Study On The Temporal And Spatial Variation Law Of Blue-green Water And Its Influencing Factors In The Jing River Basin

Water resources are important natural resources required for human life and agricultural production.In the process of water consumption,water resources are usually divided into blue water and green water due to the different sources of water consumption.With the rapid development of society,blue and green water resources are increasingly affected by human activities and climate change,and the problem of shortage and imbalance of blue and green water resources has emerged one after another around the world.Especially in the arid regions of northwest China,where the water ecology is fragile,the Jing River basin,as a secondary tributary of the Yellow River basin,plays a very important role in maintaining the stable development of the regional ecosystem by studying the spatial and temporal distribution of its blue and green water resources and the main factors affecting them.Therefore,this paper uses the Jinghe River basin as the study area and builds a SWAT model based on geographic and hydrometeorological data to quantitatively analyze the amount of blue and green water resources in the basin and to clarify the extent to which climate and land use scenarios affect blue and green water resources.Firstly,the SWAT model was established by combining basic data such as DEM elevation data,meteorological database,land use and soil database in the basin area;the model was calibrated and validated based on the monthly runoff data from Zhangjiashan hydrological station,the main stream outlet hydrological station of Jinghe River basin;then the blue and green water volumes were calculated by the output of SWATOutput of the SWAT model;finally,the quantitative analysis of blue and green water volumes in the basin Finally,we quantified the response of blue-green water to climate change and land use in the watershed.The main results obtained in the thesis study are as follows:(1)The long series of change patterns of blue-green water resources-related elements such as hydro-meteorological elements and land use patterns in the study area were analyzed,and the analysis results showed that the Jing River basin showed a significant increasing trend in temperature and a non-significant increasing trend in precipitation during the period 1970-2019;the average annual runoff fluctuated and changed.The land use types in the Jing River Basin have formed a pattern with grassland as the absolute dominant,unused land and forest land as the main types,with a smaller proportion of arable land,water and construction land.the magnitude of changes in land use types in the Jing River Basin during 1995-2015 is not significant.(2)The SWAT distributed hydrological model of the Jing River Basin was established based on geographic information and hydro-meteorological data.The simulation results of monthly runoff from Zhangjiashan hydrological station in the Jinghe River basin during the rate period(1976-1996)and the validation period(1997-2019)achieved the expected results.Its determination coefficient R2 for the rate period is 0.87,Nash efficiency coefficient NSE is 0.86,and the relative error Re is 8.71%;the determination coefficient R2 for the validation period is0.83,Nash efficiency coefficient NSE is 0.78,and the relative error Re is 10.85%.(3)The hydrological model simulations reveal the differences of blue-green water resources in the Jinghe River basin under different land use types and climate change.The spatial distribution pattern of blue and green water resources showed an increasing trend from the northwest to the southeast;the spatial distribution of green water coefficient showed a trend of high in the northwest and low in the southeast.Under the single climate scenario,from scenario 1(1970-1989)to scenario 3(2000-2019),the green water volume tends to increase;the blue water volume and green water coefficient both show a decreasing trend;the spatial distribution of blue and green water volume shows an increasing trend from northwest to southeast regions;the green water coefficient shows a decreasing trend from northwest to southeast regions.Under the single land use scenario,from scenario 1 to scenario 3,the green water volume tends to increase,while the blue water volume and green water coefficient tend to decrease;the spatial distribution of blue and green water volume shows an increasing trend from the northwest to the southeast;the green water coefficient shows an overall trend of high in the northwest and low in the southeast.By comparing the contribution of climate change and land use change to the blue-green water quantity,it shows that climate change contributes more to the blue-green water in Jinghe River Basin.(4)The degree of influence of climate change and land use on blue-green water resources in the basin was studied and clarified.Under the combined effect of meteorological and land use factors,the contribution of climate change to blue water quantity in Jinghe River basin is72.6% and 81.4% to green water quantity;the contribution of land use change to blue water quantity in the basin is 28.4% and to green water quantity is 18.6%.