混合分布在非一致性洪水频率分析的应用

Non-Stationary Flood-Frequency Analysis Based on Mixed Distribution

大清河流域由于兴建防洪工程,改变了原天然河道的洪水径流关系,使得用于大型水库防洪调度的入库洪水序列失去了一致性.本文以龙门水库的年洪峰序列、固定时段的年最大洪量序列(1日、3日和6日)为例,首先对此4个洪水序列采用水文变异诊断系统进行变异分析,识别非一致性洪水序列的变异点.并在2个分布组成的混合分布假设下,研究非一致性洪水序列的频率计算问题,用模拟退火算法对混合分布进行参数估计,并将混合分布给出的设计洪水与不考虑变异情况的设计洪水以及1985年水利部规划总院(WRHPDGI)审定的设计洪水进行了比较分析.结果表明,相比不考虑变异情况的设计洪水值,考虑变异情况下的不同设计标准的设计洪水值均有不同程度的减小,且变异的程度均较明显,说明大清河流域下垫面和人类活动的变化导致入库洪水减少的现象较明显,进行设计洪水的校核和修订很有必要.

As flood control projects have been built in Daqing river basin, the flood-runoff of the original rivers has been changed, thus causing reservoir inflow flood series to become non-stationary. In this paper, annual flood peak series and fixed-period annual maximum flood volume series （1-day, 3-day and 6-day） in Longmen reservoir were taken as an example for analysis. First, the above four flood series were used for non-stationary diagnosis by several diagnosis methods, and if the series were non-stationary, their aberrance points would be recognized. And then, the key part focused on establishing the mixed distribution model which is composed of two independent distributions to re- solve non-stationary flood-frequency calculation problem, and estimating the mixed distribution parameters with simu- lated annealing algorithm. Finally, the design flood comparative analysis of the mixed distribution model, the tradi- tional method which does not consider non-stationary and Water Resources and Hydropower Planning and Design General Institute （WRHPDGI） approved in 1985 was made. The results reveal that, compared with the design floods calculated by the traditional method, those with various probabilities of occurrence are all reduced to a certain extent, with obviously different degree. It further demonstrates that the impacts of reservoir inflow floods which result from underlying surface change are obvious in Daqing river basin and it is essential to review and revise the design flood.