FAO (Food and Agriculture Organization of the United Nations) data indicate that annually 2500 km3 of freshwater are used for agricultural production, which amounts to 70% of the water resources the whole of humanity consumes in a year. With the global population continuing to grow at a high pace, it is essential to optimize the use of water resources and to increase agricultural production in view of the prospect of having to feed 8 billion humans in 2030. Scientists have for many years been using remote-sensing satellite observations to improve water balance and farming yield assessment on large geographical scales (at the level of irrigated agriculture areas, catchment basins and so on).