Lake Mohegan is a productive, nutrient-rich eutrophic lake in Westchester County, New York. Water quality is graded D based on 1 sampling years through 2020. Compared to the 5 other monitored lakes in Westchester County, Lake Mohegan ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, New York DNR, last sampled 2020-09-28. 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
Murky, only visible to about 3.4 ft. Trophic State Index: 59.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.4 ft | D |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 59 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake Mohegan
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Fishing Lake Mohegan
Location
County Ranking
Ranked #2 of 6 lakes in Westchester County
Nearby Lakes in Westchester County
Explore Lake Mohegan across LakeGrade
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Species activity outlook by water temperature and season
Where to stay at New York's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
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Other Grade D Lakes in New York
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More records, surveys & data sources
EPA Impairment Status
Lake Mohegan 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 NY1301-0149 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
9 EPA-permitted facilities operate within about 5 miles of Lake Mohegan under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 3 facilities have a reported Clean Water Act violation in the past three years.
- Yorktown Heights Sd WwtpYorktown Heights · 4.4 mi away · NPDES NY0026743MajorRecent violation
- Valeria Sewer Treatment PlantCortlandt, Town Of · 4.5 mi away · NPDES NY0035050Recent violation
- Coachlight Square Wwtp Aka Kings FerryMontrose · 4.6 mi away · NPDES NY0037036Recent violation
- Mobil Cortlandt Ss#06-G6JPeekskill · 2 mi away · NPDES NY0166413
- Mobil SS06-G7J - YorktownYorktown Heights · 2.1 mi away · NPDES NY0250317
- Lakeside Village StpYorktown Heights · 2.1 mi away · NPDES NY0026727
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
Most recent sample: 2020-09-28
Monitoring stations: 1