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Durham – Where Great Things Happen

Upper Falls Lake Water Quality, 2010-2015

Michelle Woolfolk and R. Travis Marion

Presented at the WRRI Annual Meeting

March 18, 2016

The Falls Lake Monitoring Program

• Who monitors?

City of Durham’s Stormwater Quality Group

• Why do they monitor?

a requirement to satisfy the NDWRF permit

• Where do they monitor?

two locations for grab samples and two locations for photic samples

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Ellerbe

Creek

Ellerbe

Cove

I-85

SR-1801

North Durham Water

Reclamation Facility

0

1

2

3

4

5

6

7

2012 2013 2014 2015

De

pth

(m

)

Sampling Years

Avg. Depth

I-85

SR1801

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3

0

5

10

15

20

25

30

35

40

2012 2013 2014 2015

NTU

Sampling Year

I-85

SR1801

Avg. Turbidity (NTU)Avg. Turbidity (NTU)

State Standard

22

22.5

23

23.5

24

24.5

25

2010 2011 2012 2013 2014 2015

Ce

lsiu

s

Sampling Year

Avg. Surface Temperature

I-85

SR1801

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4

I-85 Bridge (2013)

Apr.10th May 30th

July 19th

Sept. 7th Oct.27th

De

pth

(m

)

I-85 Bridge (2015)

Apr.10th May 30th

July 19th

Sept. 7th Oct.27th

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Jittered…Not Jittered…

April through October

I-85 Bridge

Ellerbe Cove

SR-1801

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April through October

Ellerbe Cove

I-85 Bridge

SR-1801

Ellerbe Cove

I-85 Bridge

SR-1801

April through October

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Are in-lake nutrient and

chlorophyll a levels better?.

Blue line: Best fit line

April through October monitoring

p=0.0019*

p=0.0055*

p=0.4658 Ellerbe Cove

I-85 Bridge

SR-1801

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p=0.0045*

p=0.2574

p=0.2269

Blue line: Best fit line

April through October monitoring

Ellerbe Cove

I-85 Bridge

SR-1801

p=0.1238

p=0.0004*

p=0.0001*

Blue line: Best fit line

April through October monitoring

Ellerbe Cove

I-85 Bridge

SR-1801

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Decreasing

concentrations

everywhere?

“Trend lines” NO

Lines of best fit. YES

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10

25%36%

53%42%

53%

20%

2010 2011 2012 2013 2014 2015

Elle

rbe

Co

ve

I-85

Brid

ge

SR

-18

01

Brid

ge

44%

77%71%

35%

23%

45%

2010 2011 2012 2013 2014 2015

35%

23%13%

5%

2010 2011 2012 2013 2014 2015

Percent of samples exceeding 40 µg/L State Chlorophyll a Standard

Goal: 10% or less

Eno River

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Eno River, nothing there

Ellerbe Creek

p= 0.0156*

Total Nitrogen, significant decrease

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NDWRF Effluent

Total Nitrogen, significant decrease

Total Phosphorus, significant decrease

p=<0.0001*

p= 0.0052*

Is the strategy working?.

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2010 20152009 2017

Falls Lake Watershed:Nutrient Management Activities

New D: New Development

Blue line: Best fit line

April through October monitoring

p=0.0019*

p=0.0055*

p=0.4658

I-85 Bridge

SR-1801

Ellerbe Cove

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Why are we monitoring?

(get higher resolution pic from

SAS)

Photo courtesy of SAS Institute

The most reliable way to anticipate the

future is to understand the present.

John Naisbitt, Author of Megatrends (1982)

Thank you foryour attention.

Michelle WoolfolkAssistant Water Quality Manager919.560.4326 x30219Michelle.woolfolk@durhamnc.gov

R. Travis MarionWater Quality Technician919.560.4326Roy.marion@durhamnc.gov