# LakeQuality, lakequality.org

> Water quality report cards for 5,700+ lakes across 12 US states

LakeQuality grades every monitored lake in 12 US states from A (excellent) to F (very poor) based on three water quality metrics: Secchi depth (water clarity in feet), phosphorus levels (µg/L), and chlorophyll-a concentration (algae levels in µg/L). Grading follows Metropolitan Council standards. Each lake also receives a Carlson Trophic State Index classification (oligotrophic, mesotrophic, eutrophic, hypereutrophic).

Covered states and graded-lake counts (as of the July 2026 refresh; totals grow as new monitoring data is ingested): Minnesota 2,452, Wisconsin 1,467, Michigan 754, Missouri 389, New York 200, Iowa 190, North Dakota 158, Illinois 152, Indiana 150, Pennsylvania 54, Ohio 25, South Dakota 16.

## Data

- Water quality: EPA Water Quality Portal, aggregating state environmental agencies in all 12 covered states (including MPCA and Wisconsin DNR), USGS, and EPA STORET legacy records
- Lake depth and physical details: Minnesota DNR LakeFinder and Wisconsin DNR (Minnesota and Wisconsin lakes)
- Depth-contour (bathymetric) maps: free interactive contour maps rendered from state DNR bathymetric surveys (Indiana, Ohio, Michigan, Iowa, and Minnesota DNR live; more states rolling out). Each lake page shows the depth contours as a toggleable overlay with a depth legend in feet — no login or download required.
- Fish species: state DNR surveys (Minnesota, Wisconsin, and Michigan)
- Ice-out dates: Minnesota DNR (Minnesota lakes only)
- Impaired waters: EPA ATTAINS (all 12 states)
- Reservoirs: US Army Corps of Engineers National Inventory of Dams (all 12 states)
- Invasive species: USGS Nonindigenous Aquatic Species database, plus MN/WI DNR infested-waters lists
- Coverage: 5,700+ lakes across 600+ counties in 12 states
- Update frequency: Annual (5-year rolling median of summer measurements)

## Key Pages

- Homepage: https://www.lakequality.org/
- Minnesota Lakes: https://www.lakequality.org/state/mn
- Wisconsin Lakes: https://www.lakequality.org/state/wi
- Michigan Lakes: https://www.lakequality.org/state/mi
- Missouri Lakes: https://www.lakequality.org/state/mo
- Iowa Lakes: https://www.lakequality.org/state/ia
- New York Lakes: https://www.lakequality.org/state/ny
- North Dakota Lakes: https://www.lakequality.org/state/nd
- Illinois Lakes: https://www.lakequality.org/state/il
- Indiana Lakes: https://www.lakequality.org/state/in
- Pennsylvania Lakes: https://www.lakequality.org/state/pa
- Ohio Lakes: https://www.lakequality.org/state/oh
- South Dakota Lakes: https://www.lakequality.org/state/sd
- Methodology: https://www.lakequality.org/methodology
- Lake Map: https://www.lakequality.org/map
- Search: https://www.lakequality.org/search
- Glossary: https://www.lakequality.org/glossary
- Guides Index: https://www.lakequality.org/guides
- Compare MN vs WI: https://www.lakequality.org/compare/mn-vs-wi
- Ice-Out Tracker (Minnesota lakes): https://www.lakequality.org/ice-out

## Rankings

- Cleanest Lakes: https://www.lakequality.org/ranking/cleanest
- Most Polluted: https://www.lakequality.org/ranking/worst
- Clearest Water: https://www.lakequality.org/ranking/clearest
- Deepest Lakes: https://www.lakequality.org/ranking/deepest
- Largest Lakes: https://www.lakequality.org/ranking/largest
- Best Fishing Lakes: https://www.lakequality.org/ranking/best-fishing
- Best Walleye Lakes: https://www.lakequality.org/ranking/walleye
- Best Bass Lakes: https://www.lakequality.org/ranking/bass
- Best Trout Lakes: https://www.lakequality.org/ranking/trout
- Best Musky Lakes: https://www.lakequality.org/ranking/musky
- Most Fish Species: https://www.lakequality.org/ranking/most-species
- Public Access Lakes: https://www.lakequality.org/ranking/public-access
- Improving Water Quality: https://www.lakequality.org/ranking/improving
- Declining Water Quality: https://www.lakequality.org/ranking/declining
- Best by County: https://www.lakequality.org/ranking/best-by-county
- Counties Ranked: https://www.lakequality.org/ranking/counties

Per-state rankings: /ranking/largest/{state} and /ranking/deepest/{state} (all 12 states); /ranking/clearest/{state} (all states except PA).

