Resolution 25 (Cg-XIII) of the WMO Congress reflects the needs of Member States and organizations to have access to hydrological data and products for a variety of uses. Data and information exchange is beneficial for transboundary water resources management and the provision of services in support of the protection of life and property and the well-being of all peoples. Data exchange is also beneficial for sustaining programmes and projects of international organizations active in hydrology and water resources research.
Enabling participating countries to exchange data therefore a priority, necessitating data transmission, management infrastructure, human capacity in the National Hydrological Services, and an enabling legal framework.
Strengthening regional cooperation on water related issues is one of the main objectives of each HYCOS component. As a preliminary step toward this goal, the data from the HYCOS stations of each component is shared among participating countries to meet regional and international requirements and pursue common development objectives.
Such exchange is done in accordance with the internationally agreed policy framework contained in WMO Resolution 40 (Cg-XII) - WMO Policy and Practice for the Exchange of Meteorological and Related Data and Products, and WMO Resolution 25 (Cg-XIII) - Exchange of Hydrological Data and Products. The general principles on data exchange enshrined in Resolution 40 and 25 require an agreed tool, indicating the type of data, the stations and the frequency of observation and transmission for the exchange policy.
Another WHYCOS objective is to promote global data exchange and scientific cooperation. Therefore, project generated data and information are used by global data centres operating under the aegis of or in cooperation with WMO, such as the Global Runoff Data Centre (GRDC), the Global Precipitation Climatology Centre (GPCC) and the Global Environmental Monitoring System - Water (GEMS-WATER).
A key element for facilitating this exchange of data and information is the establishment of hydrological information systems, especially in regions where modern data management software is not widely available. Such systems provide a medium for easy, fast dissemination and exchange of water-related data and information. Participating National Hydrological Services establish sites on the World Wide Web to enable easy access to selected information. Raw data are usually available in near-real time, although the service responsible for each monitoring station will subsequently carry out data quality assurance, according to WHYCOS criteria of data standards and timeliness. Derived products, such as maps of specific runoff, may be subject to cost recovery for the hydrological services.