Coonamessett Pond
Barnstable County, MassachusettsView mapDirections
Nutrients and algae sit mid-range for this region.
- Eutrophic
- Impaired · Biotoxins
- #7 of 8 in the county
- 30 ft max depth
- Public access
- Limited data
Coonamessett Pond in Barnstable County, Massachusetts has a water quality grade of C (Fair). Chlorophyll-a (algae): 16.7 µg/L.
- Max depth
- ~30 ft est.
- Type
- Eutrophic
- Chlorophyll-a
- 16.7 µg/L
- Public access
- Yes
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Watch Coonamessett Pond’s letter
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Coonamessett Pond is a productive, nutrient-rich eutrophic lake in Barnstable County, Massachusetts with an estimated average depth of about 30 feet. Water quality is graded C based on 1 sampling years through 2018. Limited fish-species data available. Public access is available. Compared to the 7 other monitored lakes in Barnstable County, Coonamessett Pond ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, MassDEP, last sampled 2018-09-13. 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. Coonamessett Pond is listed impaired under Clean Water Act §303(d) (IR 5) for biotoxins, mercury, nutrients (phosphorus, nitrogen), oxygen depletion (low DO). Check local advisories before you swim.
Water Quality Grade: C (Fair)
No clarity data. Chlorophyll-a 16.7 µg/L. TSI 58. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 16.7 µg/L | Fair |
| Trophic State Index (TSI) | 58 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~30 ft est. |
| Average Depth | ~12 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Massachusetts has not published bathymetry for Coonamessett Pond.
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 Coonamessett Pond
EPA Impairment Status
Coonamessett Pond is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MA96004 · Official waterbody report · Matched by proximity (2.91 km)
County Ranking
Ranked #7 of 8 lakes in Barnstable County
Nearby Lakes in Barnstable County
Frequently asked questions about Coonamessett Pond
Where is Coonamessett Pond?
- Coonamessett Pond is a lake in Barnstable County, Massachusetts. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Coonamessett Pond?
- Coonamessett Pond in Barnstable County, Massachusetts has a water quality grade of C (Fair). Chlorophyll-a (algae): 16.7 µg/L.
Is Coonamessett Pond safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Coonamessett Pond is listed impaired under Clean Water Act §303(d) (IR 5) for biotoxins, mercury, nutrients (phosphorus, nitrogen), oxygen depletion (low DO). Check local advisories before you swim.
How deep is Coonamessett Pond?
- No published bathymetric survey covers Coonamessett Pond, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 30 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Coonamessett Pond 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
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Planning a trip around Cape Cod?
Coonamessett Pond is about 34 miles from Cape Cod National Seashore. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Cape Cod →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, 2018. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Massachusetts Department of Environmental Protection (MassDEP)
MASSDEP3 samples · 2018
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)