Reservoirs in Massachusetts
64 of 829 graded Massachusetts lakes (8%) are man-made reservoirs in the USACE National Inventory of Dams. 51 carry a High or Significant hazard rating.
Reading the Massachusetts reservoir landscape
64 reservoirs in Massachusetts appear in the USACE National Inventory of Dams. That's a meaningful share — reservoir lakes carry their own ecology and access patterns distinct from natural lakes, including managed water levels, drawdowns timed to the dam's purpose, and shoreline mix dominated by structures built post-impoundment.
Recreation is the headline purpose for the largest share of Massachusetts's reservoirs — lakes where the dam exists explicitly to create surface water for fishing, boating, and adjacent shoreline development. Pool levels are typically maintained more stably than at flood-control or hydro reservoirs, which supports fixed-dock access, consistent boat ramps, and the kind of shoreline economy that natural-lake counterparts in the state share.
The USACE National Inventory of Dams (NID) catalogs every dam in the United States above a size threshold — typically 25 feet in height or 50 acre-feet in maximum storage, plus all dams classified as high-hazard regardless of size. The reservoir records below pull NID fields (year built, hazard class, maximum storage, surface area at normal pool, dam length, primary purpose) and pair them with water-quality data where the impoundment also appears in EPA's lake-monitoring inventory.
Why these Massachusetts reservoirs were built
All 64 Massachusetts reservoirs (by surface area)
| Reservoir | County | Grade | Surface area | Year built | Purpose | Hazard |
|---|---|---|---|---|---|---|
| Wachusett Reservoir | Worcester | NR | 4,160 ac | 1906 | Water Supply | High |
| Webster Lake | Worcester | NR | 1,442 ac | 1957 | Recreation | Significant |
| Sudbury Reservoir | Worcester | A | 1,300 ac | 1899 | Water Supply | High |
| Silver Lake | Plymouth | NR | 602 ac | 1908 | Water Supply | Low |
| Cambridge Reservoir | Middlesex | C | 546 ac | 1897 | Water Supply | High |
| Hamilton Reservoir | Hampden | A | 400 ac | — | Recreation | High |
| East Brimfield Reservoir | Worcester | C | 360 ac | 1960 | Flood Risk Reduction | High |
| Bare Hill Pond | Worcester | A | 324 ac | 1837 | Recreation | Significant |
| White Island Pond | Plymouth | NR | 322 ac | — | Irrigation | Significant |
| Ezekiel Pond | Plymouth | A | 322 ac | — | Irrigation | Significant |
| Cleveland Pond | Plymouth | D | 300 ac | 1992 | Recreation | Significant |
| Lake Pearl | Norfolk | A | 288 ac | 1920 | Recreation | Significant |
| Ponkapoag Pond | Norfolk | A | 285 ac | 1930 | Recreation | Significant |
| Walden Pond | Essex | A | 243 ac | 1890 | Water Supply | High |
| Indian Lake | Worcester | NR | 233 ac | 1920 | Flood Risk Reduction | Significant |
| Sherman Reservoir | Franklin | NR | 218 ac | 1927 | Hydroelectric | High |
| Little River Lake | Worcester | C | 200 ac | 1958 | Flood Risk Reduction | High |
| Upper Mystic Lake | Middlesex | NR | 185 ac | 1860 | Flood Risk Reduction | Significant |
| Crystal Lake | Essex | A | 170 ac | 1930 | Water Supply | Significant |
| Santuit Pond | Barnstable | NR | 165 ac | — | Recreation | Low |
| Wrights Reservoir | Worcester | A | 163 ac | 1965 | Flood Risk Reduction | High |
| Buckley-Dunton Lake | Berkshire | C | 154 ac | 1870 | Recreation | High |
| Fitchburg Reservoir | Middlesex | A | 153 ac | 1916 | Water Supply | Low |
| Nabnasset Pond | Middlesex | C | 146 ac | 1926 | Recreation | Significant |
| Queen Lake | Worcester | A | 142 ac | 1824 | Recreation | Significant |
| Upper Artichoke Reservoir | Essex | D | 130.7 ac | 1920 | Water Supply | Low |
| Wachusett Lake | Worcester | A | 130 ac | 1905 | Flood Risk Reduction | Significant |
| Stodge Meadow Pond | Worcester | D | 125.8 ac | 1863 | Recreation | Low |
| Ten Mile River Lake | Bristol | D | 111 ac | 1890 | Flood Risk Reduction | High |
| Ashley Lake | Berkshire | A | 106 ac | 1901 | Water Supply | High |
| Wankinco River Lake | Plymouth | A | 105 ac | — | Recreation | High |
| Horn Pond | Middlesex | D | 103 ac | 1989 | Water Supply | Significant |
| Ames Long Pond | Bristol | D | 94.7 ac | — | Recreation | Significant |
| Damon Pond | Hampshire | A | 85 ac | 1760 | Recreation | Significant |
| Robbins Pond | Plymouth | A | 85 ac | 1930 | Fire Protection, Stock, Or Small Fish Pond | Significant |
| Fall Brook Reservoir | Worcester | A | 83 ac | 1896 | Water Supply | High |
| South Reservoir | Middlesex | A | 80 ac | 1882 | Water Supply | High |
| Lower Spectacle Pond | Berkshire | D | 70 ac | — | Recreation | Low |
| Muddy Brook Lake | Worcester | D | 69 ac | — | Recreation | Significant |
| Sargent Pond | Worcester | C | 66 ac | — | Recreation | Significant |
| West Branch Walker Brook Lake | Berkshire | A | 65 ac | 2013 | Recreation | Significant |
| Tully Pond | Franklin | A | 65 ac | — | Recreation | Significant |
