Spatial distribution of evapotranspiration by fractional vegetation cover index on irrigated cropland banana (Musa Spp.) in the semiarid

Abstract

Water management can be done in many ways, but the methods that use evapotranspiration (ET) are the most common. The Penman-Monteith FAO56 (PM) standard method is effectively used to estimate evapotranspiration and, in this way, ensure proper water application. In addition, remote sensing is also used for water management. The free availability of software and high-resolution satellite imagery opens many possibilities. Methods such as spatial distribution of ET provide an overall view that contributes to better use of water resources. In this sense, the objective of this study is to demonstrate the spatial distribution of ET determined by the PM method by using an index that measures fractional vegetation cover (Fc). For this purpose, data from weather stations and Landsat 8 collection 2 level 1 image from the OLI/TIRS sensor in spectral bands 4 and 5 were used. The study area is a dwarf silver banana plantation located in the semiarid region of northeastern Brazil, in the Missão Velha city area. The spatialization starts with the determination of the normalized difference vegetation index (NDVI), followed by the determination of the Fc, using the ET from the PM method together with the crop coefficient (Kc). Evapotranspiration mapping images with internalized calibration (METRIC) corresponding to the same location and date were also used to compare and analyze the results. The novelty of this study is utilizing the ET determinate with weather station data and make the spatial distribution of ET (SPD-ET) in satellite images, from a practical and easy way, which can be quickly replicated and used by anyone. The linear regression between SPD-ET and METRIC-ET gives an R2 above 0.80; similar results were obtained for the linear regression between EToF and Fc, with an R2, also above 0.80. The mean values between METRIC-ET and SPD-ET have a deviation of 1.62 mm d-1. The mean absolute percent error between METRIC-ET and SPD-ET was 9.75%, while between EToF and Fc 5.28%. The mean absolute percent error between METRIC-ET and SPD-ET was 9.75%, whereas between EToF and Fc it was 5.28%. Since the difference between the methods is just under 10%, we can conclude that spatializing ET with Fc is as accurate as ET, which was obtained from METRIC.