Quantitative Assessment Of Runoff Variation Attribution In Upper Zhanghe Basin Based On Hydrological Simulation

Research on water cycle under environmental change has become a hot issue in water science research in the 21 st century.Revealing the impact of environmental change on runoff has become an urgent issue for water resources management.The upper reaches of the Zhanghe River is located at the junction of the three provinces.The competition for water resources has frequently occurred,and it has become one of the sharpest water conflicts in the country.Quantitative evaluation of the attribution of runoff changes in the upper reaches of the Zhanghe River provides relevant evidence for water resources management in the basin,and is of great significance for achieving harmony between people and water in the basin.This study selected monthly runoff data and meteorological data from 1959 to 2017 in the upper reaches of the Zhanghe River,and used various statistical methods to analyze the annual runoff change trends and abrupt nodes of each hydrological station;Construct a distributed VIC model for runoff simulation in the upper reaches of Zhanghe River.Using the meteorological elements and underlying data as the scenario control factors to evaluate the model,the VIC model driving the impact of environmental changes on runoff is used to quantitatively assess the attribution of climate change and human activities to runoff changes.The results of attribution analysis were compared and verified.The results show:(1)The trends of annual runoff of the main stream of Zhang River and the two major tributaries(Zhuozhang River and Qingzhang River)are basically the same,and both show a significant decrease trend.The decrease rate of annual runoff of the two major tributaries is gradually increasing from upstream to downstream,and the decrease rate increases with the increase of the basin area.And the mutation occurred in the late 1970 s,the statistical analysis results of the mutation points of the annual runoff time series were combined with the investigation of human activities in the river basin.The base period for comprehensively judging the runoff time series is 1959-1978,and the change period is 1979-2017.(2)Based on the digital elevation model(DEM)and soil data of the river basin,combined with the land cover and hydrometeorological data in the base period,a distributed VIC model for the river basin runoff simulation is constructed.Using the Nash efficiency coefficient and Relative error as the model appraisal indicators,the parameters of the VIC model were calibrated,and the applicability of the hydrological model to the upper reaches of the Zhang River was verified.The evaluation results show that the VIC model can accurately restore the runoff process in the base period of the upper Zhanghe River basin,and the model has good applicability in the study area.(3)Based on the hydrological simulation method and the slope change ratio of accumulative quantity evaluate the attribution of runoff changes in the upper Zhanghe river basin,consistent results were obtained: throughout the upper Zhanghe river basin,human activities dominated the runoff change in the upper Zhanghe River.Zhuozhang River is more affected by human activities than Qingzhang River.Specifically,in the Zhuozhang River Basin,the contribution of human activities to the runoff changes of the hydrological stations in the basin is relatively consistent,and the change amplitude is not large.In the Qingzhang River Basin,the contribution rate of human activities to runoff changes increases as the area of the control basin increases.