High resolution (1 km) soil moisture and precipitation for developing a Digital Twin Earth for hydrology

In recent years, the availability of high-resolution observations (<1km, sub-daily) from remote sensing, in situ monitoring networks and new sensors/techniques (drones, citizen science), in addition to the increased computational and storage capacity, have fostered the development of modelling systems at high resolution for hydrological applications. The European Commission (EC) is promoting these developments through the EU’s digital strategy, the Green Deal, and specifically the Destination Earth initiative. The development of digital twins of the Earth System is currently in the EC agenda as one of the most pressing activities to be accomplished to build a resilient society able to cope with adverse extreme events (flood, drought, heatwaves, landslides), exacerbated by global and climate changing. Despite the high-resolution hydrology is an important opportunity for future research and operation applications, the challenges to be addresses are quite a lot and non-trivial. First, the increased computational capabilities are far from being sufficient to develop high resolution hydrological systems because observations (e.g., precipitation, evapotranspiration, soil moisture, river discharge) have to be available not only at high resolution, but also with sufficient accuracy. A second problem is related to the representation of physical processes that, at high resolution, are significantly different from processes at coarse resolution (20km), currently modelled at large scale. Last but not least, the human impact on the water cycle (e.g., irrigation, reservoir management, river water diversion) acting at very high resolution, challenges the current attempts of reproducing a digital replica of the Earth. The launch of Sentinel-1 satellites has opened a number of opportunities for developing high resolution satellite soil moisture and precipitation products. These products are an important element for building a Digital Twin Earth (DTE) for Hydrology, i.e., for the reconstruction of the water cycle at high resolution. In this contribution we will present the recent advances over this topic carried out under European Space Agency projects DTE Hydrology and Irrigation+. Specifically, we will present the application of high-resolution products for hydrological applications: flood simulation, landslide risk prediction and irrigation water management. Finally, the main challenges to be addressed will be discussed.