DYNAMICS OF ACTUAL CROP EVAPOTRANSPIRATION BASED IN THE COMPARATIVE ANALYSIS OF SEBAL AND METRIC-EEFLUX

DYNAMICS OF ACTUAL CROP EVAPOTRANSPIRATION BASED IN THE COMPARATIVE ANALYSIS OF SEBAL AND METRIC-EEFLUX     ROBERTO FILGUEIRAS1; EVERARDO CHARTUNI MANTOVANI2; DANIEL ALTHOFF3; RAYSSA BALIEIRO RIBEIRO4; LUAN PERONI VENANCIO5 E ROBSON ARGOLO DOS SANTOS6   1 Department of Agricultural Engineering, Federal University of Vicosa, Peter Henry Rolfs avenue, s/n –University Campus, Vicosa - MG, 36570-900, Vicosa, MG, Brazil, roberto.f.filgueiras@ufv.br. 2 Department of Agricultural Engineering, Federal University of Vicosa , Peter Henry Rolfs avenue, s/n –University Campus, Vicosa - MG, 36570-900, Vicosa, MG, Brazil, everardo@ufv.br. 3 Department of Agricultural Engineering, Federal University of Vicosa , Peter Henry Rolfs avenue, s/n –University Campus, Vicosa - MG, 36570-900, Vicosa, MG, Brazil, daniel.althoff@ufv.br. 4 Department of Agricultural Engineering, Federal University of Vicosa , Peter Henry Rolfs avenue, s/n –University Campus, Vicosa - MG, 36570-900, Vicosa, MG, Brazil, rayssa.ribeiro@ufv.br. 5 Department of Agricultural Engineering, Federal University of Vicosa , Peter Henry Rolfs avenue, s/n –University Campus, Vicosa - MG, 36570-900, Vicosa, MG, Brazil, luan.venancio@ufv.br. 6 Department of Agricultural Engineering, Federal University of Vicosa , Peter Henry Rolfs avenue, s/n –University Campus, Vicosa - MG, 36570-900, Vicosa, MG, Brazil, robson.argolo@ufv.br.     1 ABSTRACT   Obtaining spatial evapotranspiration requires that the user has knowledge of the energy balance equation, as well as digital image processing. This fact has made researchers create and make available an actual evapotranspiration (ETa) product for scientific community, EEFLUX (Earth Engine Evapotranspiration Flux). Based on this, the present work aimed to compare ETa from the SEBAL (ETa-SEBAL) algorithm, with ETa based on the METRIC algorithm, which is available by EEFLUX (ETA-EEFLUX). For this, 14 Landsat images were used throughout the 2018 crop season, for maize crop irrigated by central pivot, in western Bahia, Brazil. The results showed that the product available by EEFLUX presents a higher estimate of evapotranspiration, when compared to SEBAL, for the areas with lower NDVI values and higher surface temperature, and the opposite was also observed. In addition, the SEBAL algorithm was more correlated with the NDVI variables and surface temperature. However, ET-EEFLUX showed agreement with the results obtained by the SEBAL algorithm, being an important information available to the scientific community and decision makers in the practice of irrigated agriculture, since it does not require in-depth technical knowledge.   Keywords: water demand, crop monitoring, remote sensing     FILGUEIRAS, R.; MANTOVANI, E. C.; ALTHOFF, D.; RIBEIRO, R. B.; VENANCIO, L. P.; SANTOS, R. A. DINÂMICA DA EVAPOTRANSPIRACAO BASEADO NA ANALISE COMPARATIVA DO ALGORITMO SEBAL E DO METRIC-EEFLUX           2 RESUMO   A obtencao da evapotranspiracao espacializada requer que o usuario tenha conhecimento da equacao do balanco de energia, bem como de processamento digital de imagens. Este fato fez com que pesquisadores criassem e disponibilizassem um produto de evapotranspiracao real (ETa) para a comunidade cientifica, o EEFLUX (Earth Engine Evapotranspiration Flux). Baseado nisso, o presente trabalho teve como objetivo comparar a ETa proveniente do algoritmo SEBAL (ETa-SEBAL), com a ETa baseada no algoritmo METRIC, que esta disponivel pelo EEFLUX (ETa-EEFLUX). Para isso, utilizaram-se 14 imagens Landsat. Os resultados demonstraram que o produto disponivel pelo EEFLUX apresenta uma estimativa maior de evapotranspiracao, quando comparado com o SEBAL, para as areas que apresentam valores de NDVI mais baixos e de temperatura da superficie mais elevada, sendo o contrario tambem observado. Alem disso, o algoritmo SEBAL se mostrou mais correlacionado com as variaveis NDVI e temperatura de superficie. Entretanto, o ET-EEFLUX apresentou concordância com os resultados obtidos pelo algoritmo SEBAL, sendo uma importante informacao disponivel para comunidade cientifica e tomadores de decisao na pratica da agricultura irrigada, visto que dispensa conhecimento tecnico aprofundado.   Palavras-chave: demanda hidrica, monitoramento de cultura, sensoriamento remoto.