Tennessee reservoir · state assessment record
Nickajack Reservoir
Assessment decisions reported by Tennessee to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2024 reporting cycle.
- 10,370
- Assessed acres
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
Nickajack Reservoir, a reservoir in Tennessee, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (2024). By assessed acreage it sits among the largest 1% of assessed lakes nationally (38,628 lakes with a filed area); its impairment list is among the longest nationally (2 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as fully supporting.
- Not Supporting
- overall status
- P99
- Assessed size nationally
- P10
- 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 Nickajack 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 Nickajack Reservoir nationally is assessed size: 10,370 acres, larger than 99% of the 38,628 lake-type units with an area on file.
Mixed use determinations
This record splits: Not Supporting on recreation, Fully Supporting on aquatic life. The divergence is inside the designated-use matrix, not a single all-or-nothing label.
Nickajack Reservoir: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Nickajack Reservoir. 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 Nickajack Reservoir 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, Tennessee carries 117 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Nickajack 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, Tennessee filed the assessment basis as Monitored Data. Those are EPA's own words, not PlainLakes' summary of them. Tennessee filed its own confidence on the 6 definitive verdicts it rated: Good and Excellent. 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 |
|---|---|---|
| Domestic Water Supply | Drinking-water supply designation | Fully Supporting Filer confidence: Good |
| Fish and Aquatic Life | Aquatic-life or related | Fully Supporting Filer confidence: Good on toxicological; Excellent on physical/chemical |
| Industrial Water Supply | Other | Fully Supporting Filer confidence: Good |
| Irrigation | Other | Fully Supporting Filer confidence: Good |
| Livestock Watering and Wildlife | Other | Fully Supporting Filer confidence: Good |
| Recreation | Recreation | Not Supporting Filer confidence: Good |
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 |
|---|---|---|---|
| Dioxin in Fish Tissue | Recreation | 2026 | TMDL priority: Low |
| PCBs in Fish Tissue | Recreation | 2026 | 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.
- Dioxin in Fish Tissue
- Contaminated Sediments (suspected)
- PCBs in Fish Tissue
- Contaminated Sediments (suspected)
Reading the record
Where Nickajack Reservoir sits among peers
70% of Tennessee's lakes assessed this deeply also came out mixed
Tennessee ruled definitively on 6 designated uses at Nickajack Reservoir and found 1 of 6 not supported. The dataset shows 44 Tennessee lakes judged to that same depth.
Tennessee's assessed lakes are most often judged on 5 or more uses, as this one was.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 0 | 0 | 0 | 5 | 13 |
| Mixed | Not possible | 0 | 3 | 11 | 31 (this record) |
| None supported | 10 | 2 | 1 | 0 | 0 |
Ringed cell: Nickajack Reservoir. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Nickajack Reservoir is one of 117 lake-type waterbodies reported to EPA from Tennessee, and one of 73 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 10,370 assessed acres it ranks 305th 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 304 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 Nickajack 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
10,370 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
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 Nickajack Reservoir. Hover or tap any bar for its full count and share.
In context
Tennessee context
ATTAINS carries 117 lake-type waterbodies in Tennessee, 60 assessed as not supporting at least one use and 16 fully supporting. Among the 73 indexed units there, Nickajack Reservoir ranks 19th by listed-cause count (2 listed causes) and 20th by assessed size among the 73 with an area filed; it sits in the not-supporting set (60 statewide) . Its listed causes include PCBs in Fish Tissue, which also appears among Tennessee's most-filed impairment causes (led by Mercury in Fish Tissue). It also lists Dioxin in Fish Tissue, outside that top-five list.
| Other large assessed lakes in Tennessee | Assessed acres |
|---|---|
| Kentucky Reservoir Fully Supporting | 99,500 |
| Chickamauga Reservoir Fully Supporting | 35,400 |
| Watts Bar Reservoir Not Supporting | 34,075 |
| Douglas Reservoir Fully Supporting | 30,400 |
| Old Hickory Reservoir Fully Supporting | 27,439 |
| Cherokee Reservoir Not Supporting | 25,964 |
Peers near Nickajack Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (10,370 acres here).
- Millwood Lake · 10,344 acres · AR
- Manistique Lake · 10,336 acres · MI
- Big Lake at Peter Dana Point · 10,334 acres · ME
- Agency Lake · 10,323 acres · OR
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 TN06020001001_1000. 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.