State water-quality picture · #26 by reported lake-type waterbodies
Maine lakes and reservoirs
Every figure on this page is computed from the assessment decisions Maine and the Penobscot Nation reported to the U.S. Environmental Protection Agency under Clean Water Act sections 303(d) and 305(b) (reporting cycles 2002–2024), plus daily water-level observations from the U.S. Geological Survey.
- 339
- Reported waterbodies
- 31
- Not supporting a use
- 6
- Fish use not supporting
- 0
- Gauged lakes
Maine in one line
339 lake-type waterbodies in Maine are reported to EPA ATTAINS across reporting cycles 2002–2024: 31 assessed as not supporting at least one designated use, 272 fully supporting, and 36 without a definitive overall verdict. The most-listed impairment cause is Phosphorus, Total, on 21 waterbodies.
- 339
- reported waterbodies
- 31
- not supporting a use
- 272
- fully supporting
- 10%
- of definitive verdicts impaired
An unassessed waterbody is neither confirmed clean nor confirmed impaired; states assess on multi-year cycles.
Maine's mid-size register with a lighter not-supporting share
Maine sits in the middle third by inventory size (339 units) and in the lowest third for ruled not-supporting share (10%).
Data updated 2026-08-17
According to the U.S. Environmental Protection Agency's ATTAINS program, Maine and the Penobscot Nation reported 339 lake-type waterbodies in Maine in the August 2026 extract. See our methodology for filer attribution and multi-year reporting cycles.
Overall-status mix on Maine's mid-size inventory
Every reported lake-type unit in Maine falls into exactly one overall-status bucket. This bar is the inventory partition; the cause chart and national gauge below answer different questions.
Most-listed impairment causes in Maine
Waterbodies carrying each listed cause, most first
- Phosphorus, Total
Phosphorus, Total
21 waterbodies
- Secchi Disk Transparency
Secchi Disk Transparency
21 waterbodies
- Habitat Alterations 6
Habitat Alterations
6 waterbodies
- PFAS in Fish Tissue 6
PFAS in Fish Tissue
6 waterbodies
- Habitat Assessment 1
Habitat Assessment
1 waterbodies
What this shows Phosphorus, Total is the most-listed impairment cause in Maine, on 21 of the lake-type waterbodies reported there.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
Maine: 10% of ruled verdicts are not-supporting, against a national share of 53%, 5.3× below the national rate.
Reporting practice
Nearly all of Maine's inventory carries a definitive verdict
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.
Maine holds the 26th-largest reported lake-type inventory in the country, 339 assessment units, carrying a definitive verdict on 89.4% of it. The counts above describe the 303 units carrying a verdict, not all 339 reported.
The states reporting at the nearest rates are Alabama (89.8%) and Texas (88.5%).
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 Maine. 36 of them were filed by a sovereign tribal nation 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: Penobscot Nation (36). Those decisions are theirs, not Maine's.
Maine against every comparable state
Share of reported lake-type waterbodies carrying a definitive verdict
89.4% 13th of 47 higher than 34 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 Maine
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 | Moosehead Lake Fully Supporting | 79,454 |
| 2 | Sebago Lake Fully Supporting | 45,624 |
| 3 | Spednick Lake Fully Supporting | 35,904 |
| 4 | Chesuncook Lake Fully Supporting | 34,926 |
| 5 | Mooselookmeguntic Lake Fully Supporting | 32,243 |
| 6 | West Grand Lake Fully Supporting | 31,174 |
| 7 | West Branch Penobscot River (3) Fully Supporting | 25,876 |
| 8 | Webster Brook Fully Supporting | 21,919 |
| 9 | Flagstaff L Not Supporting | 20,300 |
| 10 | Eagle Lake Fully Supporting | 20,281 |
| 11 | Graham Lake Fully Supporting | 18,173 |
| 12 | East Machias River Fully Supporting | 15,289 |
By cause count
Most-listed waterbodies in Maine
Waterbodies carrying the most listed impairment causes among the lake-type units reported by Maine and by the Penobscot Nation.
| # | Waterbody | Listed causes |
|---|---|---|
| 1 | China L Not Supporting | 3 |
| 1 | Unity P Not Supporting | 3 |
| 3 | Alamoosook L Not Supporting | 2 |
| 3 | Annabessacook L Not Supporting | 2 |
| 3 | Arnold Brook L Not Supporting | 2 |
| 3 | Aziscohos L Not Supporting | 2 |
| 3 | Christina Reservoir Not Supporting | 2 |
| 3 | Cross L Not Supporting | 2 |
| 3 | Daigle P Not Supporting | 2 |
| 3 | Graham L Not Supporting | 2 |
Every row in this table ties with at least one other on the ranked value: 2 at 3 (rank 1), 8 at 2 (rank 3). 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.
States near Maine's lighter not-supporting load
Two EPA ATTAINS peer sets outside Maine. The reporting-practice chart above stays on definitive-verdict share; these neighborhoods highlight register-size and not-supporting peers while Maine's ruled impairment share sits in the lowest third.
Similar reported inventory
Nearest states by lake-type units on the register (339 here).
- North Dakota · 340 units · 1 off
- Colorado · 344 units · 5 off
- Kansas · 328 units · 11 off
- Iowa · 371 units · 32 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: 89.4% of the inventory reported from Maine carries a definitive verdict, 13th 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 Maine 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 Maine and the Penobscot Nation 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 Maine and by the Penobscot Nation, 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.