Effects Of Climate Change And Human Activities On Hydrological Drought In The Kaidu River Source Region

Drought has been one of the key problems restricting the development of human society.Hydrological drought can reflect the relative level of imbalance between water supply and demand in the process of water circulation.As a good supplement to meteorological drought index,agricultural drought index and socio-economic drought index,the research results of analysis based on hydrological drought index will have a guiding role in the drought prevention and drought prevention in the region.Taking Kaidu River source region as the research object,this paper used CN05.1grid meteorological observation data to analyze the change trend and mutation point of meteorological factors and hydrological factors,so as to preliminarily determine the baseline period and human activity period.Based on the monthly runoff data,the percentage of runoff anomaly(R_a),hydrological dry wet index(D_i)and Standardized Runoff Index(SRI)were calculated;and the hydrological drought index suitable for the region was selected to analyze the variation trend of hydrological drought.Based on the hydrological drought index method,cumulant slope change method and climate elasticity coefficient method,the impact of climate factors and human factors on hydrological drought were quantified.The main results are as follows:(1)From 1979 to 2016,the annual average temperature in the Kaidu River source region showed a fluctuating upward trend,with an increasing rate of 0.34?/10a,and the year of abrupt change was 1990.The annual precipitation in this region showed an increasing trend,the increasing rate was 0.346 mm/10a,and the year of abrupt change is1986.The annual average runoff of the region showed an increasing trend,and the increasing rate of runoff was(7.713m~3/s)/10a,and the abrupt change of average runoff occurred in 1990.(2)The main land use types in Kaidu River source region were grassland,water body and unused land,and the cultivated land and construction land area were the smallest.The areas of cultivated land and forest land have not changed from 1980 to1990;but since 1990,the area of cultivated land has been increasing while the area of forest land has been decreasing.After 1990,human activities in the region have intensified.Based on 1990,forest land decreased by 13.19 km~2,grassland increased by2623.61 km~2 and water body decreased by 3617 km~2 in 2015.(3)According to the statistical data of drought for verification,SRI is a hydrological drought index more suitable than R_a,and D_i for the Kaidu River source region.As for the annual trend of hydrologic drought,the periods of serious hydrologic drought occurred in 1985 and 1986.As for the seasonal variation trend,the minimum values of spring,summer,autumn and winter hydrological drought index SRI appeared in April 1986,June 1986,November 1985 and December 1986,respectively,consistent with the annual trend.(4)Both climate change and human activities have impacts on hydrological drought.The contribution rate of climate change and human factors was 73.02%and26.98%respectively,based on the hydrological drought index method.According to the cumulant slope change method,the contribution rate of climate change to hydrological drought was about 97.04%,and the contribution rate of human activities was only2.96%.Combined with the method of climate elasticity coefficient,the contribution rates of climate change and human activities were 69.31%and 30.69%respectively.The contribution rate of climate change in the Kaidu River source region was relatively large,accounting for 69.31%?73.02%,and the contribution rate of human activities is about26.98%?30.69%.