GIS Coverage of the National Water Quality Assessment Program: Surface Water Nutrient Sampling Sites for the EPA Clean Air Mapping and Analysis Program (C-MAP)
Entry ID: NAWQA_NU

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Summary
Abstract: This is a point coverage of the sampling sites for the U.S. Geological Survey
National Water-Quality Assessment (NAWQA) Program Study-Unit investigations of
Surface Water Nutrients for the conterminous United States, excluding the High
Plains Regional Ground-Water Study. It is intended for use with NAWQA_NU.DBF
and as an overlay with NAWQA, the NAWQA study units boundary coverage.

The National Water-Quality Assessment Program is designed to describe the
status and trends in the quality of the Nation's ground- and surface-water
resources and to provide a sound understanding of the natural and human factors
that affect the quality of these resources (Leahy and others, 1990). A "Study
Unit" is a major hydrologic system in which NAWQA studies are focused. Study
Units are geographically defined by a combination of ground- and surface-water
features (Gilliom and others, 1995).

As part of the NAWQA program, Study-Unit investigations were planned for 60
areas throughout the Nation to provide a framework for national and regional
water-quality assessments (Leahy and others, 1990). The 60 planned Study-Units
were divided into three groups of 20. Each group would be intensively studied
on a rotational basis with 20 studies beginning in fiscal year 1991 (FY 1991
runs from October 1990-September 1991), 20 more studies beginning in fiscal
year 1994 (October 1993-September 1994), and the final 20 studies beginning in
fiscal year 1997 (October 1996-September 1997). Each study cycle would span 10
years. In 1996, the number of Study-Units was scaled back to 59 when two of the
original 60 Study Units combined. Also, because of budgetary restraints, some
of the original planned Study Units have been scheduled to start later than
originally planned and others have not even been scheduled to start yet.

This coverage contains basic geographic information about the 213 surface water
sites that were sampled for nutrients as part of NAWQA within the conterminous
United States, excluding the High Plains Regional Ground Water-Study, which was
conceived in late 1997. The coverage also includes the NAWQA standard
abbreviation of each Study Unit, the station identification code, sampling
type, land-use type, percentages of specific land use types, and latitude and
longitude coordinates.

The stream data are the results from 8459 water samples collected at 213
surface water sites across the conterminous United States. All of the sampling
sites are located in the 20 major watersheds that comprise the first group of
NAWQA study units. Samples were collected from October 1991 through December
1996. About 90 percent of the samples were collected during 1993, 1994, and
1995. All samples were flow-weighted and cross-sectionally integrated by
standard USGS methods (Ward and Harr, 1990).

Sampling at many sites was not spaced evenly throughout the year. Sampling at
the intensive fixed sites was more frequent during periods when pesticide
levels were expected to be elevated. At the basic fixed sites, extra samples
were collected during extreme flow conditions. Thus, care must be used in the
interpretation of these data. For example, summary statistics such as the mean
or median concentration for a specific compound may be biased unless procedures
are used to account for the uneven sampling frequency.

In addition, the number of samples collected varied considerably among the
sites. Thus, the results shown in the surface water data file are influenced
more by conditions at some sites than others. Data analysis procedures that
account for this unequal distribution of samples among the sites must be used
to avoid biased interpretations. This data set is used primarily to display the
location of NAWQA Surface Water Nutrient Study Sites and for use with the NAWQA
Study Unit boundaries coverage (NAWQA) for analysis of data at the national
scale. It is not recommended for either local or regional analysis due to the
small scale of most of the features.

Results from the first cycle of National Water-Quality Assessment Program
(NAWQA) water-quality data collection during 1992-1996 include analyses of 8
nutrient species and 11 other inorganic constituents from about 2,200 samples
of ground water and from about 8,500 samples of streams and rivers in 20 of the
nation's major watersheds (NAWQA study units). The characteristics of the NAWQA
nutrients data are described below, followed by viewable samples of the data
and downloadable data files. The data set used for national synthesis is from
the February 1998 compilation.

Overview of Sampling Design and Considerations for Data Interperation:

NAWQA studies are based on a complex sampling design that targets specific land
use and hydrologic conditions in addition to assessing the most important
aquifers and large streams and rivers in each area studied.

For streams, rivers, and ground water, a major component of the sampling design
is to target specific watersheds and shallow ground water areas that are
influenced primarily by a single dominant land use (agricultural or urban) that
is important in a particular area of the United States. This aspect of the
sampling design facilitates summarizing results by agricultural and urban land
use settings for both streams and ground water. However, the results from this
design require careful interpretation, because this design results in a biased
representation of all streams or shallow ground water in agricultural settings.
For agricultural land use, the focus was limited to the most important
agricultural settings within the first 20 study units. Thus, some agricultural
activities that may be important in other parts of the nation may not be
included. The user is encouraged to consider the detailed descriptions of the
nature and limitations of the stream and ground water data that are provided.

[Summary provided by the EPA.]

Related URL
Link: GET RELATED DATA SET METADATA (DIF)
Description: GCMD metadata on the National Water Quality Assessment Program
(NAWQA). This record provides metadata on the original tabular
nonspatial data.


