Satellite-Based Innovative Methodological Procedure for Estimation of Daily Actual Crop Evapotranspiration in Vulnerable Agroecosystems: A Case Study in Castilla-La Mancha, Spain

This study deals with the estimation of daily actual evapotranspiration (ETa) values above selected agricultural fields located in the semi-arid region of Albacete at the autonomous region of Castilla-La Mancha, Spain, for the growing season of 2020-21. ESA’s Sentinel free imagery was utilized for the satellite-based estimation of ETa values. A modification of Sen-ET SNAP graphical user interface by ESA was introduced, as well as meteorological data from the Weather Research and Forecast (WRF) model. The estimated values are compared against ETa values derived from lysimeter observations acquired in-situ from the study region (ET0). Initial results showed a high correlation (R²=0.75) between the proposed model and lysimeter measurements, but with systematic underestimation which was corrected by introducing an intercept in the proposed linear relationship, improving ETa estimations. Validation with 2022-2023 data confirmed the reliability of the corrected method, which, although is not as accurate as FAO Penman-Monteith (R²=0.99), it offers a significant advantage at the ET estimation used for local agricultural and hydrological applications.