State Key Laboratory of Water Environment, School of Environment, Beijing Normal University, Beijing 100875, China.
State Key Laboratory of Water Environment, School of Environment, Beijing Normal University, Beijing 100875, China.
Sci Total Environ. 2017 Nov 15;598:353-364. doi: 10.1016/j.scitotenv.2017.04.074. Epub 2017 Apr 24.
Environmental models can be used to better understand the hydrologic and sediment behavior in a watershed system. However, different processes may dominate at different time periods and timescales, which highly complicate the model interpretation. The related parameter uncertainty may be significant and needs to be addressed to avoid bias in the watershed management. In this study, we used the time-varying and multi-timescale (TVMT) method to characterize the temporal dynamics of parameter sensitivity at different timescales in hydrologic and sediment modeling. As a case study, the first order sensitivity indices were estimated with the Fourier amplitude sensitivity test (FAST) method for the Hydrological Simulation Program - Fortran (HSPF) model in the Zhangjiachong catchment in the Three Gorge Reservoir Region (TGRR) in China. The results were compared to those of the traditional aggregate method to demonstrate the merits of the TVMT method. The time-varying nature of the hydrologic and sediment parameters was revealed and explained mainly by the variation of hydro-climatic conditions. The baseflow recession parameter, evapotranspiration (ET) parameter for the soil storage, and sediment washoff parameter showed high sensitivities almost across the whole period. However, parameters related to canopy interception and channel sediment scour varied notably over time due to changes in the climate forcing. The timescale-dependent characteristics was observed and was most evident for the baseflow recession parameter and ET parameter. At last, the parameters affecting the sediment export and transport were discussed together with the inferred conservation practices. Reasonable controls for sediment must be storm-dependent. Compared to management practices on the land surface, practices affecting channel process would be more effective during storm events. Our results present one of the first investigations for sediment modeling in terms of the importance of parameter sensitivity in both time periods and evaluation timescales for the model calibration, diagnostic evaluation, and prioritizing efforts for conservation practices.
环境模型可用于更好地了解流域系统中的水文和泥沙行为。然而，不同的过程可能在不同的时间和时间尺度上占主导地位，这使得模型解释变得非常复杂。相关参数的不确定性可能很大，需要加以解决，以避免流域管理中的偏差。在本研究中，我们使用时变多时间尺度（TVMT）方法来描述水文和泥沙建模中不同时间尺度上参数敏感性的时间动态。作为案例研究，我们使用傅里叶幅度灵敏度测试（FAST）方法对中国三峡库区张家冲流域的水文模拟程序 - Fortran（HSPF）模型的一阶灵敏度指数进行了估计。将结果与传统的综合方法进行了比较，以证明 TVMT 方法的优点。揭示并解释了水文和泥沙参数的时变性质，主要由水热条件的变化引起。基流退水参数、土壤储存的蒸发蒸腾（ET）参数和泥沙冲刷参数几乎在整个时期都表现出很高的敏感性。然而，由于气候强迫的变化，与冠层截留和河道泥沙冲刷有关的参数随时间变化显著。观察到了与时间相关的特征，并且在基流退水参数和 ET 参数中最为明显。最后，讨论了影响泥沙输出和输移的参数，并与推断的保护实践相结合。泥沙的合理控制必须依赖于风暴。与对地表的管理实践相比，影响河道过程的实践在风暴事件期间将更加有效。我们的研究结果首次从模型校准、诊断评估以及保护实践的优先排序方面，探讨了时间和评价时间尺度上参数敏感性在泥沙建模中的重要性。
