Windham County Lake Quality
Connecticut, 7 lakes, average grade D (Nutrient-rich)
Only 7 lakes in Windham County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. The county-wide average grade is D — water quality issues are persistent across most of the monitored basins. 0 lakes fall into the F bracket outright.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Alexander Lake (C); the most-stressed is Roseland Lake (D).
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Quick Answers for Windham County
Planning a trip? Check special fishing regulations for Alexander Lake — or check the official Connecticut fishing regulations.
All Lakes in Windham County
7 lakes · 3 graded, 4 not rated3 graded lakes · 4 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | CAlexander LakeWindham | C | No recent samples | 27 µg/L | 0.9 µg/L | No recent samples | Not recorded |
| 2 | DRoseland LakeWindham | D | No recent samples | 66 µg/L | 41.8 µg/L | No recent samples | Not recorded |
| 3 | DWest Thompson LakeWindham | D | 5.3 ft | 22 µg/L | 8.5 µg/L | No recent samples | Not recorded |
| NRAshford LakeWindham | NR | 5 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRBlack PondWindham | NR | 16.6 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRHalls PondWindham | NR | 8.1 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLake ChaffeeWindham | NR | No recent samples | 23 µg/L | 3.7 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.
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Other Counties in Connecticut
See how Windham County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 49 states and 2 Canadian provinces.
Source: EPA National Aquatic Resource Surveys, 2026.