Link: VIEW EXTENDED METADATA
Description: FGDC metadata on &National Water-Quality Assessment Program:
Surface Water Nutrient Sampling Sites&.


Link: VIEW RELATED INFORMATION
Description: Homepage of the USGS National Water Quality Assessment Program (NAWQA).


Geographic Coverage
 N: 48.25 S: 22.87  E: -65.35  W: -127.88

Data Set Citation
Dataset Originator/Creator: Hitt, K.J. and Nakegaki, N.
Dataset Title: National Water-Quality Assessment (NAWQA) Study-Unit Investigations in the conterminous United States : Surface Water Nutrient Sampling Sites
Dataset Release Date: 1999-07-01
Dataset Release Place: Reston, VA
Dataset Publisher: USGS
Data Presentation Form: Map
Online Resource: http://www.epa.gov/airmarkets/


Location Keywords
CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA


Science Keywords
HUMAN DIMENSIONS >ENVIRONMENTAL GOVERNANCE/MANAGEMENT >WATER MANAGEMENT    [Definition]
TERRESTRIAL HYDROSPHERE >GROUND WATER >AQUIFERS    [Definition]
TERRESTRIAL HYDROSPHERE >GROUND WATER >SPRINGS    [Definition]
TERRESTRIAL HYDROSPHERE >SURFACE WATER    [Definition]
TERRESTRIAL HYDROSPHERE >WATER QUALITY/WATER CHEMISTRY >DISSOLVED GASES    [Definition]
TERRESTRIAL HYDROSPHERE >WATER QUALITY/WATER CHEMISTRY >ORGANIC MATTER    [Definition]
TERRESTRIAL HYDROSPHERE >WATER QUALITY/WATER CHEMISTRY >OXYGEN    [Definition]
TERRESTRIAL HYDROSPHERE >WATER QUALITY/WATER CHEMISTRY >PHOSPHOROUS COMPOUNDS    [Definition]
TERRESTRIAL HYDROSPHERE >WATER QUALITY/WATER CHEMISTRY >WATER TEMPERATURE    [Definition]
HUMAN DIMENSIONS >ENVIRONMENTAL GOVERNANCE/MANAGEMENT >ENVIRONMENTAL ASSESSMENTS    [Definition]


ISO Topic Category
ENVIRONMENT
GEOSCIENTIFIC INFORMATION
HEALTH
INLAND WATERS


Project
ESIP >Earth Science Information Partners Program    [Information]
C-MAP >Clean Air Mapping and Analysis Program    [Information]


Quality
This data set is used primarily to display the location of NAWQA
Nutrient Study Sites and for use with the NAWQA Study Unit boundaries
coverage (NAWQA) for analysis of data at the national scale. It is not
recommended for either local or regional analysis due to the small
scale of most of the features.

The dataset was created from Latitude/Longitude coordinates using
ArcView GIS. A shapefile was created from lat/long coordinates and was
then converted into a coverage using ArcInfo. The coverage was
re-projected into Albers for use with other CAMD GIS coverages.


Access Constraints
None


Keywords
GIS
USGS
National Water Quality Assessment Program
NAWQA
Surface Water
Ground Water
Drinking Water
Fresh Water
Human Health
Environmental Health
Water Quality
Nutrients
Sampling Sites
Water Resources


Data Set Progress
COMPLETE


Originating Center
USGS


Data Center
Clean Air Markets Division, U.S. Environmental Protection Agency    [Information]
Data Center URL: http://www.epa.gov/airmarkets/

Data Center Personnel
Name: EPA CLEAN AIR MARKETS DIVISION
Phone: 202-564-9180
Email: camdgis at epa.gov
Contact Address:
US EPA
Clean Air Markets Division
1200 Pennsylvania Avenue, NW
Mail Code 6204J
City: Washington
Province or State: DC
Postal Code: 20460
Country: USA


Water Resources Maps and GIS Information, Water Resources Division, U.S. Geological Survey, U.S. Department of the Interior    [Information]
Data Center URL: http://water.usgs.gov/lookup/getgislist

Data Center Personnel
Name: KERRIE J. HITT
Phone: 703-648-6854
Email: kjhitt at usgs.gov
Contact Address:
U.S. Geological Survey
12201 Sunrise Valley Drive
City: Reston
Province or State: VA
Postal Code: 20192
Country: USA



Distribution
Distribution_Media: electronic
Distribution_Size: 20 KB
Distribution_Format: ArcView shapefile
Fees: No fees


Personnel
TYLER B. STEVENS
Role: DIF AUTHOR
Phone: (301) 614-6898
Fax: 301-614-5268
Email: Tyler.B.Stevens at nasa.gov
Contact Address:
NASA Goddard Space Flight Center
Global Change Master Directory
City: Greenbelt
Province or State: MD
Postal Code: 20771
Country: USA



Creation and Review Dates
DIF Creation Date: 2002-11-15
Last DIF Revision Date: 2008-09-23

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