Interim Update: Preliminary Analyses of Excursions in the A.R.M. Loxahatchee National

Wildlife Refuge

August 18, 2009

Prepared by SFWMD and FDEP as part of a Working Group of the Technical Oversight

Committee

Data Analyses

• Analyses of the environmental conditions leading up to the November 2008 and June 2009 sample collections included: TP concentrations and loads Rainfall Stage Water depths

Loxahatchee National Wildlife Refuge TP and Stage Data presented at June 30, 2009 TOC Meeting

Additional TP and Stage Data

MonthGeometric Mean TP Concentration

(ppb)

Long-term Level (ppb)

Difference (ppb)

Average Stage (ft NGVD 1929)

Number of TP Samples

Jun-08 8.9 14.9 -6.0 15.68 8Jul-08 9.2 10.3 -1.1 16.37 14Aug-08 8.6 10.2 -1.6 16.39 14Sep-08 7.7 8.3 -0.6 16.81 14Oct-08 7.2 7.2 0.0 17.42 14Nov-08 7.4 7.2 0.2 17.22 14Dec-08 6.3 7.8 -1.5 16.95 14Jan-09 7.0 8.8 -1.8 16.68 14Feb-09 4.7 10.4 -5.7 16.35 12Mar-09 7.5 13.5 -6.0 15.86 9Apr-09 9.7 14.9 -5.2 15.69 8May-09 11.0 N/A N/A 15.01 1

1st sample collection in June 2009

13.2 12.1 1.1 16.05 12

MonthGeometric Mean TP Concentration

(ppb)

Long-term Level (ppb)

Difference (ppb)

Average Stage (ft NGVD 1929)

Number of TP Samples

2nd sample collection in June 2009

9.7 12.8 -3.1 15.96 14

Jul-09 7.4 9.8 -2.4 16.47 14

Estimates of stage were available at all three gauges during all sample collections

Analysis of Rainfall DataAnalysis of Rainfall Data

Analysis of daily rainfall from S-5A, S-6 and S-39: 6-month period prior to May 2009 was driest in 45 years of record

November - April Rainfall Amounts: 1963-2009

The 6-month period preceding May 2009 was the driest on record

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 5 10 15 20 25 30 35 40Rainfall (inches)

Fre

quen

cy o

f L

ower

Rai

nfal

l

1963-2009 Period

1978-1983 Base Period

November 2008 - April 2009 4.99 inches

Analysis of daily rainfall from S-5A, S-6 and S-39: May 2009 was 4th wettest on record; last 2 weeks was 2nd wettest on record

May Rainfall Amounts: 1963-2009May 2009 was the 4th wettest on record; greater than 42 other years

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0Rainfall (inches)

Fre

qu

ency

of

Low

er R

ain

fall

1963-2009 period

1979-1983 base period

May 2009

Analysis of Stage DataAnalysis of Stage Data

Analysis of daily stages from 1-7, 1-8C and 1-9: Rapid fluctuation in stage; lowest 3-gauge average stage was 14.86 ft on May 12, 2009

Refuge Stage: May and June 2009

14.5

15.0

15.5

16.0

16.5

17.0

5/1/

2009

5/8/

2009

5/15

/200

9

5/22

/200

9

5/29

/200

9

6/5/

2009

6/12

/200

9

6/19

/200

9

6/26

/200

9

3-G

auge

Ave

rage

(ft

NG

VD

)

June 1 & 2 2009 Sampling: 16.05 ft

May 2009 Sampling: 15.01 ft

Lowest Stage: 14.86 ft on May 12 2009

June 17 & 19 2009 Sampling: 15.96 ft

Analysis of daily stages from 1-7, 1-8C and 1-9: The monthly change in stage was 3rd highest in 200 months that TP samples

were collected (June 1979-June 2009).

Cumulative Frequency Distribution of Stage ChangeSample Collections from June 1978 to June 2009

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

-1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Monthly Change in Stage (ft/month)

Fre

quen

cy o

f L

ower

Cha

nge

in S

tage

1994-2009

1978-1983 Base Period

June 1 & 2 2009

June 1 & 2 2009: Stage change was greater than

98% of all months

Analysis of hydraulic gradient: East rim canal stage - minimal opportunity for movement of canal water into interior marsh

Comparison of East Canal Stage to Marsh StageAnd Potential Load from STA-1E (assuming 0.1 ft threshold to sustain flow)

