Tully Lake
Cortland County, New YorkView mapDirections
NY DEC publishes the water-quality measurements for Tully Lake. Here is what has been measured.
- Impaired · Oxygen depletion (low DO)
- 57 ft max depth
- Limited data
Tully Lake in Cortland County, New York has water-quality measurements published by NY DEC, shown here as reported. Water clarity: 11.9 ft visibility.
Tully Lake is a lake in Cortland County, New York with an estimated average depth of about 57 feet.
Source: EPA Water Quality Portal sampling records, NYSDEC, last sampled 2020-09-20. Methodology: how these readings are compared.
What Tully Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11.9 ft of visibility
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Tully Lake is listed impaired under Clean Water Act §303(d) (IR 5) for oxygen depletion (low DO). Check local advisories before you swim.
Whether Tully Lake is safe to swim in today is a call for the New York Department of Environmental Conservation and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Tully Lake
These are the measurements NY DEC publishes for Tully Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 11.9 ft. TSI 41.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 11.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 41 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Tully Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~57 ft est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. New York has not published bathymetry for Tully Lake.
Lake Size & Watershed
Watershed (drainage) area
11 sq mi
HydroLAKES / HydroSHEDS
Surface area
178 acres
HydroLAKES / HydroSHEDS
Shoreline
3.9 mi
HydroLAKES / HydroSHEDS
Elevation
1,188 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
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Fishing Tully Lake
EPA Impairment Status
Tully Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life.
Source: EPA ATTAINS assessment unit NY0602-0018 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Tully Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Tully (V) StpTully · 1.9 mi away · NPDES NY0026824Recent violation
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.
Nearby Lakes in Cortland County
Frequently asked questions about Tully Lake
Where is Tully Lake?
- Tully Lake is a lake in Cortland County, New York. Its water-quality measurements are published by NY DEC and shown on this page as reported.
What is the water quality of Tully Lake?
- Tully Lake in Cortland County, New York has water-quality measurements published by NY DEC, shown here as reported. Water clarity: 11.9 ft visibility.
Is Tully Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Tully Lake is listed impaired under Clean Water Act §303(d) (IR 5) for oxygen depletion (low DO). Check local advisories before you swim.
How deep is Tully Lake?
- No published bathymetric survey covers Tully Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 57 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
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Where this data comes from
8 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- North American Lake Management Society
NALMS8 samples · 2020
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)