Quantitative Study Of The Effects Of Climate Change And Human Activities On The Runoff In The Wuding River Basin

For a long time,increasing human activities have intangibly affected the earth's climatic environment,and the water cycle system is affected by the cyclical mutual feedback system of human activities and climate change.The redistribution of resources on the dual scales of time and space is continuing.In recent years,more and more attention has been paid to the research on the impact of climate change and human activities on water resources.The society and the government have managed to allocate and use water resources more rationally through various methods based on the research results.Under this background,the Wuding River Basin,the first tributary of the Yellow River in Yulin area of Northern Shaanxi Province,is taken as the research area.Based on the long series of hydrometeorological data,the time series of Hydrometeorological elements in the Wuding River Basin are mainly analyzed by means of Mann Kendall trend test,Mann Kendall mutation test,Pettitt mutation test,cumulative anomaly curve,linear regression and other methods Trend and mutation characteristics.Using the FAO Penman Monteith formula and the inverse distance weighting method?IDW?to calculate the annual potential evapotranspiration?ET₀?of the long series in the Wuding River Basin.Based on Budyko's hypothesis of water and heat coupling balance equation,sub basins are divided by Arc GIS hydrological analysis,spatial interpolation based on inverse distance weight method?IDW?and the first partial derivative of CY equation are used to quantitatively analyze the contribution of climate change and human activities to runoff change in the Wuding River Basin and its sub basins.NSE efficiency coefficient and fit index are used to verify the applicability of elasticity coefficient method based on Budyko assumption in the Wuding River Basin.The influencing factors of human activities combined with NDVI data are discussed more clearly.The main conclusions drawn are as follows:?1?The precipitation in the Wuding River Basin decreased in 66.67%stations,runoff in83.33%stations,and potential evapotranspiration in 83.33%stations.The occurrence point of mutation varied from 1988 to 1998,and the situation of each sub basin was different.The occurrence point of runoff mutation in the Wuding River Basin is 1996.?2?Dali River Basin?No.1?,Upstream of Wuding River?No.3?,Huaining River Basin?No.5?have similar trends in elasticity time-course changes;Lu River Basin?No.2?,Hailiutu River basin?No.4?and Yuxi River Basin?No.6?have similar trends in elasticity coefficients over time;runoff in Lu River Basin?No.2?is most sensitive to climate change and human activities,and Dali River Basin?No.1?is the least sensitive to the impact of climate change and human activities.?3?The accuracy of the model simulation is verified by comparing the simulated runoff and the actual runoff.The results show that the simulation accuracy is very high.The fitting degree of the simulated runoff and the actual runoff reaches 0.9946,and the Nash efficiency coefficient E=0.9891.It can be concluded that the simulation effect of the model is good and the reliability is high.It is proved that the balance equation of water and heat coupling based on Budyko hypothesis is suitable for the hydrological study of the Wuding River Basin.?4?The leading factors of runoff changes from the base period to the abrupt change period in Dali River Basin?No.1?,Upstream of Wuding River?No.3?and Huaining River Basin?No.5?are climate changes,and climate change factors have the greatest impact on runoff,it is because of the reduction of precipitation;the main factors of the runoff changes in the Lu River Basin?No.2?,Hailiutu River basin?No.4?and Yuxi River Basin?No.6?from the base period to the abrupt change period are human activities.?5?According to the correlation analysis results of vegetation coverage M and underlying surface parameter n,it can be found that the Wuding River Basin and its No.2,No.4 and No.6 sub-basins All of them show extremely significant positive correlations,while the sub-basins of No.1,No.3,No.5 show extremely significant negative correlations.Changes in conditions and land types are the reasons for this anomaly.In general,vegetation coverage can reflect the change of the underlying parameter n to a certain extent.The research methods and results will provide a theoretical basis and different ideas for the attribution of runoff in the arid and semi-arid areas of the Loess Plateau.The technical methods used in this paper can all be borrowed from other rivers in the arid and semi-arid areas and have certain value in popularization and application.