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 data set representing total nitrogen and total phosphorus load estimates from agricultural sources was generated from various sources. A land cover data set was used to spatially distribute nutrient application rates and specific land uses of conventional till, conservation till, and hay. Final load estimates were calculated for each SPARROW watershed segment.
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.)
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The base land-cover data set is a 25-meter cell-size grid. A separate grid of the herbaceous land cover category was created and re-sampled to a 1-kilometer cell size and used with the SPARROW watershed segment grid to calculate acres of herbaceous area withen each segment. It was assumed for the SPARROW applications that the herbaceous category within this data set represents agricultural land.
It was also assumed that acres of conventional till, conservation till, and hay land uses were distributed equally throughout the herbaceous land area.
The spatial land-cover data set used in the SPARROW applications was provided by the Chesapeake Bay Program (CBP). It was derived from a combination of land-cover data sets from various years including the Environmental Monitoring and Assessment Program (EMAP), National Oceanic and Atmospheric Administration (NOAA) Coastal Change Assessment Program (C-CAP), and USGS Geographic Information Retrieval and Analysis System (GIRAS) (Gutierrez-Magness and others, 1997, p42).
The original data set was a 25 meter cell size grid. The land-cover attribute of interest is the herbaceous category. A separate grid for herbaceous land cover was created and re-sampled to a 1-kilometer cell size and used with the SPARROW watershed segment grid to calculate acres of each land cover type. It was assumed for the SPARROW applications that the herbaceous category within this data set represents agricultural land use.
AGLOADS.PAT:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME
1 AREA 4 12 F 3
5 PERIMETER 4 12 F 3
9 AGLOADS# 4 5 B -
13 AGLOADS-ID 4 5 B -
17 ERF1## 4 8 B -
21 FN 8 18 F 6
29 FP 8 18 F 6
37 MN 8 18 F 6
45 MP 8 18 F 6
ERF1## - New unique reach identification number
FP - Total phosphorus load estimate from commercial fertilizer
FN - Total nitrogen load estimate from commercial fertilizer
MN - Total nitrogen load estimate from manure spread
MP - Total phosphorus load estimate from manure spread
Load estimates are in pounds.
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 13:02:18 1998