Spatial-Temporal Variations Of Drought And Flood In The North-South Transitional Zone Of China

The north-south transition zone in China is not only rich in biological resources,but also an important water conservation area in China.It is also the water source of the South-to-North Water Diversion Project.The watershed of China is affected by its special topography and climatic conditions.The north-south transition zone in China has many types of natural disasters,high intensity,and severe disasters.In view of this,this paper analyzes the droughts and floods in the north-south transition zone of China,and reveals the differences in the droughts and floods in the transition zone,in order to provide a basis for drought and flood management and disaster reduction in the study area under climate change.This article uses the monthly precipitation and monthly average temperature of 32 meteorological stations in the study area from 1960 to 2015,supplemented by JRC annual water classification history and DEM remote sensing data,to calculate the comprehensive meteorological drought index CI,short-term drought and flood The sharp index SDFAI,based on the Penman formula and the cumulative distance equality method,is used to discuss the spatial and temporal laws and related mechanisms of the climate and drought and flood distribution at the multi-temporal scale in the north-south transition zone of China.The main content and results of the research work include:(1)The analysis of drought shows that the drought intensity,duration of drought and the frequency of droughts of different grades in the north-south transition zone of China showed an upward trend with time,and light droughts accounted for the largest proportion of all grades of drought,55.6% The occurrence of seasonal drought has the law of seasonal change,the intensity of spring drought is the largest,and the duration is longer,and the summer drought is the most prone to occur.The frequency of autumn drought generally shows a trend of increasing first and then decreasing.The duration of drought is relatively shortest.In 80% of the years,the duration of drought is 1 month;in terms of spatial changes,the northern part of the study area is relatively dry,the southern part is relatively humid,and southern Gansu is the wettest area in the entire study area The Wudu area and the Henan area in the study area are the driest.Based on the drought situation in the Wudu area,Wudu is presumed to be a drought-prone place in the study area.In addition,analysis of the influencing factors of drought shows that except for individual stations,precipitation and CI value are significantly positively correlated(P<0.01),indicating that with the increase in precipitation,the CI value also shows an increasing trend,the less likely it is to occur Drought;sunshine hours are significantly negatively correlated with the CI value(P<0.01),that is the more sunshine hours,the smaller the CI value;the average temperature is negatively correlated with the CI value(P<0.01),that is,the higher the temperature,the CI The smaller the value,the more drought;relatively speaking,the correlation between average wind speed and CI value is not obvious.(2)The study of floods shows that the occurrence time of floods in the watershed near Qinling Mountains is consistent in the long-term sequence,and has differences in a short time.From the analysis of the maximum flood peak flow,it can be seen that the flood intensity on the south slope of Qinling is greater than that on the north,and the east is greater than the west.On this basis,the increase of seasonal rivers and permanent rivers is analyzed: in the entire study area,Hubei Province has the most abundant water,Danjiangkou Reservoir is the area with the largest water surface area,and the change in water surface area from 2000 to 2012 is small In 2015,the water surface area increased significantly.In addition,the overall fluctuation of the water volume of seasonal rivers and permanent rivers is relatively smooth.Except for the extreme water volume of permanent rivers of 9.6 billion m3 in 2002,the water volume of permanent rivers in other years is less than that of seasonal rivers.The total amount of water presents a weak downward trend.(3)Research results of drought and drought rapid turnover: When the short-term drought and drought rapid turnover index value is plus or minus 1,it can be regarded as the critical value of the occurrence of severe drought and drought turnaround.The drought and waterlogging in the study area is mainly composed of drought and waterlogging.The most severe months of drought and waterlogging are from July to August,and the most severe area is Huashan.The correlation between the drought and flood rapid index and precipitation presents a markedly low west and east high,and the north is low and the south is high.The maximum value is concentrated in Shaanxi and Henan,and the correlation coefficient of Henan is greater than 0.13.In addition,different terrains respond differently to the drought and flood rapid index.The frequency of drought and flood rapids in the plateau is the smallest,and the possibility of drought and flood rapids in the plains is the highest.