13.0

13.5

14.0

14.5

15.0

15.5

16.0

16.5

17.0

17.5

18.0

6/1/

2008

6/15

/200

8

6/29

/200

8

7/13

/200

8

7/27

/200

8

8/10

/200

8

8/24

/200

8

9/7/

2008

9/21

/200

8

10/5

/200

8

10/1

9/20

08

11/2

/200

8

11/1

6/20

08

11/3

0/20

08

12/1

4/20

08

12/2

8/20

08

1/11

/200

9

1/25

/200

9

2/8/

2009

2/22

/200

9

3/8/

2009

3/22

/200

9

4/5/

2009

4/19

/200

9

5/3/

2009

5/17

/200

9

5/31

/200

9

Stag

e (f

t N

GV

D)

0

200

400

600

800

1,000

STA

-1E

Loa

d (k

g)

Marsh

East Canal

Potential STA-1E Load

November 2008June 2009

Analysis of Hydraulic Gradient: West rim canal stage - minimal opportunity for movement of canal water into interior marsh

Comparison of West Canal Stage to Marsh StageAnd Potential Load from STA-1W (assuming 0.1 ft threshold to sustain flow)

13.0

13.5

14.0

14.5

15.0

15.5

16.0

16.5

17.0

17.5

18.0

6/1/

2008

6/15

/200

8

6/29

/200

8

7/13

/200

8

7/27

/200

8

8/10

/200

8

8/24

/200

8

9/7/

2008

9/21

/200

8

10/5

/200

8

10/1

9/20

08

11/2

/200

8

11/1

6/20

08

11/3

0/20

08

12/1

4/20

08

12/2

8/20

08

1/11

/200

9

1/25

/200

9

2/8/

2009

2/22

/200

9

3/8/

2009

3/22

/200

9

4/5/

2009

4/19

/200

9

5/3/

2009

5/17

/200

9

5/31

/200

9

Stag

e (f

t N

GV

D)

0

100

200

300

400

500

600

700

800

900

1,000

STA

-1W

Loa

d (k

g)

Marsh

West Canal

Potential STA-1W Load

November 2008June 2009

Interim Preliminary Finding #1

• An unprecedented sequence of meteorological and hydrological events preceded the June 2009 sample collection.

• A lack of sustainable hydraulic gradient between the rim canal and marsh minimized the opportunity for canal water penetration.

• Environmental conditions (rainfall and stage increase) were outside the range of conditions that were observed during the calibration period used for deriving the compliance equation.

Analysis of TP DataAnalysis of TP Data

Monthly Trend Analysis of TP concentrations at 14 Refuge stations: Statistically significant trend of reductions in TP concentrations

Compliance Period February 1999 Through June 2009

NA

NA

NA

NANA

NA

NA

NA

NA

NA

NA

NA

?

?

0

5

10

15

20

25

30

35

40

45

50

TP

Ge

om

etr

ic M

ea

n (

pp

b)

0

5

10

15

20

25

30

35

40

45

50 Concentration Below Long-term Level

Concentration Exceeding Long-term Level

NA Concentration at Mean Stage <15.42 feet ? Questionable Data

Seasonal Kendall Trend LineGeometric Mean = 9.20 - 0.20 (Year)Tau Statistic = -0.33 p <= 0.001 (p = 0.03 when adjusted for serial dependency)Trend is significant

Long-term Level Effective

Other Evidence TP Concentrations Have Improved

• TP concentrations in the interior of the Refuge compare favorably with the 1978-1979 Base Year and the extended 1978-1983 period used to calibrate the compliance equation.

The average TP concentration of the 14-station network during the June 1978 – May 1979 Base Year was 9.7 ppb, compared with the most recent June – May year average of 7.6 ppb.

The average TP concentration of the Clean 3 sites during the June 1978 – May 1979 Base Year was 7.7 ppb, compared with the most recent June – May year average of 7.5 ppb.

No adjustment in stage was made for these comparisons since extensive monthly data collected over the last fifteen years across a wide range of water levels indicate that stage is not well correlated with variations in TP concentrations in that data set.

Relationship between Stage and TP has Changed since 1978-1983 Calibration Period

Relationship Between Clean 3 Geometric Mean and Average Stage Using Data from 2/1999-7/2009

0

10

20

30

15.0 15.5 16.0 16.5 17.0 17.5 18.0

3-gauge Average Stage (ft NGVD)

Geo

met

ric

Mea

n (p

pb)

1999-2009 Data

1999-2009 Relationship

Base Period Relationship

Factors other than stage account for 80% of

variations in TP concentrations for 1999-

2009 data

Factors other than stage account for 75% of

variations in TP concentrations for 1978-

1983 data

Other Evidence TP Concentrations Have Improved

• In February 2009, the geometric mean of the 14-station network was 4.7 ppb:

the lowest concentration recorded from the 14-station network since compliance began in February 1999, and

was lower than all of the geometric mean concentrations from the Clean 3 sites during the 1978-1979 Base Year and during the extended 1978-1983 period.

