Attributes for NHDPlus Catchments (Version 1.1) for the Conterminous United States: Normalized Atmospheric Deposition for 2002, Ammonium (NH4)

This data set represents the average normalized atmospheric (wet) deposition, in kilograms, of 
Ammonium (NH4) for the year 2002 compiled for every catchment of NHDPlus for the conterminous 
United States. Estimates of NH4 deposition are based on National Atmospheric Deposition Program 
(NADP) measurements (B. Larsen, U.S. Geological Survey, written commun., 2007). De-trending 
methods applied to the year 2002 are described in Alexander and others, 2001. NADP site selection 
met the following criteria: stations must have records from 1995 to 2002 and have a minimum of 30 
observations.
		
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: ammonium-nh4, cali, california, catchment, cogb, conterminous-united-states, environment, geoscientificinformation, glmr, great-lakes-ohio-upper-mississippi-and-souris-red-rainy, inlandwaters, 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-a84f603a-293a-4dbb-a90e-fca36fbb5efb
Organization: Department of the Interior