| Because the climate in most areas of China are strongly affected by monsoon climate,the distribution of rainfall in China is extremely uneven in time and space.In recent years,due to the influence of human activities,the climate change in the Weihe River Basin is more sensitive and the ecological environment is more fragile.Extreme drought and flood disasters occur from time to time,which have a great impact on regional social and economic development in China.In the context of global paleoclimatic hydrology research,this paper focuses on analyzing both the measured hydrometeorological variation and the aggregated growth scale hydro meteorological variation,aiming to determine the hydrological and meteorological changes roundly and accurately,and providing data support and theoretical basis for river basin water resources management,ecological function area construction,regional flood control and drought relief.Taking the part – Guanzhong area of the Weihe River as the research area,this paper analyzed the measured and long-term meteorological and hydrological data in the study area from multiple angles.The main research results are as follows:(1)Using the method of literature and historical data collection,the paleoclimate and palehydrological events in the study area were integrated.It was found that the Weihe River Basin was in several periods of long-scale alternation of dry and wet,cold and warm,and climate fluctuation since 14640 a BP.And the precipitation and runoff of individual months in centennial scale and the drought and flood of the Weihe River Basin in Guanzhong area in centennial scale were also determined.(2)Moving average,variation coefficient,concentration degree and concentration period,Morlet wavelet analysis,Mann-Kendall non-parametric test and other methods were used to analyze the interannual and annual variation,period analysis and abrupt test of the measured precipitation and the runoff data.It was found that in recent 70 years,the annual precipitation and runoff of meteorological stations and hydrological stations showed a downward trend in the study area.The coefficient of variation of precipitation Cv was 0.21,the concentration degree was 44.91%-50.98%,and the concentration period was 188.79°-193°.The coefficient of variation of runoff Cv was 0.50,the concentration degree was 41.63%-43.49%,and the concentration period was calculated as 220.28°-220.59°.Morlet wavelet analysis shows that there were two main oscillation cycles of annual rainfall and three main oscillation cycles of annual average discharge in the study ares.M-K mutation test shows that the frequency of annual precipitation series mutation was higher than that of annual runoff mutation.Using SPI index algorithm and anomalous percentage algorithm combined with rainfallrunoff index drought grade table,the precipitation and runoff data were converted into drought/flood grade series for inter-annual and inter-annual drought/flood event frequency analysis.From 1965 to 2019,the annual frequency of drought and flood disasters in the study area was about 30.6%,drought was about 15.87%,and waterlogging was about 14.73%.The frequency of drought in spring and autumn is high,and the frequency of waterlogging in summer and autumn is high.(3)The existing precipitation datas in the study area were collected,and the long-scale precipitation series from April to August of 1535-2005 in Guanzhong area of Weihe River Basin were integrated by comprehensive proportional method and weighted average calculation.Drought/flood grade series,DWI series and drought/flood grade series of historical datas were transformed from precipitation/runoff data(long scale and measured data).The weighted mean and comparative calculation methods were used to integrate the drought/flood grade series of1500 to 2019,and its accuracy was verified.(4)According to the analysis of the aggregate growth scale precipitation series,it was found that the precipitation presents a downward trend,but the downward trend was obviously less than the measured precipitation downward trend.Meanwhile,it was found that the integrated precipitation data had more or less precipitation in many periods.By comparing the rainfall ensemble series with different monsoon indices,it was found that the variation trend of rainfall ensemble series is basically the same as that of EASM series and SASM series,showing that the climate change in the study area was significantly affected by the Asian monsoon.Through the mutagenicity test,it was found that the integrated precipitation change sequence had a mutation in 1954.Based on the analysis of the integrated drought-flood grade data from 1500 to 2019,it was found that the study area was more prone to drought,and the drought-flood grade generally developd from drought to wet and then to drought.According to the classification of severe drought,severe flood and above events,the frequency of drought and flood events was 22.88%,drought and flood events were 12.88% and flood and flood events were 10% in the past 520 years.Through the Morlet wavelet analysis and mutation test,it was found that the drought/flood index has obvious periodic changes in 520 years.The drought/flood index showed several abrupt changes from 2002 to 2019,indicating that the level of drought/flood was not stable at the present stage. |
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