4DHydro will build up an open-access reference dataset for hydrological variables over Europe, Rhine, Po and Tugela basins, composed of high resolution Earth Observations data. The datasets will include EO products of :
Soil moisture Precipitation (Link) Evapotranspiration (Link) Discharge (link) Snow (link)
Surface Soil Moisture (SSM) is the relative water content of the top few centimetres soil, describing how wet or dry the soil is in its topmost layer, expressed in percent saturation. It is measured by satellite radar sensors and allows insights in local precipitation impacts and soil conditions. SSM is a key driver of water and heat fluxes between the ground and the atmosphere, regulating air temperature and humidity. Moreover, in its role as water supply, it is vital to vegetation health. Vice versa, SSM is very sensitive to external forcing in the form of precipitation, temperature, solar irradiation, humidity, and wind.
The product will integrate two SM2RAIN-based (Soil Moisture to RAIN,) products applied to Sentinel-1 and ASCAT soil moisture products with GPM late Run satellite products, bearing in mind the limitations of satellite soil moisture products over mountain areas and over snow/frozen soils. Therefore, the high-resolution (1 km , 1 day) rainfall product, based on EO data, will be developed and tested in the hydrological applications.
UFZ will collect the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) product, the MODIS global evapotranspiration product and other datasets generated for this project using the HOLAPS, ALEXI and DisALEXI models. Lower resolution products widely used in the literature, like the Global Land Evaporation Amsterdam Model (GLEAM) product, will be collected for comparison purposes.
Deltares will leverage on Global Water Watch and related ESA Surface2Storage project. Within these projects high-resolution EO data is used to quantify surface water extent, level and volume, by combining data from sensors that can capture these types of dy- namics (e.g., Sentinel-2 for surface water extent, ICESat-2 for water levels), enhanced by in-situ measurements when available. The combination with hydrological models enables a detailed assessment of reservoir inflow and outflow, which in the case of large reservoirs is a critical component of the downstream flow regime