Digital data sets compiled by the U.S. Geological Survey were used as input for a collection of Spatially Referenced Regressions On Watershed (SPARROW) attributes for the Chesapeake Bay region including parts of Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia, and the District of Columbia. These regressions use a nonlinear statistical approach to relate nutrient sources and land-surface characteristics to nutrient loads of streams throughout the Chesapeake Bay watershed. A digital segmented-watershed network serves as the primary framework for spatially referencing nutrient-source and land-surface characteristic data within a geographic information system.
Flow direction and flow accumulation generated from a 30-meter cell-size Digital Elevation Model and attributes from 1:500,000-scale stream data were used to generate stream and watershed networks. Spatial data sets representing nutrient inputs of total nitrogen and total phosphorus from the early 1990's were created and compiled from numerous sources. Data include atmospheric deposition, septic systems, point-source locations, land use, land cover, and agricultural sources such as commercial fertilizer and manure. Some land-surface characteristic data sets representing factors that affect the transport of nutrients also were compiled. Data sets include land use, land cover, average-annual precipitation and temperature, slope, hydrogeomorphic regions, and soil permeability.
Nutrient-input and land-surface characteristic data sets merged with the segmented-watershed network provide the spatial detail by watershed segment required by SPARROW. Stream-nutrient load estimates for 132 sampling sites representing the early 1990's (103 for total nitrogen and 121 for total phosphorus) serve as the dependent variables for the regressions. These estimates were used to calibrate models of total nitrogen and total phosphorus depicting 1992 land-surface conditions. Examples of model predictions consist of stream-nutrient load and source percentages contributed locally to each stream reach, as well as percentages of the load that reach Chesapeake Bay.
The data set Q2_SIT represents point locations of USGS streamflow data-collection sites used in the calibration of SPARROW for the early 1990's (Version 2.0) in the Chesapeake Bay watershed. Each point is attributed with a unique station identification number, station name, the unique stream reach number the site is associated with, and total nitrogen and total phosphorus estimates for 1992.
The spatial data set Q2_SIT was created and used by the USGS specifically in the calibration process of SPARROW representing the early 1990's time period (Version 2.0) in the Chesapeake Bay watershed. Revised and updated digital spatial data sets representing point locations of USGS streamflow data- collection sites will be created and distributed as planned enhancements and applications for SPARROW are completed.
Any use of trade, product, or firm names is for descriptive purposes
only and does not imply endorsement by the U.S. Government.
Although this Federal Geographic Data Committee-compliant metadata
file is intended to document the data set in nonproprietary form,
as well as in ARC/INFO format, this metadata file may include some
ARC/INFO-specific terminology.
Nutrient stream-loading estimates were derived from water-quality
and flow data collected by State and Federal agencies (Langland and
others, 1995) using the methods described in Smith and others (1997).
Load-estimate regressions were fit on the basis of actual flow and
concentration data. Loads were then estimated using those
regressions and an average discharge time series (average daily
flow values for the period 1950 to 1995), specifying the year 1987
for the trend component. By use of this method, load estimates may
differ from those previously published because of the average
discharge values used as input for the regressions. Nutrient stream
loads were estimated for total nitrogen and total phosphorus at as
many as 132 sites within the Chesapeake Bay watershed. The nitrogen
(103 sites) and phosphorus (121 sites) load estimates were used as
the dependent variables in the calibration of the SPARROW models.
Other nutrient-load estimates may be used for calibration in future
applications of the SPARROW models.
Latitude and longitude coordinates of the streamflow sampling sites
used for nutrient stream-load estimates were obtained from the USGS
National Water Information System (NWIS) and used to generate a
point-location data set. Attributes for this point data set consist
of a station identification number for the streamflow sampling sites
and their associated water-quality sites, and 1992 load estimates
for total nitrogen and total phosphorus. Sites that do not contain a
nutrient estimate were calculated to -9999.99.
Q2_SIT.PAT:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC
1 AREA 4 12 F 3
5 PERIMETER 4 12 F 3
9 Q2_SIT# 4 5 B -
13 Q2_SIT-ID 4 5 B -
17 STAID 15 15 C -
32 NAME 42 42 C -
74 E2RF1## 4 5 B -
78 TN 8 14 F 2
86 TP 8 14 F 2
STAID Unique USGS station identification number.
NAME USGS station name.
E2RF1## Unique reach identification number.
TN 1992 Total nitrogen estimate kg/yr used in model
calibration. Sites that do not contain a TN estimate
were calculated to -9999.99.
TP 1992 total phosphorus estimate kg/yr used in model
calibration. Sites that do not contain a TP estimate
were calculated to -9999.99.
Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data.
The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials.
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