Avaliação da aplicação do modelo SWAT para simulações hidrológicas na bacia hidrográfica do rio Bicudo, em Minas Gerais

Abstract

The scarcity of water and the intense use of this resource by agricultural sector have caused social conflicts and environmental problems in the hydrographic basin of Bicudo river, an affluent of Velhas river, in Minas Gerais. The hydrographic basin of Bicudo river has some intermittent rivers, which makes water availability one of the biggest challenges for its population in periods of drought, because they are predominantly rural and use water in agricultural and livestock production. In 2015, 308 containment basins, named “barraginhas”, were built in the cities of Corinto/MG and Morro da Garça/MG, where the basin of Bicudo river is located. These constructions were financed by tax from use of water in the basin of Velhas river. In this context, this study aims to investigate whether the projects oriented to recovery of degraded areas, in this case, the containment basins, were able to promote impact over the hydrological behavior of hydrographic basin of Bicudo river. To this purpose, the basin analyzed was modeled by using the Soil and Water Assessment Tool - SWAT to simulate the containment basins implantation effects on water flow of Bicudo river. The model parameters were adjusted using the register of fluviometric station “Ponte do Bicudo” from 2002 to 2014. With the support of SWAT-CUP software, the Nash and Sutcliffe (NS) coefficient of 0,67 and 0,75 and the trend percentage (PBIAS) of -5.1% and 9.5%, were found in calibration and validation steps, respectively. These results from the NS and PBIAS indexes demonstrate that the model elaborated for Bicudo river basin performed well, based on NS index, and very well based on PBIAS index. The scenario with the containment basins built in 2015 was compared to the simulated scenario whithout these interventions. After completing the simulations, it was found that the SWAT model showed sensitivity to changes executed at digital elevation model - MDE, to represent the presence of containment basins. The scenario with “barraginhas” showed lower peak flows than that simulated without them. This result indicates that the presence of these interventions together is capable of promoting peak flow reduction in critical rainy events, favoring the permanence of water within the limits of the hydrographic basin for a longer time. Despite the uncertainties of hydrological simulation tools, the results generated in this work are useful for water resource managers, for members of hydrographic basin committees and for representatives of Brazilian hydrographic basin Agencies. This study could contribute to develop strategies focused on water resources and soil preservation in hydrographic basins with characteristics similar to those of the Bicudo river.