Updated Aug 2026
Minnesota Lake Water Quality
Water quality grades for 2,394 monitored lakes across 77 counties.
Minnesota's 2,394 graded lakes draw on monitoring done by the Minnesota Pollution Control Agency and the Minnesota DNR, plus volunteer Citizen Lake Monitoring Network samplers who do the actual Secchi-disk work most years. Around 29% of the state's lakes pull an A — 699 top-tier waters. The B and C brackets together hold most of the rest, with the F bracket capturing 237 stressed lakes mostly in the agricultural south of the state.
Most Minnesota lakes sit in the mesotrophic band — moderate productivity, decent clarity, capable of supporting both warm-water and cool-water fisheries. This is the band where well-managed working lakes tend to land. The cleanest county on average is Clay (grade A); the most-stressed is Goodhue. The gap between the top and bottom counties is large enough that "Minnesota lake water quality" hides real local variation.
Grade Distribution
All 2,394 Minnesota lakes in the index: 1,537 (64.2%) carry an A–F grade and 857 (35.8%) are not rated — their monitoring record does not meet the evidence bar.
Where to stay near Minnesota
Top-rated places to stay near Minnesota
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Browse Minnesota Lakes
Loading Minnesota lakes…
Explore Minnesota Lakes
Minnesota reports, fishing & travel
Minnesota's cleanest and most-polluted lakes, ranked A–F
Fish species and top-graded lakes across Minnesota
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its grade
Best-graded lakes within 50 miles of Minneapolis
Best-graded lakes within 50 miles of St. Paul
Best-graded lakes within 50 miles of Duluth
Best-graded lakes within 50 miles of Rochester
Best-graded lakes within 50 miles of Brainerd
Best-graded lakes within 50 miles of St. Cloud
Reservoirs in Minnesota
View all 211 reservoirs →211 of 2,394 Minnesota lakes (9%) are man-made reservoirs in the USACE National Inventory of Dams. 31 carry a High or Significant hazard rating. The oldest matched dam dates to 1864.
EPA-Impaired Lakes in Minnesota
View all 1,654 impaired lakes →1,654 of 2,394 Minnesota lakes (69%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle. 1,269 have an approved Total Maximum Daily Load (TMDL) restoration plan.
Minnesota Fishing & Recreation
Licenses, regulations, records, and where to fish across Minnesota.
Counties
All 77 Minnesota counties, ranked by average lake water quality. Compare them against every county nationwide in the county rankings, browse the full directory of graded lakes, or pick a different state.
Minnesota Lake Water Quality Dataset (2026)
Every graded Minnesota lake in one spreadsheet — A–F grade, water clarity, phosphorus, chlorophyll-a, trophic state, size, public access, and a link to each lake's report card.
Top 25 Cleanest Lakes
25 lakes25 graded lakes
| # | Lake | County | Grade | Clarity | Trophic | Max Depth | Access |
|---|---|---|---|---|---|---|---|
| 1 | ARainy Lake | Cass | A | 13.9 ft | Oligotrophic | 29 ft | Carry-in |
| 2 | ACrane Lake | Otter Tail | A | 9 ft | Mesotrophic | 43 ft | ✓ Public |
| 3 | ALobster Lake | Douglas | A | 13 ft | Mesotrophic | 65 ft | ✓ Public |
| 4 | AEast Fox Lake | Crow Wing | A | 16.4 ft | Oligotrophic | 65 ft | ✓ Public |
