HydroSHEDS

WWF's Conservation Science Program is currently developing a new and innovative global hydrological database, termed HydroSHEDS. For many parts of the world these data and the tools built to use them will open up a range of previously inaccessible analyses and applications related to freshwater conservation and environmental planning.

HydroSHEDS is based on high-resolution elevation data obtained during a Space Shuttle flight for NASA's Shuttle Radar Topography Mission (SRTM). HydroSHEDS stands for "Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales."

At the most basic level, HydroSHEDS will allow scientists to create digital river and watershed maps. These maps can then be coupled with a variety of other geo-spatial datasets or applied in computer simulations, such as hydrologic models, in order to estimate flow regimes. HydroSHEDS thus allows scientists and managers to perform analyses ranging from basic watershed delineation to sophisticated flow modeling.

HydroSHEDS can be used for a wide range of applications. WWF has already applied the data to create aquatic habitat classification maps for remote and poorly mapped regions such as the Amazon headwaters and the Guiana Shield. Taxonomists will ultimately be able to link their field site locations directly to digital river maps. And WWF researchers hope to use HydroSHEDS in the future to assess the possible impacts of climate change to freshwater ecosystems.

HydroSHEDS has been developed by the Conservation Science Program of World Wildlife Fund (WWF), in partnership with the U.S. Geological Survey (USGS), the International Centre for Tropical Agriculture (CIAT), The Nature Conservancy (TNC), and the Center for Environmental Systems Research (CESR) of the University of Kassel, Germany. Major funding for this project was provided to WWF by JohnsonDiversey, Inc.

Data for South America, the first continent to be completed, will be available in April 2006. Other continents are scheduled for completion within a year. HydroSHEDS data are freely available for non-commercial use. For more information and data download please visit http://hydrosheds.cr.usgs.gov.

Technical overview

HydroSHEDS is a new and innovative product that provides hydrographic information in a consistent and comprehensive format for regional and global-scale applications. HydroSHEDS offers a suite of geo-referenced data sets, including stream networks, watershed boundaries, drainage directions, and ancillary data layers such as flow accumulations, distances, and river topology information. The goal of developing HydroSHEDS was to generate key data layers to support regional and global watershed analyses, hydrological modeling, and freshwater conservation planning at a quality, resolution and extent that had previously been unachievable. Available resolutions range from 3 arc-second (approx. 90 meters at the equator) to 5 minute (approx. 10 km at the equator) with seamless near-global extent.

HydroSHEDS is derived from elevation data of the Shuttle Radar Topography Mission (SRTM) at 3 arc-second resolution. The original SRTM data have been hydrologically conditioned using a sequence of automated procedures. Existing methods of data improvement and newly developed algorithms have been applied, including void filling, filtering, stream burning, and upscaling techniques. Manual corrections were made where necessary. Preliminary quality assessments indicate that the accuracy of HydroSHEDS significantly exceeds that of existing global watershed and river maps.