Tully Lake
Cortland County, New YorkView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- Impaired · Oxygen depletion (low DO)
- 57 ft max depth
- Limited data
Tully Lake in Cortland County, New York is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 11.9 ft visibility.
- Clarity
- 11.9 ft
- Max depth
- ~57 ft est.
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Watch Tully Lake’s letter
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Why Tully Lake has no grade
Tully Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Tully Lake is Not Rated — not an F. Its 11.9-foot median from 8 readings collected 2020 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by NYSDEC and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
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. Grade methodology: LakeQuality methodology.
What Tully Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11.9 ft of visibility
Swimming Safety
Not ratedLimited data
The letter is 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.
Water quality measurements for Tully Lake
These readings exist but are not enough for an A–F grade — see why.
Good clarity, visible to about 11.9 ft. TSI 41.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.9 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~57 ft est. |
| Average Depth | ~11 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
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.
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
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. LakeQuality has not rated this lake (UNRATED) — the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity.
What is the water quality grade for Tully Lake?
- Tully Lake in Cortland County, New York is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 11.9 ft visibility.
Is Tully Lake safe to swim in?
- The letter is 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)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated 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)