UMISC – October 29, 2012 - bugwoodcloud.org · UMISC – October 29, 2012 . Eddie Heath* & Tim...

Effects of Winter Drawdown on the Aquatic Ecology of a Wisconsin Flowage

UMISC – October 29, 2012

Eddie Heath* & Tim Hoyman

Onterra, LLC Lake Management Planning Onterra, LLC Lake Management Planning

Introduction & Problem Identification

• Lac Sault Dore (Soo Lake) - Price County, WI • 561-acre shallow, mixed lowland drainage lake • 21-foot max depth, 6-foot average depth • Water quality is eutrophic and stained • 165,981-acre watershed (~260 sq miles)

• WS:LA = 276:1 • Overall watershed: 53% forested, 23% forested-

wetlands, 8% row-crop agriculture • EWM first discovered in 2004



• Winter Drawdown required for maintenance on the Wiemer Dam • Limited to 6-feet per specs of dam • Start drawing down after Labor Day 2010 • Refill flowage by May 1, 2011 • Planned secondary benefit to control EWM

Drawdown Scenario – 5 feet



• Soo Lake United Association (w/ WDNR Grant Assistance)

• Comprehensive Lake Management Planning Project

• Strong public participation component

• Draw-down monitoring


Monitoring Methodology • Objectives:

• Evaluate drawdown as a tool to control EWM • Understand non-target plant response • Document user perceptions of drawdown • Detect potential changes in water quality

M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S

Water Quality Sampling O2 O2 O2 O2

Point-intercept Plant SurveyCommunity Mapping SurveyEWM Peak-biomass Mapping SurveyStakeholder User SurveyWinter Drawdown

Task2010 2011 2012


Drawdown Implementation

-1

0

1

2

3

4

5

6

7

Feet

Bel

ow Fu

ll Po

olLac Sault Dore Water Levels

September October November December January February March April

September 2010 - May 2011


Results Outline • Eurasian Water Milfoil

• Point-intercept Survey • EWM Colony/Density Mapping Survey

• Native Aquatic Plants • Point-intercept Survey • Floating-leaf/Emergent Plant Community

Mapping Survey • Stakeholder User Survey


Results: EWM – Point-intercept Survey

Lac Sault Dore Lake 55-meter resolution 799 total points Surveys Completed: August 17-18, 2010 August 18-19, 2011 August 14-15, 2012

2010 PI: EWM 1Y Pre-Drawdown

36.3

0

5

10

15

20

25

30

35

40

2010 2011 2012

Freq

uenc

y of

Occ

uren

ce (%

)

0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10

Num

ber o

f Poi

nt-in

terc

ept L

ocat

ions

Depth Interval (feet)

2011 PI: EWM 1Y Post Drawdown

36.3

0.30

5

10

15

20

25

30

35

40

2010 2011 2012

Freq

uenc

y of

Occ

uren

ce (%

)

2012 PI: EWM 2Y Post Drawdown

36.3

0.3 0.50

5

10

15

20

25

30

35

40

2010 2011 2012

Freq

uenc

y of

Occ

uren

ce (%

)


Results: EWM – Colony/Density Mapping

Survey

Legend

Surface Matting

Small Plant Colony ! (

Clump of Plants ! (

Single or Few Plants ! (

Dominant Scattered Highly Scattered

Highly Dominant

2010 EWM PB 1Y Pre-Drawdown

Legend

Surface Matting


Clump of Plants ! (



Highly Dominant

2011 EWM PB 1Y Post Drawdown

Legend

Surface Matting


Clump of Plants ! (



Highly Dominant

2012 EWM PB 2Y Post Drawdown

Legend

Surface Matting


Clump of Plants ! (



Highly Dominant


Results: Native Plants – Point-intercept

Survey


Point-intercept Survey

0

5

10

15

20

25

30

35

40Fr

eque

ncy

of O

ccur

renc

e (%

)

2010 2011 2012



0

5

10

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30

35

40Fr

eque

ncy

of O

ccur

renc

e (%

)

2010 2011 2012



0

5

10

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25

30

35

40Fr

eque

ncy

of O

ccur

renc

e (%

)

2010 2011 2012



0

5

10

15

20

25

30

35

40Fr

eque

ncy

of O

ccur

renc

e (%

)

2010 2011 2012

*

* *

*

**

* *

* **

* *

Statistically valid change in occurrence from previous year (Chi-square α= 0.05)*



0

5

10

15

20

25

30

35

40Fr

eque

ncy

of O

ccur

renc

e (%

)

2010 2011 2012

*

* *

*

**

* *

* **

* *




0

5

10

15

20

25

30

35

40Fr

eque

ncy

of O

ccur

renc

e (%

)

2010 2011 2012

*

* *

*

*

*

*

*

*

* * *

* **

**

*

*

*




0

5

10

15

20

25

30

35

40Fr

eque

ncy

of O

ccur

renc

e (%

)

