Mapeamento da evapotranspiração do perímetro irrigado São Gonçalo-PB por meio de sensoriamento remoto orbital.

Abstract

Evapotranspiration is a major component of the hydrological cycle, and is thus a phenomenon of fundamental importance to life on the planet Earth. This paper aims to map the actual evapotranspiration of São Gonçalo Irrigation Project through SEBAL - Surface Energy Balance Algorithm for Land. Were acquired TM - Landsat 5 on 29 August (DAS = days in sequential years 241), September 14 (257 DSA) and 01-2008 (DSA 305) in the year 2008, which were used to obtain thematic maps of the surface albedo by three different methods of atmospheric correction, named Allen, Idaho and Metric. Together with Ts at surface were obtained maps of net radiation (Rn), soil heat flux (G), sensible heat flux (H) and latent heat flux (LE). Maps of the actual daily ET were obtained using SEBAL METRIC methods, which were validated with ETr data of a coconut dwarf crop, obtained by the product of ETo and the crop coefficient (Kc) of the coconut dwarf. It was found that the Rn ranged on average from 662.3 W m-2 (DSA 241) to 689.9 W m-2 (DSA 257), according to the method Allen and 667.8 W m-2 (DSA 241) to 700.4 W m-2 (DSA 305). The latent heat flux according to the METRIC was consistently higher than the SEBAL, which agrees with the daily values of ETr and showed the same patterns of LE. The daily evapotranspiration in the irrigated area resulted in crop coefficients (Kc) consistent with studies obtained in different areas of Northeast Brazil. It was concluded that there was an increase in plant biomass in the irrigated areas between the years of 1987 and 2008 and that the technique provides consistent estimates of the actual daily ET. The volume of water on average monthly evapotranspirated in the irrigated areas was kept around 8,400,000 m3, which represents a large volume of water compared to the capacity of the Sao Goncalo dam.