1

Chicago

April 24, 2003

16th Annual National Conference

Concord, Massachusettswwwalker.net

Enhancing the States' Lake Management Programs

Experience in Developing Phosphorus TMDLs for Lakes

William W. Walker, Jr., Ph.D.Environmental Engineer

- Conceptual Model

- Deriving TMDL Goals

- Phosphorus Mass-Balance Models

- Available Software

- Examples

Phosphorus TMDL's for LakesTopics

2

Lake Inputs Nutrients Algal Growth Water Quality Water Uses

Algal Blooms

Transparency Aesthetics

DO Depletion Recreation

pH Fisheries

Ammonia Water Supply

Turbidity

Sediments Taste & Odor

Toxic Organics

Other Controlling Factors

Causal Pathways Linking P Loads to Water Uses

Watershed P Load

Lake Mean Phosphorus

Mean Chlorophyll-a

Lake Inputs Nutrients Algal Growth Water Quality Water Uses

Algal BloomsTransparency AestheticsDO Depletion Recreation

pH FisheriesAmmonia Water SupplyTurbidity

Sediments Taste & OdorToxic Organics

Assumed or Empirically Calibrated

Lake Mean Phosphorus

Mean Chlorophyll-a

Watershed P Load

Surrogate Goal

Modeled

Conceptual Model for Lake Phosphorus TMDLs

Surrogate Goal

Surrogate Goal

TMDL

TMDL

TMDL

Source Ultimate Goal Support Use

3

- Conceptual Model

- Deriving TMDL Goals

- Phosphorus Mass-Balance Models

- Available Software

- Examples

Phosphorus TMDL's for LakesTopics

Based upon Log-Normal Frequency Distribution Models Calibrated to Various DatasetsWalker, W., "Statistical Bases for Mean Chlorophyll-a Criteria", Lake & Reservoir Mgt, 1985

Statistical Basis for Mean Chlorophyll-a CriteriaFrequency of Severe Nuisance Blooms vs. Mean Chl-a

0%

10%

20%

30%

40%

50%

60%

0 10 20 30 40

Mean Chlorophyll-a (mg/m3)

Perc

ent >

30

Vermont LakesCE ReservoirsSA Reservoirs

“Threshold”

4

Algal Bloom Frequency vs. Total PhosphorusSt. Paul Water Supply

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

0 10 20 30 40 50 60 70Lake Total P (ppb)

Freq

. Chl

-a >

30

ppb

PleasantVadnaisPredicted

Goal = 25 ppb

Algal Bloom Frequencies vs. Mean Chl-a in Different YearsHeiskary & Walker, "Establishing a Chlorophyll-a Goal for a Run-of-the River Reservoir"Lake & Reservoir Management, 1995

Development of a Chlorophyll-a Goalfor Lake Pepin, Minnesota

> 40 ppb

> 60 ppb

GoalMean < 30 ppb

5

Algal Bloom Frequencies vs. Mean Chl-aOnondaga Lake, New York

Near-Shore Bloom Frequencies vs. Pelagic Mean TPLake Okeechobee, Florida

0

10

20

30

40

50

0 20 40 60 80 100 120

Yearly Mean TP (ppb)

Blo

om F

requ

ency

( %

)

Chl-a > 40 ppb

Chl-a > 60 ppb

Lake P Target40 ppb

Havens & Walker, Lake & Reservoir Mgt, 2002

6

Total P Standard Based upon TransparencyPlatte Lake, Michigan

StandardMean TP = 8 ppb

Y-Axis = Frequency of Secchi Depths < 10 feet

Freq. Secchi < 4 ft vs. Predicted TPOnondaga Lake, New York

7

Derivation of P Target for Compliance with pH StandardUpper Klamath Lake, Oregon

Data from Marsh Transects along P Gradient in Water Cons. Area 2AImpact = Significant Change from Reference SitesSouth Florida Water Mgt Dist. & Florida Dept of Env. Protection, 2002

Derivation of TP Criterion for Everglades MarshPercent of Biological Indicators Impacted vs. Mean TP

DO, Macroinvert., Periphyton, Algal Mats, Open Water, Macrophytes

0%

20%

40%

60%

80%

100%

0 10 20 30 40 50

Geometric Mean TP (ppb)

% o

f Ind

ices

Impa

cted

P Criterion = 10 ppb

8

- Conceptual Model

- Deriving TMDL Goals

- Phosphorus Mass-Balance Models

- Available Software

- Examples

Phosphorus TMDL's for LakesTopics

Watershed Mass Balance:

TMDL = LAs + WLAs + Background + MOS

Total Maximum Daily Load

Non-Point Sources Point Sources Natural or

UnregulatedMargin of

Safety

Anthropogenic < Discharge Permit Undev. Watershed uncertaintyAtmospheric variability

Lake Mass Balance:

