Global River Topology (GRIT), v0.5

The Global River Topology (GRIT) is a vector-based, 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 (excl. 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 network topology (lines and nodes, upstream/downstream IDs) is available as layers and attribute information in the GeoPackage files (readable by QGIS/ArcMap/GDAL). A map of GRIT segments labelled with OSM river names is available here: https://michelwortmann.com/research/gritv05-segments-river-names/ Regions Vector files are provided in 7 regions with the following codes: AF - Africa AS - Asia (excl. Siberia) EU - Europe NA - North America SA - South America SI - Siberia SP - South Pacific/Australia The domain polygons (GRITv04_domain_GLOBAL.gpkg.zip) provide 60 subcontinental catchment groups that are available as vector attributes. They allow for more fine-grained subsetting of data (e.g. with ogr2ogr --where 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). Network segments Lines between inlet, outlet, confluence and bifurcation nodes. Files have lines and nodes layers. Attribute description of lines layer Name Data type Description cat integer domain internal feature ID global_id integer global river segment ID, same as FID catchment_id integer global catchment ID upstream_node_id integer global segment node ID at upstream end of line downstream_node_id integer global segment node ID at downstream end of line upstream_line_ids text comma-separated list of global river segment IDs connecting at upstream end of line downstream_line_ids text comma-separated list of global river segment IDs connecting at downstream end of line direction_algorithm float code of RivGraph method used to set the direction of line width_adjusted float median river width in m without accounting for width of segments connecting upstream/downstream length_adjusted float segment length in m without accounting for width of segments connecting upstream/downstream in m is_mainstem integer 1 if widest segment of bifurcated flow or no bifurcation upstream, otherwise 0 strahler_order integer Strahler order of segment, can be used to route in topological order length float segment length in m azimuth float direction of line connecting upstream-downstream nodes in degrees from North sinuousity float ratio of Euclidean distance between upstream-downstream nodes and line length, i.e. 1 meaning a perfectly straight line drainage_area_in float drainage area at beginning of segment, partitioned by width at bifurcations, in km2 drainage_area_out float drainage area at end of segment, partitioned by width at bifurcations, in km2 drainage_area_mainstem_in float drainage area at beginning of segment, following the mainstem, in km2 drainage_area_mainstem_out float drainage area at end of segment, following the mainstem, in km2 bifurcation_balance_out float (drainage_area_out - drainage_area_mainstem_out) / max(drainage_area_out, drainage_area_mainstem_out), dimensionless ratio grwl_overlap float fraction of the segment overlapping with the GRWL river mask grwl_value integer dominant GRWL value of segment name text river name from Openstreetmap where available, English preferred name_local text river name from Openstreetmap where available, local name n_bifurcations_upstream integer number of bifurcations upstream of segment domain text catchment group ID, see domain index file Attribute description of nodes layer Name Data type Description cat integer domain internal feature ID global_id integer global river node ID, same as FID catchment_id integer global catchment ID upstream_line_ids text comma-separated list of global river segment IDs flowing into node downstream_line_ids text comma-separated list of global river segment IDs flowing out of node node_type text description of node, one of bifurcation, confluence, inlet, coastal_outlet, sink_outlet, grwl_change grwl_value integer GRWL code at node grwl_transition text GRWL codes of change at grwl_change nodes cycle integer >0 if segment is part of an unresolved cycle, 0 otherwise continuity_violated integer 1 if flow continuity is violated, otherwise 0 drainage_area float drainage area, partitioned by width at bifurcations, in km2 drainage_area_mainstem float drainage area, following the mainstem, in km2 n_bifurcations_upstream integer number of bifurcations upstream of node domain text catchment group, see domain index file Network 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. A simplified version with no vertices between nodes is also provided. Files have lines and nodes layers. Attribute description of lines layer Name Data type Description cat integer domain internal feature ID segment_id integer global segment ID of reach global_id integer global river reach ID, same as FID catchment_id integer global catchment ID upstream_node_id integer global reach node ID at upstream end of line downstream_node_id integer global reach node ID at downstream end of line upstream_line_ids text comma-separated list of global river reach IDs connecting at upstream end of line downstream_line_ids text comma-separated list of global river reach IDs connecting at downstream end of line grwl_overlap float fraction of the reach overlapping with the GRWL river mask grwl_value integer dominant GRWL value of node grwl_width_median float median width of the GRWL river mask, meters grwl_width_std float standard deviation of width of the GRWL river mask, meters length float length of reach in meters sinuousity float ratio of eucledian distance betwen upstream-downstream nodes and line length, i.e. 1 meaning a perfectly straight line azimuth float direction of line connecting upstream-downstream nodes in degrees from North domain text catchment group, see domain index file Attribute description of nodes layer Name Data type Description cat integer domain internal feature ID segment_node_id integer global ID of segment node at segment intersections, otherwise blank n_segments integer number of segments attached to node global_id integer global river reach node ID, same as FID upstream_line_ids text comma-separated list of global river reach IDs flowing into node downstream_line_ids text comma-separated list of global river reach IDs flowing out of node domain text catchment group, see domain index file Catchments Catchment outlines for entire river basins (network components, including coastal drainage areas). Catchments for segments (aka. subbasins) and reaches are also available on request. Attribute description Name Data type Description cat integer domain internal feature ID global_id integer global catchment ID, same as global_id of segment/reach ID if is_coastal == 0 for respective catchments or the catchment_id for component_catchments, same as FID area float catchment area in km2 is_coastal integer 1 for coastal drainage areas, 0 otherwise domain text catchment group, see domain index file Raster Upstream drainage area, flow direction and other raster-based products are also available upon request.