Montana lake · state assessment record
Hungry Horse Reservoir
Assessment decisions reported by Montana to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2006 reporting cycle.
- 23,596
- Assessed acres
- Lake, Freshwater
- Water type
- Oligotrophic
- Reported trophic class
- 3,553.2 ft
- Water Surface Elevation (provisional)
This waterbody in one line
Hungry Horse Reservoir, a lake in Montana, is assessed as fully supporting its designated uses, with no impairment causes listed in the state's most recent Integrated Report cycle (2006). By assessed acreage it sits among the largest 1% of assessed lakes nationally (38,628 lakes with a filed area); its impairment list is shorter than on half of assessed lakes (0 listed causes). Aquatic life is assessed as fully supporting. A USGS gauge tracks its water surface elevation daily.
- Fully Supporting
- overall status
- P100
- Assessed size nationally
- P51
- Shorter cause list
- Fully 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 Hungry Horse Reservoir 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: assessed size
The number that most separates Hungry Horse Reservoir nationally is assessed size: 23,596 acres, larger than 100% of the 38,628 lake-type units with an area on file.
Shorter than most cause lists
Only 0 causes on file, shorter than 51% of assessed lake-type units. Pair the short list with the use matrix: a single Not Supporting use can still be the whole story.
Every ruled-on use is fully supporting
The filed use determinations for recreation, aquatic life are all Fully Supporting. Where an overall IR category still flags the unit, look at the cause list and report standing rather than treating the use row as empty.
IR category in the supporting band
EPA's Integrated Report category for Hungry Horse Reservoir is 1. 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, Montana carries 73 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Hungry Horse 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. 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 | Fully Supporting |
| Aquatic Life | Aquatic-life or related | Fully Supporting |
| Drinking Water | Drinking-water supply designation | Fully Supporting |
| Primary Contact Recreation | Recreation | Fully Supporting |
The record
Listed impairment causes
The state's reported assessment lists no impairment causes for this lake.
Reading the record
Hungry Horse Reservoir: Category 1 reading
1 Category 1: all designated uses supported
Montana filed this assessment unit as Category 1: every designated use assessed here was reported as supported. That is the filer's Integrated Report classification, not a PlainLakes score.
Scale and rank
Hungry Horse Reservoir 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 23,596 assessed acres it ranks 134th 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 133 lakes with a larger one.
Water level
A USGS gauge tracks this lake's water surface elevation daily, and the latest reading is 5.54 ft below the reading 30 days earlier, against a 365-day observed range of 21.3 ft. 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
Oligotrophic 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.
Water level: 365-day record
Daily water surface elevation values, feet above the National Geodetic Vertical Datum of 1929 (NGVD 29), from USGS gauge 12362000 (Hungry Horse Reservoir Nr Hungry Horse Mt), shown weekly. Readings are daily-batch snapshots, not real-time conditions. Each daily value is a single reading taken at 24:00, not a daily mean. It is the only daily statistic USGS files for this gauge.
- Latest reading
- 3,553.2 ft 5.539999999999964ft vs 30 days earlier
- 2026-08-15 · Provisional, subject to USGS revision
Water level: 365-day record
Subscribe to water level updates for Hungry Horse Reservoir (RSS)
Every daily value in this window is provisional and subject to USGS revision: USGS has not yet approved any value in the trailing 365 days of this record.
Of the 365 daily values in this record, 14 were estimated by USGS rather than measured. USGS marks these individually; approval and estimation are separate judgements and a value can carry both.
Full gauge record: USGS monitoring location 12362000
In context
Where Hungry Horse 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
23,596 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
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 Hungry Horse Reservoir. 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, Hungry Horse Reservoir ranks 29th by listed-cause count (no listed causes) and 5th by assessed size among the 52 with an area filed; it is one of the 28 fully-supporting indexed records in the state .
| 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 |
| Lake Elwell (Tiber Reservoir) Fully Supporting | 15,041 |
| Hebgen Lake Not Assessed | 12,407 |
Peers near Hungry Horse Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (23,596 acres here).
- Grays Lake · 23,678 acres · ID
- Stockton Lake · 23,680 acres · MO
- American Falls Reservoir (Snake River) Tribal Waters · 23,785 acres · ID
- Priest Lake · 23,342 acres · ID
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
- Water levels shown are daily snapshots. Seasonal drawdown and datum conventions matter when comparing levels. How to read level data
- 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 MT76J002_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.