Attributes for NHDPlus Catchments (Version 1.1) for the Conterminous United States: Level 3 Ecoregions

This data set represents the estimated area of level 3 ecological landscape regions (ecoregions), 
as defined by Omernik (1987), compiled for every catchment of NHDPlus for the conterminous 
United States. The source data set is Level III Ecoregions of the Continental United States 
(U.S. Environmental Protection Agency, 2003).
		
The NHDPlus Version 1.1 is an integrated suite of application-ready geospatial datasets that 
incorporates many of the best features of the National Hydrography Dataset (NHD) and the 
National Elevation Dataset (NED). The NHDPlus includes a stream network (based on the 
1:100,00-scale NHD), improved networking, naming, and value-added attributes (VAAs). 
NHDPlus also includes elevation-derived catchments (drainage areas) produced using a 
drainage enforcement technique first widely used in New England, and thus referred to 
as "the New England Method." This technique involves "burning in" the 1:100,000-scale 
NHD and when available building "walls" using the National Watershed Boundary Dataset 
(WBD). The resulting modified digital elevation model (HydroDEM) is used to produce 
hydrologic derivatives that agree with the NHD and WBD. Over the past two years, an 
interdisciplinary team from the U.S. Geological Survey (USGS), and the U.S. Environmental 
Protection Agency (USEPA), and contractors, found that this method produces the best 
quality NHD catchments using an automated process (USEPA, 2007). The NHDPlus 
dataset is organized by 18 Production Units that cover the conterminous United States.
		
The NHDPlus version 1.1 data are grouped by the U.S. Geologic Survey's  Major River 
Basins (MRBs, Crawford and others, 2006).  MRB1, covering the New England and 
Mid-Atlantic River basins, contains NHDPlus Production Units 1 and 2.  MRB2, covering 
the South Atlantic-Gulf and Tennessee River basins, contains NHDPlus Production Units 
3 and 6.  MRB3, covering the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy 
River basins, contains NHDPlus Production Units 4, 5, 7 and 9.  MRB4, covering the 
Missouri River basins, contains NHDPlus Production Units 10-lower and 10-upper.  MRB5, 
covering the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf River basins, contains 
NHDPlus Production Units 8, 11 and 12.  MRB6, covering the Rio Grande, Colorado and 
Great Basin River basins, contains NHDPlus Production Units 13, 14, 15 and 16.  MRB7, 
covering the Pacific Northwest River basins, contains NHDPlus Production Unit 17.  MRB8, 
covering California River basins, contains NHDPlus Production Unit 18.

Tags: cali, california, catchment, cogb, conterminous-united-states, environment, geoscientificinformation, glmr, great-lakes-ohio-upper-mississippi-and-souris-red-rainy, inlandwaters, level-3-ecoregions, lmtg, lower-mississippi-arkansas-white-red-and-texas-gulf, major-river-basin, missouri, mori, mrb, mrb1, mrb2, mrb3, mrb4, mrb5, mrb6, mrb7, mrb8, nawqa, nema, new-england-and-mid-atlantic, nhdplus, pacific-northwest, panw, rio-grande-colorado-and-great-basin, sagt, south-atlantic-gulf-and-tennessee, sparrow, usgs-5195c150-c6e6-4a3a-b995-9085f827907a
Organization: Department of the Interior