Long Pond
Barnstable County, MassachusettsView mapDirections
Clarity, phosphorus, and algae all sit in the cleanest band for this region.
↑ up from B at the last regrade
- Mesotrophic
- Impaired · Algal growth
- #1 of 8 in the county
- 38 ft max depth
- Limited data
Long Pond in Barnstable County, Massachusetts has a water quality grade of A (Excellent). Chlorophyll-a (algae): 6 µg/L.
- Max depth
- ~38 ft est.
- Type
- Mesotrophic
- Chlorophyll-a
- 6 µg/L
- Trend
- ↓ Declining
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Watch Long Pond’s letter
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Long Pond is a mesotrophic lake in Barnstable County, Massachusetts with an estimated average depth of about 38 feet. Water quality is graded A based on 1 sampling years through 2018. Overall water quality is declining over recent sampling years. Compared to the 7 other monitored lakes in Barnstable County, Long Pond ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, MassDEP, last sampled 2018-09-26. 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. Long Pond is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, biotoxins, habitat alterations, nutrients (phosphorus, nitrogen), pH / acidity, turbidity. Check local advisories before you swim.
Water Quality Grade: A (Excellent)
No clarity data. Chlorophyll-a 6 µg/L. TSI 48. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | 6 µg/L | Good |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~38 ft est. |
| Average Depth | ~10 ft est. |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Massachusetts has not published bathymetry for Long 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 Long Pond
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Chlorophyll-a | ↓ Declining | +23.2 µg/L/yr | 2 |
EPA Impairment Status
Long Pond 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 MA96277 · Official waterbody report · Matched by proximity (1.82 km)
County Ranking
Ranked #1 of 8 lakes in Barnstable County
Nearby Lakes in Barnstable County
Frequently asked questions about Long Pond
Where is Long Pond?
- Long Pond is a lake in Barnstable County, Massachusetts. LakeQuality grades it A for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Long Pond?
- Long Pond in Barnstable County, Massachusetts has a water quality grade of A (Excellent). Chlorophyll-a (algae): 6 µg/L.
Is Long Pond safe to swim in?
- The A is nutrients and algae, not a swimming clearance. Long Pond is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, biotoxins, habitat alterations, nutrients (phosphorus, nitrogen), pH / acidity, turbidity. Check local advisories before you swim.
How deep is Long Pond?
- No published bathymetric survey covers Long Pond, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 38 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Long Pond 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
Massachusetts's cleanest and most-polluted lakes, ranked
Planning a trip around Cape Cod?
Long Pond is about 27 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 A Lakes in Massachusetts
Mesotrophic 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)