Correlation Analysis Of Runoff In Typical Sections Of Seven Watershed In China Based On Connection Number

The water regime of seven major river basins in China,such as Songhua River,Liaohe River,Haihe River,Yellow River,Huaihe River,Yangtze River and Pearl River,affects nearly 80% of the Chinese population.The atmospheric circulation in East Asia is an important factor affecting the water regime of each basin in China.Every year,the main rain belt of summer monsoon passes through South China,Jianghuai Basin,Huanghuai Basin,North China and Northeast China one after another,forming a precipitation process in each basin,and then causing the runoff of typical sections of the seven basins to change.In order to discuss the correlation of runoff in these basins,based on the monthly runoff data of Harbin Station in Songhua River Basin,Tieling Station in Liaohe River Basin,Panjiakou Station in Haihe River Basin,Huayuankou Station in Yellow River Basin,Bengbu Station in Huaihe River Basin,Datong Station in Yangtze River Basin and Wuzhou Station in Pearl River Basin from 1981 to 2021,the variation law of runoff and the correlation between flood and drought in each basin were analyzed.According to the differences of geographical location and climatic characteristics of each basin,taking the Yellow River as the boundary,the seven basins in China are divided into Songhua River Basin,Liaohe River Basin,Haihe River Basin in the north and Yellow River Basin,Huaihe River Basin,Yangtze River Basin and Pearl River Basin in the south.This paper analyzes the annual distribution,annual variation trend and abrupt change of runoff of representative hydrological stations in each basin,uses the mean standard deviation method,set pair analysis method and fuzzy set pair analysis method to divide the annual runoff of each hydrological station,establishes the correlation analysis model of runoff of representative hydrological stations in seven major basins based on the connection number,and quantitatively calculates the correlation degree between hydrological stations in two groups of time scales,which provides theoretical support and reference for further understanding the variation trend of runoff in major basins and the relationship between them.The main research results are as follows:(1)In order to master the long-term runoff variation law of each basin,the annual distribution,annual variation trend and abrupt change characteristics of runoff at typical sections of each basin are studied and analyzed by mathematical statistics.The results show that: The annual runoff of the representative hydrological stations in the seven major river basins is mainly concentrated in the flood season,and the average peak months of Harbin Station,Tieling Station,Panjiakou Station,Huayuankou Station,Bengbu Station,Datong Station and Wuzhou Station are August,August,August,July,July and June,respectively.The non-uniformity of runoff in the representative hydrological stations in the northern basin is greater than that in the southern basin.Except for Bengbu station in Huaihe basin,the annual runoff distribution of other representative stations tends to be uniform,and the runoff concentration basically shows a downward trend.Except Datong Station and Wuzhou Station,the annual runoff of other representative stations showed a decreasing trend.The runoff of each representative station showed a downward trend in flood season,among which Harbin Station,Panjiakou Station and Huayuankou Station decreased significantly in flood season.The annual runoff of Harbin Station,Panjiakou Station,Huayuankou Station and Wuzhou Station suddenly changed around 1999,2000,1995 and 1993,respectively.The flood season runoff of Harbin Station,Tieling Station,Panjiakou Station,Huayuankou Station,Datong Station and Wuzhou Station was in 1999,1999,2000,1991 and 1991 respectively.This paper systematically studies the runoff characteristics of typical sections in each watershed and the relationship between watersheds,in order to provide the basis for forecasting and early warning of flood control and drought resistance in watersheds and measures for water resources development and utilization.(2)In order to objectively describe the state of runoff abundance in each watershed,based on the mean standard deviation method and set pair analysis method,and considering the annual distribution of annual runoff,a fuzzy set pair analysis method is put forward and applied to the annual runoff abundance grade evaluation in each watershed.The results show that: The average standard deviation method determines that the dry year,the normal year and the wet year of each hydrological station account for about 33%,and the set pair analysis method determines that Harbin Station,Tieling Station,Panjiakou Station,Huayuankou Station and Bengbu Station have the highest frequency in the dry year,while Datong Station and Wuzhou Station have the highest frequency in the normal year.When fuzzy set pair analysis is used to divide the flood and drought levels,the highest probability of occurrence of each station is in a normal year.Because the fuzzy set pair analysis method can fully consider the contribution degree of monthly runoff in the statistical years,it makes the division result of abundant and dry season reliable.By comparing the results of various assessment methods,it can provide theoretical guidance for solving the evaluation problems of water resources in various river basins in the later period.It is of scientific significance to use scientific and effective evaluation model to divide the annual runoff level of each basin,so as to know the occurrence law of flood and drought disasters in China.(3)In order to analyze the variation characteristics and correlation of runoff in typical sections of each watershed,on the basis of calculating the combination probability of runoff between hydrological stations by traditional mathematical methods,a correlation analysis model of runoff in watersheds based on connection number is established and applied to the correlation analysis of runoff in seven watersheds in China.The results show that: The runoff of Panjiakou Station and Wuzhou Station in flood season is the most prone to continuous flood/even flood/continuous drought,while that of Datong Station in flood season is the most prone to the alternation of flood and drought,and the evolution of flood and drought in Bengbu Station and Wuzhou Station is highly synchronous.The multi-year average maximum monthly runoff of Panjiakou Station and Huayuankou Station is the most prone to continuous peak/even peak/continuous dry season,and the multi-year average maximum monthly runoff of Bengbu Station is the most prone to the alternation of peak and dry season,and the evolution of peak and dry season in August of Tieling Station and Panjiakou Station has a good synchronization.The runoff consistency of representative hydrological stations in seven major river basins is negatively correlated with the distance between hydrological stations,and the consistency of runoff between hydrological stations in the northern river basin is stronger than that among hydrological stations in the southern river basin.It has the strongest correlation with flood season runoff of Tieling Station in Harbin,Bengbu Station and Datong Station,Datong Station and Wuzhou Station,and Huayuankou Station and Wuzhou Station have the weakest correlation.The correlation between the runoff of Tieling Station and Panjiakou Station in August is the strongest,that of Datong Station and Wuzhou Station in June,and that of Bengbu Station and Wuzhou Station in July is the strongest.In typical flood years of each basin,the runoff of representative stations in the corresponding basin is basically negatively correlated with other basins.The analysis and research on the runoff variation of typical sections in each basin and the correlation between runoff abundance and drought is of great practical significance to the flood control and drought relief work in the basin,and provides a new idea for the discussion of inter-basin water resources regulation.