Simulação da resposta hidrológica à mudanças de uso e cobertura da terra em uma bacia hidrográfica no leste da Amazônia

Abstract

The loss of vegetation in the Amazon has been occurring for some decades and the growth of annual deforestation rates is noticeable. The agricultural expansion is indicated as a new agent in this dynamic by the overthrow of the vegetation for the cattle raising and later implantation of mechanized agriculture. This work explored the potential relationships between hydrological variability and landscape organization in the Uraim River Basin at Northeast of Pará. The possible effects of land use and land cover changes effect on streamflow were investigated from Soil hydrological modeling and Water Assessment Tool (SWAT) combined with the projections of future scenarios generated by the Conversion of Land Use and its Effects at Small Region Extent (CLUE-S), the SWAT efficiency was also evaluated in simulating the monthly streamflow when fed by evapotranspiration (ET) of the Surface Energy Balance Algorithm for Land (SEBAL). The results showed the skill of SEBAL to estimate ET under different land use and land cover identified in the watershed. The algorithm presented overestimations, but good precision with the values measured in the field, having greater accuracy in the dry season and using average eight days MODIS images. The SWAT model streamflow simulations were better when ET estimated by SEBAL were applied, which were confirmed by reduction in absolute and relative errors and by the efficient calibration of the most sensitive parameters. The modeling was considered from good to very good according to the NSE, RSR and PBIAS coefficients found. Almost all the variables used in CLUE-S modeling forced land use and land cover changes, mainly biophysical parameters. The projected scenarios indicate agricultural expansion for the northwestern sector of the watershed and greater concentration in the southwest portion. Agricultural areas will increase its by 93.2 km2, corresponding to 13.4% of watershed until 2034, which indicate to a reduction of 34.4% in the streamflow to dry season and an increase of 38.6% in the rainy season. The results suggest that climate change may have played a more pronounced role in the hydrological pattern than the very land use and land cover change projected by CLUE-S. It is intended, therefore, to provide subsidies for environmental monitoring, informing about necessary interventions, targeting the decision-making regarding the sustainable use of water resources.