TMDL = QS P* + U P*

Input Flushing Net Retention

TMDL EquationsLong-Term-Average Mass Balances

<--- Expected Long-Term-Average Load to Lake --->

Σ Σ

n

9

"Internal Load"Sediment

Hypolimion

Sediment

Water Water Water Epilimion

Not Recommended

Phosphorus Mass Balance Models for TMDL Applications

One-Box One Box / Internal Load Two-Box Three-Box

- Conceptual Model

- Deriving TMDL Goals

- Phosphorus Mass-Balance Models

- Available Software

- Examples

Phosphorus TMDL's for LakesTopics

10

BATHTUB Software ( Windows Version )U.S. Army Corps - Fall, 2003

BATHTUB Main Menu

11

BATHTUB Segmentation Schemes

Single Lake or ReservoirWell-Mixed

Spatially SegmentedMultiple Arms

ImpoundmentsIn Series

AlternativeLoading

Scenarios

BATHTUB - Load Response AnalysisBloom Frequency vs. Total P Load

12

- Conceptual Model

- Deriving TMDL Goals

- Phosphorus Mass-Balance Models

- Available Software

- Examples

Phosphorus TMDL's for LakesTopics

13

14

Long-Term Trends in Bloom Frequency & Total Pin Pelagic Zone of Lake Okeechobee

Near-Shore Bloom Frequencies vs. Pelagic Mean TPLake Okeechobee, Florida

0

10

20

30

40

50

0 20 40 60 80 100 120

Yearly Mean TP (ppb)

Blo

om F

requ

ency

( %

)

Chl-a > 40 ppb

Chl-a > 60 ppb

Lake P Target40 ppb

Havens & Walker, Lake & Reservoir Mgt, 2002

15

Decline in Net Settling RateLoss of Assimilative Capacity- Sediment Enrichment- Decrease in Calcium Loads

Lake P Goal = 40 ppb

Coupled Water Column & Sediment Modelfor Lake Okeechobee

LA

LX QO C

YC FC C AKR SL KG C fO A

SC SL KO SO SO

KB SC KB SL KB SO

Water Column

Calcium P Labile P Organic P

M = Total P Mass

C = Total P Conc

KG C (1-fO) A

16

Long-Term Simulation of Lake Okeechobee TP Levels

0

20

40

60

80

100

120

140

160

1900 1920 1940 1960 1980 2000 2020 2040

Lake

TP

Con

c (p

pb)

ObservedPredictedGoal

TMDL Load -->Basin Development -->

17

Upper Klamath Lake

18

19

Seasona l Varia ti ons - Uppe r Kl amath Lake

'" ~TP

'" ____ Chla

~ ~pH

'" ,

'" , '" ~

" ---"----

9 " " " Monlh

100% ~------------------------------------,

,,% i.!: 80% ~

~ 70%

J 60% _ 50%

~ 40%

1 ~

SOlrlr Ralllfltlon

____ pH,. 9.0

____ DO < 6 ppm

Month

Model Structure

10 11 12

10.0

9 .'

9 .'

.. , 'a

.. , ,., ,.,

OutfloW

Do,,, WalerTernperall..fe 1---------1-~t---------------t-------1 pH

POOSp/lorUs FkJ~

COriroi Pathway

• •

SOOiller1s

8l1ial

20

Observed & Predicted Values - Upper Klamath Lake Model

050

100150200250300350400450500

1991 1992 1993 1994 1995 1996 1997 1998 1999

Tota

l P (p

pb)

LakeOutflowCalibration

Calibration Period ------------>

050

100150200250300350400450

1991 1992 1993 1994 1995 1996 1997 1998 1999

Chl

orop

hyll-

a (p

pb)

7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

1991 1992 1993 1994 1995 1996 1997 1998 1999

pH

Water Quality Standard

pH Violation Frequency vs. Average Inflow P ConcentrationUpper Klamath Lake

21

Evaluation of Phosphorus Standards for Cherry Creek Reservoir

presentation before Colorado Water Quality Commission

William W. Walker, Jr. , Ph. D. Environmental Engineer

September 11 , 2000

22

Y Axis: Percent of Days in July - September with Chl-a Exceeding 10, 20, or 30 ppb

Cherry Creek Reservoir, ColoradoAlgal Bloom Frequencies vs. Mean Chlorophyll-a

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 5 10 15 20 25 30July-Sept. Mean Chlorophyll-a (ppb)

Alg

al B

loom

Fre

quen

cyAlgae Visible> 10 ppb

NuisanceBloom

> 20 ppb

Severe Nuisance> 30 ppb

"Goal"Mean Chl-a < 15 ppb

Summer Mean Chl-aStandard Error ~ 34%

Linkage of Models Used to ForecastCherry Creek Reservoir Chlorophyll-a Levels

P Balance Model

Watershed Model

Management Scenario

Uncertainty

Chla- Model

Climate

Reservoir Total P

Reservoir Chl-a

Runoff & P Load

Depth & Area

23

Risk Frequency of Years with July-Sept Mean Chl-a > 15 ppbMean Average Risk or Frequency over 10 Years (1989-1998)Max Risk in Highest Runoff Year (1998)

Risk of Exceeding 15 ppb Mean Chl-a vs.Alternative Total P Standards

Based upon Simulation of 1989-1998 Hydrologic Record

Cherry Creek Reservoir, Colorado

0%

10%

20%

30%

40%

50%

60%

70%

40 50 6010-Year Max Total P (ppb)

Ris

k (

Chl

-a >

15

ppb

) MeanMax