The role of protected and deforested areas in the hydrological processes of Itacaiúnas River Basin, eastern Amazonia.

To protect indigenous land and avoid the spread of deforestation in the Amazon, state and federal Brazilian agencies recognized several protected areas since the 1990s. However, the importance of these protected areas in the water cycle and the hydrologic connection with surrounding landscapes is little analyzed. In this study, we evaluated the role of preserved and deforested areas in the water balance in the Itacaiúnas River Basin using the MGB hydrological model. We estimated the impacts of land cover changes on evapotranspiration and discharge for four scenarios: Preserved (1984 land cover), Recent (2013 land cover, with 50% deforestation), Hypothetical deforestation of protected areas (70% deforestation) and complete deforestation of protected areas (79% deforestation). We showed that deforestation of the remaining preserved area could be responsible for a decrease of 23% (3.5 km³/year) in water transfer to the atmosphere by evapotranspiration. Furthermore, we showed that each 15% of deforestation occurring between the Preserved and Recent scenarios increased the average discharges by 5.4% (40 m³/s). Additionally, past land cover changes in the headwaters of the Itacaiúnas River Basin caused statistically significant changes in discharges inside the protected areas. This insight is considered important due to the association between increases in discharges and water quality issues. The results suggest that headwater areas of secondary drainages that run into the forested domains should be prioritized for reforestation programs. Likewise, the reforestation of nonprotected areas could be responsible for restoring ecosystem services, including hydrological functions, biodiversity and water quality.

Three decades of reference evapotranspiration estimates for a tropical watershed in the eastern Amazon

ABSTRACT This study estimated the reference evapotranspiration rate (ETo) for the Itacaiúnas River Watershed (IRW), Eastern Amazonia, and measured the accuracy of eight empirical equations: Penman-Monteith (PM), Priestley-Taylor (PT), Hargreaves and Samani (HS), Camargo (CAM), Thornthwaite (TH), Hamon (HM), Kharrufa (KF) and Turc (TC) using monthly data from 1980 to 2013. In addition, it verifies the regional applicability to the IRW using a for the Marabá-PA station. The methods TC and PM (FAO56) presented the best results, which demonstrate that radiation and higher temperatures are the dominant drivers in the Evapotranspiration process, while relative humidity and wind speed have a much smaller impact. The temporal and spatial variability of ETo for IRW show has strong seasonality, increasing during the dry season and decreasing during the rainy season. The statistical analyses at 1% level of significance, indicates that there is no correlation of the residuals between the dry and rainy seasons, and test of the physical parameters such as mean temperature, solar radiation and relative air humidity explains the variations of ETo.