中文摘要：

水文极值计算是水资源系统工程风险分析和计算的难点和关键问题之一．现代极值理论可以用来描述和研究洪水、干旱、海浪和风速等极限现象，是水文极限分析的工具之一．介绍了现代极值理论的基本思想和方法，着重分析了传统频率分析法和现代极值理论进行水文极限分析的优劣势．同时研究应用超阈值（POT）方法建立了水文统计极值估算模型，并对水文极值估算的不确定性和该模型对阈值选取的敏感性进行了分析．最后通过一个洪水算例演示和验证了所建立的模型的实用性和可操作性．研究成果表明，现代极值理论物理统计意义较强，其计算结果具有良好的可靠性，是水文分析的有效方法之一．介绍的不确定和敏感性分析方法则可以为工程设计和管理提供有效的决策依据．

英文摘要：

Hydrological extreme analysis is one of the most difficult but key aspects for water resources risk analysis. Modern extreme value theory can be used to describe hydrological extremes such as flood, draught, wave and wind speed. This paper studies the merits and demerits of applying conventional frequency analysis and modern extreme value theory to analyze hydrological extremes. Besides, in this paper, modern extreme value theory is introduced and the Peak Over Threshold（POT） method is adopted to build models to estimate extreme hydrological statistics. Afterwards, an example is used to estimate flood extremes and their corresponding uncertainty, and the sensitivity of flood extremes to different thresholds is also analyzed. The results show that modern extreme value theory has strong statistical-physical meaning, and applying such theory to estimate hydrological extremes and their uncertainty can provide efficient decision support to engineering design and management.