| Watson Pond | Bristol | C | 65 ac | — | Recreation | Significant |
| Stiles Pond | Essex | D | 60 ac | 1920 | Recreation | Significant |
| Field Pond | Essex | C | 57 ac | 1930 | Recreation | Significant |
| Long Pond | Barnstable | NR | 53 ac | 1966 | Recreation | Low |
| Atkins Reservoir | Franklin | A | 51 ac | 1930 | Water Supply | High |
| Bartlett Pond | Worcester | F | 44 ac | 1885 | Recreation | Low |
| Patch Reservoir | Worcester | NR | 34 ac | 1896 | Recreation | High |
| Card Pond | Berkshire | A | 30.1 ac | 1910 | Recreation | High |
| Nashawannuck Pond | Hampshire | F | 30 ac | — | Recreation | High |
| Windsor Lake | Berkshire | C | 25 ac | 1883 | Recreation | High |
| Wedge Pond | Middlesex | F | 21 ac | 1900 | Recreation | Low |
| Roaring Brook Lake | Franklin | A | 20 ac | 1975 | Water Supply | High |
| Gaston Pond | Worcester | A | 16 ac | 1915 | Recreation | Significant |
| Hallockville Pond | Franklin | A | 16 ac | — | Recreation | Significant |
| Lower Crow Hill Pond | Worcester | A | 13 ac | 1956 | Recreation | Significant |
| Vinica Pond | Hampden | C | 10.6 ac | — | Recreation | Low |
| Billerica Impoundment Lake | Middlesex | NR | 8.6 ac | 1828 | Flood Risk Reduction | Significant |
| Lake Quinsigamond | Worcester | NR | 1.5 ac | 1896 | Recreation | Significant |
| Mashpee Pond | Barnstable | B | 1 ac | — | Other | Significant |
| Congamond Lakes | Hartford | D | — | — | — | Undetermined |
| Cooks Pond | Plymouth | F | — | — | — | Undetermined |
| Fresh Pond | Plymouth | B | — | — | — | Undetermined |
Frequently Asked Questions
How many reservoirs are in Massachusetts?
64 of 829 graded Massachusetts lakes (8%) are man-made reservoirs in the USACE National Inventory of Dams. 51 are rated High or Significant hazard, meaning failure would put downstream lives or property at substantial risk. The oldest matched dam dates to 1760.
What's the largest reservoir in Massachusetts?
The largest matched reservoir in Massachusetts is Wachusett Reservoir in Worcester County at 4,160 acres of normal surface area, impounded by the Wachusett Reservoir Dam (completed 1906).
What's the difference between a reservoir and a natural lake?
A reservoir is a body of water impounded by a man-made dam — typically built for flood control, hydroelectric power, water supply, irrigation, or recreation. A natural lake formed without human intervention, usually from glacial scouring, volcanic activity, or river meandering. Reservoirs typically have shoreline that fluctuates with seasonal water level management, while natural lakes have more stable shorelines. The USACE National Inventory of Dams classifies every regulated dam in the United States, which is how we identify which LakeQuality lakes are actually reservoirs.
What does the hazard class mean?
USACE assigns each dam a hazard potential classification based on what would happen downstream if the dam failed — NOT how likely the dam is to fail. "Low" hazard means dam failure would cause no probable loss of life and only low economic loss. "Significant" means probable loss of life is unlikely but appreciable economic damage would occur. "High" means probable loss of life and significant economic damage. The classification is about consequence, not condition. Many High-hazard dams are perfectly safe; they're rated High because populated areas have grown downstream over time.
Where does this reservoir data come from?
Every reservoir record on this page is matched to the USACE National Inventory of Dams (NID), the federal database of all dams ≥25 ft tall or impounding ≥50 acre-feet, plus any dam that poses a Significant or High hazard regardless of size. The NID is published by the U.S. Army Corps of Engineers and updated annually. Surface area, storage capacity, dam height, and hazard classification come directly from NID records.
Where to stay near Massachusetts reservoirs
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More on reservoirs and water quality
Dam-built reservoirs and natural lakes graded side by side on the same nutrient and algae measurements — the gap, the reasons behind it, and the exceptions.
Surveyed maximum depth against A–F nutrient-and-algae grades: the pattern, the shallow lakes that still grade an A, and why land use beats bathymetry.
How lakes are graded A–F on nutrients and algae using EPA ecoregion condition classes, what each letter means in the water, and why an A is not a clearance.
How phosphorus and nutrient runoff drive algae growth and turn lakes green, where the nutrients come from, and what it means for a lake's grade.
Data source
Reservoir data from the USACE National Inventory of Dams (NID), the federal database of all regulated dams. Dam attributes (height, year completed, storage capacity, hazard class) are matched to LakeQuality lakes by proximity and dam-name similarity. Some lakes may be reservoirs that aren't matched if the dam record uses a name substantially different from our lake name.