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Federal
Hydrologic landscape regions of the United States
Department of the Interior —
Hydrologic landscape regions (HLRs) in the United States were delineated by using geographic information system (GIS) tools and statistical methods including... -
Federal
Attributes for NHDPlus Catchments (Version 1.1) for the Conterminous United States: Level 3 Ecoregions
Department of the Interior —
This data set represents the estimated area of level 3 ecological landscape regions (ecoregions), as defined by Omernik (1987), compiled for every catchment of...