Estimativa do balanço hídrico da bacia hidrográfica do Rio Pajeú utilizando o modelo Soil and Water Assessment Tool (SWAT)

Abstract

Human interference with the environment changes the characteristics of the ecosystem as well as processes related to water resources. These changes have been studied through tools such as hydrological models. One of the models that has been applied in several countries is the Soil and Water Assessment Tool (SWAT). In this context, the objective of this study was to estimate the water balance for the Pajeú river basin through the SWAT hydrosedimental model, aiming to find the hydrological processes for the period from 2008 to 2017. In order to make the estimation of the water balance, the SWAT model requires some input data, they are: Digital Elevation Model (MDE), map of land use and occupation, types of soil, meteorological and pluviometric data. After insertion of all input data and hydrological simulation, the model generated 25 sub-basins and 191 Hydrological Response Units (HRUs). The results of average values of the hydrological processes for the study period were: surface runoff of 110,12 mm, precipitation of 477,6 mm, actual evapotranspiration of 150,6 mm, potential evapotranspiration of 1.667,8 mm, and percolation 213,9 mm. The rise of the shallow aquifer resulted in 33,31 mm and the recharge of the deep aquifer in 11,69 mm. When comparing the observed and simulated flows to the basin, it was observed that the SWAT simulated flow peaks were larger than the observed peaks. Likewise, differences were found between the base flow estimates between the model and the observed data. During the dry season, the model simulated a large part of the flow reaching zero, this fact is related to the characteristic of intermittent rivers. The coefficient of determination (R²) was 0,36, which shows a very weak relation between observed and simulated data. This fact indicates that the SWAT model requires calibration and validation to be used in the Pajeú River basin in future studies, as for example, for prediction studies of the impacts of future climate changes on the basin water balance.