The Global Hydrological Status and Outlook System (HydroSOS)

The Global Hydrological Status and Outlook System – monitoring and predicting global freshwater hydrological conditions  

Approximately 20 million people are at risk from flooding, with the damage costing nearly US$ 80 billion; this could rise to 50 million people affected in just 15 years' time, according to the World Resources Institute. The World Economic Forum estimates that the effects of drought across the world cost up to US$8 billion a year from losses in agricultural and related businesses. These challenges will only intensify with future climate change, population growth and increasing economic activities. According to the UN, there will be 9.7 billion people living on our planet by 2050; this in itself presents a significant challenge in a world beset by hydrological variability on a global scale. Water features heavily in the new United Nations Sustainable Development Goals, not only in the explicit aim to ensure availability and sustainable management of water and sanitation for all but also because of the underpinning nature of water-related issues across many development areas. 

With further exacerbation of the situation due to climate change, population growth and increased economic activities, the WMO Global Hydrological Status and Outlook System (HydroSOS) addresses the need for prediction by regularly reporting on: 

  • the current global hydrological status, including groundwater, river flow and soil moisture; 
  • an appraisal of where the current status is significantly different from ‘normal,’ for example indicating potential drought and flood situations; and 
  • an assessment of whether this is likely to get better or worse over the coming weeks and months. 

By coupling global-scale applications at relevant spatial and temporal resolution, thanks to numerical weather prediction techniques and hydrological models, and using satellite data products on hydrometeorological variables and ground-based observations, HydroSOS uses: 

  • Local-scale ground-based data: River flow, soil moisture, large lake levels and groundwater depths, 
  • Global/Regional-scale remotely sensed satellite data: Precipitation, soil moisture, aquifers and snow cover/depth, 
  • Global/Regional weather and climate forecast models: Precipitation and temperature, and 
  • Global/Regional/Basin-scale hydrological models: River flow, soil moisture, groundwater. 

HydroSOS directly builds on existing and planned WMO initiatives in relation to hydrological monitoring, data sharing and sub-seasonal to seasonal meteorological forecasting, to deliver a unique operational system providing up-to-date hydrological information and products from National Meteorological and Hydrological Services to a range of end-users. This, will be achieved by collaborating with different partners. 

Global map displaying the implementation status of hydrosos projects across different regions as of march 2024.

While the HydroSOS’s information and products are global, they are also provided at regional and national scales. The operational system supports the activities of National Meteorological and Hydrological Services and provides easily accessible hydrological information and products that can be made accessible to government bodies, regional and international aid agencies, and the public.

More information about HydroSOS on the WMO Community Platform.