Kasoag Lake is a 58-acre mesotrophic lake in Oswego County, New York. Water quality is graded C based on 1 sampling years through 2020. Compared to the 3 other monitored lakes in Oswego County, Kasoag Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, New York DNR, last sampled 2020-09-13. 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 8.1 ft. Trophic State Index: 47.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.1 ft | C |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 47 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 58 acres |
Where to stay near Kasoag Lake
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Fishing Kasoag Lake
Location
County Ranking
Ranked #2 of 4 lakes in Oswego County
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Moderate nutrients, good water quality
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Reservoir Info (USACE NID)
Kasoag Lake is a man-made reservoir impounded by the Kasoag Lake Dam (completed 1820), built primarily for recreation on the WEST BRANCH FISH CREEK; earth-type dam, 10 ft tall and 180 ft long.
- Surface area
- 58 ac
- Normal storage
- 192 ac-ft
- Max storage
- 192 ac-ft
- Hazard class
- Low
- Owner
- Oswego County
Source: USACE National Inventory of Dams, NID ID NY01423 · Operator website
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 Kasoag Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Omega Wire Inc - Williamstown Ny FacilityWilliamstown · 3.7 mi away · NPDES NY0106780Recent violation
- Salmon River Fish HatcheryAltmar · 4.7 mi away · NPDES NY0109053
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2020-09-13
Monitoring stations: 1