Wachusett Lake
Worcester County, Massachusetts130 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Mesotrophic
- Impaired · Mercury
- #10 of 24 in the county
- 47 ft max depth
- Limited data
Wachusett Lake in Worcester County, Massachusetts has a water quality grade of A (Excellent). Chlorophyll-a (algae): 2.4 µg/L. Surface area: 130 acres.
- Max depth
- ~47 ft est.
- Area
- 130 acres
- Type
- Mesotrophic
- Chlorophyll-a
- 2.4 µg/L
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Watch Wachusett Lake’s letter
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Wachusett Lake is a 130-acre mesotrophic lake in Worcester County, Massachusetts with an estimated average depth of about 47 feet. Water quality is graded A based on 1 sampling years through 2017. Compared to the 23 other monitored lakes in Worcester County, Wachusett Lake ranks #10 for water quality.
Source: EPA Water Quality Portal sampling records, MassDEP, last sampled 2017-09-19. 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 A is nutrients and algae, not a swimming clearance. Wachusett Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
No clarity data. Chlorophyll-a 2.4 µg/L. TSI 39. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 2.4 µg/L | Good |
| Trophic State Index (TSI) | 39 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~47 ft est. |
| Average Depth | ~15 ft est. |
| Surface Area | 130 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 Wachusett Lake.
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 Wachusett Lake
Reservoir Info (USACE NID)
Wachusett Lake is a man-made reservoir impounded by the Wachusett Lake Dam (completed 1905), built primarily for flood risk reduction on the Tributary to North Nashua River; earth-type dam, 4 ft tall and 400 ft long.
- Surface area
- 130 ac
- Normal storage
- 187 ac-ft
- Max storage
- 579 ac-ft
- Drainage area
- 1.52 sq mi
- Hazard class
- Significant
- Owner
- City of Fitchburg
Source: USACE National Inventory of Dams, NID ID MA00642 · Operator website
EPA Impairment Status
Wachusett Lake 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 MA81146 · Official waterbody report
County Ranking
Ranked #10 of 24 lakes in Worcester County
Nearby Lakes in Worcester County
Frequently asked questions about Wachusett Lake
Where is Wachusett Lake?
- Wachusett Lake is a lake in Worcester County, Massachusetts. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Wachusett Lake?
- Wachusett Lake in Worcester County, Massachusetts has a water quality grade of A (Excellent). Chlorophyll-a (algae): 2.4 µg/L. Surface area: 130 acres.
Is Wachusett Lake safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Wachusett Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury. Check local advisories before you swim.
How deep is Wachusett Lake?
- No published bathymetric survey covers Wachusett Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 47 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 130 acres.
Explore Wachusett Lake across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Massachusetts's top lakes, each with its grade
Moderate nutrients, good water quality
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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)