Nutrient Criteria Nutrient Criteria Development for Lakes: Development for Lakes: Minnesota’s Approach & Minnesota’s Approach &

TimelineTimelineSteve Heiskary, Steve Heiskary,

Research Scientist IIIResearch Scientist III

Minnesota Pollution Control AgencyMinnesota Pollution Control AgencyEnvironmental Analysis & Outcomes Environmental Analysis & Outcomes

Div.Div.

MDNR MeetingMDNR MeetingApril 2007April 2007

Background & OverviewBackground & Overview1. Present draft criteria1. Present draft criteria2. Overview of our approach, which considers:2. Overview of our approach, which considers:• Assessment of ecoregion patterns;Assessment of ecoregion patterns;• Varying uses of lakes;Varying uses of lakes;• Considerations for shallow lakes (collaboration w/ Considerations for shallow lakes (collaboration w/

Ecoservices & Wildlife);Ecoservices & Wildlife);• Fishery considerations (Collaboration w/ Fisheries)Fishery considerations (Collaboration w/ Fisheries)• Use of sediment cores to reconstruct WQ Use of sediment cores to reconstruct WQ

(collaboration w/ Science Museum);(collaboration w/ Science Museum);• Criteria for both “causative” (TP) & “response” Criteria for both “causative” (TP) & “response”

(Secchi & chlorophyll-a) variables;(Secchi & chlorophyll-a) variables;• Allowance for site specific criteria, e.g. reservoirs;Allowance for site specific criteria, e.g. reservoirs;3. Application of criteria – from TMDLs to protection;3. Application of criteria – from TMDLs to protection;4. Timeline for rulemaking4. Timeline for rulemaking

Minnesota’s Draft Eutrophication Minnesota’s Draft Eutrophication Criteria. Criteria.

Ecoregion TP Chl-a Secchi  ppb ppb meters

NLF – Lake trout (Class 2A) < 12 < 3 > 4.8NLF – Stream trout (Class 2A) < 20 < 6 > 2.5NLF – Aquatic Rec. Use (Class 2B) < 30 < 9 > 2.0 

CHF – Stream trout (Class 2a) < 20 < 6 > 2.5CHF – Aquatic Rec. Use (Class 2b) < 40 < 14 > 1.4CHF – Aquatic Rec. Use (Class 2b) Shallow lakes

< 60 < 20 > 1.0

 

WCP & NGP – Aquatic Rec. Use (Class 2B)

< 65 < 22 > 0.9

WCP & NGP – Aquatic Rec. Use (Class 2b) Shallow lakes

< 90 < 30 > 0.7

Definitions (include in rule)• Need to differentiate among lakes (shallow vs. Need to differentiate among lakes (shallow vs.

deep), reservoirs, wetlands & riversdeep), reservoirs, wetlands & rivers• ““LakeLake” – enclosed basin…max. depth > 15 ft. ” – enclosed basin…max. depth > 15 ft.

(4.5m) -- 10 acres (4 ha) minimum size for (4.5m) -- 10 acres (4 ha) minimum size for “lakes”;“lakes”;

• ““Shallow lakeShallow lake” - max. depth 15 ft. (4.5 m) or ” - max. depth 15 ft. (4.5 m) or less or 80% or more littoral (drawn from less or 80% or more littoral (drawn from Schupp); generally not wetlands;Schupp); generally not wetlands;

• ““ReservoirReservoir” – natural or artificial basin where ” – natural or artificial basin where outlet is controlled by control structure. outlet is controlled by control structure. Differentiated from rivers based on Tw of 14 Differentiated from rivers based on Tw of 14 days or more as determined based on a days or more as determined based on a summer “120 day Q10”;summer “120 day Q10”;

• Index period – summer (June – September);Index period – summer (June – September);

6 – 17 m. deep20 – 140 ha

5 – 15 m deep25 – 160 ha

2.5 – 5 m deep45 – 283 ha

Minnesota’s Ecoregions & Reference Lakes:98% of MN lakes located in these 4 ecoregions;Reference lake monitoring began in 1985 - ~ 90 “minimally-impacted, representative lakes (candidates to consider for long-term or trend monitoring)WQ & morphometry varies among regions;

