Study On The Relationship Between Rainfall And Runoff In The Source Region Of The Yellow River Based On VIC Model

As an ecologically fragile and sensitive area,the Yellow River basin has been affected by climate variation and activities of humankind,causing serious phenomena such as degradation of the ecological environment and reduction of regional water volume.Study on the relationship between rainfall and runoff can more clearly analyze the changes of runoff,which is of importance to the lasting development of water in the future.In this paper,the VIC(Variable Infiltration Capacity)model is used to simulate the runoff above the Tangnaihai Hydrological Station.The area was divided into 1859 grids with a spatial resolution of 0.083°×0.083° to study the runoff changes from 1989 to 2018,and the adaptability of the VIC model in this region was evaluated.In addition,the Mann-Kendall trend test and mutation test,and Double Mass Curve were used to specifically estimate the transformation relationship of them in the study area.The main research results are as follows:1.According to the Nash and Er,the VIC model has great adaptability in the area.The Nash is 0.856 and the Er is 0.04% in the calibration period.And the Nash and Er in the validation period is 0.837 and 0.08%.They are all within a reasonable range.The results of parameter sensitivity analysis show that the variable infiltration curve equation power B and the second soil thickness d2 are the most sensitive parameters in the study area,and both can affect runoff directly.2.According to the Mann-Kendall trend test and mutation test,the rainfall in the study area shows a weak growth trend from 1989 to 2018,and the Z value of the trend test is 0.46,and there is a sudden change in rainfall in 2007.However,there is basically no change in runoff from 1989 to 2018,and the trend test Z value is 0.14,and there is no catastrophe point during the study period.The rainfall-runoff relationship is roughly linear.According to the Double Mass Curve,the contribution rate of nonrainfall factors to the change of runoff is 88.01%.But the contribution rate of rainfall to runoff changes is only 11.99%.It shows that the runoff in study area mainly comes from base flow,and a small part may come from glacier melting.Non-rainfall factors,such as climate change and human activities,are the main reasons of runoff changes.Based on the VIC hydrological model,this paper studies the relationship between rainfall and runoff in the study area.Although some results have been obtained,there are also some shortcomings.Due to the influence of its own mechanism,the VIC hydrological model cannot accurately make the simulation result exactly the same as the actual situation.The study on the relationship only considers rainfall factors and non-rainfall factors.But does not consider non-rainfall factors in more detail,such as climate change and human activities.The above aspects will be improved in the future research.