Vulnerability of shallow ground water and drinking-water wells to nitrate in the United States: Model of predicted nitrate concentration in U.S. ground water used for drinking (simulation depth 50 meters) -- Model output data set (gwava-dw_out)

This data set represents predicted nitrate concentration in
ground water used for drinking, in milligrams per liter, in the
conterminous United States, and was generated by a national
nonlinear regression model based on 14 input parameters.
Nolan and Hitt (2006) developed two national models to predict
contamination of ground water by nonpoint sources of
nitrate. The nonlinear approach to national-scale Ground-WAter
Vulnerability Assessment (GWAVA) uses components representing
nitrogen (N) sources, transport, and attenuation.
One model (GWAVA-S) predicts nitrate contamination of shallow
(typically less than 5 meters deep), recently recharged ground
water, which may or may not be used for drinking.  The other
(GWAVA-DW) predicts ambient nitrate concentration in deeper
supplies used for drinking.
This data set is a national map of nitrate concentration (in
milligrams per liter) in U.S ground water used for drinking as
predicted by the GWAVA-DW model. The data set is one of 14
spatial data sets (1 output data set and 13 input data sets)
associated with the GWAVA-DW model. Full details of the model
development are in Nolan and Hitt (2006).
This data set represents the model output, which is depicted in
figure 3 of Nolan and Hitt (2006) that shows predicted nitrate
concentration in milligrams per liter in ground water used for
drinking. The model results can be used to indicate areas of the
Nation that may be vulnerable to nitrate contamination.
For inputs to the model, spatial attributes representing 13
nitrogen loading and transport and attenuation factors were
compiled as raster data sets (1-km by 1-km grid cell size) for
the conterminous United States (see table 1).
&gt;Table 1.-- Parameters of nonlinear regression model for
&gt;           nitrate in ground water used for drinking (GWAVA-DW)
&gt;           and corresponding input spatial data sets.
&gt;           [kg, kilograms; km2, square kilometers.]
&gt;
&gt;Nitrogen Source Factors                  Data Set Name
&gt;   1 farm fertilizer (kg/hectare)        gwava-dw_ffer
&gt;   2 confined manure (kg/hectare)        gwava-dw_conf
&gt;   3 orchards/vineyards (percent)        gwava-dw_orvi
&gt;   4 population density  (people/km2)    gwava-dw_popd
&gt;
&gt;Transport to Aquifer Factors
&gt;   5 water input (km2/cm)                gwava-dw_wtin
&gt;   6 glacial till (yes/no)               gwava-dw_gtil
&gt;   7 semiconsolidated sand aquifers      gwava-dw_semc
&gt;     (yes/no)
&gt;   8 sandstone and carbonate rocks       gwava-dw_sscb
&gt;     (yes/no)
&gt;   9 drainage ditch (km2)                gwava-dw_ddit
&gt;  10 Hortonian overland flow             gwava-dw_hor
&gt;     (percent of streamflow)
&gt;
&gt;Attenuation Factors
&gt;  11 fresh surface water withdrawal      gwava-dw_swus
&gt;     for irrigation (megaliters/day)
&gt;  12 irrigation tailwater recovery (km2) gwava-dw_twre
&gt;  13 Dunne overland flow                 gwava-dw_dun
&gt;     (percent of streamflow)
&gt;  14 well depth (meters)                 -
"Farm fertilizer" is the average annual nitrogen input from
commercial fertilizer applied to agricultural lands, 1992-2001, in
kilograms per hectare.
"Confined manure" is the average annual nitrogen input from
confined animal manure, 1992 and 1997, in kilograms per
hectare.
"Orchards/vineyards" is the percent of orchards/vineyards land
cover classification.
"Population density" is 1990 block group population density, in
people per square kilometer.
"Water input" is the ratio of the total area of irrigated land
to precipitation, in square kilometers per centimeter.
"Glacial till" is the presence or absence of poorly sorted
glacial till east of the Rocky Mountains.
"Semiconsolidated sand aquifers" is the presence or absence of
semiconsolidated sand aquifers.
"Sandstone and carbonate rocks" is the presence or absence of
sandstone and carbonate rock aquifers.
"Drainage ditch" is the area of National Resources Inventory surface
drainage, field ditch conservation practice, in square kilometers.
"Hortonian overland flow" is infiltration excess overland flow
estimated by TOPMODEL, in percent of streamflow.
"Fresh surface water withdrawal for irrigation" is the amount of
fresh surface water withdrawal for irrigation, in megaliters per day.
"Irrigation tailwater recovery" is the area of National
Resources Inventory irrigation system, tailwater recovery
conservation practice, in square kilometers.
"Dunne overland flow" is saturation overland flow estimated by
TOPMODEL, in percent of streamflow.
"Well depth" is the depth of the well, in meters.  Well depth
was not compiled as a spatial data set.  Well depth equals 50
meters for the model simulation being presented.
Reference cited:
Nolan, B.T. and Hitt, K.J., 2006, Vulnerability of shallow
ground water and drinking-water wells to nitrate in the United
States: Environmental Science and Technology, vol. 40, no. 24,
pages 7834-7840.

Tags: drinking-water, environment, geoscientificinformation, ground-water, ground-water-contamination, ground-water-pollution, ground-water-susceptibility, inlandwaters, national-water-quality-assessment-program, nawqa, nitrate, nitrate-concentration, nonlinear-model, nutrients, usgs-efcd2e83-59aa-45bb-9f26-e1b6d464ef82
Organization: Department of the Interior