Simulation And Prediction Of Runoff Process In Tumen River Basin Under Changing Environment

The Tumen River basin is an important cross-border international river connecting China,South Korea and Russia,which is one of the most important international rivers in China.Water resource situation has a bearing on the economic development of the countries in the basin.Taking the Tumen River Basin as the research object,b ased on the analysis of the characteristics of changes in hydrometeorological elements,this paper identified the attribution of runoff in the Tumen River Basin,and studied runoff changes in the basin under the joint influence of climate change and human activities in the future.The main conclusions are as follows:(1)Mann-kendall trend analysis,Mann-Kendall mutation analysis,Cumulative Offset Verification,Ordered Clustering method and Wavelet analysis were used to analyze the meteorological and hydrological evolution of the Tumen River basin,land use dynamic attitude and land use transfer matrix was used to analyze the temporal and spatial changes of the Tumen River Basin.From the perspective of annual scale,the precipitation showed an insignificant upward trend,and the periodic change was most obvious at 28a scale.The mean annual temperature showed a significant upward trend,and the abrupt change point was 1989,with the most obvious periodic change at 28a scale.From 2000 to 2020,the land use spatial change was mainly from cultivated land to woodland and grassland,and the maximum land movement of unused land was 65.88%.(2)The Budyko hypothesis and SWAT model were used to analyze the influence degree and contribution rate of climate change and human activities on runoff quantitatively.The calculation results based on Budyko hypothesis show that:The runoff depth decreased by19.35mm due to human activities,and the corresponding contribution rate was 250.3%;the runoff depth increased by 11.62mm due to climate change due to climate change,and the corresponding contribution rate was-150.3%.The calculation results based on SWAT model show that:Because of human activities,the average annual discharge decreased by 17.5m~3/s and the corresponding contribution rate was 216.32%;due to climate change,the average annual discharge increased by 9.41m~3/s,and the corresponding contribution rate was-116.32%.The calculation results of the two methods are consistent.Human activities are the main factor leading to the decreased of runoff While climate change increases runoff.(3)Based on SDSM model,this paper downscales meteorological data of three scenarios under MRI-ESM2-0H and Nor ESM2-MM atmospheric models in CMIP6 to analyze the changes of future meteorological elements in the Tumen River basin.Based on PLUS model,land use data of 2010 and 2020 were used to simulate the changes of land use in the future.The results show that the future precipitation,maximum temperature and minimum temperature in the Tumen River Basin have the same change rule,showing a trend of increasing gradually with time,and SSP585 scenario has the fastest growth rate,followed by SSP245 and SSP126.The changes of future land use change in the future will continue the historical development trend,showing that the area of cultivated land,water area,construction land and unused land will increase,while the area of forest land and grassland will decrease.(4)Using the SWAT model driven by the meteorological data under the GCMs scenario and the future land use data,the paper analyzes the short-term,medium-term and long-term runoff changes in the Tumen River Basin under the synergistic effects of future climate change and land use change.The results show that the annual runoff in the future of the Tumen River Basin presents a trend of gradual increase with time,and the fastest growth rate is in the SSP558scenario.From the perspective of time scale,the near-term and medium-term runoff is the smallest in the SSP245 scenario,and the long-term runoff is the smallest in the SSP126 scenario.