基于二维Gumbel分布的长距离输水系统水文风险评估

在现行的水文风险组合计算中，往往需要对非正态分布的水文变量进行正态化处理，这必然引起畸变，从而影响分析计算结果的准确性。针对这一问题，在以往的研究基础上，根据Ditlevsen界限，进一步建立了基于二维Gumbel分布的长距离输水系统的综合水文风险评估模型，从而巧妙地解决了串联系统风险计算中如何建立n维联合概率分布函数的难题。并以南水北调中线工程河北省段的21条主要河流为例，分析了采用Gumbel联合分布来研究降雨量或洪水的联合分布特征的可行性，进行了实际水文概率的组合计算，结果表明南水北调中线工程河北省北段的综合防洪风险是3．1％，其防洪安全是有保证的。

Hydrological Risk Assessment of Long-distance Water Transfer System Based on the Two-dimensional Gumbel Distribution

Normalization transformation of non-normal distribution variable is always necessary in assessment of integrated hydrological risk. But accuracy is reduced due to this kind of deformation. According to previous study and Ditlevsen boundary, the hydrological risk assessment model for long-distance water transfer system is established based on two-dimensional Gumbel distribution. The problem of establishing n-dimensional joint probability distribution function in risk calculation of the series system is overcome. Taking 21 river basins along the middle route of South to North Water Transfer System in Hebei province as an example, the feasibility to study the characteristics of joint distribution of precipitation and flood is analyzed by using the Gumbel joint distribution. The combinatorial calculation of actual hydrological probability is made. The result shows that the flood risk in the middle route of South to North Water Transfer System in northern Hebei province is 3. 1% and its flood control safety is reliable.