Updated Aug 2026
Maine Lake Water Quality
Water quality grades for 18 monitored lakes across 4 counties.
Maine has 18 graded lakes in our dataset, sampled across 4 counties, drawing on monitoring by the Maine Department of Environmental Protection plus federal and volunteer measurements. Roughly 89% of the state's graded lakes carry an A — 16 lakes that earn the top bracket on the combined Secchi/phosphorus/chlorophyll-a rubric. That share is high by national standards and reflects the depth and natural clarity of glacial lakes in the region.
Most Maine 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. Washington ranks highest on average county grade (A). Washington sits lowest. With only 4 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.
Grade Distribution
All 18 Maine lakes in the index: 16 (88.9%) carry an A–F grade and 2 (11.1%) are not rated — their monitoring record does not meet the evidence bar.
Top-Graded Maine Lakes
The highest water-quality grades in Maine — clarity, depth, and A-F grade at a glance.
Lake Map
Maine reports, fishing & travel
Maine Fishing & Recreation
Licenses, regulations, records, and where to fish across Maine.
Counties
All 4 Maine 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.
Cleanest Maine Lakes
16 lakes16 graded lakes
| # | Lake | County | Grade | Clarity | Trophic | Access |
|---|---|---|---|---|---|---|
| 1 | ABig Lake | Washington | A | 16.7 ft | Mesotrophic | Not recorded |
| 2 | AEast Musquash Lake | Washington | A | 20.5 ft | Mesotrophic | Not recorded |
| 3 | AGrand Falls Flowage Lake | Washington | A | 14 ft | Mesotrophic | Not recorded |
| 4 | AJunior Lake | Penobscot | A | 25.9 ft | Oligotrophic | Not recorded |
| 5 | AKillman Pond | Hancock | A | 12.7 ft | Mesotrophic | Not recorded |
| 6 | ALewey Lake | Washington | A | 15 ft | Mesotrophic | Not recorded |
| 7 | ALong Lake | Washington | A | 15.6 ft | Mesotrophic | Not recorded |
| 8 | AMiddle Chain Lake | Hancock | A | 14.1 ft | Mesotrophic | Not recorded |
| 9 | APleasant Lake | Washington | A | 27.2 ft | Oligotrophic | Not recorded |
| 10 | APocumcus Lake | Washington | A | 27.9 ft | Oligotrophic | Not recorded |
| 11 | AScraggly Lake | Washington | A | 19.4 ft | Mesotrophic | Not recorded |
| 12 | ASide Pistol Lake | Hancock | A | 16.7 ft | Mesotrophic | Not recorded |
| 13 | ASysladobsis Lake | Washington | A | 27.8 ft | Oligotrophic | Not recorded |
| 14 | AUpper Chain Lake | Hancock | A | 14.5 ft | Mesotrophic | Not recorded |
| 15 | AWest Grand Lake | Washington | A | 36.7 ft | Oligotrophic | Not recorded |
| 16 | AWest Musquash Lake | Washington | A | 31 ft | Oligotrophic | Not recorded |
Maine Lakes Needing Attention
16 lakes16 graded lakes
| # | Lake | County | Grade | Clarity |
|---|---|---|---|---|
| 1 | AWest Musquash Lake | Washington | A | 31 ft |
| 2 | AWest Grand Lake | Washington | A | 36.7 ft |
| 3 | AUpper Chain Lake | Hancock | A | 14.5 ft |
| 4 | ASysladobsis Lake | Washington | A | 27.8 ft |
| 5 | ASide Pistol Lake | Hancock | A | 16.7 ft |
| 6 | AScraggly Lake | Washington | A | 19.4 ft |
| 7 | APocumcus Lake | Washington | A | 27.9 ft |
| 8 | APleasant Lake | Washington | A | 27.2 ft |
| 9 | AMiddle Chain Lake | Hancock | A | 14.1 ft |
| 10 | ALong Lake | Washington | A | 15.6 ft |
| 11 | ALewey Lake | Washington | A | 15 ft |
| 12 | AKillman Pond | Hancock | A | 12.7 ft |
| 13 | AJunior Lake | Penobscot | A | 25.9 ft |
| 14 | AGrand Falls Flowage Lake | Washington | A | 14 ft |
| 15 | AEast Musquash Lake | Washington | A | 20.5 ft |
| 16 | ABig Lake | Washington | A | 16.7 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.
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Source: EPA National Aquatic Resource Surveys, 2026.