Idaho lake · state assessment record
Juniper Basin Reservoir
Assessment decisions reported by Idaho to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2014 reporting cycle.
- 242
- Assessed acres
- Lake, Freshwater
- Water type
This waterbody in one line
Juniper Basin Reservoir, a lake in Idaho, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (2014). 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
- P84
- 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.
Where Juniper Basin 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: in-state cause rank
Inside Idaho, cause-list rank is the local separator: Juniper Basin Reservoir is 22 of 186 indexed units by listed-cause count, toward the top of that state's filed lists.
Every ruled-on use is not supporting
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.
Juniper Basin Reservoir: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Juniper Basin Reservoir. Read the listed causes and any cleanup actions filed beside them before treating the overall status tile as a finished restoration story.
Large assessed unit
At 241.8 acres, Juniper Basin Reservoir clears the upper tercile of assessed lake-type units with an area on file (6,258 still larger). Size comparisons use the portal's deduplicated lake ranking population, not raw ATTAINS row counts.
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.
According to the U.S. Environmental Protection Agency's ATTAINS program, Idaho carries 630 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Juniper Basin 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. Idaho filed its own confidence on the 2 definitive verdicts it rated: 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 |
|---|---|---|
| Cold Water Aquatic Life | Aquatic-life or related | Not Supporting Filer confidence: Good |
| Secondary Contact Recreation | Recreation | Not Supporting Filer confidence: Good |
| Aesthetic | Other | Not Assessed |
| Agricultural Water Supply | Other | Not Assessed |
| Industrial Water Supply | Other | Not Assessed |
| Wildlife Habitat | Other | 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 |
|---|---|---|---|
| Sedimentation/Siltation | Cold Water Aquatic Life | 1994 | TMDL approved |
| Escherichia coli (E. coli) | Secondary Contact Recreation | 2010 | TMDL priority: Low |
Reading the record
Where Juniper Basin Reservoir sits among peers
37% of Idaho's lakes assessed this deeply also had no use supported
Idaho ruled definitively on 2 designated uses at Juniper Basin Reservoir and found none of them supported. The dataset shows 51 Idaho lakes judged to that same depth.
Idaho's assessed lakes are most often judged on 5 or more uses; this one was judged on 2.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 6 | 25 | 8 | 12 | 147 |
| Mixed | Not possible | 7 | 3 | 0 | 0 |
| None supported | 17 | 19 (this record) | 5 | 0 | 0 |
Ringed cell: Juniper Basin Reservoir. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Juniper Basin Reservoir is one of 630 lake-type waterbodies reported to EPA from Idaho, and one of 186 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 242 assessed acres it ranks 6,259th 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 6,258 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 Juniper Basin 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
242 Top 16% larger than 84% 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 Juniper Basin Reservoir. Hover or tap any bar for its full count and share.
In context
Idaho context
ATTAINS carries 630 lake-type waterbodies in Idaho, 51 assessed as not supporting at least one use and 198 fully supporting. Among the 186 indexed units there, Juniper Basin Reservoir ranks 22nd by listed-cause count (2 listed causes) and 46th by assessed size among the 186 with an area filed; it sits in the not-supporting set (51 statewide) . Its listed causes include Sedimentation/Siltation, which also appears among Idaho's most-filed impairment causes (led by Phosphorus, Total). It also lists Escherichia coli (E. coli), outside that top-five list.
| Other large assessed lakes in Idaho | Assessed acres |
|---|---|
| Pend Oreille Lake Not Supporting | 80,829 |
| Bear Lake Not Assessed | 34,454 |
| American Falls Reservoir (Snake River) Not Supporting | 31,724 |
| Cascade Reservoir Not Supporting | 25,040 |
| American Falls Reservoir (Snake River) Tribal Waters Not Assessed | 23,785 |
| Grays Lake Not Assessed | 23,678 |
Peers near Juniper Basin Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (242 acres here).
- Big Watab · 242 acres · MN
- Swan · 242 acres · MN
- McGregor Lake · 242 acres · WI
- Slab Creek Reservoir (El Dorado County) · 242 acres · CA
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 ID17050104SW005L_0L. 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.