• The November 2008 14-station geometric mean that was determined to be an excursion was 7.4 ppb

This concentration was lower than four of the five geometric means at the Clean 3 sites during the 1978-1979 Base Year, and

lower than the 10 ppb annual average of the individual geometric means for the Clean 3 sites during the 1978-1979 Base Year.

The 3-gauge average stage for the November sample collection was 17.22 ft which is above the highest stage that occurred in the 1978-1979 Base Year, and above the highest stage that occurred in the extended 1978-1983 period used to calibrate the compliance equation.

Monthly Analysis of TP concentrations at 14 Refuge stations and external loading: Excursions occurred despite significant reductions

in controllable external TP loading

0

25

50

75

100

125

150

175

200

09/21/04 03/07/05 09/21/05 03/07/06 09/19/06 03/05/07 09/17/07 03/05/08 09/17/08 03/09/09

TP

Lo

ad

(M

etr

ic T

on

s/y

ea

r)

0

25

50

75

100

125

150

175

200

TP

Co

nc

en

tra

tio

n (

pp

b)

Inflow TP Load

Inflow TP Conc

Interior TP Conc

2009 data are preliminary and subject to revisionSince September 2004, the excursion frequency has been 6%, well below the compliance method limit

Jun-2009

Excursion: November 200812-month inf low = 406,000 AF

12-month load = 14.5 metric tons12-month concentration = 29 ppb

Excursion: June 2, 200912-month inf low (through May) = 379,100 AF

12-month load (through May) = 15.2 metric tons12-month concentration (through May) = 32 ppb

June 2, 2009 interior TP = 13.2 ppb

Approximate TP Load From Atmospheric Deposition:

20.3 metric tonsExcursion: October 200712-month inflow = 159,300 AF

12-month load = 9.0 metric tons12-month concentration = 46 ppb

Analysis of TP concentrations and water depths at 14 Refuge stations: Short-term spike in June 2009 (median=4 ppb) may likely

be the result of dryout and rewetting of organic sediment

Increase in TP Concentration Following DryoutMay 1999 - 1st data collection in June 2009

-10

0

10

20

30

40

50

Cha

nge

in T

P (

ppb)

Maximum Increase

Median Increase

June 2009 Increase

Maximum Increase 6.0 47.0 13.0 5.0 18.0 10.0 15.0 9.0 7.0 5.0 7.0 7.0 4.0 10.0

Median Increase 1.0 2.0 0.0 3.0 -1.0 5.0 3.0 2.5 2.5 0.0 2.0 4.5 2.0 1.0

June 2009 Increase 0.0 20 0 -8 -8 2 4 9 7 5 4 3 0

LOX3 LOX4 LOX5 LOX6 LOX7 LOX8 LOX9 LOX10 LOX11 LOX12 LOX13 LOX14 LOX15 LOX16

NCNC

NC = No sample collected due to dry conditions

Historical median increase in TP following rewetting was 2 ppb

Comparison of TP Concentrations in June 2009June 1 & 2: Geometric mean=13.2 ppb; average stage=16.05 ft

June 17 & 19: Geometric mean=9.7 ppb; average stage=15.96 ftCombined geometric mean = 11.5 ppb; average stage of 16.01 ft

0

5

10

15

20

25

30

TP

Con

cent

rati

on (

ppb)

June 1 & 2

June 17 & 19

June 1 & 2 25 10 20 8 15 14 14 14 12 12 11 11

June 17 & 19 11 12 13 9 14 9 9 10 11 6 7 11 7 10

LOX3 LOX4 LOX5 LOX7 LOX8 LOX9 LOX10 LOX6 LOX11 LOX12 LOX13 LOX14 LOX15 LOX16

Analysis of TP concentrations at 14 Refuge stations: Short-term spike observed in initial June sampling had subsided 2½ weeks later

Analysis of 2003-2004 soil TP concentrations in 0-10 cm depth at 14 Refuge stations: With 1-2 exceptions, the areas in the vicinity of the 14 stations are not “Impacted” as defined by Florida’s TP Water Quality

Standard for the Everglades (500 mg/kg)

StationRadius

(km)Ave. TP in the Area Near

Station (mg/kg)

