Many hydrological studies and analyses require the availability of long time series. Experience shows that a significant amount of time within a project is dedicated to identifying, accessing and formatting appropriate datasets. Thus, it is strongly desirable to ease the data discovery process through data portals. Examples from academia are for instance the CUAHSI portal (Consortium of Universities for the Advancement of Hydrologic Science, Inc, https://www.cuahsi.org/data-models/portals/ ) which allows to publish datasets on a voluntary base. The GEOSS platform of the Group on Earth Observations can also be cited.
The WMO Commission of Hydrology is developing the new phase of the WMO Hydrological Observing System WHOS as the hydrological contribution to the WMO Integrated Global Observing System (WIGOS), the over-arching general framework for the coordination and optimized evolution of all WMO observing systems. In its current version, WHOS is a simple pointer system, a map interface that allows access to available datasets of national hydrological services which open their data (http://www.wmo.int/pages/prog/hwrp/chy/whos/index.php ). However, discovering and downloading data, and making use of them for an intended purpose can still be tedious as metadata are not easily available and data formats may be different; furthermore the national web portal may be in languages not familiar to the user. In its next version, WHOS should provide users with a user-friendly brokering system that allows easy discovery and download capacities of existing historical and real-time data, from national services and from other acknowledged sources. It will be a fully WIS/WIGOS-compliant, services-oriented framework linking hydrologic data providers and users through a hydrologic information system enabling data registration, data discovery, and data access. A primary concern of WMO being data quality assessment, quality checks and meta information will build trust in the datasets.
Long time series of historical data are gathered and distributed by WMO Global Data Centres such as the Global Runoff Data Centre for Surface Runoff, hosted by Germany, the International Groundwater Assessment Centre hosted by the Netherlands and especially its Global Groundwater Network (GGMN) for Groundwater and the Hydrology of Lakes and Reservoirs (HYDROLARE) Centre, hosted by the Russian Federation.
These WMO Global Data Centres fulfil the following main duties:
- Collect and provide hydrological time series with database management systems
- Contribute to data rescue
- Support data collection efforts and data management projects
- Coordinate and disseminate information about national data holdings and about the conditions of data access, data quality and meta-information
- Supply data for scientific and educational purposes, modelling, development