Middlesex County, Massachusetts · 42.41°N · Water Quality Report Card
Spy Pond
Spy Pond in Middlesex County, Massachusetts has a water quality grade of D (Poor). Chlorophyll-a (algae): 29.7 µg/L.
- Mean depth
- ~14 ft est.
- Type
- Eutrophic
- Trend
- ↓ Declining
Spy Pond is a productive, nutrient-rich eutrophic lake in Middlesex County, Massachusetts with an estimated average depth of about 14 feet. Water quality is graded D based on 1 sampling years through 2019. Overall water quality is declining over recent sampling years. Compared to the 10 other monitored lakes in Middlesex County, Spy Pond ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, MassDEP, last sampled 2019-10-30. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D (Poor)
No clarity data. Chlorophyll-a: 29.7 µg/L. Trophic State Index: 64.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 29.7 µg/L | Poor |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~14 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Massachusetts has not published bathymetry for Spy Pond.
Where to stay near Spy Pond
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Fishing Spy Pond
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.289 m/yr | 5 |
Location
County Ranking
Ranked #7 of 11 lakes in Middlesex County
Nearby Lakes in Middlesex County
Explore Spy Pond across LakeGrade
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High nutrients, frequent algae, reduced clarity
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Other Grade D Lakes in Massachusetts
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More records, surveys & data sources
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.
Where this data comes from
10 measurements from 2 monitoring stations, 2019. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Massachusetts Department of Environmental Protection (MassDEP)
MASSDEP10 samples · 2019
Analytical methods
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (2)
Grade thresholds come from the U.S. EPA National Lakes Assessment 2022 Technical Support Document (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated.
Data Sources
Water quality data from the EPA Water Quality Portal
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2019-10-30
Monitoring stations: 2