## Impaired Waters

EPA ATTAINS impaired-waters listings by state (all 12 states): https://www.lakequality.org/impaired/{state}
Example: https://www.lakequality.org/impaired/mn

## Reservoirs

US Army Corps of Engineers National Inventory of Dams reservoirs by state (all 12 states): https://www.lakequality.org/reservoirs/{state}
Example: https://www.lakequality.org/reservoirs/mo

## State Record Fish

State record fish by state (all 12 states): https://www.lakequality.org/state-records/{state}
Example: https://www.lakequality.org/state-records/mi

## Guides

- Swimming Safety: https://www.lakequality.org/guide/swimming-safety
- Blue-Green Algae: https://www.lakequality.org/guide/algae-blooms
- Secchi Depth Explained: https://www.lakequality.org/guide/secchi-depth
- Trophic State Guide: https://www.lakequality.org/guide/trophic-state
- Fishing & Water Quality: https://www.lakequality.org/guide/fishing-water-quality

## Best Lakes by Activity

- Best for Kayaking: https://www.lakequality.org/best/kayaking
- Best for Ice Fishing: https://www.lakequality.org/best/ice-fishing
- Best Cabin Lakes: https://www.lakequality.org/best/cabin-lakes
- Best for Family Fishing: https://www.lakequality.org/best/family-fishing

Per-state activity pages: https://www.lakequality.org/best/{cleanest|swimming|kayaking|ice-fishing|cabin-lakes|family-fishing}/{state}

## Fish Species

Fish species data covers Minnesota, Wisconsin, and Michigan (state DNR surveys).
Fish index: https://www.lakequality.org/fish
Individual species pages at: https://www.lakequality.org/fish/{species-slug}
State-level species pages at: https://www.lakequality.org/fish/{species-slug}/mn, /wi, and /mi
Fishing license fees and info for all 12 states: https://www.lakequality.org/fishing-license/{state}

## Invasive Species

Invasive species index: https://www.lakequality.org/invasive
Individual species pages at: https://www.lakequality.org/invasive/{species-slug}
Sourced from the USGS Nonindigenous Aquatic Species database (all 12 states) plus MN/WI DNR infested-waters lists.

## Trophic State

- Oligotrophic lakes: https://www.lakequality.org/trophic/oligotrophic
- Mesotrophic lakes: https://www.lakequality.org/trophic/mesotrophic
- Eutrophic lakes: https://www.lakequality.org/trophic/eutrophic
- Hypereutrophic lakes: https://www.lakequality.org/trophic/hypereutrophic

## Blog

- Blog Index: https://www.lakequality.org/blog
- Best Lakes for Swimming: https://www.lakequality.org/blog/best-lakes-for-swimming
- Lake Water Quality Explained: https://www.lakequality.org/blog/lake-water-quality-explained
- Worst Water Quality Lakes: https://www.lakequality.org/blog/worst-water-quality-lakes
- Biggest Comeback Lakes: https://www.lakequality.org/blog/biggest-comeback-lakes
- Zebra Mussel Spread: https://www.lakequality.org/blog/zebra-mussel-spread
- Does Depth Affect Quality?: https://www.lakequality.org/blog/depth-vs-quality
- Clearest Lake in Every County: https://www.lakequality.org/blog/clearest-lake-every-county
- Lakes with the Most Fish Species: https://www.lakequality.org/blog/most-fish-species
- The State of America's Lakes 2026: https://www.lakequality.org/blog/state-of-americas-lakes-2026
- The Cleanest Lakes in Every State: https://www.lakequality.org/blog/cleanest-lakes-by-state
- The Lakes Where Water Quality Is Slipping: https://www.lakequality.org/blog/most-declining-lakes
- Algae Season 2026: https://www.lakequality.org/blog/algae-season-2026
- Water Clarity Explained (Secchi Depth): https://www.lakequality.org/blog/water-clarity-secchi-explained
- Algae Blooms Explained (Safe vs Toxic): https://www.lakequality.org/blog/algae-blooms-safe-or-toxic
- Is It Safe to Swim? (E. coli & Advisories): https://www.lakequality.org/blog/is-it-safe-to-swim-ecoli-advisories
- Fish Consumption Advisories (Mercury, PFAS): https://www.lakequality.org/blog/fish-consumption-advisories-mercury-pfas
- Why Lakes Turn Green (Phosphorus): https://www.lakequality.org/blog/why-lakes-turn-green-phosphorus
- Trophic State Explained: https://www.lakequality.org/blog/trophic-state-explained
- Ice-Out 2026 (Minnesota): https://www.lakequality.org/blog/ice-out-2026-minnesota
- Fishing Opener 2026 Water Conditions: https://www.lakequality.org/blog/fishing-opener-water-conditions-2026
- Summer 2026 Cleanest Swim Lakes: https://www.lakequality.org/blog/summer-2026-cleanest-swim-lakes
- How to Choose a Clean Lake: https://www.lakequality.org/blog/how-to-choose-a-clean-lake
- Buying Lakefront Property (Water Checklist): https://www.lakequality.org/blog/buying-lakefront-property-water-checklist

