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.
Impacts on global water resources may be intensifying due to the growing and differentiated forms of land use and occupation, which influence the water cycle and thus the maintenance of life. In the Amazon, the effect may be even worse, as it is one of the world's most vulnerable regions to these changes. This work aimed to analyze the response of the components of the water balance to changes in land use and cover in the Eastern Amazon over three decades (1980–2013). First, soil texture maps were prepared. These combined with the classes of use in each decade let us estimate the values of storage and variation in storage (ΔS) of water in the soil. The behavior of the components of the water balance [precipitation, potential evapotranspiration, actual evapotranspiration (E), and ΔS] were analyzed according to the Budyko model on the annual scale as a function of the aridity and evaporative indices. For the seasonal scale, a new parameter (y0) was introduced to explicitly represent the additional water available for E, in addition to instantaneous precipitation. The seasonality of the rains and the seasonal dynamics of storage were directly incorporated into the model developed, which allowed us to understand what the dominant control factors of water balance are. In the decade from 2000 to 2009, the remaining forest cover is only 48.91%, while the cover formed by pasture is 50.47%, meaning the water storage capacity in the soil decreased 8.1%. In the 1990s, to 1999, precipitation shows a reduction, probably as a reflection of the very strong events of La Niña and El Niño (1988–1989 and 1997–1998). Observing the sum of the surface area of water bodies in the region and the relationship of forest vs. pasture, it is possible to infer that the elevation in evapotranspiration is more related to the increase in evaporation due to the increase in the pasture area than to the reduction transpiration due to forest loss, reinforcing the hypothesis that evapotranspiration increases with pasture area.
We present this manuscript as a methodological approach and general guidelines for geochemical mapping and background/baseline projects for environmental assessment in tropical areas. A case study was carried out in the Itacaiúnas River watershed (IRW), Eastern Amazon, to fill in a gap in knowledge on the distribution of chemical elements, particularly those potentially toxic, in the near-surface environment of the area. The high-impact results of this research project revealed the need for similar scientific investigation across the globe with the implementation of a systematic methodology. The study shows, for example, the importance of well-planned field activities, multi-medium sampling, analytical methods, laboratory procedures, database construction, and general aspects of data processing and statistical treatment. The importance of this contribution is that it can be used as a reference in support of geospatial analysis in research within the scope of geochemical mapping and background-baseline projects. The database is accessible through a web-based geographic information system front-end; a Geochemical Atlas of the IRW will be available as soon as possible.
O bioma amazônico vem apresentando complexas formas de apropriação do território associados a sistemas produtivos diversificados. A dinâmica espacial da Amazônia paraense vem sofrendo transformações com o avanço das fronteiras dos grandes empreendimentos e seus impactos ambientais significativos. O objetivo deste trabalho foi compreender os principais eventos relacionados à políticas públicas que incentivam a ocupação e/ou expansão dos grandes empreendimentos, os instrumentos regulatórios ambientais que legalizam o funcionamento das atividades, e refletir sobre licenciamento ambiental como instrumento legitimador do espaço ocupado. Realizou-se revisão sistemática de literatura científica e documental. Agrupou-se os eventos sob diferentes cenários governamentais. Efetuou-se o levantamento dos instrumentos regulatórios ambientais, destacando aqueles que concedem permissão para implantação de atividades com impactos significativos. Posteriormente, houve análise interpretativa sobre a presença dos efeitos socioambientais significativos mesmo após a criação do licenciamento ambiental. Os resultados indicam a Amazônia como território absorvedor de impactos ambientais significativos desde os primeiros grandes empreendimentos implantados. O licenciamento ambiental vem legitimar a ocupação do território e uso dos recursos naturais em larga escala, e, portanto, deve-se ponderar para que não haja legitimação de impactos sem o tratamento eficiente, assim como conflitos agrários e acidentes socioambientais com danos severos e irreversíveis, principalmente envolvendo populações tradicionais. Diante do exposto, ratifica-se a necessidade de aprofundar debates envolvendo a sociedade, como parte interessada e atingida, em conjunto com os empreendimentos, comunidade científica e poder público, abordando a responsabilidade socioambiental desses empreendimentos e estratégias de política pública para o planejamento ambiental e desenvolvimento territorial.
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