Condition of Indiana Lakes

Presented May 2, 2012 at the

National Water Quality Monitoring Conference

By

Stacey Sobat, Senior Environmental Manager

Indiana Department of Environmental Management

Objectives for 2007National Lakes Assessment

• Report on condition of nation’s lakes

• Determine baseline lake condition forfuture trend assessment

• Develop state programs for monitoringand assessing lakes

Presentation

• Target population of lakes

• Biological, chemical, and physical data

• Determining thresholds for expectations

• Comparison of results between Indiana andthe nation’s lakes

• Policy implications

• 2012 National Lakes Assessment

Target Population

• Natural and man-made freshwater lakes,ponds and reservoirs, greater than 10 acreswith at least 0.25 acres open water, and aminimum depth of one meter

• Statistical survey design generated 1,028lakes from 50,000 lakes in lower 48 states

• Twenty-one lakes in Indiana for NationalLakes Assessment plus 29 for total of 50lakes to perform statewide assessment

Extent of Lake Origin

59%

41%

National

Natural Man-Made

55%

45%

Indiana

Data Collected

• Biological: phytoplankton (algae),zooplankton, sediment diatoms, algaldensity (chlorophyll-a)

• Chemical: total phosphorus, total nitrogen,turbidity, dissolved oxygen, temperature,pH, acid neutralizing capacity, salinity

• Physical: riparian zone, shallow waterhabitat, habitat complexity, lakeshoredisturbance

Determining Expectations• Fixed thresholds

– Dissolved oxygen, algal risk, lake trophic status

• Reference thresholds

– Biological/physical data, nutrients, turbidity

(Figure 5 from National Lakes Assessment Report)

Biological Condition

PlanktonicTaxa Loss

Diatom Index ofBiotic Integrity

23

40

22

1

27

37

21

25

47

23

56

74

0 20 40 60 80 100

National

Indiana

National

Indiana

Percentage of Lakes

Good

Fair

Poor

1

0

6

0

19

3

18

0

6

0

16

22

27

39

24

25

88

100

78

78

54

58

58

75

0 20 40 60 80 100

National

Indiana

National

Indiana

National

Indiana

National

Indiana

Percentage of Lakes

Good

Fair

Poor

TotalPhosphorus

Turbidity

TotalNitrogen

DissolvedOxygen

Chemical Stressors

Habitat Quality

17

43

33

26

20

9

36

10

48

20

20

25

21

41

18

22

35

37

47

49

59

50

46

68

0 20 40 60 80 100

National

Indiana

National

Indiana

National

Indiana

National

Indiana

Percentage of Lakes

Good

Fair

Poor

RiparianZone

ShallowWaterHabitat

HabitatComplexity

LakeshoreDisturbance

Harmful Algal Bloom Risk

7

1

12

19

20

25

29

7

73

74

59

74

0 20 40 60 80 100

National

Indiana

National

Indiana

Percentage of Lakes

LowModerateHigh

Chlorophyll-a

Cyanobacteria

• Extent of microcystin: Indiana 49% (0% level ofconcern) vs. 30% in nation (1% level of concern)

Trophic Status

20

21

30

7

37

67

13

5

0 20 40 60 80 100

National

Indiana

Percentage of Lakes

Oligotrophic (<=2 ug/L)

Mesotrophic (>2 to 7 ug/L)

Eutrophic (>7 to 30 ug/L)

Hypereutrophic (>30 ug/L)

Chlorophyll-a(“Carlson” thresholds)

Policy Implications

• Prioritize stressors to planktonic loss withattributable risk analysis

– Relative Extent of Stressor: percentage of Indianalakes rated poor for each stressor

– Relative Risk: severity of stressor’s effect onplanktonic taxa loss

– Attributable Risk: combines relative risk and extentinto a single measure of overall stressor impact onsevere planktonic taxa loss for Indiana lakes

Stressors to Biological Condition

3

9

10

26

43

1

6

17

18

19

20

33

36

0 20 40 60 80 100

Total NitrogenShallow Water Habitat

Riparian ZoneHabitat Complexity

Lakeshore Disturbance

Dissolved OxygenTurbidity

Lakeshore DisturbanceTotal Phosphorus

Total NitrogenShallow Water Habitat

Habitat ComplexityRiparian Zone

Percentage of Lakes Rated Poor for Each Stressor

National Relative Extent

Indiana Relative Extent

0

1.28

1.12

9.15

7.19

0.6

2.1

1.4

2.3

2.5

2.3

1.96

3

0 2 4 6 8 10

Relative Risk

Relative Risk

-2.8

2

1

68

73

0

6.2

6.6

19.3

21.9

20.4

23.9

42.5

-20 0 20 40 60 80100

Percentage of Lakes

Attributable Risk

Policy Implications

• Severe planktonic taxa loss could be reducedby 73% if lakeshore disturbance was eliminated

• Poor habitat complexity is estimated to occurin 26% of Indiana lakes and is nine times morelikely to cause severe planktonic taxa lossrelative to other stressors

• Compared to other stressors, total nitrogen hasno relative risk to severe planktonic taxa loss

• Evaluation of management strategies byassessment of trends in biological andrecreational condition as well as trophic status

– Biological (planktonic taxa loss):

74% good, 25% fair, 1% poor

– Recreational (algal toxin, microcystin):

Present in 49% of Indiana lakes, none at level of concern

– Trophic status (Chlorophyll-a):

21% hypereutrophic

79% lower nutrient enrichment levels

Policy Implications

2012 National Lakes Assessment

• Indiana University School of Public andEnvironmental Affairs (IU SPEA)

• Twenty-seven lakes in Indiana for NationalLakes Assessment plus 23 for total of 50 lakes

• Evaluate 2012 results for changes in conditionand stressors of Indiana lakes using 2007baseline data

• Compare 2012 Indiana lake results to nation

Acknowledgements

• U.S. EPA 2007 National Lakes Assessment Report:

http://water.epa.gov/type/lakes/lakessurvey_index.cfm

• IU SPEA: Bill Jones and Melissa Clark

• U.S. EPA: David Peck and Mari Nord

• IDEM: Jim Stahl

Contact Information

Stacey Sobat

317-308-3191

ssobat@idem.IN.gov