Simulation And Prediction Of Runoff In The Upper Reaches Of Heihe River Basin Under Climate Change Conditions

From the point of view of geological history,the earth is currently in the interglacial period,and the warm climate is due to natural laws and is more suitable for human survival.However,the rapid development of human industrialization in the past 100 years has led to the early transition of the Earth to the greenhouse climate.Climate change gradually changes the amount of water resources and the spatial and temporal distribution by affecting the intensity and frequency of the hydrological cycle,further affecting the Earth's ecological environment and human survival and development.It is important to study the response of future runoff under climate change for water resources planning,management,disaster prevention and mitigation.In this paper,the upper reaches of the Heihe River Basin is used as the research area.Firstly,the characteristics of meteorological and hydrological elements under historical climatic conditions are analyzed.Then the SWAT model is constructed to simulate the hydrological process of the basin,and the applicability of 18 General Cliamte Models in the study area is evaluated by TOPSIS method.The future precipitation and temperature data output by the four GCMs are corrected by Delta deviation and input into the SWAT model to predict the runoff response in the upper reaches of the Heihe River Basin under future climate change conditions.The research results are as follows:(1)In the historical period,The interannual precipitation and temperature series showed an increasing trend.The average annual runoff of the river basin exports is 1.6×10~9m~3.The annual runoff is mainly from June to September,and the annual runoff at all stations shows an increasing trend,which is related to the increase of precipitation and the increase of snowmelt runoff caused by the rise of temperature.(2)During the calibration period(1965-1987)and verification period(1990-1997),the runoff simulation results of SWAT model in the three stations were 0.72~0.89 in NSE,0.78~0.96 in R~2,and 0.04~0.24 in RBIAS,which all meet the model evaluation criteria,which proves that the built SWAT model is in the upper reaches of the Heihe River Basin has good applicability.(3)Among the 18 GCMs,CSIRO-Mk3.6.0,CCSM4,CanESM2,and MPI-ESM-LR models have better simulation capabilities for precipitation and temperature in the upper reaches of the Heihe River Basin.Four GCMs predict that annual precipitation and annual temperature will increase in the future(2021-2050/2051-2080).Most GCMs predict an increase in precipitation in the future,while all GCMs predict an increase in temperature in the future,compared to the multi-year average of historical periods.(4)The runoff of the study area is basically increasing in the future period.The distribution process during the year is also close to the historical period,but the total runoff is lower than that of the historical period.The Qilian station and the Zamashike station are particularly obvious.For the Yingluoxia Station at the outlet of the basin,the total amount of runoff in the future period obtained from different time periods and different modes is increased or decreased compared with the historical period,the base flow has a larger decrease than the historical period.It is closely related to the change of precipitation and evapotranspiration in the same period and in the same mode.In general,there is a greater possibility of reducing runoff and baseflow in the study area under future climate change conditions,which will aggravate the contradiction of local water use and the risk of hydrological drought in the basin.