Monitoring satellite-based crop irrigation water requirements for maize, cotton and hay in distinct Mediterranean regions

The water requirements of plants are crucial for the sustainable water resources management since in the Mediterranean region, agriculture is the major consumer of water. In recent decades, remote sensing (Landsat, Sentinel, etc) has been used with appropriate methodologies that allow the estimation of evapotranspiration. The proposed methodology in this research has been developed in parallel with a similar methodology by the European Space Agency (ESA), based on a double energy balance. The proposed method has received an improvement as compared to the ESA’s method, since the Weather Research & Forecasting Model (WRF) is used instead of ERA5, the fifth generation ECMWF, for better estimation of the meteorological conditions. Despite the improvement, the method still presents a systematic overestimation in relation to the field values mainly in the second half of the growing season. To address this problem and to successfully estimate daily actual evapotranspiration (ETa) values, the calibration and validation of the method for two crops (maize, cotton) and hay (mixture of forage crops) is presented. The first two crops were based on experiments carried out in central Greece and the third (hay) in experimental fields in southern France. Soil-water balance models, AquaCrop (for Greece) and PILOTE (for France), are used to monitor the daily crop irrigation water requirements throughout the growing season. The adopted satellite ETa adjustment factor in all crops is close to 0.59–0.63 and R2 ranges from 0.87 to 0.97. The results show that a reliable estimation of ETa can be obtained using satellite data.