分布式水文模型亚流域合理划分水平刍议

Discussion on Reasonable Subdivision Level of Watershed for Distributed Hydrologic Model

不同的亚流域划分对流域径流和泥沙负荷模拟的影响源于地形、土壤、土地利用以及气候特征输入的空间分布不均匀性。假设当亚流域划分充分考虑流域输入数据空间分布不均匀性时,流域模拟的输出结果趋于稳定,并应用分布式水文模型——SWAT作为研究工具,在GIS技术支持下,选择两个面积不同的流域采用不同的亚流域划分数量进行流域径流和泥沙负荷模拟。模拟结果表明,当亚流域划分数量达到一定水平时,增加亚流域划分对模型输出结果的影响较小,这在一定程度上证实了上述假设。在此基础上,以简化模型输入数据和输出结果分析处理工作且保证模拟精度为原则,对分布式水文模型亚流域划分的合理划分水平进行了探讨。

Distributed hydrologic models use spatially variable input parameters to predict watershed response, and a widely used method for representing watershed is to aggregate input data on the basis of subwatershed. However, model output could be affected by the spatial extent over which input data are aggregated to produce parameters. It was hypothesized that model output stabilized at the point where spatial characteristics of watershed were fully considered. With the support of GIS technology, distributed hydrologic model--SWAT (Soil and Water Assessment Tool) was used in two watersheds with different area to model the impact of different subdivisions of watershed on runoff and sediment yield, and to some extent the results validate the above hypothesis. Then reasonable subdivision level of watershed for distributed hydrologic model was discussed, increasing the subwatershed number beyond this level does not significantly affect the runoff volume and sediment yield. This reasonable subdivision level could be used to optimize input data preparation requirements and simplify the interpretation of results without compromising simulation accuracy.