Abstract
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.
Highlights
Water, the dynamic component of the hydrosedimentological cycle, is part of the weathering and erosion processes of the rocky and pedological substrate, transporting and depositing sediments through surface runoff and river flow
The present study evaluated the simple and multi-site calibration techniques in nested 6th (RPW) and 5th (Caunal Dam) order river basins with reservoirs
The following conclusions were formulated: (a) For a 6th order river basin it was found that with simple calibration, and considering only the parameters of the intrinsic processes of the watershed and management of rural areas, the evaluation indices as well as the annual totals were better than performing the multi-site calibration
Summary
The dynamic component of the hydrosedimentological cycle, is part of the weathering and erosion processes of the rocky and pedological substrate, transporting and depositing sediments through surface runoff and river flow. The hydrological cycle is articulated with other matter and energy cycles, and must be analyzed according to the diversity of its components within the system that integrates them, which will present a unique dynamic because of its spatial/temporal magnitude (KLEMES, 1983; BLOSCHL; SIVAPALAN, 1995; TUCCI; MENDIONDO, 1997). A model that is often used in several parts of the world (GASSMAN et al, 2007), including Brazil (BRESSIANI et al, 2015), is the Soil and Water Assessment Tool - SWAT (ARNOLD et al, 1998, 2012a). This model was developed by researchers from the Agricultural Research Service of the USA (ARS – USDA) and Texas A&M University. Its objective is to evaluate the impact of climate changes, land use/cover and agricultural management on water and sediment balance, nutrients and pesticides for long periods (ARNOLD et al, 2012a)
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