The Impact Of Land Use And Climate Change On Runoff In The Weihe River Basin

As one of the most important freshwater resources for mankind,runoff in the basin is mainly affected by climate factors and land use factors.The Weihe River Basin has a shortage of water resources and environmental change in the present.Cultivated land is the largest land use type of the Weihe River Basin,,accounting for47.5% of the total area of the basin(2000).In 2002,China has implemented “grain for green” policy on the Loess Plateau which has serious watershed problems.This measure had a significant influence on the land use type of the Weihe River Basin.In addition,the fifth assessment report of the IPCC has further confirmed the fact of global warming,and the impact of climate change on the Weihe River Basin will be further intensified.It is necessary to research the runoff response of the Weihe River Basin under the changing environment in the context of global climate change and large-scale changes in land use types of the Weihe river basin.And it has a great influence to alleviate the negative impact of water shortages in the Weihe River Basin.In order to obtain the future climate change of the Weihe River Basin,this paper processes data of the Can ESM2 global climate model under RCP4.5 ? RCP8.5meteorological emission path based on the SDSM model.Besides,this paper processes land use data based on the CA-Markov model to obtain the land use type of the basin in 2030?2050.The VIC model was used as a tool to simulate the monthly runoff changes in the Weihe River Basin from 1986 to 2015,and three scenarios including climate change scenarios,land use change scenarios,and comprehensive scenarios were set to quantitatively analyze the basin runoff response in the future environment.The main research conclusions are as follows:(1)Substitute the RCP4.5 and RCP8.5 meteorological emission scenario data under the Can ESM2 climate model from 2021-2050 into the calibrated SDSM model to generate future climate scenario data for the basin.The results show that the basin is in RCP4.5 and RCP8.5.Both of the two meteorological emission scenarios present the characteristics of increased temperature and increased precipitation.(2)Using the CA-Markov model,through the application of Markov chain and domain relationship analysis and simulation,the land use data of the river basin in2030 and 2050 are obtained.The results show that the largest land use type in the Weihe River Basin is cultivated land,and the land use change in the watershed is present.The proportion of cultivated land is declining rapidly,the proportion of grassland and forest land is gradually increasing,and the unused land and water bodies are almost unchanged.(3)Calibrate and verify the constructed Weihe River Basin VIC model.The results show that the regular relative error Er and Nash efficiency coefficient Ef are8.63% and 0.79,respectively,and the relative error Er and Nash efficiency coefficient Ef during the verification period are 12.6%,respectively.0.64,indicating that the VIC model has good applicability in the Weihe River Basin.(4)Set up three scenarios,including climate change scenarios,land use change scenarios,and comprehensive scenarios,and analyze the basin runoff response under different scenarios.The results show that under the two meteorological emission scenarios of RCP4.5 and RCP8.5,the runoff of the basin shows a decreasing trend;under the spatial pattern of land use in 2030 and 2050,the runoff of the basin shows an increasing trend;under the comprehensive scenario,that is,under comprehensive environmental changes,The runoff of the river basin shows a decreasing trend.(5)Comparing the runoff response between different scenarios,the results show that the runoff change in the basin is jointly affected by land use change and climate change,and the runoff response in a comprehensive environment is not equal to the superposition of the runoff response under two single element changes,namely The impact of land use and climate change on watershed runoff is non-linearly related.In the future environment of the Weihe River Basin,runoff changes in the basin will be mainly affected by climate change,and the impact of land use changes will be relatively weak.