黄河流域分布式水文模型开发和验证

Development and Verification of a Distributed Hydrologic Model for the Yellow River Basin

研究目的是开发和验证大流域分布式水文模型,为黄河流域水资源评价和演化规律分析服务。在综合了分布式水文模型和陆面过程模型各自优点的基础上,开发出模拟对象为“天然—人工”二元水循环系统的WEP-L模型。该模型以“子流域内等高带”为计算单元,并用“马赛克”法考虑计算单元内土地覆被的多样性,避免了采用过粗网格单元产生的模拟失真问题。针对各水循环要素过程时间尺度不同的特点,计算时采用了1h至1d的“变时间步长”,既合理表述了水循环动力学机制又提高了计算效率。将全黄河流域划分为具有空间拓扑关系的8485个子流域和38720个等高带,采用45年(1956～2000年)水文气象系列数据及相应下垫面条件进行了模拟计算,并根据黄河流域主要水文站逐月和逐日径流系列进行了模型校验。验证结果表明,所构建的模型具有较高模拟精度,可应用于黄河流域二元水循环过程模拟和水资源演变规律分析。

This study is to establish a tool for water resources assessment and analyzing the evol-utionary laws of water resources in the Yellow River Basin by developing a distributed hydrologic model applicable to large basins.On the basis of combining the merits of distributed watershed hydrologic models and land surface processes models,we developed WEP-L(Water and Energy Transfer Processes in Large River Basins) model in which 'natural-artificial' dualistic water cycle system is modeled in a coupling way.In the WEP-L model,contour bands inside sub-watersheds are used as computation units and the mosaic approach is adopted to reflect the heterogeneity of land covers inside a computation unit.In this way,the model can avoid possible serious distortions of flow modeling,which may occur if coarser grid cells are used as computation units.Variable time steps from 1 hour to 1 day are adopted in the model in accordance with different time scales of various hydrologic processes,which has improved the computation efficiency and ensures rational description of hydrologic dynamics.The Yellow River Basin was subdivided into 8 485 sub-watersheds and 38 720 contour bands,45-year(1956～2000)continuous simulations were carried out for corresponding land cover conditions,and model verification was performed by comparing simulated discharges with observed monthly and daily discharges at main gauge stations.The verification shows that the newly established WEP-L model has quite high simulation accuracies,thus it is applicable to water resources assessment and evolutionary laws analysis of water resources in the Yellow River Basin.