Upper Mystic Lake
Middlesex County, Massachusetts185 acresView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- Impaired · Algal growth
- 54 ft max depth
- Public access
- Limited data
Upper Mystic Lake in Middlesex County, Massachusetts is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 28.1 µg/L. Surface area: 185 acres.
- Max depth
- ~54 ft est.
- Area
- 185 acres
- Phosphorus
- 28.1 µg/L
- Trend
- ↑ Improving
- Public access
- Yes
Stays via Stay22
Stays near Upper Mystic Lake
Compare lakeside cabins, hotels, and vacation rentals near Upper Mystic Lake in Middlesex County, Massachusetts — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Upper Mystic Lake
Prices for Sep 11–13, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip? Cabins and lodging at Upper Mystic Lake → · more Massachusetts lake trips
Watch Upper Mystic Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Why Upper Mystic Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Upper Mystic Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded phosphorus, but not water clarity and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MassDEP and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
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. Grade methodology: LakeQuality methodology.
What Upper Mystic Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming Safety
Not ratedBacteria advisory
The letter is not a swimming clearance. Upper Mystic Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pathogens (E. coli, fecal). Check local advisories before you swim.
Water quality measurements for Upper Mystic Lake
These readings exist but are not enough for an A–F grade — see why.
No clarity data. Phosphorus 28.1 µg/L. TSI 52.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 28.1 µg/L | Not graded |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 52 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Current Conditions
USGS snapshot Sep 7, 2026, 3:00 PM from gauge 01102505 (UPPER MYSTIC LAKE, GATE HOUSE, AT WINCHESTER, MA). Station page ↗ — a live reading replaces this snapshot when the gauge responds. Missing live data is not an all-clear.
→ Upper Mystic Lake water level: the live USGS gauge reading
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~54 ft est. |
| Average Depth | ~17 ft est. |
| Surface Area | 185 acres |
| 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 Upper Mystic Lake.
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.
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
Fishing Upper Mystic Lake
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↑ Improving | -2.23 µg/L/yr | 4 |
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
EPA Impairment Status
Upper Mystic Lake 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 MA71043 · Official waterbody report
Graded lakes near Upper Mystic Lake
Upper Mystic Lake has no grade, but these lakes within a short drive do.
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. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Upper Mystic Lake?
- Upper Mystic Lake in Middlesex County, Massachusetts is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 28.1 µg/L. Surface area: 185 acres.
Is Upper Mystic Lake safe to swim in?
- The letter is not a swimming clearance. Upper Mystic Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, nutrients (phosphorus, nitrogen), oxygen depletion (low DO), pathogens (E. coli, fecal). 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.
What is the water level at Upper Mystic Lake?
- The USGS snapshot on this page for Upper Mystic Lake is 114.4 ft of water-surface elevation, recorded Sep 7, 2026, 3:00 PM at gauge 01102505. Current Conditions hydrates a live NWIS reading from that same station when the gauge responds. A missed live fetch is not an all-clear.
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.
Explore Upper Mystic Lake across LakeQuality
More Massachusetts Lake Rankings
Other Lakes in Massachusetts
Eutrophic Lakes in Massachusetts
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)
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)
Named boat-access points from the USGS National Boat Ramps inventory