Estimation Model And Prediction Of Rainfall Erosivity In Poyang Lake Basin Under Climate Change

This study established a grading rainfall model for rainfall erosivity by analyzing the characteristics of rainfall in the Poyang Lake Basin and the historical rainfall erosivity model.The grading rainfall model was further reliably demonstrated by comparing it to others models established by Zhang Wenbo,Shi Zhihua and Ma Liang,respectively.According to the existing method of time-descent,a modified method of rainfall condition transition probabilities and a modified method of daily rainfall variance method were amended through weighted-average method and linear regression method.The annual and interannual changes of rainfall erosivity at representative stations in the basin during the historical period were calculated and analyzed with the rainfall erosivity graded rainfall model.The time scale of the future monthly simulation data of the CMIP5 global climate model under the high emission scenario RCP8.5 was performed by using the modified time scale method.What's more,the interannual variation of rainfall erosivity that may occur at each station in the next 80 years(2021~2100)were analyzed.The main conclusions were as follows:(1)In the Poyang Lake Basin,the light rain days generally showed a downward trend,and annual rainfall,annual rainfall and annual rainstorm days all increased.These results reflected that rainfall intensity and the frequency of extreme rainfall events were increase in the river basin.(2)Compared with Zhang Wenbo's model,Shi Zhihua's model and Ma Liang's model,the grading rainfall model reflected much more influence of rainfall intensity on rainfall erosivity,but also offered more accuracy.This model was applicable to estimate the rainfall erosivity in Poyang Lake Basin.(3)The results of calculation and analysis of rainfall erosivity during the period from1956 to 2015 in Poyang Lake Basin showed that rainfall erosivity was mainly concentrated from April to July,and the interannual variation was larger with different degrees of rising trend.The rainfall erosivity increased by 702.20 MJ·mm/(hm~2·h)every 10 years,with the largest increase for Nancheng City,which reflected increase in the potential risk of soil erosion was due to the increase in rainfall erosivity in Nancheng area.(4)The modified method of calculating the rainfall conditional transition probabilities with the weighted average method was better than the previous method.Furthermore,the modified method of daily rainfall variance established with the linear regression method was also better than the previous estimation method.(5)From 2021 to 2100,the total rainfall,erosive rainfall,moderate rainfall in the river basin may show a downward trend in both rainfall and rainfall days,while the characteristic of heavy rain may not be obvious.the annual rainfall erosivity in the four stationsof Jixian,Ji'an,Nancheng,and Nanchang may increase in different degrees,while the annual rainfall erosivity may decline in Jingdezhen.Compared with historical periods from 1956 to 2015,the increase in rainfall erosivity in the basin may decrease.