Penobscot County Lake Quality
Maine, 2 lakes, average grade A (Excellent)
Penobscot County has 2 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. The county's average grade is A — among the cleanest in Maine. 1 lakes pull an A on their own, and almost none fall into the D or F brackets.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Junior Lake (A) is the cleanest in the county.
Quick Answers for Penobscot County
Planning a trip? Check special fishing regulations for Junior Lake — or check the official Maine fishing regulations.
All Lakes in Penobscot County
2 lakes · 1 graded, 1 not rated1 graded lake · 1 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | AJunior LakePenobscot | A | 25.9 ft | 6 µg/L | 2 µg/L | No recent samples | Not recorded |
| NRDolby PondPenobscot | NR | No recent samples | No recent samples | 0.7 µg/L | No recent samples | Not recorded |
NR = not rated: the monitoring record does not meet the evidence bar for a grade. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
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.
Other Counties in Maine
See how Penobscot County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 39 states and 2 Canadian provinces.
Where to stay near Penobscot County
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Source: EPA National Aquatic Resource Surveys, 2026.