essential for grasping the evolution of regional river systems,and can provide a basis for the ecological restoration and management of regional river systems.The Beijing-Tianjin-Hebei region is located at the core of China's Bohai Rim,and its economic scale is the largest in northern China,but it also faces extremely serious ecological problems.Due to frequent human disturbances and climatic conditions in the region,the river water system connectivity has changed dramatically,the flow is severe,and the freshwater environment is fragmented.As a result,the flood storage capacity gradually declined,the water environment was seriously degraded,and the production and life of the region had different degrees of negative impact.Therefore,this paper takes the Daqing River Basin in the hinterland of Beijing-Tianjin-Hebei as an example to carry out the interannual variation of the water system structure and functional connectivity in the Daqing River Basin,and analyzes the interannual variation of the potential flood risk in the basin based on the change of the river network.Carry out a comparative analysis of the inter-annual variation laws.It is of great significance for the management department to carry out the reconstruction and restoration of the water system network in the Daqing River Basin by revealing the changes and influences of the water system connectivity in the Daqing River Basin.The main research contents and results of this paper are as follows:(1)The evolution law of the structural connectivity of the Daqing River Basin.Based on the remote sensing image data of the Daqing River Basin in 1980,1990,2000,2010 and 2017,the corresponding river and lake data were extracted and the interannual variation analysis of the water system was carried out.The water system structural connectivity index evaluation system was constructed from two aspects of water system structure and connectivity form to quantitatively analyze the interannual variation of water system structural connectivity in the Daqing River Basin.The evaluation results show that since the 1980s,the basic parameters and structural indicators of the Daqing River Basin have declined as a whole,indicating that the Daqing River Basin water system is decreasing and the river network structure is simplified;The water system ring a,the node connection rate ? and the water system connectivity y index showed a significant change trend first and then increased,which indicates that the water system structural connectivity of the Daqing River Basin first deteriorated and then gradually recovered.(2)The evolution of functional connectivity of the Daqing River Basin.From the two aspects of the natural function and social function of the water system,the evaluation system of water system functional connectivity index was constructed,and the functional connectivity of the water system was quantified by means of the set pair analysis method to analyze the functional connectivity of the Daqing River Basin.The law of change.The evaluation results show that the functional connectivity of the Daqing River Basin is generally at a moderately lower level.And in the 1990s,the natural,social functions and comprehensive functional connectivity of the Daqing River Basin water system reached the lowest value.(3)The evolution law of potential flood hazard in the Daqing River Basin.Based on the idea of disaster system,the flood risk assessment of Daqing River Basin is carried out,and the evaluation results are compared with the change law of water system connectivity.The evaluation results show that from the time point of view,the flood hazard of the Daqing River Basin declined from 1980 to 2017.The proportion of potential severely hazardous areas to total area gradually decreased from 4 years,accounting for 5.5%,5.1%,4.1%,and 4.0%,respectively.The potential medium-risk areas were 23.2%,25.8%,17.6%,and 16.7%in four years.From a spatial perspective,the potential hazard of flooding in the Daqing River Basin is similar to that of river water network changes,mainly distributed in the basin and eastern coastal areas.There is a negative correlation between the change trend of water system connectivity morphological indicators in the Daqing River Basin and the potential flood risk in the Daqing River Basin.Finally,this paper makes a preliminary discussion on the shortcomings of the research and the possible hot issues in the future.