Environmental Management Commission Information Item January 8, 2015 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.

OUTLINE Description of Lake and Watershed Impairment History Addressing the Impairment Role of Technical Advisory Committee Next Steps

High Rock Lake Watershed Neuse Yadkin Cape Fear

High Rock Lake Watershed Population: 850,000

2007 Land Cover 47% Forest 30% Pasture/Crop 18 % Developed

Point Sources Municipal and Industrial Wastewater

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

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

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

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.)

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

Nutrient Response Model Lake Response Chl-a Result of Model Determines nutrient load reductions that will achieve water quality standards Existing loading from all sources Lake Response Chl-a Reduced loading

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

High Rock Lake TAC Members APGI Keep Iredell Clean DHHS – Environmental Health Section Kernersville Piedmont-Triad Regional Council Dept of Transportation Div of Soil and Water Conservation Salisbury Winston-Salem DWR Yadkin Riverkeeper Duke Energy

TAC Modeling Training TAC Inputs: Modeling Goals Monitoring Plan Model Performance Targets Model Review – “Tell us how to make it better”

(Step 1 in NMS Development Process Completed) Next Steps Finalize nutrient response model Final TAC meeting END of TOOL DEVELOPMENT (Step 1 in NMS Development Process Completed)

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

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”

Questions? Pam Behm pamela.behm@ncdenr.gov 919-807-6419