The efficient management of water resources for irrigation is of vital importance in arid and semi-arid countries, but often farmers lack access to data and information for adjusting irrigation in relation to the actual crop needs and the actual availability of water resources. Mature technologies based on Earth Observation data and Information Communication Technologies have already been developed by the industry sector; thanks to the Copernicus Sentinel satellite constellation of European Space Agency, EO-services for irrigation management have evolved from prototype level to complete and qualified systems (TRL7-8), i.e. IRRISAT© (www.irrisat.com). The spectral characteristics and the radiometric quality of the imaging sensor on board the Sentinel 2A and 2B satellite have allowed the application of physically-based algorithms which are able to monitor important biophysical crop parameters (e.g. Leaf Area Index, albedo, fractional vegetation cover, canopy water content) for the evaluation of evapotranspiration under a wide range of conditions. In particular, shortwave infrared (SWIR) spectral bands from Sentinel-2 can be used to evaluate the water status of soil and canopy system, allowing the estimation of actual evapotranspiration by using alternative methods to thermal infrared observations, available only from Landsat 8, with limited spatial and temporal resolution. The IRRISAT irrigation advisory system is based on the application of the classical Penman-Monteith for ET calculation and crop water requirements but using the above mentioned biophysical parameters instead of the crop coefficient. Under optimum soil water availability, the surface resistance in P-M equation is mainly dependent on Leaf Area Index. However, when considering arid and semi-arid conditions, the surface resistance are dependent also on the soil water status. IRRISAT has been improved to include SWIR observations to increase the surface resistance when aridity conditions occurs.