RESUMODiante da importância da irrigação em um cenário marcado pela crescente demanda por alimentos, é cada vez mais necessária a adoção de técnicas que possibilitem o devido monitoramento das áreas irrigadas a fim de se observar a dinâmica das condições dos cultivos. Isso se faz possível, de uma maneira rápida e de baixo custo, por meio de técnicas de sensoriamento remoto. Nesse contexto, o presente trabalho teve como objetivo avaliar, com auxílio do sensoriamento remoto, a variabilidade espaço-temporal das condições da vegetação em uma área irrigada por pivô central como subsídio ao manejo da agricultura irrigada. Para tanto, foi utilizada uma série de imagens Sentinel 2A, referente ao período de março a julho de 2016. As imagens foram submetidas ao pré-processamento, para, posteriormente, ser realizada a análise da vegetação através dos índices NDVI (Normalized Difference Vegetation Index) e do VCI (Vegetation Condition Index). A utilização do sensoriamento remoto no presente estudo possibilitou o acompanhamento da variabilidade da condição de vegetação, tendo os índices de vegetação se mostrado sensíveis às variações do vigor da mesma, e constituindo, portanto, uma importante fonte de informação na tomada de decisão para o manejo de irrigação.Palavras-chave: manejo da irrigação, sensoriamento remoto, índices de vegetação. SPATIO-TEMPORAL VARIABILITY OF VEGETATION CONDITION IN IRRIGATED AGRICULTURE THROUGH SENTINEL-2A IMAGES ABSTRACTGiven the importance of irrigation in a scenario which is highlighted by the increasing demand for food, it is increasingly necessary to adopt techniques that allow proper monitoring of irrigated areas in order to observe the dynamics of crop conditions. This is possible, in a fast way and with low cost, using remote sensing techniques. In this context, this study aimed to
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 Viçosa, Peter Henry Rolfs avenue, s/n –University Campus, Viçosa - MG, 36570-900, Viçosa, MG, Brazil, roberto.f.filgueiras@ufv.br. 2 Department of Agricultural Engineering, Federal University of Viçosa , Peter Henry Rolfs avenue, s/n –University Campus, Viçosa - MG, 36570-900, Viçosa, MG, Brazil, everardo@ufv.br. 3 Department of Agricultural Engineering, Federal University of Viçosa , Peter Henry Rolfs avenue, s/n –University Campus, Viçosa - MG, 36570-900, Viçosa, MG, Brazil, daniel.althoff@ufv.br. 4 Department of Agricultural Engineering, Federal University of Viçosa , Peter Henry Rolfs avenue, s/n –University Campus, Viçosa - MG, 36570-900, Viçosa, MG, Brazil, rayssa.ribeiro@ufv.br. 5 Department of Agricultural Engineering, Federal University of Viçosa , Peter Henry Rolfs avenue, s/n –University Campus, Viçosa - MG, 36570-900, Viçosa, MG, Brazil, luan.venancio@ufv.br. 6 Department of Agricultural Engineering, Federal University of Viçosa , Peter Henry Rolfs avenue, s/n –University Campus, Viçosa - MG, 36570-900, Viçosa, 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 EVAPOTRANSPIRAÇÃO BASEADO NA ANÁLISE COMPARATIVA DO ALGORITMO SEBAL E DO METRIC-EEFLUX 2 RESUMO A obtenção da evapotranspiração espacializada requer que o usuário tenha conhecimento da equação do balanço de energia, bem como de processamento digital de imagens. Este fato fez com que pesquisadores criassem e disponibilizassem um produto de evapotranspiração real (ETa) para a comunidade científica, 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 está disponível pelo EEFLUX (ETa-EEFLUX). Para isso, utilizaram-se 14 imagens Landsat. Os resultados demonstraram que o produto disponível pelo EEFLUX apresenta uma estimativa maior de evapotranspiração, quando comparado com o SEBAL, para as áreas que apresentam valores de NDVI mais baixos e de temperatura da superfície mais elevada, sendo o contrário também observado. Além disso, o algoritmo SEBAL se mostrou mais correlacionado com as variáveis NDVI e temperatura de superfície. Entretanto, o ET-EEFLUX apresentou concordância com os resultados obtidos pelo algoritmo SEBAL, sendo uma importante informação disponível para comunidade científica e tomadores de decisão na prática da agricultura irrigada, visto que dispensa conhecimento técnico aprofundado. Palavras-chave: demanda hídrica, monitoramento de cultura, sensoriamento remoto.
Regionalization is an important technique for estimating the flow of hydrographic sections with a lack of data. First, it is necessary to identify hydrologically homogeneous regions (HHRs), which are commonly validated via statistical analyses. Because this step is understood to be subjective, studies that contribute to a greater reliability in identifying regions are needed. In this context, the objective was to evaluate the inclusion of a physical analysis of the average regionalized flow rates as an aid to identify HHRs. The groupings were defined on the basis of geographical convenience methods and cluster analysis. For the assessment of regionalized flows, six statistical indices were used with a physical analysis that was performed via a comparison of the runoff coefficient to the spatial distribution of precipitation values. It was concluded that the physical analysis reduced the subjectivity in the identification of HHRs.
The knowledge of the spatial-temporal dynamics of evapotranspiration is of great importance for the accomplishment of agroclimatic zoning and, therefore, for the design of irrigation systems and management of water use in irrigated perimeters. In this context, this study aimed to generate, with the aid of geotechnologies, information that can support irrigation systems planning and design, based on the temporal distribution of daily climatological normals and on evapotranspiration mapping for the irrigated perimeter of Gorutuba/MG. Climatic data were obtained from the meteorological station of the National Institute of Meteorology (INMET) of the municipality of Janaúba/MG in the period from 1985 to 2014. It was verified the non-tendentiousness and the temporal dependence of the climate data using variogram analysis and the temporal dependence index, respectively. For the interpolation, it was used ordinary kriging. The evapotranspiration mapping was conducted from 180 monthly images, from 2000 to 2014, of the MODIS sensor MOD16A product. The results generated for the irrigated perimeter provided relevant information for decision making of the irrigated agriculture management.
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