Alberto M Arroyo Avilez, Julian David Ome Narváez and Julian Fernando-Mateus Rodriguez
Colombian Sugarcane Research Center (Centro de Investigación de la Caña de Azúcar de Colombia), Cenicaña Experiment Station, Km 26 Road Cali-Florida, Colombia: amarroyo@cenicana.org
Accurate estimation of actual evapotranspiration (ETa) is essential for sustainable water management. This study was conducted from 2022 to 2024 in the Cauca River Valley of Colombia, over one sugarcane growing cycle, using Sentinel-2 satellite images to estimate ETa with the SAFER (Simple Algorithm for Evapotranspiration Retrieving) model. Data was processed in R using the Agriwater package. Potential evapotranspiration (ETp) was calculated from reference evapotranspiration (ETo), estimated using the Penman-Monteith method, with weather data and crop coefficients (Kc) from FAO 56. The SAFER model showed an average ETa of 4.04 mm/day, with a minimum of 0.1 mm at the initial growth stage of the cycle and a maximum of 8.1 mm at 270 days during the middle growth stage. The ETp had an average of 4.5 mm/day, with a minimum of 0.14 mm/day in the initial growth stage and a maximum of 6.1 mm/day during the middle growth stage. The relationship between ETa and ETp showed an R² of 0.88 and an RMSE of 0.56. ETp values were higher than those estimated by SAFER, which can be attributed to the assumption of no water limitations in the ETp calculation, while SAFER reflects actual field conditions. Results indicate that ETp represents the crop’s potential under optimal conditions, while SAFER accounts for real-world water availability. Overall, the SAFER model was consistent with similar studies and proved useful for managing irrigation in sugarcane fields. The model’s ability to track evapotranspiration under real conditions can help optimize irrigation practices and improve water efficiency in semi-arid regions like the Cauca River Valley.