Temporal And Spatial Changes Of Extreme Precipitation And Flood Disaster Risk Projection In The Wei River Basin Based On CMIP6 Models

Under the background of global warming,extreme precipitation events are showing a trend of frequent occurrence in China.As the main disaster-causing factor of flood disasters,extreme precipitation is likely to cause serious natural disasters and pose a threat to the safety of people’s lives and properties.Carrying out research on extreme precipitation events,revealing the evolution rules and characteristics of extreme precipitation events,predicting the spatiotemporal variation characteristics of future extreme precipitation and the comprehensive risk of flood disasters,can provide reference for risk management of regional disaster prevention and mitigation,emergency infrastructure construction,and scientific formulation of comprehensive planning for flood disaster risk warning and prevention,etc.This paper takes the Wei River Basin as the research object,based on meteorological observation data and CMIP6 climate model data,selects five international extreme precipitation indices,namely total precipitation(PRCPTOT),Simple pricipitation intensity index(SDII),consecutive wet days(CWD),heavy precipitation days(R10mm)and maximum five-day precipitation(Rx5day).And uses methods such as moving average,cumulative anomaly,MannKendall trend analysis and Kriging interpolation to analyze the temporal and spatial variation characteristics of extreme precipitation in the Wei River Basin from 1961 to 2020;The simulation effects of five CMIP6 climate models on the extreme precipitation in the Wei River Basin were evaluated.And based on this,estimated the spatiotemporal variation characteristics of extreme precipitation in the Wei River Basin from 2021 to 1960 under different scenarios(SSP126,SSP245,and SSP585)using Multi-Model Ensemble;Finally,using extreme precipitation indices,topography,socio-economic and land use data,from the risk of disasterinducing factors,sensitivity of disaster-inducing environment and vulnerability of disasterbearing bodies,the comprehensive risk of flood disasters in the Wei River Basin under different scenarios in the near-term(2021-2040)and long-term(2041-2060)is estimated.The main conclusions are as follows:(1)From 1961 to 2020,the interannual fluctuations of the five extreme precipitation indices in the Wei River Basin were relatively large.On the whole,except for SDII showing a slight upward trend(the change rate was 0.007(mm/d)/a),PRCPTOT,CWD,R10 mm and Rx5 day all showed a downward trend,and the change rates were-0.709 mm/a,-0.019 d/a,-0.019 d/a,-0.026 d/a,-0.054 mm/a.The lowest interdecadal average values of the five extreme precipitation indices were all in the 1990 s,and the Wei River Basin was in a relatively dry period in the 1990 s.The spatial distribution of each extreme precipitation index in the whole Wei River Basin varies greatly.The interannual variation trend and spatial distribution characteristics of R10 mm are highly consistent with PRCPTOT,indicating that heavy precipitation in the Wei River Basin occupies a relatively high proportion of the total precipitation.(2)Over the next 40 years from 2021 to 2060,each index will show an upward trend under all three scenarios,but the change rate under the SSP585 scenario is slightly lower than that under the SSP126 and SSP245 scenarios.The change rates of PRCPTOT in SSP126,SSP245,and SSP585 scenarios were 12.83 mm/10 a,10.03 mm/10 a,and 4.59 mm/10 a,respectively.The change rates of SDII,CWD,R10 mm,and Rx5 day were relatively weak in the three scenarios.Under the three scenarios,the rise rate of PRCPTOT in the eastern part of the Wei River Basin is greater than that in the western part,and with the increase of radiation forcing,the rise rate gradually decreases.In the western loess hilly area,it shows a downward trend under the SSP585 scenario.SDII shows a weak downward trend in the western part of the Wei River Basin,while other regions show a weak upward trend.The change rate of CWD in all three scenarios shows a gradual increasing trend from northwest to southeast.R10 mm shows an upward trend in most areas except for the western loess hilly area under three scenarios.With the increase of radiation forcing,the range of the downward trend gradually increases,the rate of decline gradually increases,and the rate of rise gradually decreases.Rx5 day shows a downward trend in the west and an upward trend in the east under all three scenarios.The spatial distribution of extreme precipitation index extreme values in the future is generally consistent with historical periods.The spatial distribution pattern of extreme precipitation in the Wei River Basin will not change significantly in the future,and will still exhibit a distribution characteristic of low in the northwest and high in the southeast.(3)The risk of disaster-inducing factors in the Wei River Basin in the near and long term will gradually increase from northwest to southeast under the three scenarios.High risk areas are mainly distributed in the Guanzhong Plain and the northern foothill of Qinling Mountains,which have high precipitation and intensity.The spatial distribution trend of sensitivity of disaster-inducing environment is basically consistent with the direction of confluence in the watershed water system.The highly sensitive areas are mainly distributed in the middle and lower reaches of the main stream of the Wei River,the middle and lower reaches of the Jing River Basin,and the middle and lower reaches of the Beiluo River Basin,where the river network is dense.The areas with high vulnerability of disaster-bearing bodies are mainly concentrated in the main urban area of Xi’an,where the economy is developed and the population is highly concentrated.The comprehensive risk of flood disasters in the Wei River Basin generally presents a spatial distribution pattern that is lower in the northwest and higher in the southeast.The high-risk areas are mainly concentrated in the Guanzhong Plain area with high extreme precipitation,high density of river network,dense population and developed economy.In the SSP126 scenario,the scope of long-term high-risk and relatively high-risk areas decreased compared with the near-term;In the SSP245 and SSP585 scenarios,the scope of high-risk and relatively high-risk areas in the long term has expanded compared to the nearterm,and the comprehensive risk of flood disasters in the Wei River Basin is on the rise.