Variation Characteristics And Driving Factors Of Runoff In The Upper Yellow River

The Yellow River is the largest water supply source for Northwest China and North China,but there is a serious shortage of water resources and the conflict between human and water is prominent.The social and economic development in the basin is seriously limited by the supply of water resources,and the understanding of the water resources issues of the Yellow River is related to the high-quality development of the Yellow River basin.Therefore,firstly,Analyzed the characteristics of runoff changes in the main water-producing area of the Yellow River basin(the upper reaches of the Yellow River)during the past 60 years,secondly,explored the driving factors which caused the runoff changes and clarified the main reason of runoff changes,To provide a reference for the integrated management and scientific and rational allocation of water resources in the Yellow River Basin.The upper reaches of the Yellow River above the Toudaoquai hydrological station are used as the study area.It is divided into 3 sub-study areas based on the physical geography and the drivers of runoff formation and change,including Zone?(above Tang Naihai station),Zone ?(Tang Naihai-Xia Heyan station),Zone ?(Xia Heyan-Tou Daokuai).Trend and abrupt change analysis were carried out for the runoff climate elements of the upper Yellow River and it's sub-areas,then,A correlation analysis of between them was performed.Statistical and comparative analyses of the drivers of runoff change in each zone of the upper reaches:subsurface factors,human water use conditions,were conducted separately.The relationship between the variability characteristics of the upper Yellow River runoff and its driving factors is clarified.In addition,quantified the main causes of runoff changes in the upper reaches were also analyzed.The main study findings are as follows.(1)The runoff of the upper Yellow River declined significantly at a rate of 1.94 billion m~3/10 a from 1956 to 2017,with an abrupt change in 1986,when the runoff decreased by 8.6 billion m~3 on average from 1986 to 2017,a reduction of up to35%;the runoff of all three subzones showed a decreasing trend,with zones II and III being more significant,with zone I in 1989,zone II in 1968 and 1988,and zone III produced runoff fluctuations in 1997,respectively,and the average value of runoff decreased after the fluctuations.(2)Among the climatic factors,the change of precipitation affects the long-term change of runoff;the increase of temperature and evapotranspiration promotes the decreasing trend of runoff in zones ? and ?;among the subsurface factors,the small part of permafrost degradation due to the increase of temperature may have a smaller impact on the annual runoff in zone ?;the increase of irrigation area and the increase of human water withdrawal also lead to the decrease of runoff,and zone ? > zone ? > zone ?;the large reservoir directly regulates the annual seasonal runoff,which is the direct cause of the abrupt change of runoff,i.e.the completion of Longyangxia Reservoir in 1986 and the beginning of water storage caused the abrupt change of upstream runoff.(3)Considering Zone I as the reference period,quantitative analysis of the influence of precipitation and other factors on the change of runoff in Zone II and III,the study found that the influence of precipitation on runoff in Zone II accounted for 37.23% and other factors accounted for 62.77%;the contribution of precipitation in Zone III was 30.97% and other factors was 69.03%.