Lake Pearl
Norfolk County, Massachusetts288 acresView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
- Oligotrophic
- Impaired · Nuisance exotic species
- #1 of 2 in the county
- 42 ft max depth
- Limited data
Lake Pearl in Norfolk County, Massachusetts has a water quality grade of A (Excellent). Chlorophyll-a (algae): 1.8 µg/L. Surface area: 288 acres.
- Max depth
- ~42 ft est.
- Area
- 288 acres
- Type
- Oligotrophic
- Chlorophyll-a
- 1.8 µg/L
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Watch Lake Pearl’s letter
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Lake Pearl is a 288-acre cold, clear oligotrophic lake in Norfolk County, Massachusetts with an estimated average depth of about 42 feet. Water quality is graded A based on 1 sampling years through 2017. Compared to the 1 other monitored lakes in Norfolk County, Lake Pearl ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, MassDEP, last sampled 2017-08-29. 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. Lake Pearl is listed impaired under Clean Water Act §303(d) (IR 4A) for nuisance exotic species, oxygen depletion (low DO). Check local advisories before you swim.
Water Quality Grade: A (Excellent)
No clarity data. Chlorophyll-a 1.8 µg/L. TSI 36. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 1.8 µg/L | Good |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~42 ft est. |
| Average Depth | ~15 ft est. |
| Surface Area | 288 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 Lake Pearl.
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 Lake Pearl
Reservoir Info (USACE NID)
Lake Pearl is a man-made reservoir impounded by the Red Dam (completed 1920), built primarily for recreation on the Eagle Brook; earth-type dam, 10 ft tall and 270 ft long.
- Surface area
- 288 ac
- Normal storage
- 1,400 ac-ft
- Max storage
- 2,260 ac-ft
- Drainage area
- 7.46 sq mi
- Hazard class
- Significant
- Owner
- Town of Wrentham
Source: USACE National Inventory of Dams, NID ID MA00170 · Operator website · Matched by proximity (0.41 km)
EPA Impairment Status
Lake Pearl is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MA72092 · Official waterbody report
County Ranking
Ranked #1 of 2 lakes in Norfolk County
Nearby Lakes in Norfolk County
Frequently asked questions about Lake Pearl
Where is Lake Pearl?
- Lake Pearl is a lake in Norfolk County, Massachusetts. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Pearl?
- Lake Pearl in Norfolk County, Massachusetts has a water quality grade of A (Excellent). Chlorophyll-a (algae): 1.8 µg/L. Surface area: 288 acres.
Is Lake Pearl safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Lake Pearl is listed impaired under Clean Water Act §303(d) (IR 4A) for nuisance exotic species, oxygen depletion (low DO). Check local advisories before you swim.
How deep is Lake Pearl?
- No published bathymetric survey covers Lake Pearl, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 42 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 288 acres.
Explore Lake Pearl across LakeQuality
Species activity outlook by water temperature and season
Where to stay at Massachusetts's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
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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)