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LakeQuality
Pink and orange afterglow over the treeline on Slim Lake after sunset

Updated August 2026

The State of Massachusetts's Lakes 2026

Of 103 lakes in Massachusetts, 50.6% sit in EPA's favourable condition classes for nutrients and algae and 30.9% in its poorer ones. 98 lakes (95.1%) are on an official impaired-waters list.

Data Report

103
Monitored lakes sampled
B
Average readings
50.6%
low nutrient and algae readings
95.1%
On impaired list

Massachusetts nutrient and algae readings

Cleanest lakes in Massachusetts

Cleanest combined nutrient and algae readings, 2026.

No qualifying lakes with sufficient data.

Highest measured algae

Highest measured chlorophyll-a (algae) concentration.

  1. 1.Wedge Pond — Middlesex County70 µg/L chlorophyll-a
  2. 2.Billerica Impoundment Lake — Middlesex County69 µg/L chlorophyll-a
  3. 3.Barkers Pond — Middlesex County55 µg/L chlorophyll-a
  4. 4.Santuit Pond — Barnstable County52 µg/L chlorophyll-a
  5. 5.Cooks Pond — Plymouth County48 µg/L chlorophyll-a
  6. 6.Furnace Pond — Plymouth County47 µg/L chlorophyll-a
  7. 7.Gleasons Pond — Middlesex County44 µg/L chlorophyll-a
  8. 8.South Watuppa Pond — Bristol County43 µg/L chlorophyll-a
  9. 9.Bartlett Pond — Worcester County38 µg/L chlorophyll-a
  10. 10.Nashawannuck Pond — Hampshire County32 µg/L chlorophyll-a

Trending lakes

Improving

  1. 1.Ezekiel Pond — Plymouth County
  2. 2.Monponsett Pond — Plymouth County
  3. 3.Snows Pond — Plymouth County
  4. 4.Upper Mystic Lake — Middlesex County
  5. 5.White Island Pond — Plymouth County

Declining

  1. 1.Lower Spectacle Pond — Berkshire County
  2. 2.Buckley-Dunton Lake — Berkshire County
  3. 3.Long Pond — Barnstable County
  4. 4.Farm Pond — Middlesex County
  5. 5.Spy Pond — Middlesex County
  6. 6.Wachusett Reservoir — Worcester County
  7. 7.Santuit Pond — Barnstable County
  8. 8.White Oak Brook Lake — Plymouth County

Impaired waters in Massachusetts

98 lakes appear on the EPA/state 303(d) impaired-waters list (61 formally listed, 32 with a cleanup plan/TMDL).

Algal growth · 49Mercury · 43Nuisance exotic species · 40Oxygen depletion (low DO) · 26Nutrients (phosphorus, nitrogen) · 22Noxious aquatic plants · 16Turbidity · 10Habitat alterations · 9

Explore Massachusetts lakes

Lake Fishing Forecast

Species activity outlook by water temperature and season

Massachusetts Lake Trips

Where to stay at Massachusetts's top lakes, each with its readings

Readings combine total phosphorus, total nitrogen, chlorophyll-a, and turbidity from the EPA Water Quality Portal and state agencies. See the full methodology, the national State of America’s Lakes report, or all Massachusetts lakes.

Cite this report: LakeQuality, “The State of Massachusetts's Lakes 2026”.