High Rock Lake
Nutrient Modeling Update
Pam Behm - NC Division of Water Resources
Environmental Management Commission
Information Item
January 8, 2015
PURPOSE
To provide an update on the status of the
High Rock Lake nutrient modeling and
information on the next steps in the process
of developing a Nutrient Management
Strategy for the lake.
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OUTLINE
• Description of Lake and Watershed
• Impairment History
• Addressing the Impairment
• Role of Technical Advisory Committee
• Next Steps
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High Rock Lake Watershed
Yadkin
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Population:
850,000
High Rock
Lake
Watershed
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2007 Land Cover
47% Forest
30% Pasture/Crop
18 % Developed
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Point Sources
Municipal and Industrial
Wastewater
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Impairment History
• Mid-1970s – Highly nutrient over-enriched
conditions first documented
• 1992 – DWQ NC Lake Assessment Report
– One of the most nutrient over-enriched lakes in NC
– Recommended “management strategies”
• 303(d) List
– Entire lake listed for chlorophyll-a
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Addressing the Impairment
Questions
• Where are the nutrients coming from and how
much?
▫ Tool: Watershed Model
• What reductions in nutrient loading are necessary
to achieve water quality standards in the lake?
Nitrogen? Phosphorus? Both?
▫ Tool: Nutrient Response Model
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Addressing the Impairment
• 2005 – DWQ formed Technical Advisory
Committee (TAC)
• 2007 – 319-grant awarded to Yadkin/Pee Dee
River Basin Association (YPDRBA) for an
intensive monitoring study of the
lake/watershed
• 2009 – EPA contract awarded to Tetra Tech for
model development
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Watershed Model
• Estimates what is
happening on land that
results in nutrient export
to receiving water
(i.e. High Rock Lake)
• Provides relative loading
by source (agriculture,
developed, point sources,
etc.)
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Watershed Model – NMS uses
• Used to:
▫ Determine nutrient concentrations entering
High Rock Lake
▫ Assist with evaluation of potential source
reduction scenarios
• No direct application to NMS
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Nutrient Response Model
Result of Model
Determines
nutrient load
reductions that
will achieve water
quality standards
Existing loading from
all sources
Lake
Response
Chl-a
Reduced loading
Lake
Response
Chl-a
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Technical Advisory Committee (TAC)
WHO:
Stakeholders – state and local agencies
PURPOSE:
Assist … with the development of
mathematical tools for the management of
nutrients and turbidity in High Rock Lake
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High Rock Lake TAC Members
• APGI
• DHHS – Environmental
Health Section
• Dept of Transportation
• Div of Soil and Water
Conservation
• DWR
• Duke Energy
• Keep Iredell Clean
• Kernersville
• Piedmont-Triad
Regional Council
• Salisbury
• Winston-Salem
• Yadkin Riverkeeper
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TAC
• Modeling Training
• TAC Inputs:
▫ Modeling Goals
▫ Monitoring Plan
▫ Model Performance Targets
▫ Model Review – “Tell us how to make it better”
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Next Steps
• Finalize nutrient response model
• Final TAC meeting
END of
TOOL DEVELOPMENT
(Step 1 in NMS Development
Process Completed)
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Nutrient Management Strategy
Development Process
Step 1: Build the tools
Who:
• DWR and TAC
What:
• Monitoring
• Modeling
Step 2: Develop the strategy
Who:
• DWR and Stakeholders
What:
• Model scenarios
• Reduction targets
• Point and nonpoint
strategies
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EMC Role
• Nutrient Response Model Approval
▫ Not required for High Rock Lake
▫ Has been required for previous strategies
▫ “Appropriate tool to use for strategy
development”
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Questions?
Pam Behm
[email protected]
919-807-6419
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