Time continuous two-source energy-water balance modelling of heterogeneous crops: FEST-2-EWB

An accurate knowledge of the water and energy exchanges in the soil-crop-atmosphere system is critical for a precise and aware control of all agricultural operations, from field management to irrigation and harvest. This concern is more complex to address in heterogeneous systems, with the presence of bare soil or simple grass in between the main crop. In this work, a two-source energy-water balance model is developed, joining the advantages of the single-source FEST-EWB model (internal computation of surface temperature and time-continuous modelling) and those of two-source approaches (employing two surface temperatures to accurately characterize the intra-pixel heterogeneity). In order to validate the model results, a laboratory experiment has been designed over a lysimeter, with the target of obtaining partitioned estimates of Evaporation and Transpiration over a heterogeneous grass crop. These partitioned fluxes were supported by a safe error margin in the scaling procedure (less than +/- 1 mm/d). The FEST-EWB and FEST-2-EWB models were first calibrated using surface temperature obtained from thermal camera observations (with roughly 1.7 degrees C of average bias). Then, they were validated against the partitioned estimated. The single-source modelling showed a consistent overestimation of the estimated Transpiration, by an amount roughly 20% of the average irrigation event. On the other hand, the two-source model shows much lower (6%) errors, portraying more accurately the Transpired water volume. Such an improvement in crop water consumption estimation can provide a successful reference to optimize the use of the irrigation water resource, with consistent water savings.