Characteristics Of Temporal And Spatial Evolution Of Hydrological And Meteorological Drought In The Wei River Basin

Due to the effects of climate change and human activities,the runoff and rainfall in the Wei River Basin are constantly changing.The water resources in the basin are in short supply,and siltation and frequent droughts occur.Analyzing the temporal and spatial variation of hydrological and climatic droughts basin is of great significance for the scientific allocation of governance measures in the Wei River basin.Based on more than 50 years of hydrological and meteorological data from 2 hydrological stations and 20 meteorological stations in the Wei River Basin,this paper uses the Mann-Kendall trend test,wavelet analysis and PCA principal component analysis to analyze the temporal and spatial changes of hydrological and meteorological droughts in the Wei River Basin.Systematic analysis was conducted to investigate the mutability,periodicity,and trend changes.Finally,using the run-length theory to identify the main characteristics of drought in the Wei River Basin,based on this,the response relationship between hydrological drought and meteorological drought was established,the meteorological drought was calculated to correspond to the critical conditions of hydrological drought,and the time delay of hydrological drought corresponding to meteorological drought was calculated..The main conclusions are as follows:(1)The frequency of occurrence of meteorological drought in the Wei River Basin during 1960-2013 was over 50%,of which the frequency of light drought was relatively high,accounting for about 33%,and about 12% of the time was in moderate drought state.Between 3% and 5%.The frequency of meteorological droughts in the Wei River Basin since the 1970 s and the 1990 s is relatively high and the intensity is high.The frequency of occurrence of moderate drought in Basin I during the period from 2000 to 2009 was approximately 20%,and the frequency of occurrence of drought in 1970-1979 was approximately 15%.The frequency of heavy drought during 1990-1999 was about 10%.In c? atchment II,the frequency of moderate and severe droughts was also high,and the frequency of moderate droughts in 1970-1979 was 45%.The frequency of heavy drought in 1990-1999 was about 10%.There is a main cycle of 16-20 years in the meteorological drought in the Wei River Basin.(2)The Wei River Basin shows a weakening degree of drought in the eastern part of the country and a clear trend of aggravation of drought in the western region.The trend of aridization in different seasons is different,among which summer changes are most obvious.The M-K test value range of SPI is larger than that of SPEI,indicating that SPEI responds to drought changes more than SPEI because of the influence of evaporation.The frequency of drought occurrence in the Wei River Basin during the period 1960-2013 was between 48% and 55%,and the frequency difference in the study area was around 6%.The occurrence frequency of spring drought was high in the east and low in the west.The frequency of summer drought was generally lower than other seasons,and the frequency of drought in most parts of the basin was not much different.The frequency of autumn drought was roughly between 45% and 55%.From west to east,the frequency of winter drought is generally higher.(3)In 1960-2013,the frequency of hydrological drought in the Wei River basin was above 50%,of which 30% was in light drought state,12%-13% in moderate drought state,and the proportion of severe drought was about 3% to 5%.The probability of extreme droughts is small,generally not exceeding 1%.The hydrological drought in the Wei River Basin has the characteristics of alternating wet and dry.In the 1970 s and 1990 s,the hydrological drought was more serious,and the frequency of drought was high and the intensity was high.For the standard drought index(SDI),the Wei River basin is at normal-micro-dry level.The SBI mutations at Huaxian Station occurred in 1972,1982,and 1995,respectively,and the SBI mutations at the Zhangtou Station occurred around 1971,1984,and 2000,respectively.From 1970 to 1980,the SBI value of Huaxian Station and Zhuangtou Station was always less than 0 and showed a gradual decline.The Wei River Basin was in a state of continuous drought and the drought situation was intensifying.There is a main cycle of hydrological drought at Huaxian Station and Zhuangtou Station for about 16 years.(4)As the calculation scale of the drought index increases,the fewer identifiable droughts,the corresponding intensity of each drought increases.The largest drought in the basin 2 relative to the basin 1 was short and the drought intensity was small.In the calculation scale of 1,3,6 and 12 months,for basin I,when the critical duration of meteorological drought was 2.60,2.033,5.12,0.53,the critical intensity was 1.35,2.74,1.59,5.44;According to catchment II,the criticality of meteorological drought lasted 0.78,0.38,1.58,and-0.07,and the critical intensity was 1.37,0.10,-9.42,and 6.83.The response of hydrological drought in Wei River basin to meteorological drought is most sensitive when it lags 3 months.