Montana lake · state assessment record
Lake Bowdoin
Assessment decisions reported by Montana to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2000 reporting cycle.
- 3,932
- Assessed acres
- Lake, Freshwater
- Water type
- Eutrophic
- Reported trophic class
This waterbody in one line
Lake Bowdoin, a lake in Montana, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (2000). By assessed acreage it sits among the largest 5% 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
- P98
- 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.
Lake Bowdoin 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 Lake Bowdoin nationally is assessed size: 3,932 acres, larger than 98% 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, 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 Bowdoin: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Lake Bowdoin. Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
Longer than most cause lists
2 listed causes puts this unit above 80% of assessed lake-type records by list length. Treat that as a coding-and-sampling signal: states that split pollutants finely mint longer lists without proving worse water.
Overall status: not supporting
The filer's overall status for Lake Bowdoin is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
According to the U.S. Environmental Protection Agency's ATTAINS program, Montana carries 73 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Lake Bowdoin 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. For the definitive verdicts on this record, Montana filed the assessment basis as Monitored & Extrapolated Data. Those are EPA's own words, not PlainLakes' summary of them; where a verdict is filed as extrapolated, the state did not reach it from monitoring alone.
| Designated use | Group | Verdict |
|---|---|---|
| Agricultural | Other | Not Supporting |
| Aquatic Life | Aquatic-life or related | Not Supporting |
| Drinking Water | Drinking-water supply designation | Not Supporting |
| Primary Contact Recreation | Recreation | 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 |
|---|---|---|---|
| Salinity | Agricultural, Aquatic Life, Drinking Water | 1990 | TMDL priority: Low |
| Selenium | Aquatic Life, Drinking Water | 2000 | TMDL priority: Low |
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.
- Salinity
- Dam or Impoundment (suspected) Agriculture (suspected) Crop Production (Irrigated) (suspected)
- Selenium
- Dam or Impoundment (suspected) Agriculture (suspected) Crop Production (Irrigated) (suspected)
Reading the record
Assessment basis on Lake Bowdoin
1 filed assessment basis on this record
For the definitive verdicts on this record, Montana filed the assessment basis as Monitored & Extrapolated Data. Those are EPA's own words, not PlainLakes' summary of them; where a verdict is filed as extrapolated, the state did not reach it from monitoring alone.
The cycle is when the state reported; the monitoring year, where filed, is when it measured. How to read assessment currency.
Scale and rank
Lake Bowdoin is one of 73 lake-type waterbodies reported to EPA from Montana, and one of 52 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 3,932 assessed acres it ranks 789th 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 788 lakes with a larger one.
Awaiting a filing
The state has not yet filed a definitive fish-consumption verdict and a definitive recreation verdict for this record; those fields populate when it reports them 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.
Why no water-level record
Lake Bowdoin 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 Lake Bowdoin 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
3,932 Top 2% larger than 98% 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 Lake Bowdoin. Hover or tap any bar for its full count and share.
In context
Montana context
ATTAINS carries 73 lake-type waterbodies in Montana, 28 assessed as not supporting at least one use and 28 fully supporting. Among the 52 indexed units there, Lake Bowdoin ranks 19th by listed-cause count (2 listed causes) and 15th by assessed size among the 52 with an area filed; it sits in the not-supporting set (28 statewide) . Its listed causes include Salinity and Selenium, which also appear among Montana's most-filed impairment causes (led by Flow Regime Modification).
| Other large assessed lakes in Montana | Assessed acres |
|---|---|
| Fort Peck Reservoir Not Supporting | 233,296 |
| Flathead Lake Not Supporting | 57,305 |
| Canyon Ferry Reservoir Not Supporting | 32,810 |
| Lake Koocanusa Not Supporting | 28,875 |
| Hungry Horse Reservoir Fully Supporting | 23,596 |
| Lake Elwell (Tiber Reservoir) Fully Supporting | 15,041 |
Peers near Lake Bowdoin's size or cause load
Similar assessed acres
Nearest filed extents (3,932 acres here).
- Pelican · 3,941 acres · MN
- Lake Palestine · 3,949 acres · TX
- Lake Lavon · 3,952 acres · TX
- Choke Canyon Reservoir · 3,912 acres · TX
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 MT40M003_010. 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.