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National Kxposure Research Laboratory
Research Abstract

Government Performance Results Act (GPRA) Goal #4
Annual Performance Measure #320

Significant Research Findings:

GIS modeling tool (ArcView Extension) to target water body risks of TMDL exceedance
	for nutrients and sedimentation: the mid-Atlantic Region case study.	

Scientific	Declining water quality is a major concern. Limited resources make

Problem and	comprehensive sampling of water bodies infeasible, so a method of cost-

Policy Issues	effectively identifying potentially impaired waters is highly desirable. This tool

provides this capability. Based on landscape metrics, it will locate stream reaches
that are more likely to be impaired to make sampling more efficient, saving time,
money and improving the state of water quality data.

Research	The tool is written in Visual Basic and requires ArcGIS 8 or newer with the

Approach	Spatial Analyst extension. It also requires watersheds with Pfaffstetter attribution

and landscape metrics generated from ATtlLA (Analytical Tools Interface for
Landscape Assessments), another extension written by the Landscape Ecology
Branch. The model included in the tool is taken from a peer reviewed journal
article. Models added in the future will also be peer reviewed.

The user selects watersheds of interest, a model (only dissolved P is now
available), and a loading threshold. The tool calculates loadings for all
selected watersheds individually and including any upstream contributing
area.

Results and
Impact

Research
Collaboration and
Research
Products

The tool generates a map of impaired/non-impaired watersheds based on a
user defined threshold. Loadings for individual watersheds and upstream
contributing areas are stored in the watershed attribute table. This tool could
benefit all EPA staff and state personnel involved with the TMDL (Total
Maximum Daily Load) program.

Development was completed within the Landscape Ecology Branch. The
tool will be available from the branch website through
www.epa.gov/nerlesdl

Future Research Additional models will be added in the future.

Contacts for

Additional

Information

Questions and inquiries can be directed to:

Tim Wade

U.S. EPA, Office of Research and Development
National Exposure Research Laboratory
E243-05
RTP, NC 27711

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Phone: (919) 541-4119
E-mail: wade.timothv@,epa.gov

Funding for this project was through the U.S. EPA's Office of Research and
Development, National Exposure Research Laboratory, and the work was
conducted by the Environmental Sciences Division.

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