World Hydrological Cycle Observing System (WHYCOS)

The World Hydrological Cycle Observing System (WHYCOS) aims to strengthen national capacities in basic observation, foster basin-wide, regional and international cooperation and promote the free exchange of hydrological data. 

Its ultimate goal is to support decision-making in water management through the provision of reliable data and information. It envisions bolstering sustainable socio-economic development, environmental protection, mitigation and adaptation to climate change effects, and conflict prevention, especially in transboundary catchments. 

The programme underwent a full review in 2011 that highlighted the need to enhance the sustainability and effectivity of the projects achievements (both financial and operational). As a response, the WHYCOS programme is now at the core of the WMO HydroHub. 

A new strategy is under development for the next generation of HYCOS components. The paradigm shift takes into consideration the lessons learned during the implementation of WHYCOS activities. In particular, they concern the need to enhance the sustainability and effectiveness of the projects' achievements, both from a financial and an operational point of view.


The WHYCOS is implemented through regional components called HYCOS projects. Since its formation in 1993, over 14 HYCOSs projects have been undertaken around the world. HYCOS projects are based on user requirements, and operate in a bottom-up approach - from the country level up through a basin, regional and global scale. They focus primarily on surface water streamflow, but also consider other elements, such as precipitation, groundwater and basic water quality variables. These projects are implemented independently, and aim to improve the technical and institutional capacities of National Meteorological and Hydrological Services (NMHSs).