Some of these decisions are EPA's. 100 of these 13,176 records carry a Clean Water Act cleanup plan EPA established rather than Minnesota and the Red Lake Band of Chippewa Indians, the Minnesota Chippewa Tribe (Fond du Lac Band) and the Minnesota Chippewa Tribe (Grand Portage Band). They are counted in every figure on this page, and each record page names which.
State water-quality picture · #2 by reported lake-type waterbodies
Minnesota lakes and reservoirs
Every figure on this page is computed from the assessment decisions Minnesota and the Red Lake Band of Chippewa Indians, the Minnesota Chippewa Tribe (Fond du Lac Band) and the Minnesota Chippewa Tribe (Grand Portage Band) reported to the U.S. Environmental Protection Agency under Clean Water Act sections 303(d) and 305(b) (reporting cycles 1998–2024), plus daily water-level observations from the U.S. Geological Survey.
- 13,176
- Reported waterbodies
- 1,798
- Not supporting a use
- 1,241
- Fish use not supporting
- 1
- Gauged lake
Minnesota in one line
13,176 lake-type waterbodies in Minnesota are reported to EPA ATTAINS across reporting cycles 1998–2024: 1,798 assessed as not supporting at least one designated use, 1,566 fully supporting, and 9,812 without a definitive overall verdict. The most-listed impairment cause is Mercury in Fish Tissue, on 1,238 waterbodies. This ranks the cause names filed in Minnesota, not distinct pollutants: mercury appears under 3 of them, together listed on 1,256 waterbodies.
- 13,176
- reported waterbodies
- 1,798
- not supporting a use
- 1,566
- fully supporting
- 53%
- of definitive verdicts impaired
An unassessed waterbody is neither confirmed clean nor confirmed impaired; states assess on multi-year cycles.
A large Minnesota inventory with a lighter ruled-impairment share
13,176 reported lake-type units put Minnesota in the largest third of state registers, while its ruled not-supporting share (53%) sits in the lowest third. Scale and load pull apart on this page.
Data updated 2026-08-17
According to the U.S. Environmental Protection Agency's ATTAINS program, Minnesota and the Red Lake Band of Chippewa Indians, the Minnesota Chippewa Tribe (Fond du Lac Band) and the Minnesota Chippewa Tribe (Grand Portage Band) reported 13,176 lake-type waterbodies in Minnesota in the August 2026 extract. See our methodology for filer attribution and multi-year reporting cycles.
How Minnesota's large inventory splits across overall status
Each of the 13,176 lake-type units reported by Minnesota and by the Red Lake Band of Chippewa Indians, the Minnesota Chippewa Tribe (Fond du Lac Band) and the Minnesota Chippewa Tribe (Grand Portage Band) lands in exactly one overall-status bucket. On a register this large, the bar is an inventory partition, the cause chart and national gauge below answer different questions.
Most-listed impairment causes in Minnesota
Waterbodies carrying each listed cause, most first
- Mercury in Fish Tissue
Mercury in Fish Tissue
1,238 waterbodies
- Nutrients
Nutrients
687 waterbodies
- Fish Bioassessments 164
Fish Bioassessments
164 waterbodies
- Chloride 35
Chloride
35 waterbodies
- Sulfate 34
Sulfate
34 waterbodies
What this shows Mercury in Fish Tissue is the most-listed impairment cause in Minnesota, on 1,238 of the lake-type waterbodies reported there. This ranks the cause names filed in Minnesota, not distinct pollutants: mercury appears under 3 of them, together listed on 1,256 waterbodies.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
Minnesota: 53% of ruled verdicts are not-supporting, against a national share of 53%, in line with the national rate.
Reporting practice
A definitive verdict is still missing for most of Minnesota's inventory
Each reporting authority decides how much of the water it files to EPA it actually assesses in a cycle. That decision sets the denominator behind every count on this page.
Minnesota holds the 2nd-largest reported lake-type inventory in the country, 13,176 assessment units, carrying a definitive verdict on 25.5% of it. The counts above describe the 3,364 units carrying a verdict, not all 13,176 reported. Minnesota has also retired 114 lake-type assessment units, superseded filings that are kept on the site but not counted here.
The states reporting at the nearest rates are Wisconsin (23.7%) and New York (28.8%).
Assessing more of an inventory is a reporting choice, set by cycle length, monitoring budget and how finely a state splits its waters into units. It is not a measure of water quality, and it is why a raw count from one state does not sit beside a raw count from another. How assessment coverage varies.
Not every unit counted here was assessed by Minnesota. 124 of them were filed by 3 sovereign tribal nations reporting directly to EPA under Clean Water Act section 518, which lets a tribe set and apply its own water quality standards in the same manner as a state: Red Lake Band of Chippewa Indians (83), Minnesota Chippewa Tribe (Fond du Lac Band) (25), Minnesota Chippewa Tribe (Grand Portage Band) (16). Those decisions are theirs, not Minnesota's.
