Analysis And Driving Attribution Of Hydrological Variation Transfer Law In Wei River Basin

Since the 20 th century,global climate change has become increasingly intense,coupled with the impact of large-scale human activities,the hydrological system of the river basin has undergone significant changes,and the measured hydrological series often show significant nonstationary,resulting in severe challenges to the traditional hydrological and water conservancy calculation methods based on the stationarity assumption.Therefore,it is of theoretical significance and practical value for scientific and efficient management and rational development and utilization of river basin water resources to explore the mechanism of hydrological evolution and nonstationary changes in the changing environment.In this study,the Wei River basin was taken as the research object,and the trend,periodicity and variability of hydrological and meteorological elements were diagnosed.Based on the analysis of spatial and temporal transmission mechanism of variation types and variation,the potential influence of hydrological variation in the upper reaches of Wei River basin on the lower reaches was explored,and the main driving sources of hydrological variation in each region were clarified.In addition,based on the quantitative analysis of runoff changes in Wei River basin and various regions,the driving factors of hydrological variation types in different regions were analyzed from meteorological conditions,water conservancy projects,vegetation cover,land use,social economy and other aspects,and the leading factors of various variation types occurred on a large scale in Wei River basin were found out.The main research results of this paper are as follows:(1)A baseline survey was conducted on the geographical location,topography,water system distribution,hydrometeorology,vegetation cover and land use,water conservancy project construction,and social economy of the Wei River basin.Through the analysis,it can be seen that hydrometeorological elements such as runoff and precipitation in the Wei River basin showed a decreasing trend over time.The vegetation cover in the basin showed a good trend under the influence of the policy of returning farmland to forest and grassland.The cultivated land area showed a downward trend;Many water conservancy projects(reservoirs,warping dams,etc.)were built in the river basin in the 1970 s,which had a great influence on the change of runoff.The socio-economic development in the basin has been rapid,especially after 2000,the water consumption has increased sharply,and the problem of supply and demand continues to exist.Based on the study and analysis of the baseline of Wei River basin,it is found that the Wei River basin has been greatly influenced by human activities since 1970 s,and the temporal and spatial distribution of human influence has caused complex hydrological changes in the basin.(2)According to the trend test of the hydrometeorological elements in Wei River basin,it is found that the hydrometeorological elements in Wei River basin have shown a significant trend of decline since 1990 s.Through the periodic analysis of runoff and precipitation data in Wei River basin,it can be found that the main cycle of runoff in Wei River basin is basically maintained at about 30 years,while the main cycle of precipitation series is around 35 years.Based on the diagnosis results of mean value and variance variation points of runoff,precipitation and sediment data from major hydrological stations in Wei River basin,it can be seen that the mean value variation and variance variation occurred on a large scale in Wei River basin in the 1970 s.(3)The runoff variation period was delimited,and the hydrological variation was divided into five types(?-? type).The driving quantity of variation in the measured runoff series of each hydrological gauge was deduced by using quantitative separation method,and then the hydrological variation transfer mechanism of Wei River basin was sorted out.When the transfer mechanism of mean and variance variation driving is considered simultaneously,the variation driving amount of each hydrological station will change,and the driving amount will be superimposed or offset.This indicates that when the runoff series of a station is nonstationary,it may be caused by the coupling of multiple driving factors.The results show that 64.7% of the hydrologic variation driving quantity in Wei River basin comes from the source of the main stream,35.3% came from the tributaries;In the main stream,the Beidao-xianyang interval and the Xianyang-huaxian county interval are the main sources of the variation driving quantity,accounting for 32.9% and 24.9% respectively,that is,the hydrologic variation source of the Wei River basin is mainly the middle and lower reaches.In addition,the study found that in the tributaries,the Zhangjiashan,Hulu river,Hei river and Qian river are also the main driving sources of hydrologic variation in the Wei River basin.(4)Based on the analysis of the driving mechanism of hydrological variation in Wei River basin,it can be seen that the variation of runoff in Wei River basin is mainly caused by the change of climatic factors and human activities,and human activities have become the leading factor affecting the variation of runoff.The influence of climate change on runoff is mainly reflected in the decrease of precipitation and the change of evapotranspiration.In view of the above the Beidao,Beidao-xianyang,Zhangjiashan and Xianyang-huaxian,from the meteorological conditions and water conservancy project construction,vegetation cover and land use,social and economic driving factor variation analysis,the results show that the ? type of hydrological variation of Wei River basin is mainly caused by the water conservancy project construction in the 70 s,causing ? kind of Wei River basin hydrological variation occurs is probably the main motors of the meteorological factors in the evaporation of significant change,Cause large-scale basin ? class hydrological variation of main drive may be basin precipitation reduction and increased social demand due to the development of social economy and the area of the joint effect of the construction of the water conservancy project.