Wisconsin lake · state assessment record
Lake Denoon
In Racine and Waukesha counties. Assessment decisions reported by Wisconsin to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2026 reporting cycle.
- 167
- Assessed acres
- Lake, Freshwater
- Water type
- Eutrophic
- Reported trophic class
This waterbody in one line
Lake Denoon, a lake in Wisconsin, is assessed as not supporting one or more designated uses, with one listed impairment cause in the state's most recent Integrated Report cycle (2026). By assessed acreage it sits in the upper quartile by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (one listed cause vs 23,610 assessed lakes). Aquatic life is assessed as not supporting.
- Not Supporting
- overall status
- P79
- Assessed size nationally
- P20
- Shorter cause list
- Not Supporting
- aquatic life
Assessment verdicts are the state agency'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.
Where Lake Denoon stands in the filed 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: in-state cause rank
Inside Wisconsin, cause-list rank 252 of 1,219 is mid-pack, the state peer table is not driven by an extreme list length here.
Every filed use falls short
On the uses this filer ruled on, recreation, aquatic life, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Lake Denoon: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Lake Denoon. 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 Lake Denoon is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
Large assessed unit
At 167.2 acres, Lake Denoon clears the upper tercile of assessed lake-type units with an area on file (8,273 still larger). Size comparisons use the portal's deduplicated lake ranking population, not raw ATTAINS row counts.
According to the U.S. Environmental Protection Agency's ATTAINS program, Wisconsin carries 19,871 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Lake Denoon without modification. See our methodology for reporting-unit limits and gauge linking rules.
The record
Designated-use assessments
Fully Supporting and Not Supporting are the state's definitive verdicts; other entries mean the use was not conclusively assessed in this cycle. The latest monitoring Wisconsin filed against this record runs through 2025. For the definitive verdicts on this record, Wisconsin filed the assessment basis as Monitored Data. Those are EPA's own words, not PlainLakes' summary of them. Wisconsin filed its own confidence on the one definitive verdict it rated: Low and Good. That rating is the filer's, in EPA's own field, and EPA publishes no definition of the four words it offers.
| Designated use | Group | Verdict |
|---|---|---|
| Fish and Aquatic Life | Aquatic-life or related | Not Supporting Filer confidence: Low on physical/chemical; Good on biological |
| Recreation | Recreation | Not Supporting |
| Fish Consumption | Fish-consumption or fishery | Not Assessed |
| Public Health and Welfare | Recreation | Not Assessed |
| Wildlife | Aquatic-life or related | Not Assessed |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this lake, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Phosphorus, Total | Fish and Aquatic Life; Recreation | 2026 | TMDL priority: High |
Probable sources named by the state
Each source below is listed under the cause the state filed it against, and carries the word the state filed with it — confirmed, or suspected.
- Phosphorus, Total
- Non-Point Source (suspected)
Reading the record
Cleanup queue for Lake Denoon
1 listed cause ranked High in the TMDL queue, still without a plan
Wisconsin ranked Phosphorus, Total high in its TMDL development queue, and no cleanup plan is on file for that listing yet. That queue rank is the state's own scheduling signal, not an EPA national rule.
A High ranking names a position in the state's plan-writing queue; it is not a measure of how impaired the water is. How listing and cleanup work.
Scale and rank
Lake Denoon is one of 19,871 lake-type waterbodies reported to EPA from Wisconsin, and one of 1,219 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 167 assessed acres it ranks 8,274th 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 8,273 lakes with a larger one.
Not yet on record
The state has not yet filed a definitive fish-consumption verdict for this record; that field populates when it reports it in a future Integrated Report cycle.
Reported trophic class
Eutrophic is the trophic class the filing agency reported to EPA ATTAINS for this assessment unit. It describes nutrient enrichment, not whether the water is safe, and it is not a PlainLakes inference. What the trophic scale measures.
In context
Where Lake Denoon 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
167 Top 21% larger than 79% 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 Lake Denoon. Hover or tap any bar for its full count and share.
In context
Wisconsin context
ATTAINS carries 19,871 lake-type waterbodies in Wisconsin, 493 assessed as not supporting at least one use and 4,225 fully supporting. Among the 1,219 indexed units there, Lake Denoon ranks 252nd by listed-cause count (one listed cause) and 543rd by assessed size among the 1,170 with an area filed; it sits in the not-supporting set (493 statewide) . Its listed causes include Phosphorus, Total, which also appears among Wisconsin's most-filed impairment causes (led by Phosphorus, Total).
| Other large assessed lakes in Wisconsin | Assessed acres |
|---|---|
| Lake Winnebago Not Supporting | 131,942 |
| Lake Pepin Not Supporting | 25,503 |
| Petenwell Lake Not Supporting | 23,001 |
| Lake Poygan Not Supporting | 14,024 |
| Lake Chippewa Fully Supporting | 13,616 |
| Turtle Flambeau Flowage Not Supporting | 12,943 |
Peers near Lake Denoon's size or cause load
Similar assessed acres
Nearest filed extents (167 acres here).
- Beaver Dam Lake · 167 acres · NY
- Todd Lake · 167 acres · NH
- Brick Lake · 167 acres · OR
- Little Loon · 167 acres · MN
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 WI10006131. 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.