Study On Rainfall-Runoff Simulation And Driving Factors In Typical Watershed Of The Three-River Headwaters

As a sensitive area responding to global warming,the Three-River Headwaters region has undergone great changes in its ecological environment in recent years,posing a threat to the sustainable development of the region.Therefore,understanding the evolution trend of climate elements in the Three-River Headwaters region and assessing the response of climate change play an important role in the development and utilization of water resources,in making water conservation planning decisions and improving the ecological environment.In this paper,the Three-River Headwaters region is used as the research area,and the applicability of the ITPCAS dataset is evaluated by using the measured data of meteorological stations with several evaluation indicators.The VIC model was constructed for the headwaters of the Yellow River Basin.The hydrological process under the assumed climate scenarios was simulated with the ITPCAS dataset and VIC model,and the impact of climate change on the runoff in the study area was analyzed.The main conclusions are as follows:1.The ITPCAS data set has high precision.it has increased in different degrees about the average annual temperature and precipitation in the TRH region.In terms of space,it has been quite different of the temperature change rate,both increasing and decreasing.The change rate of temperature is the highest in autumn,and the smallest in summer.The precipitation decreased with latitude increasing from southeast to northwest.The average annual precipitation in most areas of the study area has been shown an increasing trend,and the change rate of precipitation is the smallest in winter.2.The VIC model has a good simulation effect.The Nash efficiency coefficient is greater than 0.8,the relative error is less than 10%,and the correlation coefficient is above 0.9 in both the calibration and verification periods.The simulated runoff has a high consistency with the measured runoff.The VIC hydrological model can better simulate the runoff process in the study area,and it can be applied to the study of the study of hydrological cycle.Analysis of parameter sensitivity found that the variable infiltration curve equation power B and the second layer soil thickness d2 are the two most sensitive parameters in the study region.3.The temperature in the headwaters of the Yellow River Basin has been increased overall,and the growth rate has also been increased in recent years.The annual precipitation has a slight decreasing trend,and the precipitation after the mutation has been increased in fluctuation.The overall trend of the runoff is not obvious in the Jimai hydrological station,but It began to increase rapidly after 2003.Analyzing the change of runoff in hypothetical climatic scenario reveals that the runoff will increase the most when the temperature will be constant and the precipitation will increase by 10%.When the temperature will increase by 1.5 °C,and the precipitation will decrease by 10%,the runoff will decrease the most.When the temperature will rise by 1.5 °C,even if the precipitation will increase by 10%,the runoff will still reduce by 1.96% compared with the base period.It can be seen that the runoff is slightly more sensitive to temperature.The process of analyzing the freezing depth of frozen soil and the amount of glacial snowmelt in the basin shows that the freezing depth of frozen soil will be increased and the thickness of soil layer will be increased.The proportion of groundwater replenished by the precipitation will be increased.It will lead to a reduction in surface runoff from precipitation.As a result,the temperature will have more impact on the runoff in the study area.