Minnesota against every comparable state
Share of reported lake-type waterbodies carrying a definitive verdict
25.5% 42nd of 47 higher than 5 of 47 states
the 47 comparable states, by definitive-verdict share
Each bar is a band; taller bars hold more states. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA ATTAINS · Reporting cycles 1987–2026
Each bar counts states whose definitive-verdict share falls in that 10-point band. The 47 states shown are those reporting at least 25 lake-type units; a share off a smaller inventory is precision the data does not have.
By size
Largest assessed lakes in Minnesota
By assessed acreage as reported in ATTAINS. Acreage is the assessed unit's size, which can differ from a lake's full surface area.
| # | Waterbody | Assessed acres |
|---|---|---|
| 1 | Superior Not Supporting | 13,182,720 |
| 2 | Lake of the Woods Not Supporting | 301,348 |
| 3 | Red (Lower Red) Not reported | 164,699 |
| 4 | Lower Red Lake Fully Supporting | 164,689 |
| 5 | Mille Lacs Not Supporting | 128,076 |
| 6 | Red (Upper Red) Not Supporting | 119,279 |
| 7 | Upper Red Lake Fully Supporting | 118,943 |
| 8 | Leech (Main Basin) Not Supporting | 101,949 |
| 9 | Lake Superior Fully Supporting | 86,000 |
| 10 | Rainy Not Supporting | 45,734 |
| 11 | East Vermilion Not Supporting | 25,604 |
| 12 | Pepin Not Supporting | 25,477 |
By cause count
Most-listed waterbodies in Minnesota
Waterbodies carrying the most listed impairment causes among the lake-type units reported by Minnesota and by the Red Lake Band of Chippewa Indians, the Minnesota Chippewa Tribe (Fond du Lac Band) and the Minnesota Chippewa Tribe (Grand Portage Band).
| # | Waterbody | Listed causes |
|---|---|---|
| 1 | St Louis Bay Not Supporting | 8 |
| 2 | Upper Estuary Not Supporting | 7 |
| 3 | Middle Twin Not Supporting | 5 |
| 3 | Upper Twin Not Supporting | 5 |
| 5 | Gervais Not Supporting | 4 |
| 5 | Green Not Supporting | 4 |
| 5 | Lower Twin Not Supporting | 4 |
| 5 | Nokomis Not Supporting | 4 |
| 5 | St. Croix Not Supporting | 4 |
| 10 | Agnes Not Supporting | 3 |
7 of the 10 rows in this table tie on the ranked value: 2 at 5 (rank 3), 5 at 4 (rank 5). Tied rows share a rank and are listed in no meaningful order; where a tie reaches the top the medal is shared, because nothing separates those rows.
Gauge network
Lakes with a daily level record in Minnesota
Lakes with a linked USGS gauge and a daily water-level record. Readings are daily-batch snapshots, not real-time.
States near Minnesota's lighter not-supporting load
Two EPA ATTAINS peer sets outside Minnesota. The reporting-practice chart above stays on definitive-verdict share; these neighborhoods highlight register-size and not-supporting peers while Minnesota's ruled impairment share sits in the lowest third.
States with a similar reported inventory
Nearest states by lake-type units on the register (13,176 here).
- Wisconsin · 19,871 units · 6,695 off
- Michigan · 4,307 units · 8,869 off
- New Hampshire · 2,786 units · 10,390 off
- New York · 2,231 units · 10,945 off
Comparable not-supporting counts
Nearest states by units assessed not supporting a use (1,798 here). Inventory peers above are omitted.
- Massachusetts · 678 not supporting · 1,120 off
- Florida · 636 not supporting · 1,162 off
- New Jersey · 583 not supporting · 1,215 off
- Illinois · 434 not supporting · 1,364 off
Peers are nearest-neighbor matches on EPA ATTAINS register size and not-supporting counts among states with at least 25 reported units. Impairment peers skip states already listed in the inventory column so the two link sets stay distinct.
Using this state picture
- Comparisons across states hold on shares, not counts: 25.5% of the inventory reported from Minnesota carries a definitive verdict, 42nd of 47 comparable states. National rankings
- Fish-consumption verdicts here are assessment decisions. Species-level meal advice comes from the state fish-advisory program. Consumption guide
- Browse every named Minnesota waterbody with a populated record. Browse waterbodies
PlainLakes renders state assessment decisions and federal gauge observations without modification.
Figures on this page are computed from the assessment decisions Minnesota and the Red Lake Band of Chippewa Indians, the Minnesota Chippewa Tribe (Fond du Lac Band) and the Minnesota Chippewa Tribe (Grand Portage Band) reported to EPA's ATTAINS system and from USGS National Water Information System daily values, no number is typed in by an editor. State counts aggregate every lake-type assessment unit reported by Minnesota and by the Red Lake Band of Chippewa Indians, the Minnesota Chippewa Tribe (Fond du Lac Band) and the Minnesota Chippewa Tribe (Grand Portage Band), including unnamed units that never receive their own page. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-08-17. Primary sources: EPA ATTAINS and USGS National Water Information System.