Nebraska lake · state assessment record
Gallagher Canyon Reservoir
Assessment decisions reported by Nebraska to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2020 reporting cycle.
- 131
- Assessed acres
- Lake
- Water type
This waterbody in one line
Gallagher Canyon Reservoir, a lake in Nebraska, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (2020). 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.
Where Gallagher Canyon 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: 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 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.
Gallagher Canyon Reservoir: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Gallagher Canyon Reservoir. 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 Gallagher Canyon Reservoir 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 131 acres, Gallagher Canyon Reservoir clears the upper tercile of assessed lake-type units with an area on file (9,772 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, Nebraska carries 554 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Gallagher Canyon 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 |
|---|---|---|
| Aesthetics | Other | Fully Supporting |
| Agricultural Water Supply | Other | Fully Supporting |
| Aquatic Life | Aquatic-life or related | 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 |
|---|---|---|---|
| Mercury in Fish Tissue | Aquatic Life | 2022 | TMDL priority: Medium |
| Phosphorus, Total | Aquatic Life | 2022 | TMDL priority: Medium |
Reading the record
Where Gallagher Canyon Reservoir sits among peers
58% of Nebraska's lakes assessed this deeply also came out mixed
Nebraska ruled definitively on 3 designated uses at Gallagher Canyon Reservoir and found 1 of 3 not supported. The dataset shows 107 Nebraska lakes judged to that same depth.
Nebraska's assessed lakes are most often judged on 4 uses; this one was judged on 3.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 41 | 34 | 45 | 16 | 2 |
| Mixed | Not possible | 35 | 62 (this record) | 97 | 3 |
| None supported | 21 | 1 | 0 | 0 | 0 |
Ringed cell: Gallagher Canyon Reservoir. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Gallagher Canyon Reservoir is one of 554 lake-type waterbodies reported to EPA from Nebraska, and one of 250 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 131 assessed acres it ranks 9,773rd 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 9,772 lakes with a larger one.
Open in the register
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.
In context
Where Gallagher Canyon 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
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 Gallagher Canyon Reservoir. Hover or tap any bar for its full count and share.
In context
Nebraska context
ATTAINS carries 554 lake-type waterbodies in Nebraska, 219 assessed as not supporting at least one use and 138 fully supporting. Among the 250 indexed units there, Gallagher Canyon Reservoir ranks 98th by listed-cause count (2 listed causes) and 57th by assessed size among the 247 with an area filed; it sits in the not-supporting set (219 statewide) . Its listed causes include Mercury in Fish Tissue; and Phosphorus, Total, which also appear among Nebraska's most-filed impairment causes (led by Mercury in Fish Tissue).
| Other large assessed lakes in Nebraska | Assessed acres |
|---|---|
| Lewis and Clark Lake Not Supporting | 25,174 |
| Lake C. W. McConaughy Fully Supporting | 24,868 |
| Harlan County Reservoir Not Supporting | 12,821 |
| Calamus Reservoir Not Supporting | 5,028 |
| Swanson Reservoir Not Supporting | 4,660 |
| Sutherland Reservoir Fully Supporting | 2,954 |
Peers near Gallagher Canyon Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (131 acres here).
- Big Cedar Lake (Put & Take Trout) · 131 acres · IN
- Lake Holiday Hide-Away · 131 acres · IN
- Lake Winthrop · 131 acres · MA
- Miller · 131 acres · IL
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 NE-MP2-L0570. 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.