洪水序列变异条件下的频率分析与计算

海河流域由于兴建大量防洪和水保工程,改变了流域下垫面条件,导致天然洪水产汇流特性发生变化,洪水系列不再满足一致性假定,进行设计洪水的修订势在必行。以海河大清河水系南支沙河上游的王快水库入库年洪峰序列和年最大洪量序列为例,基于各序列变异点诊断结果,应用混合分布法和条件概率分布法,直接对非一致性洪水序列进行频率分析,得到基于变异序列的设计洪水成果。并将两种方法得到的设计洪水成果分别与1985年水利部规划总院(WRHPDGI)审定的王快水库设计洪水成果及不考虑变异条件下的P-Ⅲ曲线拟合设计洪水成果进行对比,结果表明,考虑变异条件下的不同标准的设计洪水值均较1985年设计洪水值有所减小,年洪峰减小幅度为15%~30%,年最大时段洪量减小幅度为5%~30%;较不考虑变异条件下的P-Ⅲ曲线拟合设计洪水成果也有一定程度的减小,年洪峰、年最大1日洪量、年最大6日洪量减小幅度小于10%,年最大3日洪量减小幅度为1%~15%。该结论可为大清河流域设计洪水的修订提供一定的理论依据。

Flood frequency analysis considering variation in flood time series

As a large number of flood control and soil-water conservation projects have been constructed in the Haihe River Basin, the underlying surface conditions and the characteristics of the runoff yield and concentration are changed, which leads to the nonstationarity of the reservoir inflow flood time series. Hence it is very necessary to revise the previous design flood. In this paper, the annual flood peak discharge series and the annual maximum flood volume series of Wangkuai Reservoir, which lies in the Shahe, the south branch of the Daqing River, were used as the basic data. The mixed distribution method and the conditional probability distribution method were used to directly analyze the frequency of the non-stationary flood time series based on their respective change point diagnosis results. The design flood calculated with these two methods were compared to the 1985 design flood which was approved by the WRHPDGI (Water Resources and Hydropower Planning and Design General Institute) in 1985, and to the design flood calculated by the P-Ⅲ curve which considers the flood time series as stationary. The results reveal that the design values with different return periods are reduced to some extent compared with the 1985 design flood, with a decrease of about 15% to 30% for annual flood peak discharge, and about 5% to 30% for annual maximum flood volume; Compared with the P-Ⅲ curve results, the decrease of annual flood peak discharge and annual maximum flood volume(1-day and 6-day) are less than 10%, the decrease of annual maximum flood volume(3-day) is about 1% to 15% . The results may lay a basis for the revision of the design flood in the Daqing River Basin.