Cossayuna Lake is a mesotrophic lake in Washington County, New York. Water quality is graded C based on 1 sampling years through 2020. The lake supports 1 documented fish species including Tiger Muskellunge. Public access is available with 1 public boat landing. Compared to the 2 other monitored lakes in Washington County, Cossayuna Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, New York DNR, last sampled 2020-09-22. Grade methodology: LakeGrade methodology.
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Swimming Safety
Generally safe for swimming, moderate water quality
Water Quality Grade: C, Fair
Moderate clarity, visible to about 8.8 ft. Trophic State Index: 46.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.8 ft | C |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 46 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Cossayuna Lake
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Fish Species
Click a species to see every graded lake where it is documented.
Fishing Cossayuna Lake
Recreation & Access
Location
County Ranking
Ranked #2 of 3 lakes in Washington County
Nearby Lakes in Washington County
Explore Cossayuna Lake across LakeGrade
Fish species and top-graded lakes across New York
Species activity outlook by water temperature and season
Where to stay at New York's top lakes, each with its grade
Moderate nutrients, good water quality
New York's cleanest and most-polluted lakes, ranked
More New York Lake Rankings
Other Grade C Lakes in New York
Mesotrophic Lakes in New York
More records, surveys & data sources
EPA Impairment Status
Cossayuna Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit NY1103-0002 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Cossayuna Lake under Clean Water Act (NPDES) discharge permits.
- Argyle Central High SchoolArgyle · 3.9 mi away · NPDES NY0023663
- Covidien LpArgyle · 4.7 mi away · NPDES NY0110141
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2020-09-22
Monitoring stations: 1