The WHYCOS programme is implemented through various components (HYCOSs) at the regional and/or basin scale. Each component is implemented independently under the overall guidance provided by the WHYCOS International Advisory Group (WIAG).

Evolution of WHYCOS from 1997 to 2015
WHYCOS is based on a bottom up approach, from the country level through to a basin, regional or global scale. WHYCOS and its components primarily focus on strengthening technical and institutional capacities of National Hydrological Services (NHSs) and improving cooperation in the management of shared water resources.
WHYCOS supports the NHS’s to better fulfill their responsibilities by improving the availability, accuracy, and dissemination of water resource data and information through the development and implementation of appropriate national and regional water resources information systems, thereby facilitating sustainable socio-economic development, environmental protection and adaptation to and mitigation of climate variability and climate change effects.