分布式坦化单位线的流域汇流研究

Research on the Flow Routing of Distributed Unit Hydrograph Considering Attenuation Actions

单位线是中小流域汇流计算的常用方法,现有综合单位线法存在无法考虑降雨时空分布不均性和下垫面异质性的问题,导致预报精度欠佳;此外,传统分布式单位线计算过程复杂,且需要大量数据,限制了其在中小流域的应用。为此,本文引入分布式单位线概念,综合考虑洪水传播时间和洪峰滞时,提出了基于流域初始单位线的分布式坦化流域汇流模型,该模型通过推求一系列坦化单位线,为各雨量站适配不同的分布式单位线,进而计算流域出口断面的洪水过程。研究以梅州流域尖山水文站点以上流域为例,基于21个雨量站点实测降雨数据,构建了分布式坦化单位线汇流模型,采用洪峰相对误差、峰现时间误差、确定性系数等指标进行模型适用性评价,并与现有综合单位线法进行了比较分析,实例研究表明所提方法的洪峰相对误差、峰现时间误差小于综合单位线法,确定性系数明显提升,整体上分布式坦化单位线法预报结果优于现有综合单位线法。所提方法简化了现有分布式单位线推求步骤,提高了洪水预报精度,易于在中小流域进行推广。

The unit hydrograph method is commonly used for the calculation of flow routing in the small and medium-sized basins.However,the current synthetic unit hydrograph method cannot consider the heterogeneity of temporal and spatial distribution of rainfall and the heterogeneity of underlying surface,resulting in poor prediction accuracy.In addition,the current distributed unit hydrograph calculation process is complicated and requires plenty of data,which limits its application in small and medium-sized basins.To this end,the concept of distributed unit hydrograph is introduced in this study.Based on the flow travel time and the lag time of flow peak,a distributed unit hydrograph model considering the attenuation actions is proposed.After a group of unit hydrographs are calculated,different distributed unit hydrograph accorporates to each watershed.Then,the flood process of the outlet basin can be calculated.The Meizhou River basin is selected as a study case.A distributed unit hydrograph model considering attenuation actions is established based on the observed rainfall data of 21 rainfall stations.The relative flood peak error,flood peak appearance time error and deterministic coefficient are used to evaluate the applicability of the model,and the result of the current synthetic unit hydrograph method is compared with the proposed method.The result shows that the relative peak error and peak appearance time error of the proposed method are smaller than those of the synthetic method and the certainty coefficient is significantly improved.On the whole,the accuracy of the proposed method is better.The proposed method simplifies the calculation steps of the distributed unit hydrograph,improves the accuracy of flood prediction,which is easy to be popularized in small and mediumsized basins.