Standard Deviation (mg/kg)

Value Nearest Station (ppb)

Radius to Nearest Site

(km)LOX3 2.0 300 37 270 1.0LOX4 1.5 350 Single site 350 1.5LOX5 2.0 260 34 290 1.0LOX6LOX7 2.0 200 Single site 200 2.0LOX8 2.0 300 Single site 300 2.0LOX9 1.0 450 Single site 450 1.0

LOX10 2.0 510 161 360 1.0LOX11 2.0 320 93 390 1.5

LOX12 1.0 490 67 490 1.0

LOX13

LOX14 2.0 520 84 520 2.0

LOX15 2.0 340 77 340 2.0LOX16 1.0 380 41 380 1.0

No data within 2 km

No data within 2 km

G 3 0 0G 3 0 1

A C M E 1 D SG 3 1 0

G 9 4 DG -2 5 1

L O X 1 0 7L O X A 1 3 0

X 1

L O X 1 0

L O X 1 1

L O X 1 2 L O X 1 3

L O X 1 4

L O X 1 5L O X 1 6

L O X 3 L O X 4

L O X 5

L O X 6L O X 7

L O X 8L O X 9

X 3

Z 2

L O X A 1 0 5

L O X A 1 2 4

L O X A 1 3 6

L O X 1 7

L O X A 1 4 0

Interim Preliminary Finding #2• TP concentrations in the Refuge continue to improve.• Elevated TP readings in June 2009 were short-term and

are likely not indicative of chronic water quality problem.• The primary source of TP causing the short-term spike

may be natural and not due to long-term controllable external TP loading such as the STA discharges.

Additional evidence that external loading may not be the primary factor in the June and November sample collections is provided by comparing the concentrations at LOX8 with adjacent LOX7 and LOX9 sites. In both instances, the latter sites, although closer to the rim canals, and thereby closer to potential sources of external surface loading, reported lower concentrations than LOX8.

Question for working group:• How should the 2nd set of TP concentrations

collected in June 2009 be factored into compliance assessment?

• Precedence: During May 2000, multiple samples were collected and averaged. Both the composite geometric mean (11.0 ppb) and the individual geometric mean (9.3 ppb) were below compliance levels. Initial reports presented both values; later reports only presented composite geometric mean.

Analysis of Monthly TP Concentrations: The 14 stations in the Refuge demonstrate highly variable TP concentrations.

• Geometric mean TP concentration of 2nd sample collection in June 2009 was 3.5 ppb lower than geometric mean of 1st sample collection – yet stage and external loading were almost identical.

• In the 186 months of sample collections since January 1994 there have been seventeen instances of TP concentrations above the levels computed by the equations of Appendix B, and

• five of those occurred before compliance assessments began in February 1999.

• the geometric mean TP concentration in the month following thirteen of those was as good as or better than the computed levels.

• Since January 2000, the month following each excursion was better than the computed levels.

Interim Preliminary Finding #3

• The TP data collected at the 14 interior stations exhibit a high degree of short-term variability which are likely associated with natural marsh conditions.

• These variations can occur when factors such as stage and external loading remain fairly constant.

Summary of Interim Preliminary Analyses• Analyses of the environmental conditions leading up to

the November 2008 and June 2009 sample collections suggest that the following factors should be considered in evaluating the excursions:

fluctuations in rainfall, resulting in an rapid increase in stage prior to the June 1st and 2nd 2009 sample collection, with a potential associated flux of TP from the marsh soil upon rewetting;

natural high variability of TP concentrations in the Refuge marsh, which may be due to local factors, rather than controllable external factors; and

application of the compliance equation outside the range of environmental conditions that existed at the time of sample collections used in deriving the compliance equation.

• Analyses are continuing

Summary of Interim Preliminary Analyses

Summary of Preliminary Analyses – Matrix of Potential Contributing Factors Potential Contributing Factor Data Evaluated Finding

Data collection error Sample collection records No evidence of error Laboratory analysis error Sample analyses records No evidence of error

Unprecedented low rainfall in the six months prior to the June sample collection, followed by extremely high rainfall in the last two weeks of May preceding sample collection, resulting in an extreme rapid rise in Refuge stage following extensive

soil dry out

Daily rainfall records between 1963 and 2009; stage records

between 1978 and 2009

May be a significant contributing factor

External phosphorus loading

Daily structure flows and TP levels between 1994 and 2009; STA-1E treatment cell water

levels, flow and TP data.

Analysis suggests that external loading was

not a significant contributing factor.

• Analyses are continuing