South Lake is a 499-acre cold, clear oligotrophic lake in Herkimer County, New York. Water quality is graded A based on 1 sampling years through 2023. Overall water quality is improving over recent sampling years. The lake supports 1 documented fish species including Brook Trout. Public access is available. Compared to the 6 other monitored lakes in Herkimer County, South Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, New York DNR, last sampled 2023-07-06. Grade methodology: LakeGrade methodology.
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
No clarity data. Phosphorus level: 4 µg/L. Trophic State Index: 24.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 4 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 24 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 499 acres |
| Public Access | Yes |
Where to stay near South Lake
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Fish Species
Click a species to see every graded lake where it is documented.
Fishing South Lake
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↑ Improving | -11.9 µg/L/yr | 4 |
Water Temperature
South Lake averages about 73°F at the surface in summer, usually warmest in Jul (about 73°F) and coldest in Feb (about 33°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 32 field readings (2017–2022) via the EPA Water Quality Portal. See the full South Lake water temperature breakdown →
Location
County Ranking
Ranked #1 of 7 lakes in Herkimer County
Nearby Lakes in Herkimer County
Explore South Lake across LakeGrade
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Species activity outlook by water temperature and season
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Low nutrients, clear water, excellent for swimming
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More records, surveys & data sources
Reservoir Info (USACE NID)
South Lake is a man-made reservoir impounded by the South Lake Dam (completed 1901), built primarily for recreation on the SOUTH BRANCH BLACK RIVER; earth-type dam, 30 ft tall and 380 ft long.
- Surface area
- 499 ac
- Normal storage
- 4,840 ac-ft
- Max storage
- 5,480 ac-ft
- Hazard class
- High
- Owner
- New York State Canal Corporation
Source: USACE National Inventory of Dams, NID ID NY00317 · Operator website
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Data Sources
Water quality data from the EPA Water Quality Portal
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2023-07-06
Monitoring stations: 1