Abstract
Estimation of evapotranspiration is a key factor to achieve sustainable water management in irrigated agriculture because it represents water use of crops. Satellite-based estimations provide advantages compared to direct methods as lysimeters especially when the objective is to calculate evapotranspiration at a regional scale. The present study aimed to estimate the actual evapotranspiration (ET) at a regional scale, using Landsat 8 - OLI/TIRS images and complementary data collected from a weather station. SEBAL model was used in South-West Parana, region composed of irrigated and dry agricultural areas, native vegetation and urban areas. Five Landsat 8 images, row 223 and path 78, DOY 336/2013, 19/2014, 35/2014, 131/2014 and 195/2014 were used, from which ET at daily scale was estimated as a residual of the surface energy balance to produce ET maps. The steps for obtain ET using SEBAL include radiometric calibration, calculation of the reflectance, surface albedo, vegetation indexes (NDVI, SAVI and LAI) and emissivity. These parameters were obtained based on the reflective bands of the orbital sensor with temperature surface estimated from thermal band. The estimated ET values in agricultural areas, native vegetation and urban areas using SEBAL algorithm were compatible with those shown in the literature and ET errors between the ET estimates from SEBAL model and Penman Monteith FAO 56 equation were less than or equal to 1.00 mm day-1.
Highlights
Effective water resources management has social and environmental importance and natural resources sustainability in a watershed may be compromised in its absence
The purpose of this study was: (1) estimate and evaluate actual evapotranspiration (ET) obtained from Surface Energy Balance Algorithm for Land (SEBAL) using Landsat 8 images in agricultural areas, native vegetation and urban areas (2) validate the SEBAL algorithm results comparing with crop evapotranspiration (ETc) estimated by FAO-Penman-Monteith equation from a pasture and soybeans areas
The estimated ET in agricultural areas, native vegetation and urban areas using SEBAL algorithm were compatible with those shown in the literature
Summary
Effective water resources management has social and environmental importance and natural resources sustainability in a watershed may be compromised in its absence. Monitoring the most important components of the hydrological cycle, especially evapotranspiration since it represents water loss from surface to atmosphere, is vital to effect measures for water management (OLIVEIRA et al, 2014). The water use of crops can be measured from installation of hydrometers each irrigated field. High cost and low operability make this measure a cumbersome operational application. In this context, remote sensing becomes a low cost alternative and with a large a real coverage to obtain the actual evapotranspiration (ET) (SILVA et al, 2012)
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