降雨的空间不均性对模拟产流量和产沙量不确定的影响

在传统的水文/水质模型中,降雨被认为是在空间上均匀分布并且对模型输出的不确定性不产生影响。本文的目的是评价由于降雨的空间分布不均匀性对模型输出-产流量和产沙量-不确定性的影响。本文选取卢氏流域为研究区域,使用SWAT模型和流域内24个雨量站的降雨作为模型的输入。基于降雨空间分布均匀的假定下,每次用一个雨量站的点雨量来作为流域的面平均降雨量,模拟的产流量和产沙量的不确定性来自于降水的不均匀性。模拟的产流量和产沙量的不确定性大于降雨的不确定性,结果表明,在运用水文/水质模型时,为了准确的模拟、预测产流量和产沙量必须掌握降雨的空间分布特性并将其应用于水文、水质模拟之中。

Model Output Uncertainty Due to Spatial Variability of Rainfall

Traditionally in the application of hydrologic/water quality (H/WQ) models, rainfall is assumed to be spatially homogeneous and is considered not to contribute to output uncertainty. The objective of this study was to assess the uncertainty induced by model outputs-runoff and sediment yield- solely due to rainfall spatial variability. The study was conducted using the SWAT model and the rainfall captured by a network of 24 rain gauges in Lushi Basin. For each rainfall event, the model was run using the rainfall captured by each rain gauge, one at a time, under the assumption of rainfall spatial homogeneity in the study area, A large uncertainty in the modeled outputs was resulted from the rainfall spatial variability. The uncertainty in the modeled outputs exceeded the input rainfall uncertainty. The uncertainty of simulated sediment yield outranges that of the runoff. The uncertainty of the simulated runoff increases with the spatial variability of rainfall. The more homogeneous of the rainfall, the more certainty of the modeled runoff. The uncertainty of the modeled sediment yield increased with the increase of spatial variability of rainfall, and the uncertainty of the modeled sediment yield is inversely related with the simulated sediment yield. Results of this study indicate that spatial variability of rainfall should be captured and used in H/WQ models in order to accurately assess the model outputs.In the application of H/WQ models, the assumption of the spatial homogeneity of the rainfall may not be valid. Spatial variability of rainfall introduces uncertainty into model outputs when uniformity of rainfall is assumed. Spatial variability of rainfall should be captured and used in H/WQ models in order to accurately assess the release and transport of pollutants. Since rainfall is a driving force behind many kinds of pollutant release and subsequent transport mechanisms, ignoring this property of rainfall in the application of H/WQ models will put a limit on the accuracy of the model results.