西江流域极端降水演变规律及其对洪水径流的影响

Evolution characteristics of extreme rainfall and influence on flood runoff in Xijiang River Basin

为探究西江流域水文气象要素演变规律,分析极端降水对洪水径流的影响,基于西江流域1956—2019年水文气象资料,综合利用趋势分析、突变检验等方法剖析了西江流域极端降水、年均径流和年最大日平均流量的演变规律,并采用Pearson相关系数与双累积曲线法评估了极端降水指标与年均径流、年最大日平均流量的相关性,探讨了极端降水对洪涝灾害损失的影响。结果表明:相较于上游高海拔地区,西江流域中下游低海拔地区极端降水的变化更为明显,表现为极端降水频率增大以及降水强度增大;Rx1day、R99p和SDⅡ呈现显著上升趋势,极端降水指标多在1992年发生突变,年均径流和年最大日平均流量均呈现不显著的上升趋势,且均有两个突变点;PRCPTOT、R25、R10、R95p与年均径流呈显著相关关系,R95p、R99p、CDD和R25对洪涝灾害指标的影响相对较大;2002年后极端降水指标同洪涝灾害指标的相关关系发生了显著改变。

In order to explore the evolution law of the hydrological and meteorological elements in the Xijiang River Basin and to study the potential impact of extreme rainfall on flood runoff,based on the hydrological and meteorological data of the basin from 1956 to 2019,the evolution laws of extreme rainfall,annual runoff,and annual maximum 1-day flood volume were comprehensively analyzed using methods such as trend analysis and mutation test.The Pearson correlation coefficient and double cumulative curve method were used to evaluate the relationship between extreme rainfall and annual runoff.The impact of extreme rainfall on flood disaster losses was discussed.The results show that compared with the upper reaches of the high-altitude area,the changes of extreme rainfall in the middle and lower reaches of the Xijiang River Basin are more obvious,showing increasing frequency and intensity of the extreme rainfall.Rx1day,R99p,and SDⅡshow a significant upward trend,with extreme rainfall indicators mostly experiencing sudden changes in 1992.The average annual runoff and maximum annual flood do not significantly increase, and there exist two mutation points. PRCPTOT, R25, R10, and R95p are significantlycorrelated with runoff, while R95p, R99p, CDD, R25 have a relatively significant impact on flood disasterindicators. After 2002, the correlation between extreme rainfall indicators and flood disaster indicators hassignificantly changed.