West Thompson Lake
West Thompson Lake in Windham County, Connecticut has a water quality grade of D (Nutrient-rich). Water clarity: 5.3 ft visibility. Phosphorus: 22 µg/L. Chlorophyll-a (algae): 8.5 µg/L. Surface area: 200 acres.
- Clarity
- 5.3 ft
- Area
- 200 acres
- Type
- Eutrophic
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near West Thompson Lake →
West Thompson Lake is a 200-acre productive, nutrient-rich eutrophic lake in Windham County, Connecticut. Water quality is graded D based on 2 sampling years through 2022. Compared to the 2 other monitored lakes in Windham County, West Thompson Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2022-10-20. Grade methodology: LakeGrade methodology.
Watch West Thompson Lake water quality
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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.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 5.3 ft. Phosphorus level: 22 µg/L. Chlorophyll-a: 8.5 µg/L. Trophic State Index: 51.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.3 ft | Not graded |
| Phosphorus | 22 µg/L | Fair |
| Chlorophyll-a (Algae) | 8.5 µg/L | Poor |
| Trophic State Index (TSI) | 51 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near West Thompson Lake
Compare lakeside cabins, hotels, and vacation rentals near West Thompson Lake in Windham County, Connecticut — 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around West Thompson Lake are listed below.
Top-rated places to stay near West Thompson Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 200 acres |
No bathymetric survey has been published for West Thompson Lake, so its depth is not documented here.
Fishing West Thompson Lake
Reservoir Info (USACE NID)
West Thompson Lake is a man-made reservoir impounded by the West Thompson Dam (completed 1965), built primarily for flood risk reduction on the Quinebaug River; gravity-type dam, 70 ft tall and 2,550 ft long.
- Surface area
- 200 ac
- Normal storage
- 1,200 ac-ft
- Max storage
- 47,800 ac-ft
- Drainage area
- 174 sq mi
- Hazard class
- High
- Owner
- USACE - New England District
All listed purposes: Flood Risk Reduction;Recreation.
Source: USACE National Inventory of Dams, NID ID CT00502 · Operator website
EPA Impairment Status
West Thompson 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 CT3700-00-2+L1_01 · Official waterbody report · Matched by proximity (0.73 km)
County Ranking
Ranked #2 of 3 lakes in Windham County
Nearby Lakes in Windham County
Frequently asked questions about West Thompson Lake
Where is West Thompson Lake?
- West Thompson Lake is a lake in Windham County, Connecticut. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for West Thompson Lake?
- West Thompson Lake in Windham County, Connecticut has a water quality grade of D (Nutrient-rich). Water clarity: 5.3 ft visibility. Phosphorus: 22 µg/L. Chlorophyll-a (algae): 8.5 µg/L. Surface area: 200 acres.
Is West Thompson Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. West Thompson Lake has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 8.5 µg/L. Always check local health department advisories before swimming.
Explore West Thompson Lake across LakeGrade
More Connecticut Lake Rankings
Other Grade D Lakes in Connecticut
Eutrophic Lakes in Connecticut
Where this data comes from
27 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- USGS Connecticut Water Science Center
USGS-CT27 samples · 2022
Analytical methods
- Secchi disk method
- P, wu, WCA, persulfate CF color
- Phosphorus, wu, microKJ ASF, H+
- Plant pigments, sonication & 445
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