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Basin delineation and rivernet generation

The Major River Basins of the World is a ongoing project of the Global Runoff Data Centre (GRDC) that aims at the provision of a dedicated set of shapefiles for the use in Geographic Information Systems (GIS). This dataset was created for the generation of GRDC’s map products and will be updated from time to time whenever extensions may be required by future GRDC projects.

Based on the concept that a river basin covers all area of land that drains to the point of the lowest elevation, the delineation procedure starts at the rivers outlet (pour point), which coincides with the location of the confluence with a river, the mouth into an ocean or an endorheic sink. These "pour points" represent the locations above which the drainage basin is derived from the flow direction grid using the ESRI ARC/INFO software. We used the flow direction data set of the HYDRO1k Elevation Derivative Database on Africa, Asia, North and Sout America and Europe. As HYDRO1k does not include flow direction data from Australia, there we used the basin boundaries as defined in Australia's River Basins 1997 (http://www.ga.gov.au/nmd/products/thematic/basins.htm) . We revised and checked the basin boundaries by overlaying the rivercourses of Digital Chart of the World (ESRI, 1991). Visually detected inconsistencies of the outputs of the automated procedure were corrected by a manual post-processing. After editing the boundaries, all basins were labeled using several world atlases as references. The basin layer GRDC_405_basins_from_mouth currently comprises 405 river basins.

The associated river network was generated on the basis of Major Riverbasins (BGR, 2004) which is a combination of the Geological Map of the World 1:25,000,000 (CGMW, 2000) and the Watersheds of the World (WRI, 2003). We took all river courses from the BGR’s river layer that fitted into our generated river basins. We checked the river pattern by overlaying the river courses from the Digital Chart of the World (ESRI, 1991) and added some rivers and lakes extracted from DCW. For 687 water courses, a main stream feature was composed from single polygons and polylines. Composing these rivers, the river network layers GRDC_687_rivers and GRDC_lakes_join_rivers were created.

To display the long term average discharge along the river course, we splitted the river polylines into equidistant 0.25-length units and assigned a river discharge value to each river segment by overlaying the generated mean river discharge 1961-1990 as computed with WaterGAP 2.1 (Universities of Frankfurt and Kassel, 2007) at a spatial resolution of 0.5 degree. We grouped the modelled river discharge values into ten classes and assigned to each river segment a river class (category). Each class (category) represents an interval of discharge values in km³/year.

ClassDischarge [km³/year]
10 – 5
25 – 10
310 – 50
450 – 100
5100 – 500
6500 – 800
7800 – 1200
81200 – 2000
92000 – 3000
10> 3000

The maximum (highest) assigned category along the river was picked to label the average discharge from the drainage basin at the river's outlet.

The Major River Basins of the World dataset is provided as a set of ESRI shapefiles:

  • GRDC_405_basins_from_mouth, attributed with name and size of the drainage basin, an outlet marking, long-term mean discharge [m³/s] and the mean annual discharge [km³] of the gauging station nearest to the mouth that is represented in GRDC’s database;
  • GRDC_687_rivers, attributed with the name of the river, name and size of the drainage basin, an outlet marking, the maximum (highest) assigned category along the river and the associated classification interval;
  • GRDC_687_rivers_class, attributed with the name of the river, the name of the drainage basin, the assigned river discharge category per river segment and the associated classification interval;
  • GRDC_lakes_join_rivers, attributed with the name of the river, name and size of the drainage basin, an outlet marking, the maximum (highest) assigned river discharge category in the river and the associated classification interval.

GRDC provides the GIS layers of the WMO Subregions under the conditions of the “Declaration of the Data User”. If you are interested to use one of these GIS layer for your research, please sign the user declaration and send it to GRDC together with a brief description of the project in which the layers will be used. Please fill in the GRDC order form including your contact details. Please cite the files in all publications and products using them as: Global Runoff Data Centre (YYYY): [Name of the requested GIS Layer as given in the Order Form]. GRDC in the Bundesanstalt für Gewässerkunde, 56068 Koblenz, Germany.

Note: The Major River Basins Of the World is an ongoing project. Earlier versions of this dataset may exist. Please make sure to use the appropriate data set for your research. The latest version is of August 2007, the assignment of classified river discharges refers to the period 1961-1990.

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