Late afternoon sun over Slim Lake, scattering a bright path across wind-textured water

Middlesex County Lake Quality

Massachusetts, 97 lakes, measured by MassDEP

Middlesex County has 97 monitored lakes, enough that within-county variation matters as much as the county average. Some are deep glacial basins, others are shallow agricultural-watershed waters, and the measurements reflect that mix. 10 of those lakes carry recent nutrient and algae readings. The county-level summary describes that subset, not every water body listed. For Middlesex County the spread behind the average matters more than the average itself: a few nutrient-rich lakes among many clear ones produce the same figure as the inverse.

The county's lakes lean shallow, which makes the readings sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest measured lake is South Reservoir.

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Quick Answers for Middlesex County

Cleanest lakes in Middlesex County →Best swimming lakes in Massachusetts →

Planning a trip? Check special fishing regulations for South Reservoir — or check the official Massachusetts fishing regulations.

All Lakes in Middlesex County

97 lakes · 10 ranked on readings, 87 without enough sampling10 lakes ranked on readings · 87 without enough sampling, hidden

Include not-rated lakes (87)

#	Lake	Clarity	Phosphorus	Algae	Trophic	Max Depth	Access
1	South ReservoirMiddlesex	No recent samples	No recent samples	2.5 µg/L	No recent samples	No recent samples	Not recorded
2	Fitchburg ReservoirMiddlesex	No recent samples	No recent samples	2.8 µg/L	No recent samples	No recent samples	Not recorded
3	Nabnasset PondMiddlesex	No recent samples	No recent samples	5.7 µg/L	No recent samples	No recent samples	✓ Public
4	Cambridge ReservoirMiddlesex	No recent samples	No recent samples	7.4 µg/L	No recent samples	No recent samples	Not recorded
5	Heart PondMiddlesex	No recent samples	No recent samples	14.6 µg/L	No recent samples	No recent samples	Not recorded
6	Boons PondMiddlesex	No recent samples	No recent samples	9.8 µg/L	No recent samples	No recent samples	Not recorded
7	Horn PondMiddlesex	No recent samples	No recent samples	13.4 µg/L	No recent samples	No recent samples	✓ Public
8	Gleasons PondMiddlesex	No recent samples	No recent samples	43.9 µg/L	No recent samples	No recent samples	✓ Public
9	Barkers PondMiddlesex	No recent samples	No recent samples	54.5 µg/L	No recent samples	No recent samples	Not recorded
10	Wedge PondMiddlesex	No recent samples	No recent samples	70.4 µg/L	No recent samples	No recent samples	Not recorded
	Farm PondMiddlesex	19.5 ft	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Spy PondMiddlesex	5 ft	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Lake QuannapowittMiddlesex	1.3 ft	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Upper Mystic LakeMiddlesex	No recent samples	28.1 µg/L	No recent samples	No recent samples	No recent samples	✓ Public
	Long Pond-Richardson BeachMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Billerica Impoundment LakeMiddlesex	No recent samples	No recent samples	68.6 µg/L	No recent samples	No recent samples	Not recorded
	Ashby ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Harbor PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Heald PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Coon Tree PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Nashua River ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Plow Shop PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Eldridge PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Grove PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Sandy PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	29.9 ft	Not recorded
	Flannagan PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Long PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Spectacle PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Long PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	20 ft	✓ Public
	Fort PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Nagog PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Cramberry Bog Reservoir Number OneMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Russell MillpondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Batemans PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Warners PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	White PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	62.7 ft	Not recorded
	Fairhaven BayMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Flints PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Walden PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	108.3 ft	Not recorded
	Lower Mystic LakeMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	74 ft	Not recorded
	Upper Mystic LakeMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	88.6 ft	Not recorded
	North ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Middle ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Spot PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	40 ft	Not recorded
	Crystal LakeMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Mill Pond ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Nutting LakeMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Richardson PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Long PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	7.5 ft	Not recorded
	Ames PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Martins PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Swan PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Peters PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Flint PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	5.9 ft	✓ Public
	Althea LakeMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	15 ft	Not recorded
	Burges PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Newfield PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	21 ft	Not recorded
	Fletchers PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Long Sought-for PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Keyes PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Forge PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Whitney PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Lost LakeMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Knops PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Baddacook PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	47.9 ft	✓ Public
	Massapoag PondsMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Lower Massapoag PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Fresh PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Hardys PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Crystal LakeMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Weston ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Norumbega ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Dug PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Bracket Reservoir (Number Two)Middlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Waushakum PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	46.9 ft	Not recorded
	Lake WinthropMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Echo LakeMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	North PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	25 ft	Not recorded
	Whitehall ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	25 ft	Not recorded
	Ashland ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	48 ft	✓ Public
	Williams LakeMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Hager PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Foss Reservoir (Number Three)Middlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Farm PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	18 ft	Not recorded
	Learned PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Fisk PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Lake CochituateMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	65 ft	Not recorded
	Dudley PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Nonesuch PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Heard PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	8.5 ft	Not recorded
	Farrar PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	White PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Puffer PondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Carding MillpondMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Fort Meadow ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Fort Meadow ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded
	Millham ReservoirMiddlesex	No recent samples	No recent samples	No recent samples	No recent samples	No recent samples	Not recorded

NR = no nutrient or algae reading on record. The measurements are published as the authority reports them. Where the data comes from.

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Source: the Massachusetts Department of Environmental Protection. See data sources.