Oregon reservoir · state assessment record
Cougar Reservoir
Assessment decisions reported by Oregon to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2024 reporting cycle.
- 1,129
- Assessed acres
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
Cougar Reservoir, a reservoir in Oregon, is assessed as fully supporting its designated uses, with no impairment causes listed in the state's most recent Integrated Report cycle (2024). By assessed acreage it sits among the largest 5% by assessed acreage nationally (38,628 lakes); its impairment list is shorter than on half of assessed lakes (0 listed causes).
- Fully Supporting
- overall status
- P95
- Assessed size nationally
- P51
- Shorter cause list
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.
Reading Cougar Reservoir's filed record
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: cause-list length
The standout filed fact is a short cause list: 0 causes, shorter than 51% of assessed lake-type units. A short list can mean a focused impairment, or a shallow assessment.
Large assessed unit
At 1,129 acres, Cougar Reservoir clears the upper tercile of assessed lake-type units with an area on file (2,087 still larger). Size comparisons use the portal's deduplicated lake ranking population, not raw ATTAINS row counts.
IR category in the supporting band
EPA's Integrated Report category for Cougar Reservoir is 2. In ATTAINS that band means the assessed uses are supporting (or supporting with other waters in the unit), so the narrative weight shifts to how deep the assessment went and whether monitoring is current, not to a restoration plan.
Overall status: fully supporting
Overall status is Fully Supporting. If an IR category or cause row still appears, it usually reflects a prior listing path or a use the overall rollup does not collapse, read those sections rather than stopping at the tile.
According to the U.S. Environmental Protection Agency's ATTAINS program, Oregon carries 1,431 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Cougar Reservoir 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.
| Designated use | Group | Verdict |
|---|---|---|
| Aesthetic Quality | Other | Fully Supporting |
| Boating | Recreation | Not Assessed |
| Fish and Aquatic Life | Aquatic-life or related | Not Assessed |
| Fishing | Fish-consumption or fishery | Not Assessed |
| Hydropower | Other | Not Assessed |
| Industrial Water Supply | Other | Not Assessed |
| Irrigation | Other | Not Assessed |
| Livestock Watering | Other | Insufficient Information |
| Private Domestic Water Supply | Drinking-water supply designation | Insufficient Information |
| Public Domestic Water Supply | Drinking-water supply designation | Insufficient Information |
| Water Contact Recreation | Recreation | Insufficient Information |
| Wildlife and Hunting | Other | Not Assessed |
The record
Listed impairment causes
The state's reported assessment lists no impairment causes for this reservoir.
Reading the record
Cougar Reservoir: Category 2 reading
2 Category 2: some uses supported, others not assessed
Oregon filed this assessment unit as Category 2: some designated uses are supported and others were not assessed in this cycle. Absence of a failing verdict is not the same as a full Category 1 finding.
Scale and rank
Cougar Reservoir is one of 1,431 lake-type waterbodies reported to EPA from Oregon. It is not among the 167 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 1,129 assessed acres it ranks 2,088th 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 2,087 lakes with a larger one.
What this record holds
Oregon completed an assessment here and listed no impairment cause, so the record holds a verdict and its supporting use rows but no pollutant to track over time. The state has not yet filed a definitive fish-consumption verdict, a definitive recreation verdict, and a definitive aquatic-life verdict for this record; those fields populate when it reports them in a future Integrated Report cycle.
In context
Where Cougar Reservoir 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
1,129 Top 5% larger than 95% 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
0 Among the shortest cause lists fewer listed causes than 51% 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 Cougar Reservoir. Hover or tap any bar for its full count and share.
In context
Oregon context
ATTAINS carries 1,431 lake-type waterbodies in Oregon, 165 assessed as not supporting at least one use and 14 fully supporting.
| Other large assessed lakes in Oregon | Assessed acres |
|---|---|
| Goose Lake Not reported | 93,152 |
| Malheur Slough Not Supporting | 73,544 |
| Upper Klamath Lake Not Supporting | 62,130 |
| Columbia River Not Supporting | 55,630 |
| Lake Abert Not Assessed | 44,751 |
| Summer Lake Not reported | 31,606 |
Peers near Cougar Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (1,129 acres here).
- Upper Estuary · 1,129 acres · MN
- McKenzie Lake · 1,129 acres · WI
- Spring Lake · 1,128 acres · MI
- Schoharie Reservoir · 1,132 acres · NY
Similar cause load
Nearest listed-cause counts (0 here). Peers already in the acreage column are omitted.
- 31st Street Harbor · 0 causes · IL
- 42nd Avenue East Beach · 0 causes · MN
- 59th Street Harbor · 0 causes · IL
- 657 Dunleavy (Beach) · 0 causes · MI
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 OR_LK_1709000403_02_100753. 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.