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River discharge (GTN-H)
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Focal point: Thomas Maurer

Harmonized real-time river discharge data capturing freshwater flux into oceans.

The Global Terrestrial Network for River Discharge (GTN-R). The 380 river discharge stations along continental coastlines cover 355 of the 391 basins depicted here (status as of 24 March 2005). The colour code indicates the latest data available in the GRDC database.

Concept of GTN-R

The Global Terrestrial Network for River Discharge (GTN-R) is a recently launched project of the Global Runoff Data Centre (GRDC), aiming at improving access to near real-time river discharge data for selected gauging stations around the world, capturing the majority of the freshwater flux into oceans (Figure 1). GTN-R will draw together the already available heterogeneous information on near-real-time river discharge data provided by individual national hydrological services, and redistribute the data in a harmonized way. GTN-R is supported by an action item in the GCOS Implementation Plan, published in October 2004.


GTN-R will serve an increasing user community by supporting several activities, including the GCOS baseline river discharge network; GTN-H; future versions of the GRDC Long Term Mean Annual Freshwater Surface Water Fluxes into the World Oceans product; biogeochemical flux computations of the GEMS/Water Programme Office (UNEP/DEWA); the WHYMAP project; and an increasing number of activities and projects in the fields of climate and hydrological research and monitoring.


GRDC has identified a priority network of around 380 river discharge reference stations and associated river basins. Feedback from local institutions will allow further refinement of this initial network. A metadata file of the network can be downloaded from the GTN-R Web site, as well as tables summarizing the acquisition progress. In addition, the Web site offers four visualizations of the network: images; interactive ESRI-ArcReader map application; dataset for use with the 3D-visualization software WorldWind (NASA); and a map server based on Google-Maps.

Underlying software

The core of GTN-R is software (currently being developed at GRDC) that collects near-real-time discharge data from distributed servers via the internet, harmonizes and summarizes them, and makes them available again in a single, standard format through an FTP server. GRDC is also developing an application that will graphically display the collected and harmonized data in an interactively scaleable world map that can be accessed through the Web (similar to http://grdc.bafg.de/?9931). Absolute and relative current discharge values will be displayed as attributes.

Relation to ETN-R

GRDC has recently been contracted by the Joint Research Centre (JRC) of the European Commission to provide services very similar to GTN-R at the European scale, in support of the European Flood Alert System (EFAS), a JRC research project. Analogous to GTN-R, the associated project is called European Terrestrial Network for River Discharge (ETN-R). It significantly strengthens GRDC’s capacity, as both projects require the same software tools and all developments will symbiotically be applicable for both European-scale and global-scale purposes. Moreover, ETN-R will foster data contribution to GTN-R from European countries.

Required cooperation

The success of GTN-R is critically dependent on the regular provision of near-real-time river discharge data from the reference stations. GRDC thus kindly requests the assistance of all organizations able to assist in providing access to available data. For further information, please see the corresponding sections on the GTN-R Web site.


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© FAO   ::   Global Terrestrial Observing System - GTOS   ::   15 January 2005