Cambridge Reservoir
Middlesex County, Massachusetts546 acresView mapDirections
Nutrients and algae sit mid-range for this region.
↓ down from B at the last regrade
- Eutrophic
- Impaired · Salinity / chlorides
- #4 of 11 in the county
- 52 ft max depth
- Limited data
Cambridge Reservoir in Middlesex County, Massachusetts has a water quality grade of C (Fair). Chlorophyll-a (algae): 7.4 µg/L. Surface area: 546 acres.
- Max depth
- ~52 ft est.
- Area
- 546 acres
- Type
- Eutrophic
- Chlorophyll-a
- 7.4 µg/L
Stays via Stay22
Stays near Cambridge Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Cambridge Reservoir in Middlesex County, Massachusetts — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Cambridge Reservoir
Prices for Sep 11–13, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Massachusetts’s top lakes →
Watch Cambridge Reservoir’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Cambridge Reservoir is a 546-acre productive, nutrient-rich eutrophic lake in Middlesex County, Massachusetts with an estimated average depth of about 52 feet. Water quality is graded C based on 1 sampling years through 2017. Compared to the 10 other monitored lakes in Middlesex County, Cambridge Reservoir ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, MassDEP, last sampled 2017-09-28. Grade methodology: LakeQuality methodology.
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The C is nutrients and algae, not a swimming clearance. Cambridge Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for salinity / chlorides. Check local advisories before you swim.
Water Quality Grade: C (Fair)
No clarity data. Chlorophyll-a 7.4 µg/L. TSI 50. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 7.4 µg/L | Fair |
| Trophic State Index (TSI) | 50 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~52 ft est. |
| Average Depth | ~23 ft est. |
| Surface Area | 546 acres |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Massachusetts has not published bathymetry for Cambridge Reservoir.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Cambridge Reservoir
Reservoir Info (USACE NID)
Cambridge Reservoir is a man-made reservoir impounded by the Cambridge Reservoir Dam (completed 1897), built primarily for water supply on the Hobbs Brook; earth-type dam, 31 ft tall and 1,450 ft long.
- Surface area
- 546 ac
- Normal storage
- 7,360 ac-ft
- Max storage
- 10,380 ac-ft
- Drainage area
- 6.7 sq mi
- Hazard class
- High
- Owner
- City of Cambridge
Source: USACE National Inventory of Dams, NID ID MA00750 · Operator website
EPA Impairment Status
Cambridge Reservoir is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MA72014 · Official waterbody report
County Ranking
Ranked #4 of 11 lakes in Middlesex County
Nearby Lakes in Middlesex County
Frequently asked questions about Cambridge Reservoir
Where is Cambridge Reservoir?
- Cambridge Reservoir is a lake in Middlesex County, Massachusetts. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Cambridge Reservoir?
- Cambridge Reservoir in Middlesex County, Massachusetts has a water quality grade of C (Fair). Chlorophyll-a (algae): 7.4 µg/L. Surface area: 546 acres.
Is Cambridge Reservoir safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Cambridge Reservoir is listed impaired under Clean Water Act §303(d) (IR 5) for salinity / chlorides. Check local advisories before you swim.
How deep is Cambridge Reservoir?
- No published bathymetric survey covers Cambridge Reservoir, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 52 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 546 acres.
Explore Cambridge Reservoir across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Massachusetts's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Massachusetts's cleanest and most-polluted lakes, ranked
More Massachusetts Lake Rankings
Other Grade C Lakes in Massachusetts
Eutrophic Lakes in Massachusetts
Where this data comes from
3 measurements from 1 monitoring station, 2017. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Massachusetts Department of Environmental Protection (MassDEP)
MASSDEP3 samples · 2017
Analytical methods
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)