Characteristic Analysis Of Extreme Meteorological And Hydrological Events In Weihe River Basin

As the largest tributary of the Yellow River,the Weihe River Basin belongs to an arid and semi-arid climate zone.In recent years,extreme temperature and precipitation events such as high temperature,floods and droughts have occurred frequently,which has brought problems to the rational allocation of regional water resources and has become a constraint on the economic development of the Weihe River Basin.A "threshold".Therefore,actively carrying out the analysis of the temporal and spatial laws of extreme climate and hydrological events in the Weihe River Basin will help to understand the trend of future hydrological and climate change in the Weihe River Basin,and have certain reference significance for the rational allocation of water resources in the basin and flood prevention and mitigation in the future.The main results achieved are as follows:(1)Analysis of the temporal and spatial laws of extreme temperatures.Using the daily maximum and minimum temperature data of the Weihe River Basin from 1960 to 2008,10 representative extreme temperature indexes were calculated.The daily maximum,minimum data and extreme temperature index are analyzed for trend,persistence,abruptness,periodicity and spatial law.The results show that the overall daily high temperature of the basin shows a downward trend,and the daily low temperature trend is not significant;the extreme low temperature is extreme and extreme The high temperature is on the rise and has a positive sustainability;the daily maximum temperature mutations mostly occurred in the mid-1990 s,and the daily minimum temperature mutations mostly occurred in the 1960 s to the1970s;most extreme temperature indexes have a long first main cycle 28a;The spatial law shows that the high temperature in summer and warm winter in winter are more serious in the middle and lower reaches of the Weihe River.(2)Analysis of the temporal and spatial laws of extreme precipitation.Using daily precipitation data from 1960 to 2008 in the Weihe River Basin,10 extreme precipitation indexes were calculated,and the temporal and spatial laws of daily precipitation and extreme precipitation indexes were analyzed.The results show that most of the daily precipitation and extreme precipitation show a downward trend,and the extreme precipitation will continue for a period of time in the future;the daily precipitation mutation time is relatively scattered;the extreme precipitation cycle range is 12-28a;the spatial law shows that the precipitation in the Weihe River Basin is moving toward the total The amount is reduced,and the intensity is more concentrated.(3)Analysis of the temporal and spatial laws of extreme runoff.Using daily runoff data from 5 control stations in the Weihe River Basin(Linjiacun,Xianyang,Huaxian,Zhangjiashan,and Zhuangtou)from 1960 to 2008,a total of 49 years of daily runoff data were used to calculate 5 extreme runoff indexes,and the daily runoff data and extreme runoff data were analyzed.The results show that both daily runoff and extreme runoff in the Weihe River Basin show a downward trend,and the trend is positive and continuous;sudden changes in daily runoff mostly occurred in 1970;the first major cycle of extreme runoff was around 15 years;Gumbel Copula was used to establish Xianyang-Zhangjiashan,The joint probability distribution model of the extreme daily runoff(Max1d)index of the two combinations of Zhangjiashan and Zhuangtou,using Clayton Copula to establish the joint probability distribution model of the Huaxian-Zhuangtou one-day extreme runoff(Max1d)index,and the tributary and main stream,The analysis results of the probability of extreme runoff encounters between tributaries and tributaries can provide references for downstream flood prevention and disaster prevention.(4)Correlation analysis of extreme precipitation,extreme temperature and extreme runoff.Extreme precipitation events in the Weihe River Basin are affected by annual precipitation.As annual precipitation increases,the intensity and frequency of extreme precipitation events will also increase.However,extreme precipitation is basically not affected by extreme high temperature and extreme low temperature,and the correlation between the two is weak.According to the relationship between precipitation and runoff physics,two indexes of maximum precipitation in five days(Rx5day)and maximum runoff in one day(Max1d)are selected to establish their joint distribution,and their correlation is analyzed,in order to provide reference for disaster prevention and mitigation in the basin.