The Model Parameter Estimation Experiment (MOPEX) working group has identified 438 test watersheds in the conterminous United States for use in developing model parameters typically used in hydrologic and atmospheric models.

In collaboration with the U.S. Water Resources Discipline (WRD) and the University of California Los Angeles (UCLA), a new set of data layers has been compiled for these test watersheds. This was done primarily using the Elevation Derivatives for National Applications (EDNA) database, and additional ancillary data.

The EDNA database contains Digital Elevation Model (DEM) derivative layers commonly used for hydrologic applications including slope, flow direction, and flow accumulation. A complete description of EDNA can be found at http://edna.usgs.gov.

Using the EDNA database and related tools, test gage sites were used as seeds to create watershed delineations. The watershed delineation tool is Web-enabled, and is available via the EDNA viewer at http://edna.usgs.gov.

In order to delineate watersheds using the tool, the gage sites were snapped to the nearest EDNA synthetic stream. The resulting watersheds were then used as a mask to extract other hydrologic terrain layers and other relevant ancillary layers.

Of the 438 MOPEX test sites, watershed delineations for 431 sites have been completed.

Description of Layers

For each site, a workspace has been created that contains 14 raster layers and 3 vector layers. The data are in the Albers Equal Area projection. The workspace containing all the data layers for each site are distributed as a single zip file, for example, “06225500.zip,” where the ‘06225500’ represents the numeric ID of the gage.