Hydrosedimentological modeling with SWAT using multi-site calibration in nested basins with reservoirs

ABSTRACT Calibration and validation of hydrosedimentological models, usually performed at the outlet of a single basin, does not always correctly represent the hydrosedimentological processes in the different subdivisions of dammed river systems. The aim of this study was to evaluate simple calibration techniques (watershed outlet) and multi-site calibration (watershed outlet and internal reservoirs) with the Soil and Water Assessment Tool - SWAT model, using two nested basins in the southern region of Brazil. Three modeling procedures were analyzed, adjusting the hydrological and sedimentological parameters of the watershed and the reservoirs. It was found that (a) the simplest calibration does not correctly represent the processes in reservoirs; (b) the multi-site calibration provided a better simulation of the hydrosedimentological dynamics of the nested basins; and (c) parameterizations of the SWAT reservoir module have limitations in the context of the study area. The results showed that the multi-site calibration in watershed with reservoirs is more appropriate.摘要：通常仅在单一流域出口（watershed outlet）开展水文泥沙模型的率定与验证工作，未必能准确反映筑坝河流系统不同分区内的水文泥沙过程。本研究以巴西南部的两个嵌套流域为研究对象，采用土壤与水评估工具（Soil and Water Assessment Tool，简称SWAT）模型，对比评估了两种率定方法：仅以流域出口为校准点的单一站点率定，以及同时覆盖流域出口与内部水库的多站点率定。本次研究共分析了三类建模流程，分别针对流域与水库的水文、泥沙参数开展率定工作。研究结果显示：（a）单一站点率定无法准确表征水库内的水文泥沙过程；（b）多站点率定可更精准地模拟嵌套流域的水文泥沙动态；（c）SWAT水库模块的参数化方案在本研究区域存在一定局限性。综上，针对带有水库的流域开展多站点率定的方法更为适用。