Aquatic Ecoregions in the United States GIS Data for the EPA Clean Air Mapping and Analysis Program (C-MAP)

Ecoregions are based on perceived patterns of a combination of causal and
integrative factors including land use, land surface form, potential natural
vegetation, and soils (Omernik, 1987). This is a copy of the ecoregion coverage
of Omernik (1987) with some item names modified.

This coverage is intended for national-level studies of water resources.

Reviews_Applied_to_Data. The Ecoregions were plotted on a terminal to ensure
the EXPORT file was imported properly. No claims are made regarding the
accuracy of the original data or linework.

[Summary provided by the EPA]