2010 2011 2012

*

* *

*

*

*

*

*

*

* * *

* **

**

*

*

*

Statistically valid change in occurrence from previous year (Chi-square α= 0.05)

Statistically valid change in occurrence from 2010 to 2012 (Chi-square α= 0.05)*

x x

x

x

x

x x x x x

x


Simpson’s Diversity (1-D)

0.87

0.94

0.89

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Lac Sault Dore 2010 Lac Sault Dore 2011 Lac Sault Dore 2012

Sim

pson

's D

iver

sity

Inde

x

Ecoregion Median

Between Ecoregion Upper & Lower Quartiles


Floristic Quality

36

6.7

40.2

35

6.7

39.6

37

7.2

43.8

23.5

6.2

28.3

13

6.0

22.2

0

5

10

15

20

25

30

35

40

45

50

Number of Native Species Average Conservatism Floristic Quality

Lac Sault Dore 2010

Lac Sault Dore 2011

Lac Sault Dore 2012

NLFF Ecoregion Median

WI State Median

2010

2011

2012

2010

2011

2012

2010

2011

2012

* Error bars represent Inner Quartile Range


Total Rake Fullness

33.2 %

24.1 %23.1 %

17.6 %

2010

71.4 %11.6 %

9.0 %

7.6 %

2011

69.3 %

11.3 %

8.0%

10.9 %

2012

No Vegetation Rake-fullness = 1 Rake-fullness = 2 Rake-fullness = 3


Depth Distribution

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10

Freq

uenc

y of

Occ

urre

nce

(%)

Water Depth Interval (ft)

EWM 2010 Native Species 2010

98% of all 2010 plants located in 7 feet or less

90% of all 2010 native plants located in 5 feet or less


0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10

Freq

uenc

y of

Occ

urre

nce

(%)



Depth Distribution


0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10

Freq

uenc

y of

Occ

urre

nce

(%)




Depth Distribution



Depth Distribution

0

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1 2 3 4 5 6 7 8 9 10

Freq

uenc

y of

Occ

urre

nce

(%)







Results: Native Plants – Floating-

leaf/Emergent Plant Community Mapping Survey

2010 Com.Mapping 1Y Pre-Drawdown

2010 Com.Mapping 1Y Pre-Drawdown

Plant Community 2010 2011Emergent 1.4 0.0Floating-leaf 19.3 21.5Mixed Emergent & Floating-leaf 82.0 88.2Total 102.7 109.7

Acres

2011 Com.Mapping 1Y Post Drawdown


Results: Stakeholder User Survey


Stakeholder User Survey • October 2011, 7-page 31-questions survey

mailed to 374 riparian property owners • Survey was approved by WDNR survey

specialist • 53% response rate


Stakeholder User Survey Please rank up to three activities that are important reasons for owning your property on or near the lake. 0

20

40

60

80

100

120

140

160

180

# of

Res

pons

es

3rd

2nd

1st

#13

0

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60

80

100

120

140

160

# of

Res

pons

es

3rd

2nd

1st

#20

Please rank your top three concerns regarding Lac Sault Dore.


Stakeholder User Survey

0

5

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35

40

45

50

Never Rarely Sometimes Often Always Not Applicable

% o

f Res

pond

ents

#21

0

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45

50

Never Rarely Sometimes Often Always

% o

f Res

pond

ents

#22

Before the drawdown over the winter of 2010/2011, how often did aquatic plant growth, including algae, negatively impact your enjoyment of Lac Sault Dore during the open water season?

How often does aquatic plant growth, including algae, negatively impact your enjoyment of Lac Sault Dore during the open water season of 2011

Onterra, LLC Lake Management Planning

• Aquatic Plant Community • EWM occurrence decreased by over 99% and has

remained <1% FOO for 2Y Post • From 2010-2012, 6 native plants displayed statistically

valid reductions; 5 displayed statistically valid increases • Species diversity & floristic quality increased • Emergent & floating-leaf plant communities expanded by

7 acres (2010-2011), mostly attributed to white-water lily. Additional expansion likely in 2012

Conclusions


• Water Quality • All parameters remained within relatively similar range • Dissolved oxygen was sufficient throughout winter

• Stakeholder • Encouraged by drastic reduction in EWM and associated

nuisance conditions that were alleviated • White-water lily expansion is now primary issue

Conclusions


• How long will EWM control last? • How to more accurately perform sediment compaction

and depth-related surveys? • Will white-water lily continue to expand, or start to

retract? • How to minimize stakeholder issues

• Floating debris following drawdown • Over-fishing concerns • Realistic expectations

Discussion


• Soo Lake United Association • WDNR AIS Grant Program • Jim Kreitlow and other WDNR Staff • Bob Lepke, Price County Dam-tender • Evan Lund, Price County Conservationist • Onterra Field Crews

Acknowledgments


Thank You

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