半干旱地区洪水模拟效果差异性分析及影响因子响应评估

Differences analysis of flood simulations and response evaluation of impact factors in semi-arid areas

中国北方半干旱地区的降水与下垫面条件具有明显的时空异质性,如何完整准确地描述该类区域的水文过程是当代水文学研究的难点之一.选择半干旱地区水文实验区域--绥德流域和曹坪流域,通过构建不同时空规律的降水场,并结合3种不同产流机制的水文模型,进行大型数值模拟实验,去探究时间、空间、产流机制等因素对半干旱地区洪水模拟的影响,为该类地区水文模型的研制工作提供借鉴.结果表明:1)半干旱地区中小流域的产流对降雨强度较为敏感,因此降水输入的时间步长对洪水模拟效果的影响程度较大;相比之下,流域雨量站数量的增减,仅体现在降雨分布场的暴雨中心缺失以及面平均降雨量的微小差别,对洪水模拟效果的影响程度较小.2)水文模型能否准确描述主导水文过程是半干旱地区洪水模拟效果优良的关键,流域的尺度效应及其下垫面条件的空间异质性是半干旱地区不同水文模型研制和调整应当优先考虑的问题,无论时间步长、雨量站数量怎么组合,产流结构适宜的模型其模拟效果总是趋于较好的结果.

The precipitation and surface conditions in the semi-arid areas of northern China have significant spatial and temporal heterogeneity.How to completely and accurately describe the hydrological process in such areas is one of the challenges in contemporary hydrological research.Spatiotemporal precipitation schemes were constructed with different time steps and numbers of rainfall stations in Suide and Caoping Watersheds.To provide a reference for the development of hydrological models in semi-arid regions,large-scale numerical simulation experiments were conducted to explore the influence of precipitation spatiotemporal heterogeneity and runoff generation mechanisms on flood simulation.The results show that:1)The runoff generation in semi-arid areas is strongly influenced by the rainfall intensity in small and medium-sized watersheds,so the time step of precipitation has a great influence on the flood simulation accuracy.In contrast,the impact of the increase or decrease in the number of rainfall stations on rainfall is mainly the absence of storm recentres and small differences in the average rainfall,which has a small effect on the flood simulation.2)The ability of the hydrological model to accurately describe the dominant hydrological processes is the key to good flood simulations in semi-arid areas.The scale and spatial heterogeneity of the watershed is a priority for model development in such areas.Regardless of the combination of time step and rainfall station density,the model simulations with suitable runoff generation structures always tend to be better.