Monitoring Water Use in Almond Orchards Through Surface Energy Balance Applied to Landsat Imagery in Southeastern Spain

The objective of this work is to evaluate the performance of two classic energy balance models, METRIC (one-source) and STSEB (two-sources), in the operational monitoring of the actual evapotranspiration (ETa) in almond orchards located in the semiarid regions of southeastern Spain through Landsat 8 images. In situ energy flux measurements were available in two experimental sites. This work shows the results of the analysis of a set of Landsat 8 images from the period 2019-2020. On a daily scale, the ETa results show an average error of less than 1.0 mm d^-1 in both models, with an underestimation of 0.2 mm d^-1 for STSEB and an overestimation of 0.5 mm d^-1 for METRIC. The combined use of Landsat 8 and 9, represents a significant advance in the ability to detect situations of water stress at the field scale, and to quantify it in a distributed manner within an image.