Research On Future Runoff Changes In The Beiluo River Basin Based On CMIP6 Models

Since the 21st century,countries around the world have been facing climate issues that cannot be ignored.Leaders need to consider the future trends of local climate changes when making regional development decisions.With the rapid growth of the economy and population,humans have emitted a large amount of greenhouse gases in social production.Excessive greenhouse gases have disrupted the original atmospheric balance,leading to global warming.The global warming will accelerate the existing hydrological cycle,and the hydrological factors such as precipitation,evaporation,and runoff in the region will change accordingly.The changes in hydrological factors will have an impact on the regional water security and the surrounding ecological environment.Therefore,studying climate and hydrological changes in historical and future periods,understanding the future development trends of the research area,can provide certain reference for regional future development decisions.This paper takes the Beiluo River Basin as the research object,establishes a SWAT hydrological model for the study area,and simulates and verifies the runoff situation in the study area.The SDSM downscaling model was constructed by using the meteorological station data in the historical period(1979-2014)of the Beiluo River Basin.The large-scale meteorological data of SSP126,SSP245 and SSP585 of CMIP6 were downscaling processed,and the future precipitation and temperature of each station in the study area were predicted.Two models were coupled to predict the trend of runoff changes in the study area under three different climate scenarios from 2015 to 2100.The main conclusions of this article are as follows:(1)Analyzed the spatiotemporal changes of meteorological elements in the historical period of the Beiluo River Basin,and found that the maximum and minimum temperatures showed a significant increasing trend in interannual changes.The annual average maximum temperature showed a spatial distribution of high in the northeast and low in the southwest,while the minimum temperature showed a spatial distribution of high in the north and low in the southwest.The interannual variation of precipitation shows a trend of first decreasing and then increasing,and the average annual precipitation shows a spatial distribution of high in the north and low in the south.(2)A SWAT model suitable for the Beiluo River Basin has been constructed,with Nash coefficients and R~2 reaching 0.71 and 0.74 at regular period(2000-2010);The Nash coefficient and R~2 during the validation period(2011-2014)reached 0.83 and 0.86.The calibration results indicate that the applicability of this modeling is excellent and can be used to simulate the runoff situation in the study area.(3)By constructing the SDSM model of Beiluo River basin,the CMIP6 data is downscaling.The simulation results of the maximum and minimum temperatures at each station are good,while the precipitation effect is average.The results indicate that the model can be applied to future climate simulation in the Beiluo River Basin.Three different scenarios in Can ESM5 mode in CMIP6 were selected and simulated to obtain future temperature and precipitation data for each scenario.(4)Analyze the changes in future temperature and precipitation.Compared to the reference period(2000-2014),the future temperature will mainly increase in summer,autumn,and winter.The SSP126 scenario has a relatively small increase in temperature throughout the entire period,with the maximum and minimum temperature change rates of 0.0192℃/a and 0.0128℃/a,respectively;The SSP585 scenario shows a significant increase in temperature over time,with the maximum and minimum temperature changing rates of 0.0966℃/a and 0.0809℃/a,respectively;The warming amplitude of the SSP245 scenario is between the two,with the maximum and minimum temperature change rates being 0.039℃/a and 0.0323℃/a,respectively.The future precipitation will mainly be concentrated in the summer flood season,with the peak month being delayed by one month compared to the benchmark period.The precipitation under the three scenarios is fluctuating and increasing.The SSP126 and SSP245scenarios have a downward trend after 2080s,and the precipitation change rates for the three scenarios are 1.05 mm/a,3.56 mm/a,and 10 mm/a,respectively.(5)Simulate the future runoff process of the Beiluo River using the SWAT model.The results indicate that future runoff will mainly be concentrated in the summer flood season,with an increase in the proportion of autumn flow compared to the reference period(2002-2014),and a delay of one month in the peak month of runoff compared to the reference period.The runoff of SSP126 scenario shows a trend of first increasing and then decreasing,with a change rate of 0.36(m~3/s)/a;The runoff in the SSP245 scenario increased more than that in the SSP126scenario,showing a decreasing trend in the late stage,with a change rate of 0.81(m~3/s)/a;The SSP585 scenario has the highest trend of increasing runoff,with a change rate of 1.95(m~3/s)/a.