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 PNTSRC92 represents point-source locations acquired from the Chesapeake Bay Program and contains estimates of annual nutrient load for total nitrogen and total phosphorus. An average nutrient value for total nitrogen and total phosphorus was calculated for the years 1990, 1991, and 1992 and used with SPARROW for the early 1990's time period (Version 2.0) in the Chesapeake Bay watershed.
This spatial data set was created by the USGS specifically used with SPARROW representing the early 1990's time period (Version 2.0) 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 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.
Locations of point-source discharges, average-annual flow,
average-annual concentrations, and loads of nitrogen and phosphorus
for sites within the Chesapeake Bay watershed, were obtained from
the CBP office for the years 1984 through 1997 (Wiedeman and
Cosgrove, 1998). The data are based on information from the
Environmental Protection Agency's (EPA) Permit Compliance System
(PCS) State National Pollutant Discharge Elimination System (NPDES)
discharge monitoring reports, with modifications from individual
State agencies responsible for monitoring point-source discharges.
The original point-source data compiled by the CBP resides as
monthly-discharge data, by facility, in pounds per year (lb/yr).
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 (Wiedeman and
Cosgrove, 1998).
Latitude and longitude coordinates of discharging facilities were
used to generate a point data set attributed with facility, facility
type, NPDES number, and load averaged by facility and contaminant
from 1990, 1991, and 1992 and were then converted to kilograms per
year (kg/yr). SPARROW watershed segment numbers (E2RF1##) were
assigned to the locations by merging the polygon data set
representing SPARROW watershed segments with the point-source
location data set (INTERSECT). Loads of nitrogen and phosphorus for
each watershed were then summed for each contaminant within each
watershed segment.
PNTSRC92.PAT:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC
1 AREA 4 12 F 3
5 PERIMETER 4 12 F 3
9 PNTSRC92# 4 5 B -
13 PNTSRC92-ID 4 5 B -
17 NPDES 9 9 C -
26 FACILITY 60 60 C -
86 SIC 4 4 B -
90 TYPE 60 60 C -
150 E2RF1## 4 5 B -
154 TN90 8 16 F 3
162 TN91 8 16 F 3
170 TN92 8 16 F 3
178 TP90 8 16 F 3
186 TP91 8 16 F 3
194 TP92 8 16 F 3
202 TNAVG 8 16 F 3
210 TPAVG 8 16 F 3
218 TNREACH 8 16 F 3
226 TPREACH 8 16 F 3
AREA - Internal attribute, does not apply to point data
PERIMETER - Internal attribute, does not apply to point data
PNTSRC92# - Internal identification number
PNTSRC92-ID - User defined identification number
NPDES - State National Pollutant Discharge Elimination System
Code (NPDES)
FACILITY - Point source discharge facility, blank is unknown
SIC - Facility type code, -9999 is unknown
TYPE - Facility type, blank is unknown
E2RF1## - Unique reach identification number source is related too
TN90 - 1990 total nitrogen load for facility, kg/yr
-9999 = no data
TN91 - 1991 total nitrogen load for facility, kg/yr
-9999 = no data
TN92 - 1992 total nitrogen load for facility, kg/yr
-9999 = no data
TP90 - 1990 total phosphorus load for facility, kg/yr
-9999 = no data
TP91 - 1991 total phosphorus load for facility, kg/yr
-9999 = no data
TP92 - 1992 total phosphorus load for facility, kg/yr
-9999 = no data
TNAVG - Average total nitrogen load for facility, 1990-92, kg/yr
TPAVG - Average total phosphorus load for facility, 1990-92, kg/yr
TNREACH - Sum of average load by reach for total nitrogen, kg/yr
TPREACH - Sum of average load by reach for total phosphorus, kg/yr
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 version 2.2.5 on Thu Nov 30 13:08:47 2000