1. Nutrient Criteria Development for Lakes: Minnesota’s Approach & Timeline Steve Heiskary, Research Scientist III Minnesota Pollution Control Agency Environmental Analysis & Outcomes Div. MDNR Meeting April 2007

2. Background & Overview 1. Present draft criteria 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/ Ecoservices & Wildlife); Considerations for shallow lakes (collaboration w/ Ecoservices & Wildlife); Fishery considerations (Collaboration w/ Fisheries) Fishery considerations (Collaboration w/ Fisheries) Use of sediment cores to reconstruct WQ (collaboration w/ Science Museum); Use of sediment cores to reconstruct WQ (collaboration w/ Science Museum); Criteria for both “causative” (TP) & “response” (Secchi & chlorophyll-a) variables; Criteria for both “causative” (TP) & “response” (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; 4. Timeline for rulemaking

3. Minnesota’s Draft Eutrophication Criteria. EcoregionTPChl-aSecchi ppb ppb meters NLF – Lake trout (Class 2A) < 12< 3> 4.8 NLF – Stream trout (Class 2A) < 20< 6> 2.5 NLF – Aquatic Rec. Use (Class 2B) < 30< 9> 2.0 CHF – Stream trout (Class 2a) < 20< 6> 2.5 CHF – Aquatic Rec. Use (Class 2b) < 40< 14> 1.4 CHF – 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

4. Definitions (include in rule) Need to differentiate among lakes (shallow vs. deep), reservoirs, wetlands & rivers Need to differentiate among lakes (shallow vs. deep), reservoirs, wetlands & rivers “Lake” – enclosed basin…max. depth > 15 ft. (4.5m) -- 10 acres (4 ha) minimum size for “lakes”; “Lake” – enclosed basin…max. depth > 15 ft. (4.5m) -- 10 acres (4 ha) minimum size for “lakes”; “Shallow lake” - max. depth 15 ft. (4.5 m) or less or 80% or more littoral (drawn from Schupp); generally not wetlands; “Shallow lake” - max. depth 15 ft. (4.5 m) or less or 80% or more littoral (drawn from Schupp); generally not wetlands; “Reservoir” – natural or artificial basin where outlet is controlled by control structure. Differentiated from rivers based on Tw of 14 days or more as determined based on a summer “120 day Q10”; “Reservoir” – natural or artificial basin where outlet is controlled by control structure. Differentiated from rivers based on Tw of 14 days or more as determined based on a summer “120 day Q10”; Index period – summer (June – September); Index period – summer (June – September);

5. 6 – 17 m. deep 20 – 140 ha 5 – 15 m deep 25 – 160 ha 2.5 – 5 m deep 45 – 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;

6. Basis for “Response” Criteria Relationships among TP, chlorophyll-a, Secchi, nuisance blooms & HOD; Relationships among TP, chlorophyll-a, Secchi, nuisance blooms & HOD; User perception data from CLMP observers User perception data from CLMP observers Regional patterns in lake trophic status, fishery composition; lake morphometry, soils, land form & land use Regional patterns in lake trophic status, fishery composition; lake morphometry, soils, land form & land use

8. Fish species vary relative to lake trophic status Based on work of Dennis Schupp & paper by Schupp & Wilson 1993

9. Burntside Kabekona TP 1012 Chl 3 3 Secchi 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”

10. TP =12 ppbTP = 90 ppb Number of Fish Species as a function of TSI (Schupp)

11. Percent Piscivores as a function of TSI (Schupp) TP ~20-25 ppb

12. TP=12 ppb Percent of lakes with lake trout or carp as a function of TSI (Schupp). Implies no lake trout lakes when TP > 15 ppb.

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

14. Northern pike & black bullhead as a function of TSI (Adapted from Schupp) Argues for keeping TP < ~50 – 60 ppb where possible

15. Worked to identify thresholds for shallow lakes

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

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

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

19. 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);

21. Northern Lakes & Forests ecoregion: Generally low P, minimal change over time; predominately forested land use; P criteria noted

22. North Central Hardwoods Forests ecoregion: large range, distinct differences between shallow and deep lakes., dramatic change for many lakes over time shallow deep

23. Western Corn Belt Plains 90% or more considered shallow, highly agricultural land use, vast majority eutrophic -hypereutrophic deep shallow

24. Rulemaking timeline for Lake Criteria Finish SONARs by end of March Finish SONARs by end of March Compare our version of rule to Revisor's version - complete by end of January. Compare our version of rule to Revisor's version - complete by end of January. Submit rule to to Governor's Office and Commissioner's Office April Submit rule to to Governor's Office and Commissioner's Office April Publish in State Register, late April Publish in State Register, late April Public hearings in May-June, 2007 Public hearings in May-June, 2007 Close of hearing record in late August Close of hearing record in late August ALJ report - probably at least 60 days after record closes. ALJ report - probably at least 60 days after record closes.

25. Main Features & Approach Draft criteria (TP, chla, & Secchi) based on weight-of- evidence approach that considers: Regional patterns in lake morphometry, water quality, & watershed characteristics. Regional patterns in lake morphometry, water quality, & watershed characteristics. Within-ecoregion distributions of TP, chl-a & Secchi - reference & overall populations; Within-ecoregion distributions of TP, chl-a & Secchi - reference & overall populations; Varying uses of lakes & differences among deep & shallow lakes; Varying uses of lakes & differences among deep & shallow lakes; Fishery (aquatic life) requirements; Fishery (aquatic life) requirements; Shallow lakes - plant communities relative to P, chl-a, & Secchi; Shallow lakes - plant communities relative to P, chl-a, & Secchi; Use of sediment cores to re-affirm regional patterns & estimate background; Use of sediment cores to re-affirm regional patterns & estimate background; User perceptions; User perceptions;

26. Summary 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- impaired lakes (2002) – using the 1988 P criteria & corresponding chlorophyll-a & Secchi thresholds; MPCA developed rules for 303(d) listing of nutrient- impaired lakes (2002) – using the 1988 P criteria & corresponding chlorophyll-a & Secchi thresholds; Listing requires exceedance of causal plus one response (will maintain this approach in standards); Listing requires exceedance of causal plus one response (will maintain this approach in standards); Draft criteria are in WQ standards now being promulgated; Draft criteria are in WQ standards now being promulgated; Standards language reinforces need to protect high quality lakes (non-degradation) and account for naturally poor quality lakes; Standards language reinforces need to protect high quality lakes (non-degradation) and account for naturally poor quality lakes; Differentiate among shallow & deep lakes; Differentiate among shallow & deep lakes; Allows for site-specific criteria for reservoirs & other cases where deemed necessary (have guidance) Allows for site-specific criteria for reservoirs & other cases where deemed necessary (have guidance)

27. Track progress on adoption of lake standards on our triennial review web page & Nutrient criteria- related reports on lake assessment web page MPCA Home Water -- Regulations Proposed Water Quality Standards Rule Revision http://www.pca.state.mn.us/water/standards/r ulechange.html http://www.pca.state.mn.us/water/standards/r ulechange.html Water -- Lakes -- Lake Water Quality Assessment Report: Developing Nutrient Criteria http://www.pca.state.mn.us/water/lakequality. html#reports steven.heiskary@pca.state.mn.us 651-296-7217