1

Region IX Nutrient Criteria Program

National Nutrient Coordinators Meeting

September 21, 2004

Washington, DC

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Nutrients: Unique Problems for Criteria Development

Nutrients occur naturally, levels depend on geology and biochemistry

Too little nutrients may be a problem as well as too much

Nutrients themselves generally don’t cause impairment, it’s secondary impacts such as algal growth, impacts on DO that cause concern

Impact depends on other factors, such as light and residence time

3

Two Extremes for Criteria Development

Site-specific study:Ideal: reflects characteristics and uses

of a waterbodyBut, LOE is infeasible

Arbitrary statistical criterion:Simple, easy to applyBut, high risk (and cost) of classifying

supporting waters as impaired

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California Ecoregions

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The Importance of “getting it right”

  

Ecoregion

  

Ecoregion

Stream Total Phosphorus (approx. mg/L)Stream Total Phosphorus (approx. mg/L)

304(a) Criterion

304(a) Criterion

 Reference

75%

 Reference

75%

 % >

304(a)

 % >

304(a)

 STORET

25%

 STORET

25%

 % >

304(a)

 % >

304(a)

11 0.0100.010 0.030.03 7070 0.010.01 7070

55 0.0150.015 0.040.04 8585 0.020.02 8585

66 0.0300.030 0.090.09

0.06

0.06 8888

88 0.0110.011 nana nana

0.002

0.002 4444

99 0.0300.030 0.130.13 6767 nana nana

1414 0.0100.010 0.030.03 4747 0.030.03 8080

2222 0.0150.015 0.070.07 6262 0.020.02 9797

2323 0.0110.011 0.060.06 8585 0.0050.005 8585

2424 0.0180.018 0.070.07 5656 nana nana

7878 0.0320.032 0.050.05 2828 0.120.12 9898

7070

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Middle Ground: Tiered Approach

Rather than using a single number criterion over a large geographic area, identify sites that are clearly unimpaired (Tier I), clearly impaired (Tier III), or in a gray area between (Tier II), where additional tools are used to assess impairment

Approach falls between the extremes

Use simple analyses, but recognize site-specific characteristics

Identify where more detailed analyses needed

Tier II assessment has the potential to relate nutrient levels to support or impairment of beneficial uses

7

Modified Strategy for Developing Criteria

Focus on an individual ecoregion, not aggregated ecoregion

Greater emphasis on biological responses to link to protection of beneficial uses

Use statistical and simulation models to provide better estimates of reference loads/concentrations

Use models to predict biological & chemical responses relevant to uses

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Criteria Exist to Prevent Impairment of Uses

Concept Designated Use Condition compatible

w/ use Nutrient regime to

attain condition Mitigating factors for

site Criteria

Example Aquatic Life support Benthic algal biomass

density limit Nutrient linkage (N:P

response) Riparian cover,

velocity Nutrient limits for site

and uses

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Lik

elih

ood

of I

mpa

irm

ent

Concentration Species 1

Lik

elih

ood

of I

mpa

irm

ent

Primary Biological Response 1

Lik

elih

ood

of I

mpa

irm

ent

Concentration Species 2L

ikel

ihoo

d of

Im

pair

men

t

Primary Biological Response 2

Tier I

Tier II

Tier III

Tier I

Tier I

Tier ITier II

Tier II

Tier II

Tier IIITier III

Tier III

Form of the Standard

Includes chemical and biological parameters

Multiple parameters need to be considered simultaneously

Tier II assessment determines whether combination of factors constitutes impairment

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Consequences of Classification

Tier I: No action needed

Tier II: Further study to determine whether beneficial uses are threatened

Site specific factors influencing response

Potential anti-degradation analysis

Tier III: Nutrient load reduction may be needed; possible permit load caps and TMDLs

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12

Sorting the Tiers

TIER II

Concentration solow that impacts are

unlikely

Concentration ator below Regional

Background

Tier I:ImpactsUnlikely

(Supporting)

Yes

No

Yes

Concentration sogreat that impairment

is likely

No

Tier III:Impacts Likely

(Impaired)

Yes

No

Concentrationexceeds site-specific

targetYes

Tier II:May be

Sustaining

No

AntidegradationAnalysis for

Permits

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Tier I/II Breakpoint

Concentration (or load) causing no adverse impact on uses

At or below a percentile of natural background (presumptive approach)

Existing statistical approachModeling analysis of natural

cover/geology

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Tier II/III Breakpoint

Concentration (or load) that presents a clear risk to support of a specific use

Scientific consensusModeling analysisConcentrations at known impaired sites

Set high enough so that misclassification of impairment is at an acceptably low rate

