Chesapeake Bay restoration efforts are focused on improving water quality, living resources, and ecological habitats by 2010. One aspect of the water-quality restoration is the refinement of strategies designed to implement nutrient-reduction practices within the Bay watershed. These strategies are being refined and implemented by resource managers of the Chesapeake Bay Program (CBP), a partnership comprised of various Federal, State, and local agencies that includes jurisdictions within Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia, and the District of Columbia. The U.S. Geological Survey (USGS), an active member of the CBP, provides necessary water-quality information for these Chesapeake Bay nutrient- reduction strategy revisions and evaluations.
The formulation and revision of effective nutrient-reduction strategies requires detailed scientific information and an analytical understanding of the sources, transport, and delivery of nutrients to the Chesapeake Bay. The USGS is supporting these strategies by providing scientific information to resource managers that can help them evaluate and understand these processes. One statistical model available to resource managers is a collection of SPAtially Referenced Regressions On Watershed (SPARROW) attributes, which uses a nonlinear regression approach to relate nutrient sources and watershed characteristics to nutrient loads of streams throughout the Chesapeake Bay watershed. Developed by the USGS, information generated by SPARROW can help resource managers determine the geographical distribution and relative contribution of nutrient sources and the factors that affect their transport to the Bay.
Nutrient source information representing the late 1990s time period was obtained from several agencies and used to create and compile digital spatial datasets of total nitrogen and total phosphorus contributions that served as input sources to the SPARROW models. These data represent atmospheric deposition, point-source locations, land-use, land-cover, and agricultural sources such as commercial fertilizer and manure applications.
Watershed-characteristics datasets representing factors that affect the transport of nutrients also were compiled from previous applications of the SPARROW models in the Chesapeake Bay watershed. Datasets include average-annual precipitation and temperature, slope, soil permeability, and hydrogeomorphic regions.
Nutrient-input and watershed-characteristics datasets representing conditions during the late 1990s were merged with a connected network of stream reaches and watersheds to provide the spatial detail required by SPARROW. Stream-nutrient load estimates for 125 sampling sites (87 for total nitrogen and 103 for total phosphorus) served as the dependent variables for the regressions, and were used to calibrate models of total nitrogen and total phosphorus depicting late 1990s conditions in the Chesapeake Bay watershed.
Spatial data generated for the models can be used to identify the location of nutrient sources, while the models' nutrient estimates can be used to evaluate stream-nutrient load contributed locally by each source evaluated, the amount of local load generated that is transported to the Bay, and the factors that affect the nutrient transport. Applying the SPARROW methodology to late 1990s information completes three time periods (late 1980s, early 1990s, and late 1990s) of viable data that resource managers can use to evaluate the water- quality conditions within the Bay watershed in order to refine restoration goals and nutrient-reduction strategies.
The data set Q3_SIT represents point locations of USGS streamflow data-collection sites used in the calibration of SPARROW for the late 1990s (Version 3.0) 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 load estimates for 1997.
The U.S. Geological Survey (USGS) is investigating processes related to nutrient sources and transport through multiple studies designed to provide scientific information to resource managers responsible for the restoration and protection of the Chesapeake Bay and its' watershed. Two main goals of USGS Chesapeake Bay studies related to this report include: (1) enhancing the prediction and monitoring of nutrient delivery to the bay; and (2) disseminating information and enhancing decision-support tools.
This report describes the processes used to create, compile, and obtain the necessary digital spatial datasets generated with a geographic information system (GIS) for the purpose of applying the SPARROW methodology to develop total nitrogen and total phosphorus models in the Chesapeake Bay watershed representing the late 1990s (Version 3.0).
The spatial data set Q3_SIT was created and used by the USGS specifically in the calibration process of SPARROW representing the late 1990s time period (Version 3.0) in the Chesapeake Bay watershed.
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 ArcInfo format, this metadata file may include some
ArcInfo-specific terminology.
A log-linear regression model known as ESTIMATOR (Cohn and others,
1989) was used to estimate annual stream-nutrient loadings derived
from water-quality and stream-discharge data collected by numerous
State and Federal agencies (Langland and others, 1995) using the
methods described in Preston and Brakebill (1999). Load-estimate
regressions were calibrated based on actual stream-discharge and
concentration data. Loads based on long-term average-daily discharge
were estimated using the calibrated regressions, specifying the year
1997 for the trend component, and an average time series (average
daily flow values for the period 1950 - 2000) for the flow terms.
By use of this method, stream loads were estimated for 125
streamflow data-collection sites (87 for total nitrogen and 103 for
total phosphorus) within the Chesapeake Bay watershed, and were used
as the dependent variables (observed loads) in the calibration of
SPARROW.
Prior to the load calculations, latitude and longitude coordinates
and station identification numbers of the data-collection sites
(water quality and streamflow) were obtained from the State and
Federal data bases of the various collection agencies and used to
generate point-location datasets. A GIS was used to associate each
water-quality sampling site with an appropriate streamflow data-
collection site and stream reach. Attributes for the generated
streamflow dataset consist of a station identification number for
the water-quality and flow-collection sites, and 1997 loading
estimates for total nitrogen (87 sites) and total phosphorus
(103 sites).
Q3_SIT.PAT:
COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME
1 AREA 8 18 F 5
9 PERIMETER 8 18 F 5
17 Q3_SIT# 4 5 B -
21 Q3_SIT-ID 4 5 B -
25 STAID 15 15 C -
40 B_YEAR 4 4 I -
44 E_YEAR 4 4 I -
48 NAME 50 50 C -
98 QWSTAID 15 15 C -
113 E3RF1 4 5 B -
117 TN 8 14 F 2
125 TP 8 14 F 2
STAID Unique USGS station identification number.
B_Year Begining year of mean daily discharge measurement
E_Year Ending year of mean daily discharge measurement
NAME USGS station name.
QWSTAID Water-quality station data used to calculate load
E3RF1 Unique reach identification number, 1997 models.
TN 1997 Total nitrogen load estimate, kilograms per year
(kg/yr) used in model calibration. Sites that do not
contain a TN estimate were calculated to -9999.99.
TP 1997 Total Phosphorus load estimate, kilograms per
year (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.
More USGS GIS Data for Water Resources
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