| Climate warming accelerates the global and regional water cycle process,which will lead to an increase in the frequency of extreme hydrological events such as floods.Under the combined action of abnormal hydrometeorological factors and the characteristics of the basin,small basins are prone to floods.The upstream flood will act on the main stream through the tributaries,which will cause flood encounters.The Jinjiang Basin belongs to the subtropical monsoon humid climate.During the plum rainy period and the typhoon period,the rainfall in this basin is larger.If there is a flood encounter event,it is bound to cause serious damage to municipal projects and the masses in the downstream areas.Therefore,under the background of global warming,analyzing the changes in the probability of flood encounters under different climate scenarios in the Jinjiang Basin at present and in the future,which is of great significance to the design of water conservancy projects and the prediction of extreme hydrological events.In this study,the Jinjiang Basin is taken as the study area,the annual maximum flood magnitude and its occurrence data are used as flood characteristic variables.The optimal distribution of flood magnitude in this basin is selected.And the optimal distribution and mixed Von Mises distribution are used to construct the marginal distribution of the annual maximum flood magnitude and its occurrence data,respectively,so as to explore the probability characteristics of flood encounter at this stage of the basin.Based on this,the SDSM model is used to downscale the output results of the Can ESM2 global climate model.The climate data after the scale reduction are coupled with HSPF model,which simulates the runoff response under climate change,and analyzes the change of future flood encounter in Jinjiang Basin.The results showed that:(1)The optimal distribution of the annual maximum flood magnitude of Anxi and Honglai Station was P-III distribution.The P-III distribution and the mixed Von Mises distribution were selected to establish the marginal distribution of the annual maximum flood magnitude and its occurrence data,respectively,and the fitting effects were better.(2)The optimal Copula functions of the annual maximum flood magnitude and its occurrence data in the Jinjiang Basin were Clayton Copula and GH Copula,respectively.The probability of the same frequency flood at Anxi and Honglai Station decreased with the increase of the return period.The probabilities of once in 100years,once in 50 years,and once in 10 years flooding at Anxi and Honglai Station at the same time were 1.46×10-5,5.77×10-5,1.36×10-3.(3)The SDSM model could better simulate the daily maximum temperature,daily minimum temperature and daily rainfall in the basin,and the simulation effect of temperature was better than that of rainfall.In the future,the daily maximum temperature and daily minimum temperature,as well as the difference of monthly rainfall in the basin Controlled by Anxi Station(Xixi),would showed RCP8.5>RCP4.5>RCP2.6,while the difference of monthly rainfall in basin Controlled by Honglai Station(Dongxi)was smaller.Compared with the base period,the daily maximum temperature from January to March and the daily minimum temperature from January to February showed a downward trend,while the daily maximum and daily minimum temperature in the rest of the month showed an upward trend.The peak of monthly rainfall in Xixi and Dongxi Basins occurred earlier.The precipitation in the Xixi Basin increased significantly from January to March and July to September,and the precipitation in Dongxi Basin increased significantly from January to April and December.(4)From the perspective of annual maximum flood data encounter,the flood encounters in Xixi and Dongxi Basins under three climate scenarios mainly occurred from early March to early August.Compared with the current situation,the probability of encounter from March to May had increased,the rest of the month had decreased,and the future encounter data was generally advanced.From the flood magnitude encounter probability considering the flood occurrence data,it could be seen that the encounter probability under the three climate scenarios would show the characteristics of RCP2.6>RCP4.5>RCP8.5,and they were higher than the current situation,and the risk of future floods in the basin would increase. |
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