Global River Topology (GRIT) raster datasets

Global River Topology (GRIT) v1.0 Michel Wortmann, Louise Slater, Laurence Hawker, Yinxue Liu, Jeffrey Neal December 15, 2025 Contents 1 Introduction 1 2 Licence and citation 2 3 Feedback and reporting bugs 2 4 Change log 2 5 Regions 3 6 Vector data 4 6.1 Segments ............................................. 4 6.1.1 Lines layer ........................................ 4 6.1.2 Nodes layer ........................................ 5 6.1.3 Simple segments ..................................... 5 6.2 Reaches .............................................. 6 6.2.1 Lines layer ........................................ 6 6.2.2 Nodes layer ........................................ 6 6.3 Catchments ............................................ 7 6.3.1 Component catchments ................................. 7 6.3.2 Segment catchments ................................... 7 6.3.3 Reach catchments .................................... 7 7 Raster data 8 7.1 Drainage area ........................................... 8 7.2 Drainage direction ........................................ 8 7.3 Catchments ............................................ 8 7.3.1 1 arcmin segment catchments .............................. 8 1 Introduction The Global River Topology (GRIT) is a global river network that not only represents the tributary components of the global drainage network but also the distributary ones, including multi-thread rivers, canals and delta distributaries. It is also the first global hydrography (excluding Antarctica and Greenland) produced at 30m raster resolution. It is created by merging Landsat-based river mask (GRWL) with elevation-generated streams to ensure a homogeneous drainage density outside of the river mask (rivers narrower than approx. 30m). Crucially, it uses a new 30m digital terrain model (FABDEM, based on TanDEM-X) that shows greater accuracy over the traditionally used SRTM derivatives. After vectorisation and pruning, directionality is assigned by a combination of elevation, flow angle, heuristic and continuity approaches (based on RivGraph). The vector data including the network topology (lines and nodes, upstream/downstream IDs) is available as layers and attribute information in GeoPackage 1 files (readable by QGIS/ArcMap/GDAL). The 30m raster data is available as compressed GeoTIFF files. See Wortmann et al. (2025, https://doi.org/10.1029/2024WR038308) for more details. A map of GRIT segments labelled with OSM river names is available here: https://michelwortmann.com/research/global-river-topology-grit/ 2 Licence and citation The dataset is licensed under CC BY-NC 4.0. This means you are free to share and adapt the material as long as you give appropriate credit, provide a link to the license, and indicate if changes were made. You may not use the material for commercial purposes unless you obtain separate permission from the authors. When using GRIT, please cite the following: Wortmann, M., Slater, L., Hawker, L., Liu, Y., Neal, J., Zhang, B., et al. (2025). Global River Topology (GRIT): A bifurcating river hydrography. Water Resources Research, 61, e2024WR038308. https://doi.org/10.1029/10.1029/2024WR038308 In BibTeX format: @article{https://doi.org/10.1029/2024WR038308, author = {Wortmann, M. and Slater, L. and Hawker, L. and Liu, Y. and Neal, J. and Zhang, B. and Schwenk, J. and Allen, G. and Ashworth, P. and Boothroyd, R. and Cloke, H. and Delorme, P. and Gebrechorkos, S. H. and Griffith, H. and Leyland, J. and McLelland, S. and Nicholas, A. P. and Sambrook-Smith, G. and Vahidi, E. and Parsons, D. and Darby, S. E.}, title = {Global River Topology (GRIT): A Bifurcating River Hydrography}, journal = {Water Resources Research}, volume = {61}, number = {5}, keywords = {hydrography, river, bifurcations, branching, river network}, doi = {https://doi.org/10.1029/2024WR038308}, year = {2025} } 3 Feedback and reporting bugs Your feedback and bug reports are welcome here: GRIT bug report form The feedback may be used to improve and validate GRIT in future versions. 4 Change log v1.0 - 2025-09-26 –GRIT WRR article published, marking the v1.0 release, i.e. the first peer-reviewed version. –Vector component/segment/reach catchments were simplified (breaking the exact alignment with the raster equivalents), making them much smaller in file size and easier to process. –Vector component/segment/reach catchments all published on Zenodo. –Raster layers drainage area, drainage direction, and catchments published on Zenodo. –1arcmin raster segment catchments published on Zenodo. –Fix drainage area over estimation in the Chicago canal, upper Mississippi, the Tennessee-Tombigbee Waterway, upper Tombigbee River and the Brazo Casiquiare, upper Rio Negro. The drainage area contribution from the cross-catchment divergent flow is not accounted for yet. –Added drainage area attributes to the reaches vectors. –Coastal catchment global id is ensured to be larger than the largest reach global id, allowing them to be used in all catchment layers. 2 –Added more islands that were previously missing, such as Hawaii, Jamaica, several other Caribbean islands, more islands of Indonesia and the Philippines. –Fixed gaps between computational domains in Sahara. v0.6 - 2024-05-30 –Rivers/streams outside of the GRWL mask forced by all OSM water lines (not only those with waterway=river/canal) –Some manual directions in the Irrawaddy delta and fixed erroneous sink in the Volga delta v0.5 - 2024-02-14 –Cyclicity and discontinuities resolved through improved algorithms, bug fixes, more sophisticated cycle solving algorithms and some manually forced directions. Only insignificant cycles (non-sinks, less than 50) were removed. –Added segment and reach attributes –Computational domain fixes –Segments include OSM river names –Asia domain split into Siberia and rest of Asia –Vector files available in EPSG:8857 and EPSG:4326 v0.4 - 2023-03-11 –First globally complete dataset published 5 Regions Vector files are provided in 7 regions with the following codes: •AF - Africa •AS - Asia (excluding Siberia) •EU - Europe •NA - North America •SA - South America •SI - Siberia •SP - South Pacific/Australia The domain polygons (GRITv1.0 domain GLOBAL EPSG8857.gpkg.zip) provide 61 subcontinental catchment groups that are available as vector attributes. They allow for more fine-grained subsetting of data (e.g. with ogr2ogr --where "domain=’DANU’" or geopandas.read file(..., where="DANU") and the domain attribute). Vector files are provided both in the original equal-area Equal Earth Greenwich projection (EPSG:8857) as well as in geographic WGS84 coordinates (EPSG:4326). 3 6 Vector data 6.1 Segments Lines between inlet, outlet, confluence and bifurcation nodes. Files have lines and nodes layers. 6.1.1 Lines layer Name Data type Description cat int64 domain internal feature ID global id int64 global feature ID, same as FID catchment id int64 global catchment ID upstream node id int64 global segment node ID at upstream end of line downstream node id int64 global segment node ID at downstream end of line upstream line ids string comma-separated list of global river segment IDs connecting at upstream end of line downstream line ids string comma-separated list of global river segment IDs connecting at downstream end of line direction algorithm float64 code of RivGraph method used to set the direction of line width adjusted float64 median river width in m without accounting for width of segments connecting upstream/downstream length adjusted float64 segment length in m without accounting for width of segments connecting upstream/downstream in m is mainstem int64 1 if widest segment of bifurcated flow or no bifurcation upstream, otherwise 0 strahler order int64 Strahler order of segment, can be used to route in topological order cycle int64 length float64 segment length in m azimuth float64 direction of line connecting upstream-downstream nodes in degrees from North sinuousity float64 ratio of Euclidean distance between upstreamdownstream nodes and line length, i.e. 1 meaning a perfectly straight line drainage area in float64 drainage area at beginning of segment, partitioned by width at bifurcations, in km2 drainage area out float64 drainage area at end of segment, partitioned by width at bifurcations, in km2 drainage area mainstem in float64 drainage area at beginning of segment, following the mainstem, in km2 drainage area mainstem out float64 drainage area at end of segment, following the mainstem, in km2 bifurcation balance out float64 (drainage area out - drainage area mainstem out) / max(drainage area out, drainage area mainstem out), dimensionless ratio grwl overlap float64 fraction of the segment overlapping with the GRWL river mask grwl value float64 dominant GRWL value of segment name string river name from Openstreetmap where available, English preferred name local string river name from Openstreetmap where available, local name n bifurcations upstream int64 number of bifurcations upstream of segment domain string catchment group ID, see domain index file 4 6.1.2 Nodes layer Name Data type Description cat int64 domain internal feature ID global id int64 global feature ID, same as FID catchment id int64 global catchment ID upstream line ids string comma-separated list of global river segment IDs flowing into node downstream line ids string comma-separated list of global river segment IDs flowing out of node node type string description of node, one of bifurcation, confluence, inlet, coastal outlet, sink outlet, grwl change grwl value int64 GRWL code at node width float64 GRWL width at node in meters, 30m or NaN if grwl value is NaN grwl transition string GRWL codes of change at grwl change nodes cycle int64 greater than 0 if node was part of an unresolved cycle, 0 otherwise continuity violated int64 1 if flow continuity is violated, otherwise 0 drainage area float64 drainage area, partitioned by width at bifurcations, in km2 drainage area mainstem float64 drainage area, following the mainstem, in km2 downstream width share string n bifurcations upstream int64 number of bifurcations upstream of node domain string catchment group ID, see domain index file 6.1.3 Simple segments The simple segments global file provides only a subset of segments that overlap the GRWL river mask and all their downstream segments. This is is mainly for global applications and visualisations where smaller tributaries outside of the GRWL mask are not required. 5 6.2 Reaches Segment lines split to not exceed 1km in length, i.e. these lines will be shorter than 1km and longer than 500m unless the segment is shorter. Files have lines and nodes layers. 