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.

Climate Indicators for a Watershed in the Eastern Amazon

“…The methodology used for establishing the thresholds was adopted from Carmo et al (2015), but in this study, the thresholds were modified and adapted according to the trends observed for the IRW. The rainiest period was the four months from January to April, with the month of March being the rainiest with a threshold exceeding 85%, which agrees with the literature for the Amazon region (MORAES et al, 2005;SILVA JÚNIOR et al, 2017a). Conversely, the month of July was the driest, with the exception of the FAb station (Figure 3b), for which the month of August was the month with a value below the 15% percentile threshold (17.5 mm), 15.3 mm.…”

“…However, land use is dominated by extensive pastures that surround a mosaic of forest remnants. The IRW area includes indigenous lands and conservation areas that are protected by law, occupying 11,700 km 2 , or roughly a quarter of the watershed area (SOUZA-FILHO et al, 2016;SILVA JÚNIOR et al, 2017a, b). The climate in the region is a monsoon climate (Am), which is a tropical rainy climate (hot and humid) with a mean air temperature above 26°C (INMET, 1992;ALVARES et al, 2013).…”

“…The rainfall regime is characterized by two well-defined seasons, one rainy, regionally known as Amazonian winter, and another dry, which is called Amazonian summer (LOPES et al, 2013). The rainy (November to May) and dry (June to October) seasons are well defined, in which total annual rainfall can vary from 1,800 mm to 2,300 mm during the rainy season and from 10 mm to 350 mm during the dry season (MORAES et al, 2005;SILVA JÚNIOR et al, 2017a). The main weather system that affects the rainfall regime during the rainy season in southeastern Pará, in the IRW region, is the band of convective clouds of the Intertropical Convergence Zone (ITCZ).…”

Three methods of estimating the power of maximum temperature in TM–ET estimation equation

“…Temperature extreme and radiation are the two dominant drivers of evapotranspiration [8,21], which means, to get a reasonable estimate of ET, equations that incorporate the two parameters tend to outperform the methods that incorporate temperature alone. On the other hand, Wang et al [27] emphasize the role of wind speed as well.…”

A GEOBIA Approach for Multitemporal Land-Cover and Land-Use Change Analysis in a Tropical Watershed in the Southeastern Amazon

“…Recent publications have demonstrated the influence of mining projects on the LCLU changes in the Brazilian Amazon from "pixel-to-pixel" approach [17][18][19]. Furthermore, these LCLU conversions have collaborated to climate and water discharge changes in the context of river watersheds in the southeastern Amazon [20][21][22]. In this article, we investigate LCLU changes in the context of a tropical region, the Itacaiúnas River watershed (IRW) that encompasses the Carajás Mineral Province (CMP), which is one of the largest mining provinces in the world and is located in an arc of deforestation caused by large-scale human settlements over the last 30 years in the southeastern Amazon region (Figure 1).…”