1. High Rock Lake, Yadkin River Basin Scoping Monitoring Study
Michelle Woolfolk, NC DWQ
May 24, 2005 Stakeholder Meeting

2. What I will cover…. Highlights from the data review document
Highlights from the scoping study

4. Counties Alexander Alleghany Caldwell Davidson Davie Forsyth Guilford
Iredell
Rowan
Stokes
Surry
Watauga
Wilkes
Yadkin
Watershed area: 3,973 sqm

5. Data and model review
DENR Water Quality Data Review for High Rock Lake, North Carolina. Prepared by Tetra Tech, Inc.
Available on website

6. Previous investigations
USEPA 1973.
Study concluded that the lake is highly eutrophic, but because of short residence time, the lake resembles a slow-moving river. Phosphorus indicated as limiting nutrient.
NCDEM 1974.
NC DEM 1975.
Focus on point source discharges. Dense algal growth and high turbidity noted.

7. Previous investigations, cont.
UNC
High Rock Lake is clearly a nutrient rich aquatic system that …develops substantial algal populations.
NC DEM
Monitoring to support water quality modeling.
Chlorophyll a concentrations violated the state standard (40 ug/L) numerous times.
Largest algal populations observed in the embayment of Town Creek.

8. Previous investigations, cont.
APGI
Nutrient enrichment with elevated chlorophyll a noted.
Elevated turbidity in upper portions of the lake were noted, as well as violations of cyanide and mercury criteria.
Thermal stratification noted as “not common in the reservoir and most occurrences of a thermocline are weak and not persistent.”

9. Previous modeling NC DWQ BATHTUB model
Model provided a reasonable fit to total phosphorus. Model over-predicted total nitrogen and severely underestimated chlorophyll a.
Errors in input files
Mis-representation of vertical mixing
Tributaries loads highly uncertain
Hydraulic residence time too short

10. 2 9 10 1 3 11 4 6 12 5
NCDWQ (1997) High Rock Lake Water Quality Model Segmentation 13 15 8 14 7

11. Exploratory data analysis
Correlation analysis
Focus on summer season (June – September)
Includes nutrient concentrations, Secchi depth, and temperature.
Very little of the variability in chlorophyll a concentration in High Rock Lake is explained by nutrient concentrations.
Light explains a relatively more variability in chlorophyll a.
Mixing dynamics are probably important

12. Exploratory data analysis, cont.
Non-parametric analysis (CART)
“Total phosphorus, nonalgal turbidity, and Secchi depth were identified as statistically significant variables in predicting chlorophyll a concentrations…”

13. Data needs identified
In the period leading up to TMDL development, continue regular ambient monitoring, particularly in light of the loss of chlorophyll a data between 1997 and (SS)
If possible, obtain direct experimental evidence on the ratio of organic carbon and ash-free dry weight to chlorophyll a for different algal groups and different seasons.

14. Data needs, cont.
High frequency sampling of algae (preferably weekly or better) for at least one calibration and one validation growing season.
Major tributary water quality should be sampled with at least the same frequency (i.e., weekly or better) during intensive studies.

15. Data needs, cont. Information on the volatile solids content of TSS.
In-lake measurements of total BOD or CBOD should be obtained, and SOD measurements should be considered. (SS)
Maintain Econet station at Salisbury (weather station)
Temporal issues (SS)

16. Modeling issues identified
Problem identification and DQOs
Significant longitudinal gradients in observed water quality.
Model should incorporate a full hydrodynamic simulation with coupled water quality simulation.
Full eutrophication simulation that accounts for nutrient effects, settling, and the interaction between turbidity/light and algal growth.

17. Modeling issues, cont.
The DO/BOD cycle should be included in the model.
Model should be open source and in the public domain
Appropriate tools:
WASP5/EUTRO5
EFDC
CE-QUAL-W2

18. Purpose of Scoping Study
Gather data and information on parameters needed for modeling but not included in ambient monitoring
Get data for the late fall season to determine if critical conditions might vary from traditional summer
Build validation year dataset

19. Scoping study March through December 2005
Lake and watershed monitoring
Relies on existing USGS gages***
Less intensive than the TMDL study (but more intensive than standard ambient monitoring)

20. Scoping study includes…
Continuous temperature monitoring
Algal analyses (density and dominant species)
SOD and nutrient flux
Monthly monitoring of chemical parameters in-lake and at selected watershed locations

21. Thermister deployment

22. Thermister buoy

23. (April – May, 2005)

25. Thanks for your attention!!
Questions or comments?
Contact
Michelle Woolfolk
NCDWQ – Modeling & TMDL Unit
ext 505

26. Next steps Complete scoping study (DWQ)
Formation of Technical Advisory Committee
Stakeholder process?
Goal setting

27. Technical advisory committee?
Purpose: meet with DWQ during the formation of tools to discuss issues and make recommendations
Members
Four to five members of the general stakeholder group, DWQ Modeling & TMDL Unit, DWQ Intensive Survey Unit, DWQ QA Officer

28. TAC actions
Review data at the end of the year (i.e., 2005) for completeness
Was the correct data obtained, quantity and quality?
Was the additional data and information obtained?
Were there any logistical problems with monitoring?
Develop, with DWQ, the TMDL field study plan, with goals and budget
Develop, with DWQ, the modeling plan, with goals and budget
Methods and numeric targets

29. TAC, cont. Time Commitment Member background:
June 2005 – May 2006, 8-10 meetings
Member background:
Water quality, chemistry, statistics, water/wastewater treatment, water resources, environmental science

30. General stakeholder process
Locally run. In other areas, the Council of Governments or discharger association has taken on the coordination role
Develop meeting schedule
Decide on how to interface with the TAC

31. Next general meeting Date: July 27, 2005 Location: TBD
Duration: 1 hr, 30 minutes
Agenda: Review project goals, modify as needed and prioritize, Finalize TAC membership
Immediately following: 1st TAC meeting

32. Project goals
What are the goals of this chlorophyll-a and turbidity TMDL project?
Develop approvable TMDLs for High Rock Lake.
Estimate the relative point and nonpoint source contributions to nutrient loads
Provide individual NPDES wastewater allocations
Support the development of nonpoint source management strategies to reduce nutrient and sediment loading