6.2.1 Lines layer Name Data type Description cat int64 domain internal feature ID segment id int64 global segment ID of reach global id int64 global feature ID, same as FID catchment id int64 global catchment ID upstream node id int64 global reach node ID at upstream end of line downstream node id int64 global reach node ID at downstream end of line upstream line ids string comma-separated list of global river reach IDs connecting at upstream end of line downstream line ids string comma-separated list of global river reach IDs connecting at downstream end of line grwl overlap float64 fraction of the reach overlapping with the GRWL river mask grwl value float64 dominant GRWL value of node grwl width median float64 median width of the GRWL river mask, meters grwl width std float64 standard deviation of width of the GRWL river mask, meters drainage area in string drainage area at beginning of segment, partitioned by width at bifurcations, in km2 drainage area out string drainage area at end of segment, partitioned by width at bifurcations, in km2 drainage area mainstem in string drainage area at beginning of segment, following the mainstem, in km2 drainage area mainstem out string drainage area at end of segment, following the mainstem, in km2 length float64 length of reach in meters sinuosity float64 azimuth float64 direction of line connecting upstream-downstream nodes in degrees from North domain string catchment group ID, see domain index file 6.2.2 Nodes layer Name Data type Description cat int64 domain internal feature ID segment node id float64 global ID of segment node at segment intersections, otherwise blank n segments float64 number of segments attached to node global id int64 global feature ID, same as FID upstream line ids string comma-separated list of global river reach IDs flowing into node downstream line ids string comma-separated list of global river reach IDs flowing out of node domain string catchment group ID, see domain index file 6 6.3 Catchments Catchment outlines for entire river basins (network components, including coastal drainage areas). The catchment boundaries are simplified and therefore do not align exactly with the raster catchments. 6.3.1 Component catchments Catchments for entire river basins (network components), including coastal drainage areas with drainage areas below 50 km2and interior basin sink catchments. Name Data type Description cat int64 domain internal feature ID global id int64 global catchment ID, same as global id of segment/reach ID if is coastal/is sink == 0 for respective catchments or the catchment id for component catchments, same as FID area float64 catchment area in km2 is coastal int64 1 for coastal drainage areas, 0 otherwise is sink int64 1 for sink drainage areas, 0 otherwise domain string catchment group ID, see domain index file 6.3.2 Segment catchments Name Data type Description cat int64 domain internal feature ID global id int64 global segment catchment ID, same as global id of segment lines, same as FID catchment id int64 global catchment ID area float64 catchment area in km2 domain string catchment group ID, see domain index file 6.3.3 Reach catchments Name Data type Description cat int64 domain internal feature ID global id int64 global reach catchment ID, same as global id of reach lines, same as FID segment id int64 global segment ID of reach catchment id int64 global catchment ID area float64 catchment area in km2 domain string catchment group ID, see domain index file 7 7 Raster data The raster datasets are provided as compressed GeoTIFF files in EPSG:8857 projection with 30m pixel size. They are grouped by continental region (see Regions section) and can be mosaicked using GDAL or similar tools. A tile index file is provided in GRITv1.0 raster tile index GLOBAL EPSG8857.gpkg. 7.1 Drainage area The drainage area raster (drainage area, int32) provides the upstream contributing area for 30m each cell in km2. At bifurcations, the drainage area is partitioned according to the width of the channels. The mainstem drainage area (drainage area mainstem, int32) provides only the drainage area of the segments network without the partitioning, i.e. all drainage area is assigned to the main stem of the bifurcation. Merging both rasters yields a fully distributed drainage area with no partitioning at bifurcations. 7.2 Drainage direction The drainage direction raster (drainage direction, int8) encodes the direction of flow from each cell to its downstream neighbor, using the following D8 numbering: 3 2 1 4·8 5 6 7 7.3 Catchments Catchment rasters are provided for reaches (reach catchments, int32), segments (segment catchments, int32), and components (component catchments, int32). The component catchments include coastal drainage areas with drainage areas below 50 km2and interior basin sink catchments like the vector equivalents. The global id of those additional coastal and sink catchments are offset by the largest reach global id to ensure uniqueness across all catchment layers, i.e. they can also be combined with the segment and reach catchments. 7.3.1 1 arcmin segment catchments A global 1 arcmin resolution raster of segment catchments (segment catchments 1arcmin, int32) is available in EPSG:4326. This is suitable for large-scale applications and reduces file size for global analyses. 8