At the U.S. Geological Survey's (USGS) EROS Data Center, the USGS, the National Aeronautics and Space Administration, the United Nations Environment Program, and others are developing 1 KM (30-arc second) resolution digital elevation models (DEMs) with global coverage to be completed by October 1996. Current GIS technologies provide a means to extract the drainage basins from the DEMs at a level of detail necessary to meet modeling objectives. North America was the first continent processed and Africa is now reaching completion.
Digital drainage basin data derived from 30-arc second DEMs are available for use in GIS and models, eliminating the need for map interpretation and digitizing. The hydrologic stream and watershed data may also be customized for specific databases by user specification of the outflow points for drainage delineation.