Middlesex County Lake Quality
Connecticut, 9 lakes, average grade C (Fair)
Middlesex County has 9 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 average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
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 Bashan Lake (B); the most-stressed is Lake Beseck (D).
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Quick Answers for Middlesex County
Planning a trip? Check special fishing regulations for Bashan Lake — or check the official Connecticut fishing regulations.
All Lakes in Middlesex County
9 lakes · 5 graded, 4 not rated5 graded lakes · 4 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | BBashan LakeMiddlesex | B | No recent samples | 15 µg/L | 1.5 µg/L | No recent samples | Not recorded |
| 2 | BLake HaywardMiddlesex | B | No recent samples | 16 µg/L | 4.5 µg/L | No recent samples | Not recorded |
| 3 | BPattaconk ReservoirMiddlesex | B | No recent samples | 16 µg/L | 2.8 µg/L | No recent samples | Not recorded |
| 4 | CBlack PondMiddlesex | C | No recent samples | 18 µg/L | 3.6 µg/L | No recent samples | Not recorded |
| 5 | DLake BeseckMiddlesex | D | No recent samples | 46 µg/L | 31.7 µg/L | No recent samples | Not recorded |
| NRBeseck LakeMiddlesex | NR | 4.1 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRCedar LakeMiddlesex | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRPameacha PondMiddlesex | NR | 1.3 ft | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRUnk LakeMiddlesex | NR | No recent samples | 28 µg/L | 13.6 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 Connecticut
See how Middlesex 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.