Basis for “Response” Basis for “Response” CriteriaCriteria

• Relationships among TP, chlorophyll-a, Relationships among TP, chlorophyll-a, Secchi, nuisance blooms & HOD;Secchi, nuisance blooms & HOD;

• User perception data from CLMP User perception data from CLMP observersobservers

• Regional patterns in lake trophic status, Regional patterns in lake trophic status, fishery composition; lake morphometry, fishery composition; lake morphometry, soils, land form & land use soils, land form & land use

Summer-mean TP vs Chl-a. Based on reference lakes

y = 1.16x - 0.76R2 = 0.73

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0.0 0.5 1.0 1.5 2.0 2.5 3.0Log TP ppb

Log

chl-a

ppb (32)

(10)

(32) (100)

(100)

Fish species vary relative to lake trophic status

Based on work of Dennis Schupp & paper by Schupp & Wilson 1993

Burntside Lake 8/29/1994

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Kabekona Lake 8/16/1994

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Burntside KabekonaTP 10 12Chl 3 3Secchi 6.1 m 3.6 m

Lake Trout Lakes – consider:•Unique DO & temp. requirements – DO 6 or more, temp. 8-15 C preferred (12 C or less deemed suitable habitat, Siesennop 2000);•We Charted “optimal habitat”

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Figure 1

TP =12 ppb

TP = 90 ppb

Number of Fish Species as a function of TSI (Schupp)

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TSI

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Trap nets

Percent Piscivores as a function of TSI (Schupp)

TP ~20-25 ppb

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CarpLake trout

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Percent of lakes with lake trout or carp as a function of TSI (Schupp). Implies no lake trout lakes when TP > 15 ppb.

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Northern Pike

LargemouthBass

% of lakes with NP or LMB as a function of TSI (Schupp). Distinct decline in % lakes w/ NP as TP >40-50 ppb

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Northern pike & black bullhead as a function of TSI (Adapted from Schupp)

Argues for keeping TP < ~50 – 60 ppb where possible

Worked to identify thresholds for shallow lakes

Note: as TP increases above ~60-90 ppb, floating-leaf generally absent & 10 or fewer species present

West Central Shallow Lakes: # of submergent & floating-leaf species.

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Pelican

West-Central Shallow Lakes: # of submergent species & floating-leaf vs. mean Secchi

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At Secchi < 1.0 m floating-leaf uncommon & generally < 10 species of submergents

Rooted plants vs. chl-a. Sorted by TP

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# plants Chl-a

As P increased above ~60-90 ppb floating-leaf plants disappeared, & increased risk of loss of plant diversity & algal dominance.

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Sediment Core Study Lakes

Central Hardwood Forests

Northern Lakes & Forests

Northern Glaciated Plains

Western Corn Belt Plains

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1) “55 lakes study” lakes from NLF, CHF & WCP regions (mid 1990s);

2) SW MN study focused on 22 shallow lakes, 6 with deep cores (2002);

3) West-central focused on shallow CHF lakes with a gradient in modern-day P and macrophytes; 6 deep cores (2003);

Diatom-inferred TP: Pre-European vs. Modern-day

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NLF (n=20) CHF-Metro(n=20)

CHF-Rural(n=15)

CHF-Shallow

(n=5)

WCP - Deep(n=5)

WCP/NGP -Shallow

(n=6)

TP p

pb

Pre-E Modern

Northern Lakes & Forests ecoregion:

Generally low P, minimal change over time; predominately forested land use; P criteria noted

NLF Lakes TP Distributions.

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Pre-E MPCA-Ref MPCA-Assess EPA-Assess

TP (p

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North Central Hardwoods Forests ecoregion:

large range, distinct differences between shallow and deep lakes. , dramatic change for many lakes over time

CHF Ecoregion Lakes TP Distributions.

