Correlation Characteristics And Analysis Of Runoff In Typical Sections Of Yangtze River And Huaihe River

In order to explore the correlation characteristics and analytical problems of runoff in typical sections of two adjacent basins,this paper selects Datong and Zhengyangguan of Huaihe River as typical sections.Based on the daily average water level data of Datong of the Yangtze River and Zhengyangguan of the Huaihe River from 1951 to 2018,the water level is used to represent the state of runoff abundance and drought,and the characteristics of runoff abundance and drought are analyzed based on three time scales of year,month and day.The frequency method was used to classify the runoff abundance and drought levels,and the set pair analysis was used to analyze the runoff abundance and drought relationship at the annual,monthly and daily scales between the two typical sections.In addition,a set pair analysis with different lag periods was conducted on the runoff abundance and drought in June–July of each year between Datong of the Yangtze River and Zhengyangguan of the Huaihe River to explore the relationship between the runoff abundance and drought in Meiyu season and Huang-Huaiyu season formed by the movement of monsoon rain belt.Finally,aiming at the influencing factors of runoff abundance and drought in the Yangtze River and Huaihe River,the set pair analysis was used to quantitatively study the influence of subtropical high on runoff abundance and drought in the Yangtze River and Huaihe River Basin.The main conclusions are as follows:(1)In order to explore the runoff characteristics of Datong Station of the Yangtze River and Zhengyangguan Station of the Huaihe River at different time scales,the water level characteristics of two typical sections on three time scales were analyzed,and the following conclusions were obtained: On the annual scale,the interannual variation of the Yangtze River water level shows a non-significant increasing trend,and the Huaihe River shows a non-significant decreasing trend.On the monthly scale,the Yangtze River and Huaihe River are in the peak period of annual water level from May to September and from June to September,respectively.The highest proportion of wet months is July.On the daily scale,the water level of the Yangtze River and the Huaihe River Basin increased significantly in mid-June and late June,respectively,and the Huaihe River was about 1-2 pentads later than the Yangtze River.The time difference is basically consistent with the beginning of the Meiyu and Huanghuai rainy seasons.The multi-year daily average water level peaks of Datong of the Yangtze River and Zhengyangguan of the Huaihe River appear on July 10 and July 22,respectively.The time of the water level peaks of the Yangtze River and the Huaihe River Basin is basically consistent with the end of the rainy season in the basin.(2)Aiming at the problem of runoff correlation between Yangtze River Datong and Huaihe River Zhengyangguan,the runoff correlation between Yangtze River and Huaihe River is studied by set pair analysis method,and the following conclusions are obtained:The connection degree based on the daily scale is the largest,followed by the monthly scale,and the annual scale is the smallest.The smaller the time scale of the research data is,the higher the synchronization of runoff abundance and drought is.Analysis is made on the results of the lag-based connection degree obtained from the daily runoff data from June to July in Zhengyangguan,Huaihe River,which lags behind the Yangtze River Datong for 1-30 days.Identical degree reached a maximum when Zhengyangguan lags behind Datong for 7 days.The time difference of 7 days is close to the difference of about 10 days in the beginning time of rainy season between the Yangtze River and Huaihe River basins.The contact degree reaches maximum when Zhengyangguan lags Datong 26-29 days.Moreover,the lag time of 26 – 29 days can be corresponding to the time difference of 26 days that the rain belt affects the Yangtze River Basin and 3 days that the upper reaches of the Yangtze River converge to the downstream.At this time,the Yangtze River and Huaihe River Basin runoff synchronization is the best.(3)In order to explore the influence of climate factors on the correlation between runoff abundance and dryness between Datong of the Yangtze River and Zhengyangguan of the Huaihe River,the interannual changes of the four indexes of the Western Pacific subtropical high area index,intensity index,west extension ridge point and ridge line position were analyzed,and the following conclusions were obtained: The Western Pacific subtropical High experienced a significant mutation in 1983,1998 and2010.The runoff in the Yangtze River Basin has the greatest correlation with the subtropical high area and intensity index,and the synchronization is the best.The correlation degree of runoff abundance and drought with subtropical high area and intensity index in Huaihe River Basin is the second.The correlation between the Yangtze River and Huaihe River in the abnormal years of subtropical high in the western Pacific is higher than that in the normal years.When the area of subtropical high in the western Pacific is abnormally large,the intensity is abnormally strong,the west extension ridge point is abnormally west,and the ridge line position is abnormally south,the synchronization between the Yangtze River and Huaihe River is good,and the correlation between the runoff and the dry is high.Therefore,the West Pacific subtropical high is an important factor affecting the correlation between Yangtze River and Huaihe River runoff.