Henning Plessow (Federal Institute of Hydrology, Germany); Claudia Zentis (Federal Institute of Hydrology, Germany); Mohammadjavad Tourian (Institute of Geodesy, University of Stuttgart, Germany); Peyman Saemian (Institute of Geodesy, University of Stuttgart, Germany); Omid Elmi (Institute of Geodesy, University of Stuttgart, Germany)

River systems are an integral part of the global water cycle, which are linked to many processes on local, regional, and global scales. Terrestrial monitoring of rivers is fundamental for the sustainable management of available water resources on a regional or catchment scale.

The Global Runoff Data Centre (GRDC) operates under the auspices of the World Meteorological Organization (WMO) at the German Federal Institute of Hydrology (BfG). It holds the most substantive collection of quality-assured river discharge data on a global scale. Established in 1988 to support research on global and climate change and integrated water resources management, GRDC has been a key partner in several data collection and data management projects. It connects national hydrological and hydrometeorological services, the primary providers of river discharge data and associated metadata, with the scientific research community utilizing this unique data collection. Currently, the GRDC contains river discharge data collected at daily or monthly intervals from more than 10,000 stations in 160 countries. GRDC archives international data up to 200 years old, with an average record length of 40 years.

GRDC has been actively supporting the calibration and validation of satellite-based data, thereby strengthening the bridge between in-situ monitoring and satellite-derived data products. This includes support for the Surface Water and Ocean Topography (SWOT) satellite mission, which enhance observations of river water surface elevation (WSE), width, and slope. For rivers, the prior database, known as the SWOT River Database (SWORD), combines multiple global river- and satellite-related datasets to define the nodes and reaches that will constitute SWOT river vector data products. Each SWORD node can be identified and accessed via its individual SWORD ID, which provides valuable information about the node's topology and type.To facilitate a wide range of new analyses with flexibility, the SWOT mission provides a range of relevant data products. One product of the SWOT mission is the river vector product, stored in shapefile format for each SWOT overpass. The SWOT vector data products will be most broadly useful if they allow multitemporal analysis of river nodes and reaches covering the same river areas. The HYDROCRON website provides easy access via API to the data to produce timeseries (https://podaac.github.io/hydrocron/intro.html).

To facilitate the use of SWOT data in the vicinity of GRDC data, here we present a dataset that assigns the nearest SWORD reach ID to each GRDC gauge. Compare WISP for similar functionality for the US (WISP https://apps.usgs.gov/wisp). The coordinates of the GRDC dataset are pour-point corrected. This correction has been used for the station-based catchment calculation which snaps the stations to the river network of HydroSHEDS or MERIT Hydro (Färber et al. 2024). The corrected coordinates can be reused to assign the nearest SWORD ID to the GRDC station. This allows easy access to GRDC stations with SWOT data. The dataset is available for download at the GRDC website (https://grdc.bafg.de)

Färber, C., Plessow, H., Mischel, S., Kratzert, F., Addor, N., Shalev, G., and Looser, U., 2024: GRDC-Caravan: extending Caravan with data from the Global Runoff Data Centre, Earth Syst. Sci. Data Discuss. [preprint], https://doi.org/10.5194/essd-2024-427, in review.