Digital data sets were compiled by the U. S. Geological Survey (USGS) and used as input for a collection of Spatially Referenced Regressions On Watershed attributes for the Chesapeake Bay region. These regressions relate streamwater loads to nutrient sources and the factors that affect the transport of these nutrients throughout the watershed. A digital segmented network based on watershed boundaries serves as the primary foundation for spatially referencing total nitrogen and total phosphorus source and land-surface characteristic data sets within a Geographic Information System. Digital data sets of atmospheric wet deposition of nitrate, point-source discharge locations, land cover, and agricultural sources such as fertilizer and manure were created and compiled from numerous sources and represent nitrogen and phosphorus inputs. Some land-surface characteristics representing factors that affect the transport of nutrients include land use, land cover, average annual precipitation and temperature, slope, 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 the models. Nutrient stream loads were estimated for total nitrogen, total phosphorus, nitrate/nitrite, amonium, phosphate, and total suspended soilds at as many as 109 sites within the Chesapeake Bay watershed. The total nitrogen and total phosphorus load estimates are the dependent variables for the regressions and were used for model calibration. Other nutrient-load estimates may be used for calibration in future applications of the models.
This spatial data set was created and used by the USGS in the initial applications of the SPARROW models in the Chesapeake Bay watershed. Revised and updated digital spatial data sets will be created and distributed by the USGS as planned enhancements and applications for the SPARROW models are completed.
Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Geological Survey.
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. Users are cautioned not to be confused by this terminology. This metadata file should contain enough information to eliminate any confusion caused by the use of ARC/INFO-specific terminology.)
Locations of point-source discharges, average-annual flow, and average-annual concentrations and loads of total nitrogen and total phosphorus for sites within the Chesapeake Bay watershed were obtained from the CBP office for the years 1984 through 1995 (Wiedeman and Cosgrove, 1997). The data is based on information from the Environmental Protection Agency's (EPA) Permit Compliance System (PCS) State NPDES discharge monitoring reports with modifications from individual States agencies responsible for monitoring point-source discharges. The original point-source data compiled by the CBP resides as monthly-discharge data by facility. Details on the calculation of annual loads using concentration and flow data by discharging facility can be found in Appendix F of the EPA report Chesapeake Bay Watershed Model Application and Calculation of Nutrient and Sediment Loadings.
Latitude and longitude coordinates of discharging facilities for 570 sites were used to generate a point-data set attributed with facility, facility type, and National Pollutant Discharge Elimination System (NPDES) number. Four-hundred and eleven sites were used to average load by facility and contaminant from 1986, 1987, and 1988. Load Values were then converted from pounds per year (lb/yr) to kilograms per year (kg/yr). SPARROW watershed segment numbers (erf1##) were assigned to the locations by merging the polygon data set representing watershed segments with the point source location data set, except where watersheds were generated from reaches representing shorelines of major estuaries. Total nitrogen and total phosphorus loads for each watershed were then summed for each contaminant within each watershed segment. This data set represents locations of point-source discharge and nutrient loads used in SPARROW applications.
Locations of point sources within watershed boundaries of major estuaries are included in this data set, but ARE NOT attributed with nutrient loads.
CBWSPNTS.PAT:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME
1 AREA 4 12 F 3
5 PERIMETER 4 12 F 3
9 CBWSPNTS# 4 5 B -
13 CBWSPNTS-ID 4 5 B -
17 NPDES 9 9 C -
26 FACILITY 60 60 C -
86 SIC 4 4 I -
90 TYPE 60 60 C -
150 ERF1## 4 8 B -
154 TN 10 10 N 2
164 TP 9 9 N 2
NPDES - National Pollutant Discharge
Elimination System ID number
FACILITY - Facility name
SIC - Standard Industrial
Classification Code
TYPE - Facility type, defined by SIC
ERF1## - New unique reach identification
TN - Average Total Nitrogen load, from
1986, 1987, and 1988 in kilograms
per year (kg/yr)
TP - Average Total Phosphorus load, from
1986, 1987, and 1988 in kilograms
per year (kg/yr)
Missing TYPE values represent unknown information about the facility,
based on the SIC code.
TN & TP values of zero represent point sources that fell within
the coastal areas of the Chesapeake Bay watershed and were not used
in SPARROW applications. They are present for locational purpose only.
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.
Generated by mp on Tue Sep 22 13:02:39 1998