New York reservoir · state assessment record
Canandaigua Lake
Assessment decisions reported by New York to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2022 reporting cycle, a cycle that carries an interim EPA action. Every determination below was filed by EPA rather than by New York.
- 10,528
- Assessed acres
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
Canandaigua Lake, a reservoir in New York, is assessed as not supporting one or more designated uses, with one listed impairment cause in the state's most recent Integrated Report cycle (2022), a cycle that carries an interim EPA action. By assessed acreage it sits among the largest 1% of assessed lakes nationally (38,628 lakes with a filed area); its impairment list is among the longest nationally (one listed cause vs 23,610 assessed lakes).
- Not Supporting
- overall status
- P99
- Assessed size nationally
- P20
- Shorter cause list
Assessment verdicts are EPA's decisions as reported to EPA ATTAINS; PlainLakes renders them without modification.
A composite of this record's EPA ATTAINS designated-use verdicts, filed impairment count, and assessment currency, weighted and benchmarked against the national corpus of assessed active waterbodies. This is a water-quality standing, not a human-recreation or property-value judgment, and dimensions with no filed verdict drop out rather than count against the score.
Canandaigua Lake against the ATTAINS register
Paragraphs are selected by this unit's percentiles and use matrix: different lakes lead with different dimensions. Figures are ATTAINS / portal register arithmetic, not advice.
The signature stat: assessed size
The number that most separates Canandaigua Lake nationally is assessed size: 10,528 acres, larger than 99% of the 38,628 lake-type units with an area on file.
Every ruled-on use is not supporting
On the uses this filer ruled on, recreation, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Canandaigua Lake: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Canandaigua Lake. Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
Overall status: not supporting
The filer's overall status for Canandaigua Lake is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
Typical cause-list length
1 listed cause is a middle-tercile list length among assessed lake-type units. Look to IR category and use outcomes for the distinctive reading.
According to the U.S. Environmental Protection Agency's ATTAINS program, New York carries 2,231 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Canandaigua Lake without modification. See our methodology for reporting-unit limits and gauge linking rules.
The record
Designated-use assessments
Fully Supporting and Not Supporting are EPA's definitive verdicts; other entries mean the use was not conclusively assessed in this cycle.
| Designated use | Group | Verdict |
|---|---|---|
| Primary Contact Recreation | Recreation | Not Supporting Filed by EPA |
| Secondary Contact Recreation | Recreation | Not Supporting Filed by EPA |
| Water Supply | Drinking-water supply designation | Not Supporting Filed by EPA |
| Fishing | Aquatic-life or related | Insufficient Information |
The record
Listed impairment causes
Causes EPA listed as impairing designated uses of this reservoir, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Harmful Algal Blooms Filed by EPA | Primary Contact Recreation, Secondary Contact Recreation, Water Supply | 2022 | TMDL priority: Medium |
Reading the record
Where Canandaigua Lake sits among peers
55% of New York's lakes assessed this deeply also had no use supported
EPA ruled definitively on 3 designated uses at Canandaigua Lake and found none of them supported. The dataset shows 58 New York lakes judged to that same depth.
New York's assessed lakes are most often judged on 1 use; this one was judged on 3.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 28 | 35 | 16 | 0 | 0 |
| Mixed | Not possible | 1 | 10 | 6 | 0 |
| None supported | 406 | 86 | 32 (this record) | 10 | 0 |
Ringed cell: Canandaigua Lake. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Canandaigua Lake is one of 2,231 lake-type waterbodies reported to EPA from New York, and one of 428 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 10,528 assessed acres it ranks 300th by assessed size among the 38,628 lakes the dataset carries an area for, counting a state’s repeated filings of one water once, behind 299 lakes with a larger one.
Awaiting a filing
The state has not yet filed a definitive fish-consumption verdict and a definitive aquatic-life verdict for this record; those fields populate when it reports them in a future Integrated Report cycle.
Why no water-level record
Canandaigua Lake has no daily USGS water-level or reservoir-storage series on this page because NWIS lists a lake monitoring site named for the waterbody, but the site is not active, and PlainLakes ingests only the active inventory, so there is no series to attach. How PlainLakes links gauges.
In context
Where Canandaigua Lake sits nationally
Assessed size among U.S. lakes
Distribution of assessed acreage across ATTAINS lakes filed with an area, counting a state’s repeated filings of one water once
10,528 Top 1% larger than 99% of 38,628 lakes
lakes the dataset carries an area for, counting a state’s repeated filings of one water once, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
Listed causes vs waterbodies carrying a verdict
How many impairment causes U.S. waterbodies with a reported verdict carry
1 Longer than most more listed causes than 49% of 23,610 waterbodies carrying a verdict
named waterbodies carrying a verdict, bucketed by value
Source EPA ATTAINS · Reporting cycles 1987–2026
In both charts each bar is a band and taller bars hold more waterbodies; the dashed line and filled bar mark Canandaigua Lake. Hover or tap any bar for its full count and share.
In context
New York context
ATTAINS carries 2,231 lake-type waterbodies in New York, 563 assessed as not supporting at least one use and 79 fully supporting. Among the 428 indexed units there, Canandaigua Lake ranks 129th by listed-cause count (one listed cause) and 6th by assessed size among the 392 with an area filed; it sits in the not-supporting set (563 statewide) . Its listed causes (Harmful Algal Blooms) sit outside New York's top-five list, which is led by pH.
| Other large assessed lakes in New York | Assessed acres |
|---|---|
| Lake Champlain, Main Lake, Middle Not Supporting | 54,972 |
| Oneida Lake Not Supporting | 51,269 |
| Seneca Lake, Main Lake, Middle Fully Supporting | 40,290 |
| Cayuga Lake, Main Lake, Mid-South Fully Supporting | 33,083 |
| Lake George Not Supporting | 28,523 |
| Great Sacandaga Lake Not Supporting | 24,722 |
Peers near Canandaigua Lake's size or cause load
Similar assessed acres
Nearest filed extents (10,528 acres here).
- Toledo Bend Reservoir · 10,530 acres · TX
- Coosa River (Lay Lake) · 10,559 acres · AL
- Lake Meredith · 10,495 acres · TX
- Lake Koshkonong · 10,596 acres · WI
Similar cause load
Nearest listed-cause counts (1 here). Peers already in the acreage column are omitted.
- Aaron · 1 causes · MN
- Aaron River Reservoir · 1 causes · MA
- Abbotts Creek (including Lexington-Thomasville Water Supply Reservoir at normal reservoir elevation, Tom-A-Lex Lake) · 1 causes · NC
- Abeniki Lake · 1 causes · NH
What to do with this record
- Assessment verdicts are cycle-based, not real-time. For fish-consumption decisions, your state advisory program is the binding source. Consumption status guide
- Impairment listings follow the Clean Water Act 303(d) process; a listing is a regulatory finding, not a closure notice. 303(d) explained
PlainLakes renders state assessment decisions and federal gauge observations without modification. It does not issue advisories.
Assessment decisions on this page are rendered directly from state Integrated Report records in EPA's ATTAINS system; gauge figures are daily-value observations from the USGS National Water Information System, no number is typed in by an editor. Overall status, use verdicts, and causes are the state's reported decisions for assessment unit NY0704-0001. Counts and percentiles are computed across all lake-type records PlainLakes ingests from ATTAINS. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of 2026-08-17. Primary sources: EPA ATTAINS and USGS National Water Information System.