Dams in Massachusetts: Complete Map of All 1,340 Massachusetts Dams
Massachusetts has 1,340 dams in the National Inventory of Dams — and 336 are classified as high hazard (25% of the state’s total), meaning failure would likely cause loss of life. 47 Massachusetts dams are both high-hazard and in poor or unsatisfactory condition.
Use the interactive Massachusetts dams map below to explore every dam in the state, color-coded by hazard level. Click any dam for its condition assessment, last inspection date, and Emergency Action Plan status. Or view the full US Dams interactive map to compare Massachusetts to every other state.
Hazard
Condition
Purpose
Massachusetts Dams by the Numbers
- 1,340 total dams in Massachusetts
- 336 high hazard — failure would likely cause loss of life
- 619 significant hazard
- 385 low hazard
- 337 in poor or unsatisfactory condition (289 poor, 48 unsatisfactory)
- 47 Massachusetts dams are both high-hazard AND in poor/unsatisfactory condition
Data source: US Army Corps of Engineers, National Inventory of Dams (NID).
The Tallest Dams in Massachusetts
The tallest dam in Massachusetts is Cobble Mountain Reservoir Dam at 245 feet, completed in 1930. The 10 tallest Massachusetts dams from the National Inventory of Dams:
| Dam | Height | Year | Primary Purpose | Condition | County |
|---|---|---|---|---|---|
| Cobble Mountain Reservoir Dam | 245 ft | 1930 | Water Supply | Satisfactory | Hampden |
| Quabbin Winsor Dam | 170 ft | 1939 | Water Supply | Satisfactory | Hampshire |
| Littleville Dam | 164 ft | 1965 | Flood Risk Reduction | Not Available | Hampden |
| Bear Swamp – North Dike | 155 ft | 1974 | Hydroelectric | Satisfactory | Franklin |
| Knightville Dam | 150 ft | 1941 | Flood Risk Reduction | Not Available | Hampshire |
| Northfield Mt. – Main Dam | 145 ft | 1973 | Hydroelectric | Satisfactory | Franklin |
| Bear Swamp – South Dike | 140 ft | 1974 | Hydroelectric | Satisfactory | Franklin |
| Quabbin Goodnough Dike | 135 ft | 1938 | Water Supply | Satisfactory | Hampshire |
| Fife Brook | 130 ft | 1974 | Hydroelectric | Satisfactory | Franklin |
| Tighe Carmody Reservoir Dam | 130 ft | 1955 | Water Supply | Satisfactory | Hampshire |
High-Hazard Massachusetts Dams in Poor Condition
The most concerning dams are those classified as high-hazard that also carry a Poor or Unsatisfactory condition rating — 47 dams in Massachusetts. Notable examples:
- Notch Reservoir Dam (64 ft, Berkshire County) — Water Supply, Poor condition
- South Reservoir Dam (45 ft, Middlesex County) — Water Supply, Poor condition
- Haskell Pond Dam (43 ft, Essex County) — Water Supply, Poor condition
- Sandwash Reservoir Dam (41 ft, Berkshire County) — Water Supply, Poor condition
- Overlook Reservoir Dam (41 ft, Worcester County) — Poor condition
Filter the interactive US Dams map by hazard and condition to see all of them on one view.
Dam Safety in Massachusetts
Dam safety in Massachusetts is overseen by the state dam safety program, in coordination with federal regulators: the US Army Corps of Engineers, the Bureau of Reclamation (for federal water projects), the Tennessee Valley Authority where applicable, and the Federal Energy Regulatory Commission (FERC) for licensed hydropower dams. Emergency Action Plans are typically required for high-hazard dams under state regulations.
Frequently Asked Questions
How many dams are in Massachusetts?
Massachusetts has 1,340 dams in the National Inventory of Dams tracked by the US Army Corps of Engineers: 336 high hazard, 619 significant hazard, and 385 low hazard.
What is the tallest dam in Massachusetts?
The tallest dam in Massachusetts is Cobble Mountain Reservoir Dam at 245 feet, completed in 1930. It is primarily a water supply structure.
How many Massachusetts dams are in poor condition?
337 Massachusetts dams are currently rated as being in Poor or Unsatisfactory condition. Of those, 47 are also classified as high-hazard — meaning failure would likely cause loss of life.
