Nabnasset Pond
Middlesex County, Massachusetts146 acresView mapDirections
MassDEP publishes the water-quality measurements for Nabnasset Pond. Here is what has been measured.
- Mesotrophic
- Impaired · Algal growth
- 29 ft max depth
- Public access
- Limited data
Nabnasset Pond in Middlesex County, Massachusetts has water-quality measurements published by MassDEP, shown here as reported. Chlorophyll-a (algae): 5.7 µg/L. Surface area: 146 acres.
Nabnasset Pond is a 146-acre mesotrophic lake in Middlesex County, Massachusetts with an estimated average depth of about 29 feet. Limited fish-species data available. Public access is available. Compared to the 10 other monitored lakes in Middlesex County, Nabnasset Pond ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, MassDEP, last sampled 2017-08-24. Methodology: how these readings are compared.
Nabnasset Pond covers about 150 acres in Middlesex County. Vrbo is where to look for cabins and lake homes around Nabnasset Pond, and Booking.com and Expedia search hotels near the lake for your dates.
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Nabnasset Pond is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, mercury, nuisance exotic species. Check local advisories before you swim.
Whether Nabnasset Pond is safe to swim in today is a call for the Massachusetts Department of Environmental Protection and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Nabnasset Pond
These are the measurements MassDEP publishes for Nabnasset Pond, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Chlorophyll-a 5.7 µg/L. TSI 48.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | 5.7µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 48 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Nabnasset Pond
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~29 ft est.
Surface area
146 acres
Public access
Yes
Listed by MassDEP
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Massachusetts has not published bathymetry for Nabnasset Pond.
Lake Size & Watershed
Watershed (drainage) area
1 sq mi
HydroLAKES / HydroSHEDS
Shoreline
2.3 mi
HydroLAKES / HydroSHEDS
Elevation
177 ft
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.
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Stays near Nabnasset Pond
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Fishing Nabnasset Pond
Reservoir Info (USACE NID)
Nabnasset Pond is a man-made reservoir impounded by the Nabnasset Pond Dam (completed 1926), built primarily for recreation on the Blue Brook to Stony Brook; earth-type dam, 14 ft tall and 200 ft long.
- Surface area
- 146 ac
- Normal storage
- 961 ac-ft
- Max storage
- 1,454 ac-ft
- Drainage area
- 1.73 sq mi
- Hazard class
- Significant
- Owner
- Town of Westford
Source: USACE National Inventory of Dams, NID ID MA01182 · Operator website
EPA Impairment Status
Nabnasset Pond is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Fish consumption, Recreation, Other.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MA84044 · Official waterbody report
Nearby Lakes in Middlesex County
Frequently asked questions about Nabnasset Pond
Where is Nabnasset Pond?
- Nabnasset Pond is a lake in Middlesex County, Massachusetts. Its water-quality measurements are published by MassDEP and shown on this page as reported.
What is the water quality of Nabnasset Pond?
- Nabnasset Pond in Middlesex County, Massachusetts has water-quality measurements published by MassDEP, shown here as reported. Chlorophyll-a (algae): 5.7 µg/L. Surface area: 146 acres.
Is Nabnasset Pond safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Nabnasset Pond is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, mercury, nuisance exotic species. Check local advisories before you swim.
How deep is Nabnasset Pond?
- No published bathymetric survey covers Nabnasset Pond, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 29 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 146 acres.
Can I fish at Nabnasset Pond?
- Public access to Nabnasset Pond is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Massachusetts's fish and wildlife agency, so check its current regulations before you go.
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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)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)