下垫面变化条件下合河流域设计洪水修订

Study of the Effect of Underlying Surface Change on Design Floods of Hehe River Basin

基于新安江-海河模型,选取合河流域为研究对象,开展下垫面变化对设计洪水影响的研究。将合河流域的洪水系列分为1980年前、后两个部分,针对两个系列分别率定模型参数;再根据1980年后的参数来重新模拟1980年前的洪水,通过模拟出的次洪径流深和洪峰的变化幅度来反映下垫面变化对设计洪水的影响;同时,利用径流深的模拟结果修订设计洪水,并计算设计洪水的变化幅度。结果表明,合河流域的自由水蓄水容量和河网水消退系数均变大,流域的调蓄能力变大,设计洪水的洪峰值在减小;地下水过度开采与水利工程的建设是导致该流域设计洪水减小的主要因素。

The Xinanjiang-Haihe model is applied to assess the effect of underlying surface change on the design floods of Hehe River Basin. The flood events are separated into two periods bounded by the year of 1980. The parameters of Xinanjiang-Haihe model are calibrated for these two split periods respectively. Then, the flood events before 1980 are simulated again by using the parameter values for the period after 1980. The runoff and peak simulations are analyzed to evaluate the influence of underlying surface change on design floods. Additionally, the simulated runoff results are used to revise the design floods. The variation ranges of design floods are also calculated as well. The results indicate that the values of free water capacity and recession constant for the latter period are larger than that for the former period, the capability of flood storage of Hehe River Basin has increased after 1980, and the design flood peaks have decreased after 1980. The major reasons may be the overexploitation of groundwater and hydraulic engineering construction.