Polygon shapefile that depicts level 3 ecoregions for the Susquehanna River Basin (2006 boundary). 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.