中文摘要：

以四湖流域荆门、荆州、石首、监利、潜江5个代表性气象站点1956-2007年的日降水资料为基础,分别选取Z指数法及广义帕累托分布对各气象站春、夏、秋三季的标准降水序列及降水距平序列进行拟合,分析各气象站点在不同季节内发生旱涝灾害的频率,在此基础上采用二维Clayton Copula分布函数拟合春-夏、夏-秋的降水分布,进一步计算出各站点旱涝交替事件的发生概率.结果表明：1）Z指数法比降水距平法更适于分析四湖流域的旱涝情况;2）四湖流域在春-夏、夏-秋两时段发生旱涝交替的频率平均为16.27%,其中,潜江最容易发生旱涝异常现象.春-夏与夏-秋发生旱涝交替事件频率没有明显差别.

英文摘要：

Through the daily precipitation data of 1956-2007 at Jingmen,Jingzhou, Shishou, Jianli and Qianjiang meteorological stations in the Sihu River Basin, the sequences of the stations were fitted by Z in- dex and GP model to estimate the probability of drought and waterlogging; Clayton Copula function was used to fit the spring-summer and summer-autumn percentage of precipitation anomalies sequences and the probability of drought and waterlogging alternating were calculated. The results show that：1. The Z index performs better than GP model in the alternating events of drought and waterlogging of Sihu River Basin; 2. The drought and waterlogging alternating events are most likely to take place in Qianjiang,and the fre- quency of spring-summer and summer-autumn alternating events in Sihu River Basin are 16.27% no difference between the spring-summer alternating events of drought and waterlogging and the , there is summer autumn＇s.