Variation Diagnosis Of Hydrometeorological Elements In Weihe River Under Changing Environment Based On Multiple Methods

Under the changing environment,the hydrological factors of a watershed have changed significantly,which poses a severe challenge to the planning and management of watershed water resources.The study of hydrological variability and its driving factors under changing environment is of great theoretical significance and application value to enrich and develop the methods of non-consistent hydrological series analysis,as well as the utilization,development and management of water resources.In this thesis,the weihe River Basin is taken as the research object to clarify the relationship between rainfall and runoff,the variation characteristics and evolution law of rainfall and runoff.On the basis of eliminating the periodic interference of the sequence itself,the mutation diagnosis method is improved.The variation points of rainfall,runoff and rainfall-runoff relationship were also diagnosed.Finally,the main driving forces of climate change and human activities on the variation of rainfall-runoff relationship are quantitatively analyzed.The main achievements of this thesis are as follows:(1)Using wavelet analysis,Mann-Kendall rank test method and R/S analysis method,the periodicity,trend and persistence of annual precipitation,annual runoff,annual temperature and annual evaporation in different areas of the Weihe River are analyzed.The annual precipitation cycle is about 5,17,and 28 years.The annual precipitation shows a significant downward trend in Zhangjiashan,Beidao,and Linjiacun stations,and it will continue to be positive in the future.The cycle of annual runoff is about 6 or 17 years,and the annual runoff of each station is showing a significant downward trend,and there will be a positive sustainability in the future.The annual temperature cycle is about 15 to 26 years,and each station shows a significant increase trend,and there is a positive sustainability in the future.The cycle of annual evaporation is about 15 to 26 years,and all stations show an insignificant downward trend,and there is a positive sustainability in the future.(2)Based on cumulative anomaly method,sliding t method,Yamamoto method,Mann-kendall method,Pettitt method,and improved mutation diagnosis method based on EMD and approximate entropy to diagnose the variation of the Weihe River Basin.The variation of annual precipitation,annual evaporation and annual mean temperature in jinghe river and Beiluo River mainly occurred in the 1990 s.In the main stream and Beiluo River,the variation of annual runoff mainly occurred in the 1970 s and 1990 s,while in Jinghe River,it appeared in 1996.The relationship between annual rainfall and annual runoff in the main stream changed in the 1970 s and 1990 s,and in Jinghe river in1970 and 1997,and in Beiluo River in 1994.(3)The main driving forces of the variation of rainfall-runoff relationship were different at each station in the Weihe River Basin.Among them,human activities were the main driving force for the variation of rain-runoff relationship at Linjiacun station,Xianyang station(variation points 1 and 2),Lintong station and Huaxian Station(variation points 1 and 2),contributing 57.38% and 70.63%,75.83%,51.60%,53.79%and 51.55% respectively.Climate change was the main driving force at Beidao station(variation points 1 and 2),Zhangjiashan station(variation points 1 and 2)and Zhuangtou station,with contribution rates of 86.33% and 60.29%,63.15% and 58.67%and 173.06%,respectively.