简要地介绍了三峡工程三期明渠提前截流的背景和方案 ,以宜昌站 1 877～ 2 0 0 0年 1 1月下半月的日流量为基本资料序列 ,分别采用了历时曲线法和泊松过程分析了三期明渠提前截流的水文风险 ,结果表明 ,由于方法固有的差异 ,历时曲线法的计算结果均比泊松过程大。但是 ,两者随着日期变化的走势非常相似 ,都揭示了同一条规律 ,即随着日期的推延 ,水文风险不断减小 ,这与长江干流 1 1月份下半月的水文特性是相符的。因此 ,将历时曲线法和泊松过程应用于三期提前截流的水文风险分析是合理可行的 This paper briefly introduced the background and scheme of early closure of the Three Gorges Project open channels. Based on the daily data of the second half of January to January from January 1877 to January 2001 in Yichang Station, the diagonal curve method and Poisson process The hydrological risk of the early closure of the open channel of the third phase was studied. The results show that the calculated results of the diachronic curve method are larger than the Poisson process due to the inherent differences of the methods. However, the similar trend of the two with the change of date reveals the same law that the hydrological risk decreases with the delay of the date, which is consistent with the hydrological characteristics of the main stream of the Yangtze River in the second half of January. Therefore, it is reasonable and feasible to apply the diachronic curve method and the Poisson process to the hydrological risk analysis of the three stages of early closure