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MPCA-Ref MPCA-Assess

EPA-Assess

TP (p

pb)

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deep

Western Corn Belt Plains90% or more considered shallow, highly agricultural land use,

vast majority eutrophic -hypereutrophicWCP Ecoregion Lakes TP Distributions.

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shallow

Rulemaking timeline for Lake Rulemaking timeline for Lake CriteriaCriteria

• Finish SONARs by end of MarchFinish SONARs by end of March• Compare our version of rule to Revisor's Compare our version of rule to Revisor's

version - complete by end of January.version - complete by end of January.• Submit rule to to Governor's Office and Submit rule to to Governor's Office and

Commissioner's Office AprilCommissioner's Office April• Publish in State Register, late AprilPublish in State Register, late April• Public hearings in May-June, 2007Public hearings in May-June, 2007• Close of hearing record in late AugustClose of hearing record in late August• ALJ report - probably at least 60 days ALJ report - probably at least 60 days

after record closes.after record closes.

Main Features & ApproachMain Features & ApproachDraft criteria (TP, chla, & Secchi) based on Draft criteria (TP, chla, & Secchi) based on

weight-of-evidence approach that considers:weight-of-evidence approach that considers:• Regional patterns in lake morphometry, water Regional patterns in lake morphometry, water

quality, & watershed characteristics. quality, & watershed characteristics. • Within-ecoregion distributions of TP, chl-a & Within-ecoregion distributions of TP, chl-a &

Secchi - reference & overall populations;Secchi - reference & overall populations;• Varying uses of lakes & differences among deep Varying uses of lakes & differences among deep

& shallow lakes; & shallow lakes; • Fishery (aquatic life) requirements; Fishery (aquatic life) requirements; • Shallow lakes - plant communities relative to P, Shallow lakes - plant communities relative to P,

chl-a, & Secchi;chl-a, & Secchi;• Use of sediment cores to re-affirm regional Use of sediment cores to re-affirm regional

patterns & estimate background;patterns & estimate background;• User perceptions; User perceptions;

SummarySummary• Ecoregion-based TP criteria first developed in 1988;Ecoregion-based TP criteria first developed in 1988;• MPCA developed rules for 303(d) listing of nutrient-MPCA developed rules for 303(d) listing of nutrient-

impaired lakes (2002) – using the 1988 P criteria & impaired lakes (2002) – using the 1988 P criteria & corresponding chlorophyll-a & Secchi thresholds;corresponding chlorophyll-a & Secchi thresholds;

• Listing requires exceedance of causal plus one Listing requires exceedance of causal plus one response (will maintain this approach in standards);response (will maintain this approach in standards);

• Draft criteria are in WQ standards now being Draft criteria are in WQ standards now being promulgated;promulgated;

• Standards language reinforces need to protect high Standards language reinforces need to protect high quality lakes (non-degradation) and account for quality lakes (non-degradation) and account for naturally poor quality lakes;naturally poor quality lakes;

• Differentiate among shallow & deep lakes;Differentiate among shallow & deep lakes;• Allows for site-specific criteria for reservoirs & other Allows for site-specific criteria for reservoirs & other

cases where deemed necessary (have guidance)cases where deemed necessary (have guidance)

Track progress on adoption of lake standards Track progress on adoption of lake standards on our triennial review web page & Nutrient on our triennial review web page & Nutrient criteria-related reports on lake assessment criteria-related reports on lake assessment web pageweb pageMPCA HomeMPCA Home

Water -- RegulationsWater -- RegulationsProposed Water Quality Standards Proposed Water Quality Standards

Rule RevisionRule Revisionhttp://www.pca.state.mn.us/water/standards/rulehttp://www.pca.state.mn.us/water/standards/rulechange.htmlchange.html

Water -- Lakes -- Lake Water Quality Water -- Lakes -- Lake Water Quality Assessment Report: Developing Nutrient Assessment Report: Developing Nutrient CriteriaCriteria

http://www.pca.state.mn.us/water/http://www.pca.state.mn.us/water/lakequality.html#reportslakequality.html#reports

steven.heiskary@pca.state.mn.ussteven.heiskary@pca.state.mn.us651-296-7217651-296-7217