| 5 | ADeep Portage Lake | Cass | A | 15.4 ft | Oligotrophic | 105 ft | Carry-in |
| 6 | AClearwater Lake | Cook | A | 29 ft | Oligotrophic | 65 ft | Carry-in |
| 7 | AClearwater Lake | Wright | A | 9.8 ft | Mesotrophic | 73 ft | ✓ Public |
| 8 | AClearwater Lake | Crow Wing | A | 13 ft | Mesotrophic | 54 ft | ✓ Public |
| 9 | AClearwater Lake | Clearwater | A | 10 ft | Mesotrophic | 65 ft | ✓ Public |
| 10 | ALower Hay Lake | Crow Wing | A | 18.5 ft | Oligotrophic | 100 ft | ✓ Public |
| 11 | ALatoka Lake | Douglas | A | 19 ft | Oligotrophic | 108 ft | ✓ Public |
| 12 | ALittle Birch Lake | Todd | A | 13 ft | Mesotrophic | 89 ft | ✓ Public |
| 13 | ANorth Long Lake | Crow Wing | A | 15.1 ft | Mesotrophic | 97 ft | ✓ Public |
| 14 | ABad Medicine Lake | Becker | A | 25 ft | Oligotrophic | 84 ft | ✓ Public |
| 15 | AMud Lake | Becker | A | 12.5 ft | Mesotrophic | 34 ft | ✓ Public |
| 16 | ABig Lake | Beltrami | A | 9.7 ft | Mesotrophic | 35 ft | ✓ Public |
| 17 | ABig Lake | Carlton | A | 10 ft | Mesotrophic | 25 ft | ✓ Public |
| 18 | ABig Lake | Sherburne | A | 13.6 ft | Mesotrophic | 48 ft | ✓ Public |
| 19 | ABig Lake | St. Louis | A | 8.2 ft | Mesotrophic | 22 ft | ✓ Public |
| 20 | ABig Sugar Bush Lake | Becker | A | 16.5 ft | Oligotrophic | 42 ft | ✓ Public |
| 21 | APelican Lake | Otter Tail | A | 16.4 ft | Mesotrophic | 55 ft | ✓ Public |
| 22 | APelican Lake | Crow Wing | A | 14.3 ft | Oligotrophic | 104 ft | ✓ Public |
| 23 | AFullers Lake: East Basin | Beltrami | A | 15 ft | Oligotrophic | No recent samples | Not recorded |
| 24 | ABirch Lake | Ramsey | A | 5.9 ft | Mesotrophic | No recent samples | Carry-in |
| 25 | ABirch Lake | Wright | A | 15 ft | Mesotrophic | 52 ft | ✓ Public |
25 Lakes Needing Attention
25 lakes25 graded lakes
| # | Lake | County | Grade | Clarity |
|---|---|---|---|---|
| 1 | FMccormic Lake | Stearns | F | No recent samples |
| 2 | FEast Arctic Lake | Scott | F | No recent samples |
| 3 | FShetek Lake | Murray | F | 1.1 ft |
| 4 | FCorabelle Lake | Murray | F | 0.5 ft |
| 5 | FBloody Lake | Murray | F | 0.7 ft |
| 6 | FLime Lake | Murray | F | 0.4 ft |
| 7 | FTemperance Lake | Martin | F | 0.7 ft |
| 8 | FWest Graham Lake | Nobles | F | 4.1 ft |
| 9 | FBright Lake | Martin | F | 1 ft |
| 10 | FWillmert Lake | Martin | F | 3.3 ft |
| 11 | FEast Graham Lake | Nobles | F | 3.3 ft |
| 12 | FNorth Silver Lake | Martin | F | 4.9 ft |
| 13 | FPhelps Lake | Rice | F | 2.3 ft |
| 14 | FTitlow Lake | Sibley | F | 0.3 ft |
| 15 | FCody Lake | Rice | F | 2 ft |
| 16 | FCannon Lake | Rice | F | 4.1 ft |
| 17 | FGorman Lake | Le Sueur | F | 3.7 ft |
| 18 | FLilly Lake | Dakota | F | 2 ft |
| 19 | FNorth Stanchfield Lake | Isanti | F | 2.8 ft |
| 20 | FLamplighter Park Lake | Hennepin | F | 1.1 ft |
| 21 | FTadd Lake | Kandiyohi | F | 2 ft |
| 22 | FDowns Lake | Washington | F | 1.8 ft |
| 23 | FWilmes Lake | Washington | F | 3.5 ft |
| 24 | FSouth Stanchfield Lake | Isanti | F | 2.5 ft |
| 25 | FMountain Lake | Cottonwood | F | 1.2 ft |
Lake Match
Which lake suits how you actually use one?
Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of graded lakes that fit, with the water quality behind each one.
Source: EPA National Aquatic Resource Surveys and the EPA Water Quality Portal.