Missouri Nutrient Criteria Plan

Mark Osborn

October 20, 2005

Problems caused by nutrient enrichment

• Causative factors

– Total Nitrogen

– Total Phosphorus

• Response factors

– Turbidity

– Excessive Algae Growth

– Oxygen Reduction

– Organic Enrichment

– Hypoxia in Gulf of Mexico

EPA Response

• Criteria recommendations for each nutrient ecoregion

• Encourage development of nutrient criteria plans by states and tribes

• Development of Regional Technical Assistance Groups (RTAG)

EPA Recommendations

• Specify Criteria by Ecoregions

• Identification of Reference Conditions

• Account for cause and response relationships

• Specific Criteria Development– 25th percentile of all lakes and streams within

ecoregions– 75th percentile of reference lakes and streams

Omernic Level III Ecoregions in EPA Region VII

0 100 200 Miles

Ecoregions (Omernik Level III)27 Central Great Plains40 Central Irregular Plains29 Central Oklahoma/Texas Plains52 Driftless Area28 Flint Hills72 Interior River Valleys and Hills73 Mississippi Alluvial Plain44 Nebraska Sand Hills42 Northwestern Glaciated Plains43 Northwestern Great Plains39 Ozark Highlands26 Southwestern Tablelands47 Western Corn Belt Plains25 Western High Plains

Seston Chlorophyll-a as a function of watershed size

.1

1

10

100

1000

102 103 104 105 106 107 108 109

WATERSHED SIZE (HECTARES)

ME

AN

SE

ST

ON

CH

LO

RO

PH

YL

L

(ug

/L)

Data Trend Line

R2 = 0.4372

Mean Total Nitrogen as a Function of Watershed Size

.01

.1

1

10

100

10-1100101102103104105106107108109

WATERSHED SIZE (HECTARES)

ME

AN

TO

TA

L N

ITR

OG

EN

Data Trend Line

R2 = 0.0001

RTAG regressions of nutrient cause and response variables: x = Total Nitrogen

y Significance(α = 0.05)

R2 Trend

Macroinvertebratetaxa richness

yes 0.2737 -

Seston Chlorophyll-a no 0.0006 -

Benthic Chlorophyll-a yes 0.1281 +

RTAG regressions of nutrient cause and response variables: x = total phosphorus

y Significance(α = 0.05)

R2 Trend

Macroinvertebratetaxa richness

yes 0.3014 -

SestonChlorophyll-a

yes 0.1971 +

BenthicChlorophyll-a

no 0.0006 +

RTAG regressions of nutrient cause and response variables: x = watershed size

y Significance(α = 0.05)

R2 Trend

Taxa richness yes 0.2848 +

Turbidity yes 0.0152 +

Seston Chlorophyll-a yes 0.4372 +

Benthic Chlorophyll-a no 0.0003 +

TP yes 0.031 +

TN no 0.0001 -

RTAG regression of nutrient cause and response variable: x = Turbidity

y Significance(α = 0.05)

R2 Trend

Macroinvertebratetaxa richness

yes 0.2537 -

Missouri Nutrient Criteria Plan

• Plan has been approved by EPA

• Water body type– Lakes– Small Streams– Wetland– Big River

Nutrient Criteria Plan for Lakes in Missouri

• Substantial data has been collected by Jack Jones et al. 1976-1984, 1989-2002

• Most lakes in the state are artificial, therefore use of reference conditions is not practical

• EPA’s suggested lake nutrient criteria would place 75% of Missouri’s lakes in non-compliance

• Significant differences in TP and TN between lakes in different eco-regions

• Lake size and retention time also has impact on cause and response variable concentrations

Eco-Regions for Lakes in Missouri

Big Rivers

Ozark Highlands

Plains

Geometric Lake Means for Total Phosphorus and Chlorophyll

0

50

100

150

200

250

Ozarks Plains Big Rivers

ug/L

TP Chl-a

Nutrient Criteria Plan for Lakes in Missouri

• Issues

– Variations in cause/response relationships due to regional characteristics and lake morphology

– Low threshold for TP concentration resulting in high chlorophyll response (20 μg/L)

– Criteria for designated uses may conflict with each other

• e.g. WBC vs Aquatic Life support

Nutrient Criteria Plan for Lakes in Missouri - Approach

• Develop Criteria for Designated Uses– Whole Body Contact

– Aquatic Life Support

– Drinking Water

• Response Variables– Secchi Depth

– Turbidity

– Total Organic Carbon for Drinking Water

Nutrient Criteria Plan for Lakes in Missouri - Approach

• Lake Morphology (Obrecht, 2005)– Retention Time

– Land Use in Watershed

– Mainly applicable in Central Irregular Plain area

Nutrient Criteria Plan for Streams in Missouri

• Reference Streams– selected and identified by macroinvertebrate

taxa richness

• Data to be evaluated by ecological drainage unit– More specific than Omernik III Ecoregions– May cross boundaries from other classifications– Based on Distinctions in Aquatic Biology

Ecological Drainage Units and Reference Stream Sites in Missouri

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#

#

#

#

#

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#

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11

22

33

4455

66

77

77

88

99

1010

1111

1212

#

13

1414

#

151616

1717

1818

1919

Ecological Drainage Units

Reference Stream Sites# Need nutrient data# Nutrient data available

0 50 100 Miles

N

Nutrient Criteria Plan for Wetlands in Missouri

• Classification to be based on method by Cowardin et al.– Systems - basic hydrology (riverine, lacustrine,

palustrine)

– Subsystems - specific hydrology (lower perennial, upper perennial, intermittent, etc.)

– Class - Type of dominant vegetative and/or substrate materials

• Development schedule undetermined at this time

Nutrient Criteria for Big Rivers in Missouri

• Still under development