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1
Region IX Nutrient Criteria Program
National Nutrient Coordinators Meeting
September 21, 2004
Washington, DC
2
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
4
California Ecoregions
5
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
6
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
8
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
9
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
10
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
11
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
13
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
14
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
15
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
16
Empirical Data Analysis:Station
Classification
17
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
18
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
19
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)
20
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
21
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)
22
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
24
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
25
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.
26
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