Oregon reservoir · state assessment record
Garrison Lake
Assessment decisions reported by Oregon to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 1998 reporting cycle.
- 131
- Assessed acres
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
Garrison Lake, a reservoir in Oregon, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (1998). By assessed acreage it sits in the upper quartile by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (2 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting.
- Not Supporting
- overall status
- P75
- Assessed size nationally
- P10
- 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.
Reading Garrison Lake'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 cause-list length: 2 listed impairment causes, a longer list than 80% of assessed lake-type units (n=23,610). List length tracks how states sample and code, not a severity score.
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.
Garrison Lake: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Garrison 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 Garrison Lake 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 130.9 acres, Garrison Lake clears the upper tercile of assessed lake-type units with an area on file (9,789 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, Oregon carries 1,431 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Garrison 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 the state's definitive verdicts; other entries mean the use was not conclusively assessed in this cycle.
| Designated use | Group | Verdict |
|---|---|---|
| Aesthetic Quality | Other | Not Supporting |
| Boating | Recreation | Not Supporting |
| Fish and Aquatic Life | Aquatic-life or related | Not Supporting |
| Fishing | Fish-consumption or fishery | Not Assessed |
| Hydropower | Other | Not Assessed |
| Industrial Water Supply | Other | Not Assessed |
| Irrigation | Other | Not Assessed |
| Livestock Watering | Other | Not Assessed |
| Private Domestic Water Supply | Drinking-water supply designation | Not Assessed |
| Public Domestic Water Supply | Drinking-water supply designation | Not Assessed |
| Water Contact Recreation | Recreation | Not Assessed |
| Wildlife and Hunting | Other | Not Assessed |
The record
Listed impairment causes
Causes the state 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 |
|---|---|---|---|
| Noxious Aquatic Plants | Aesthetic Quality, Boating | 1998 | Action recorded (type not published) |
| pH | Fish and Aquatic Life | 2010 | TMDL priority: Low |
Reading the record
Where Garrison Lake sits among peers
10 of 19 Oregon lakes assessed this deeply also had no use supported
Oregon ruled definitively on 3 designated uses at Garrison Lake and found none of them supported. The dataset shows 19 Oregon lakes judged to that same depth.
Oregon's assessed lakes are most often judged on 5 or more uses; this one was judged on 3.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 4 | 2 | 6 | 2 | 0 |
| Mixed | Not possible | 4 | 3 | 0 | 37 |
| None supported | 43 | 18 | 10 (this record) | 19 | 31 |
Ringed cell: Garrison Lake. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Garrison Lake is one of 1,431 lake-type waterbodies reported to EPA from Oregon, and one of 167 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 131 assessed acres it ranks 9,790th 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 9,789 lakes with a larger one.
Open in the register
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.
In context
Where Garrison 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
131 Top 25% larger than 75% 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
2 Longer than most more listed causes than 80% 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 Garrison Lake. 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. Among the 167 indexed units there, Garrison Lake ranks 81st by listed-cause count (2 listed causes) and 115th by assessed size among the 167 with an area filed; it sits in the not-supporting set (165 statewide) . Its listed causes (Noxious Aquatic Plants and pH) sit outside Oregon's top-five list, which is led by Temperature.
| 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 Garrison Lake's size or cause load
Similar assessed acres
Nearest filed extents (131 acres here).
- Thompsons Lake · 131 acres · NY
- Lee Lake · 131 acres · MI
- Finney Lake · 131 acres · CA
- Flowing Lake · 131 acres · WA
Similar cause load
Nearest listed-cause counts (2 here). Peers already in the acreage column are omitted.
- 12th St. Beach · 2 causes · IL
- 31st St. Beach · 2 causes · IL
- 49th St. Beach · 2 causes · IL
- 57th St. Beach · 2 causes · IL
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_1710030604_02_100235. 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.