Global Hydrological Status and Outlook System (HydroSOS)

The challenge

HydroSOS Flyer 2021Globally hydrological variability poses one of the greatest threats to the world's population. There are an increasing number of people at risk from water-related hazards and rapidly growing demands on water resources. However, there is currently no global system which is capable of assessing the current status of surface and groundwater systems or predicting how they will change in the immediate future.

HydroSOS plans to provide the crucial global scale information needed to help citizens understand the current status of the world's freshwater systems and adapt in light of the near-future outlook by harnessing new technologies and link up other initiatives to enable us to better answer questions like: "How much water is there in rivers around the world at the moment?", "Is the current situation normal?", and "How might the global flood/drought situation change in the coming few months?".

The ambition

The long-term aim of this initiative is to develop a worldwide operational system at monthly timescales capable of providing:

HydroSOS 3 goals

HydroSOS brings together existing tools and approaches to develop composite products of hydrological status and outlook.

The System

This important initiative, envisioned in the Commission for Hydrology and now overseen by the WMO Hydrological Assembly, has been approved by WMO Congress (see Resolution 25 of Cg-18) and intends to provide an operational system capable of assessing the current hydrological status and its likely near-future outlook (sub-seasonal to seasonal time frames) for all areas of the globe. The System will be delivered by National Meteorological and Hydrological Services (NMHSs), offering simple, accessible hydrological information to users such as government bodies, basin managers, funding institutions, aid agencies, UN bodies, and the general public. HydroSOS is being developed in phases, with the first one being a pilot phase (2017-2021). Under this phase, pilot basins have been identified in Africa and South Asia. This initiative is part of the WMO Strategic Objectives and is aligned with WMO priorities regarding Disaster Risk Reduction, the Global Framework for Climate Services (GFCS), the WMO Integrated Global Observing System (WIGOS), and Capacity Development. HydroSOS is seen as an important tool to help NMHSs deliver their services by providing hydrological products for informed decision-making. In addition, the system, underpinned by hydrological data sharing, meteorological forecasts and climate prediction information with advances from the global research community, will support the 2030 Agenda for Sustainable Development and, in particular, the broader global community in the area of water management.


Current progress

In October 2021, HydroSOS End-of-Pilot-Phase report was approved in Cg-EXT (2021) and is available in all UN official languages: ar - zh - en - fr - rues.  The document provides information about the way forward (section 3) including recommendations on regional implementation groups and activities (section 3.4). Moreover, the document provides a list of deliverables (section 4.4) and a summary of results from the pilot phase (section 5).

The HydroSOS methodology was developed by a team of 50+ experts from 17 NMHS across the six WMO Regions, nine research/scientific institutions in seven countries, three regional organizations in Africa, and four international organizations, and it is beeing now integrated in Regional Associations’ implementation plans. Moreover, HydroSOS activities are being added to hydrological components of larger projects, for example CREWS and the Adaptation Fund.

70 WMO Members (36%) are formally engaged with the HydroSOS initiative and have provided inputs to the development of the system, such as by performing national assessments or providing relevant case studies.

Early implementation stages are ongoing informally and formally in many regions across the globe, and as of end-of-year 2021. Officially, Regional Associations I, II, III, IV and V have requested their hydrological groups to prepare HydroSOS implementation plans and countries in RA VI have decided to support the technical aspects of the initiative. WMO is currently working together with 23 Member countries (7 in RA I, 6 in RA II, 3 in RA III, and 7 in RA IV) on inception activities for HydroSOS under different projects and developing project proposals.

Annual Global State of the Water Report

As an auxiliary output of HydroSOS, WMO proposes to publish a global annual water report starting from 2022, which will present an overall picture of  stream flows in different basins globally during the previous water year. The report will depict “relative” conditions with respect to “normal” using categories recommended in the WMO Statement on the Term Hydrological Normal. Click here for the concept note.  

Message from the HydroSOS Task Team Leader

Please click here for a video about HydroSOS and the current progress achieved by the new initiative.


Contact us

For any HydroSOS-related inquire, please send an email to where to contact HydroSOS.


Related news

Active meetings

Upcoming meetings

Past meetings