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The global drainage direction map DDM30 is a raster map which describes the drainage directions of surface water with a spatial resolution of 30’ longitude by 30’ latitude.

Map description and dataset provided by: Johann Wolfgang Goethe University, Frankfurt am Main, Germany

DescriptionGlobal Drainage Direction Map

Digital drainage direction maps are a prerequisite for analyzing the flow of water on the land surface of the Earth. For continental or global studies, the most appropriate and most frequently used resolution for such data sets appears to be 30-min (longitude-by-latitude). This new global drainage direction map DDM30 is a 30-min raster map of surface drainage directions which organizes the land area of the Earth into drainage basins and provides the river network topology. 66896 individual grid cells, covering the entire land surface of the globe (without Antarctica), are connected to each other by their respective drainage direction and are thus organized into drainage basins. Each cell can drain only into one of the eight neighboring cells.



The dataset for this map was provided by: Petra Döll, Johann Wolfgang Goethe University, Frankfurt am Main, Germany


Both given base maps were upscaled to a resolution of 30-min. The resulting drainage direction map was manually corrected using the vectorized river data sets of ESRI (1992) and ESRI (1993), various atlases and the location and drainage basin sizes of 935 river discharge gauging stations from the GRDC (1999). In the course of the manual corrections, the drainage directions of 35% of the grid cells were changed. The DDM30 map was validated against drainage basin areas from the literature, against the given upstream areas of the GRDC stations and, most importantly, against information from HYDRO1k.


Please cite this map as: "GWSP Digital Water Atlas (2008). Map 30: Global Drainage Direction Map (V1.0). Available online at http://atlas.gwsp.org."

Contact Information

Petra Döll ( This e-mail address is being protected from spam bots, you need JavaScript enabled to view it ), Johann Wolfgang Goethe University, Frankfurt am Main, Germany

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