HydroSOS will be built on the following components:°In situ data: river flow, soil moisture, large lake and reservoir levels and groundwater depths;°Global/regional-scale remotely sensed satellite data: precipitation, soil moisture, aquifers, andsnow cover/depth;°Global/regional weather and climate forecast models: precipitation and temperature; and°Global/regional/basin scale hydrological models: river flow, soil moisture, groundwater