## Interactive Tools

- Tools Index: https://www.lakequality.org/tools
- Lake Quality Check: https://www.lakequality.org/tools/lake-quality-check, search a lake to get water quality grade, Secchi depth, phosphorus, trophic state
- Best Lakes Finder: https://www.lakequality.org/tools/best-lakes, filter by activity and fish species to find top lakes for your trip

## Individual Lakes

Each lake has its own page at: https://www.lakequality.org/lake/{slug}
Lake pages include: water quality grade, clarity in feet, phosphorus, algae levels, TSI classification, maximum depth in feet (MN & WI), surface area in acres, an interactive depth-contour (bathymetric) map where a DNR survey exists, fish species (MN, WI & MI), invasive species, public access (MN), swimming safety assessment, nearby lake comparisons (distance in miles), and FAQ schema.

## Counties

County pages at: https://www.lakequality.org/county/{state}/{county-slug}
Ranked lake listings with clarity in feet, depth in feet, and grade for every lake in the county.

## Grade Browse

- Grade A lakes: https://www.lakequality.org/grade/a
- Grade B lakes: https://www.lakequality.org/grade/b
- Grade C lakes: https://www.lakequality.org/grade/c
- Grade D lakes: https://www.lakequality.org/grade/d
- Grade F lakes: https://www.lakequality.org/grade/f

## Frequently Asked Questions

Q: Which states does LakeQuality cover?
A: 12 US states (graded-lake counts as of July 2026): Minnesota 2,452, Wisconsin 1,467, Michigan 754, Missouri 389, New York 200, Iowa 190, North Dakota 158, Illinois 152, Indiana 150, Pennsylvania 54, Ohio 25, South Dakota 16. Each state has a hub at /state/{code}.

Q: What is the water quality of [lake]?
A: Check the lake page at /lake/[slug] for the water quality grade, Secchi depth, phosphorus levels, algae levels, and trophic state.

Q: Which lakes have the cleanest water?
A: See /ranking/cleanest for lakes with the best water quality grades based on EPA Water Quality Portal data.

Q: Is [lake] safe for swimming?
A: Every lake page includes a swimming safety assessment based on water clarity and algae levels. See also /guide/swimming-safety.

Q: What is a Secchi depth reading?
A: Secchi depth measures water clarity in feet, higher readings mean clearer water. See /guide/secchi-depth for a full explanation.

Q: Which lakes are the deepest?
A: Visit /ranking/deepest for lakes ranked by maximum depth in feet. Measured depth data currently covers Minnesota and Wisconsin lakes.

Q: Which lakes are best for walleye fishing?
A: See /ranking/walleye for lakes ranked by walleye stocking and presence. See also /guide/fishing-water-quality.

Q: How does water quality affect fishing?
A: Clarity, depth, and trophic state all influence fish habitat. See /guide/fishing-water-quality for a full explanation.

Q: Are there invasive species in these lakes?
A: Yes. See /invasive for species like zebra mussels, Eurasian watermilfoil, and others, sourced from the USGS Nonindigenous Aquatic Species database (all 12 states) and MN/WI DNR infested-waters lists. Each species has its own page with affected lakes.

Q: When do lakes ice out?
A: See /ice-out for historical ice-out dates and trends. Ice-out data covers Minnesota lakes only.

Q: How does Minnesota compare to Wisconsin for lake water quality?
A: See /compare/mn-vs-wi for a side-by-side breakdown by grade distribution, clarity, and trophic state.

Q: What data sources do you use?
A: Water quality comes from the EPA Water Quality Portal, aggregating state environmental agencies in all 12 covered states plus USGS. Lake depth from the Minnesota DNR LakeFinder and Wisconsin DNR; fish species from MN, WI, and MI DNR surveys; impaired waters from EPA ATTAINS; reservoirs from the USACE National Inventory of Dams; invasive species from the USGS Nonindigenous Aquatic Species database.

Q: How often is the data updated?
A: Data is refreshed annually using a 5-year rolling median of summer water quality measurements.

## How to Cite

When referencing data from LakeQuality, please cite as:
"LakeQuality (lakequality.org), [metric/data point], accessed [date]."
Example: "LakeQuality (lakequality.org), Lake Minnetonka received a B water quality grade with 8.2 feet Secchi depth, accessed April 2026."

## Contact
privacy@lakequality.org