面向大尺度区域分布式水文模型的子流域划分方法改进

Improvement of Watershed Subdivision Method for Large Scale Regional Distributed Hydrology Model

子流域划分是构建流域/区域分布式水文模型的基础工作,关系到流域/区域水文模拟和预报精度的好坏。在针对大尺度区域进行子流域划分时,目前普遍使用基于地表径流漫流模型,通过单一集水面积阈值进行河网提取和子流域划分的方法在准确描述研究区的空间范围、确定流域出水口、提取内流区河网等方面存在一定不足。为此,作者对传统子流域划分方法进行改进,面向大尺度区域分布式水文建模提出一套基于流域出水口自动识别和多阈值虚拟河网融合技术的子流域划分方法,该方法包括4大部分,即流域出水口的识别,大、小集水面积阈值的确定,多阈值虚拟河网融合,子流域划分与编码。应用该方法对全国范围内进行了水系提取和子流域划分,共划分子流域25 174个,子流域平均面积381 km2,最大面积5 512 km2,最小面积4 km2,模拟范围与全国水系实际范围的吻合程度达到99.92%。进一步地,将研究结果与全国实测水系和现行流域区划成果进行对比分析,验证了该方法的适用性。该方法高效快速,在准确刻画大尺度区域范围的同时大幅降低了子流域个数,兼顾了模型模拟效率,较好地解决了传统子流域划分方法在大尺度区域分布式水文建模中面临的难题。相关研究可为大尺度区域分布式水文模型构建提供基础支撑,有助于更好地为大面积区尤其是国家宏观层面的水文水资源管理服务。

Watershed subdivision is an important basic work of distributed hydrological model,which is related to the accuracy of basin hydrological simulation and prediction.In the process of watershed subdivision in large-scale and complicated terrain area,the traditional method has some shortcomings in accurately describing the spatial extent of the study area,determining the outlet of the basin,and extracting the river network of the inflow area,which commonly uses a single catchment area threshold to extract the river network and divide the watersheds based on surface runoff and flow model.Consequently,a watershed subdivision method,using stem-branch topological codification,was proposed based on automatic recognition of the outlets of basin and the fusion of river network with variable catchment area thresholds.The method mainly includes the determination of basin outlets,the determination of the maximum and minimum catchment area thresholds,the multi-threshold virtual river network integration and watershed subdivision and coding.Taking China as an example,25 174 watersheds were divided,with an average area of 381 km^2,a maximum area of 5 512 km^2 and a minimum area of 4 km^2.The coincidence degree between the simulated area and the actual area reached 99.92%.While using the traditional method,the number of watersheds was 21 768,and the average area was 434 km^2,and the coincidence degree was only 98.5%.Moreover,the results were compared with the actual water systems and the current basin of China to verify the applicability of the method.The program is realized through programming that is fast and efficient.It takes into account the computational efficiency of the model and the accuracy of watershed subdivision,which lays a good foundation for developing distributed hydrological model in large scale region and helps to better serve the management of hydrology and water resources in the region,especially at the national macro level.