Upper Mystic Lake
Middlesex County, Massachusetts185 acresView mapDirections
MassDEP publishes the water-quality measurements for Upper Mystic Lake. Here is what has been measured.
- 54 ft max depth
- Public access
- Limited data
Upper Mystic Lake in Middlesex County, Massachusetts has water-quality measurements published by MassDEP, shown here as reported. Phosphorus: 28.1 µg/L. Surface area: 185 acres.
Upper Mystic Lake is a 185-acre lake in Middlesex County, Massachusetts with an estimated average depth of about 54 feet. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, MassDEP, last sampled 2015-06-17. Methodology: how these readings are compared.
What Upper Mystic Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Upper Mystic Lake 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 Upper Mystic Lake
These are the measurements MassDEP publishes for Upper Mystic Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 28.1 µg/L. TSI 52.
| 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 | 28.1µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 52 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Upper Mystic Lake
Answers come straight from the public measurements and survey records on this page.
→ Upper Mystic Lake water level: the live USGS gauge reading
Lake Details
Max depth
~54 ft est.
Surface area
185 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 Upper Mystic Lake.
Lake Size & Watershed
Watershed (drainage) area
49 sq mi
HydroLAKES / HydroSHEDS
Shoreline
3.1 mi
HydroLAKES / HydroSHEDS
Elevation
10 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.
Recreation & Access
- Mystic Lake (Upper)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
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Stays near Upper Mystic Lake
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Fishing Upper Mystic Lake
Water Quality Trend: Improving
Based on 4 years of monitoring (2012–2015).
Phosphorus
Improving-2.23 µg/L/yr4 years
Reservoir Info (USACE NID)
Upper Mystic Lake is a man-made reservoir impounded by the Upper Mystic Lake Dam (completed 1860), built primarily for flood risk reduction on the Aberjona River, tributary to Mystic River; earth-type dam, 16 ft tall and 1,560 ft long.
- Surface area
- 185 ac
- Normal storage
- 1,300 ac-ft
- Max storage
- 2,800 ac-ft
- Drainage area
- 27.6 sq mi
- Hazard class
- Significant
- Owner
- MA Department of Conservation and Recreation
All listed purposes: Flood Risk Reduction;Recreation.
Source: USACE National Inventory of Dams, NID ID MA00769 · Operator website
Nearby Lakes in Middlesex County
Frequently asked questions about Upper Mystic Lake
Where is Upper Mystic Lake?
- Upper Mystic Lake 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 Upper Mystic Lake?
- Upper Mystic Lake in Middlesex County, Massachusetts has water-quality measurements published by MassDEP, shown here as reported. Phosphorus: 28.1 µg/L. Surface area: 185 acres.
Is Upper Mystic Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Upper Mystic Lake?
- No published bathymetric survey covers Upper Mystic Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 54 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 185 acres.
Are there boat ramps on Upper Mystic Lake?
- Upper Mystic Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Mystic Lake (Upper). Public access is listed as yes.
Can I fish at Upper Mystic Lake?
- Upper Mystic Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. 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
40 measurements from 1 monitoring station, 2012–2015. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Mystic River Watershed Association (Massachusetts)
MYRWA40 samples · 2012–2015
Analytical methods
- 4500 P J ~ Persulfate Method for Simultaneous Determination of Total Nitrogen and Total Phosphorus
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory