Simulation And Analysis Of Runoff In The Source Region Of The Yellow River Based On CMIP6 Climate Model

Climate change plays an important role in runoff evolution,and the source region of the Yellow River is located in the sensitive region of climate change,which is also the main water producing region of the Yellow River basin.Therefore,the change of climate and runoff in the source region of the Yellow River has very important practical significance for the future planning of water resources in the whole Yellow River basin and the development of cities along the river.The research results are as follows:(1)Based on the data of digital elevation model,soil,land use and ten meteorological stations in the source region from 2011 to 2019,the SWAT model was established to evaluate the runoff simulation at Tangnaihai,Maqu and Jungong stations.The results show that the SWAT model has good applicability to the runoff simulation in the source region of the Yellow River.The BCC-CSM2-MR model precipitation and temperature data of the Sixth International Coupled Model Comparison Program(CMIP6)implemented by the World Climate Research Program(WCRP)were modified by four precipitation correction methods and three temperature correction methods,and 12 correction combinations were output to drive the calibrated SWAT model.Then,the simulated runoff at Tangnaihai,Jungong and Maqu stations from 2011 to 2019 was evaluated to determine the best correction method for BCC-CSM2-MR model data in the Source region of the Yellow River.The results showed that LS-DM(linear correction for precipitation and distribution correction for temperature)had the best correction effect.(2)The BCC-CSM2-MR precipitation,maximum and minimum temperature data under SSP1-2.6,2-4.5,3-7.0 and 5-8.5 scenarios in 2021-2100 were corrected by LS-DM.The results show that the future precipitation in the basin will increase under all scenarios,and the annual mean precipitation increment of SSP1-2.6,2-4.5,3-7.0 and 5-8.5 scenarios will increase.The maximum and minimum temperature of each scenario increased to different degrees,indicating that the basin was warming,and the overall temperature of the basin was the highest under SSP3-7.0.(3)The LS-DM method was used to modify the precipitation and temperature data from2021 to 2100.Then,annual runoff simulation was carried out by driving SWAT simulation,and mutation detection of simulated runoff was carried out by MK test and sliding T test together.The results show that under SSP1-2.6 scenario,2042 is the abrupt change year of runoff.Under SSP2-4.5 scenario,there is abrupt runoff change in 2069.In SSP3-7.0 scenario,there are two mutation years,with the mutation point occurring in 2048 and 2081 respectively.There was no significant mutation year under SSP5-8.5 scenario.Under SSP3-7.0 scenario,the coefficient of variation is the largest,and the overall trend of future runoff fluctuates more,which is the most unfavorable to the rational utilization of water resources in the middle and lower reaches of the Yellow River.(4)The analysis results of annual runoff extremum show that the maximum annual runoff of 1037.4 m~3/s will occur around 2074 under SSP1-2.6 scenario,which is also the maximum value that may occur under four scenarios simulation during 2021-2100.However,the maximum and minimum annual runoff occurred between 2060 and 2080 under the four scenarios during 2021-2100.The mean annual runoff analysis shows that the SSP5-8.5scenario,representing only high fossil energy use and high radiative forcing of 8.5W/m2,indicates that the future runoff will be higher than the current,and the other three scenarios are likely to reduce the future runoff.(5)The monthly runoff extreme value analysis results show that the SSP5-8.5 scenario predicts the runoff of 2582 m~3/s in August 2092,which is most likely to be the maximum monthly runoff until 2100.Under scenario SSP1-2.6 and SSP3-7.0,the minimum monthly runoff is 52 and 60.2 m~3/s,respectively,both occurring in March 2073.The minimum monthly runoff in scenarios SSP2-4.5 and SSP5-8.5 was 54.4 m~3/s in March 2064 and 62.63 m~3/s in February 2064,respectively.It is necessary to make corresponding strategies before the occurrence of the maximum and minimum values.The annual distribution analysis results of monthly runoff show that under climate change conditions,the runoff in autumn and winter will increase correspondingly,while the runoff in spring and summer will decrease slightly,and it has an overall tendency to lie flat.This study can provide reference for the rational planning of water resources in the Yellow River basin in the future.