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Supporting Toolbox

Detailed empirical analyses by Subecoregion

Tools to relate nutrient concentrations to endpoints that impact designated uses

Tools to evaluate first-cut site-specific modifications to criteria within Tier II

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Empirical Data Analysis:Station

Classification

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Empirical Data Analysis for Ecoregion 6:NO3 Levels in Streams by Impairment

Classification of Water Body

NO3-N, Summer Months

Minim Impact Unimpaired Imp (unknown) Imp (Nutr)

Co

nce

ntr

atio

n (

mg

/l)

0.001

0.01

0.1

1

10

100

1000

Default TNCriterion

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Modeling Natural Background with

SWAT SWAT (Surface Water

Assessment Tool) was used to estimate nutrient loads and concentrations in streams.

Designed for use without calibration.

Modified for California climate and vegetation.

A set of eight, relatively unimpaired watersheds was used for validation testing.

Goal: To identify landscape stratification features as directed by RTAG

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BATHTUB Model of Lake Response

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.63.0

3.2

3.4

3.6

3.8

4.0

4.2

Chlorophyll-a Concentration (ug/L)

N limited

Tot

al N

itro

gen

Loa

ding

nor

mal

ized

to la

ke v

olum

e (u

g/Y

ear-

L, L

og S

cale

)

Total Phosphorous Loading normalized to lake volume (ug/Year-L, Log Scale)

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Stream Periphyton Response(equations adopted from QUAL2K)

Eutrophic

Mesotrophic

Oligotrophic0

50

100

150

200

25030

8LS

U

308B

SR

304S

OQ

308M

IL

314M

IG

309P

SO

312C

UY

305F

RA

306C

AR

315S

MC

310A

RG

306M

C

305T

HU

309D

AV

310S

LB

312B

CF

312O

FC

RB 3 Sites as a function of nutrients

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Stream Periphyton Response(equations adopted from QUAL2K)

RB 3 Sites as a function of nutrients and light

Eutrophic

Mesotrophic

Oligotrophic0

50

100

150

200

25030

8LS

U

310S

CP

309A

TS

315J

AL

309N

AC

305C

HE

304A

PT

309U

SA

317C

HO

306C

AR

317E

ST

309G

RN

310C

AN

310B

ER

309S

BR

313S

AI

Max

imu

m B

enth

ic B

iom

ass

(g/m

2 A

FD

W)

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Fraction of Potential Maximum Periphyton Biomass as a Function of

Days of Accrual (Biggs, 2000)

0

0.2

0.4

0.6

0.8

1

0 50 100 150 200

da

B(d

0)/

Bm

ax

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Putting the framework work into practice

Hypothetical Scenario for Use of Tiered Criteria

Assume following tier boundaries for Total N: Tier I/II 0.1 mg/lTier II/III 2.0 mg/l

For a given concentration in a water body, describe strategies to be adopted with respect to:

Tier I, II, or III classification Assessment approach Potential for TMDL listing Impact on permitting of point source discharges

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Site

TN

Conc

(mg/l)

Tier Assessment TMDL Permitting

A 0.08 I

Site concentration is below the Tier I/II boundary; therefore the site is immediately assessed as not impaired by nutrients.

Not needed

Allocations up to the Tier I/II boundary of 0.1 don't require an antidegradation analysis for nutrients.

B 0.75 II -> III

Site potentially at risk, requiring further study. Use tools to calculate a site-specific concentration compatible withachieving uses of 0.6 mg/L.Concentration is greater than this site-specific criterion, therefore impaired.

Listed; site target - MOS = TMDL

No further wasteload allocations are available (impaired).

C 0.25 II

Site requires further study.Application of tools (SWAT, reference sites) suggests that the site-specific background should be 0.3 mg/l, higher than the general Tier I/II boundary.Concentrations does not exceed the site-specific background level

Not needed

Concentrations up to the site-specific background level of 0.3 mg/l are allocatable, between 0.3 and 0.6 mg/l are potentially allocatable subject to a more detailed analysis, and above 0.6 mg/l are not allocatable.

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Next PhasesRecommendations for 305(b) Monitoring: (CA

- SWAMP)

Refine / Finalize Assessment Tools

Modeling Framework to Develop Background Nutrient Loading and Concentration Estimates

Training Workshops

Parallel Development of Regional loading, concentration, and bio condition estimates

Development of Tier Boundaries for all Region 9 Ecoregions