Nebraska lake · state assessment record
Harlan County Reservoir
Assessment decisions reported by Nebraska to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2026 reporting cycle, a cycle that is open for public comment.
- 12,821
- Assessed acres
- Lake
- Water type
This waterbody in one line
Harlan County Reservoir, a lake in Nebraska, is assessed as not supporting one or more designated uses, with 4 listed impairment causes in the state's most recent Integrated Report cycle (2026), a cycle that is open for public comment. 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 (4 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting.
- Not Supporting
- overall status
- P99
- Assessed size nationally
- P3
- 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.
How Harlan County Reservoir reads against 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 Harlan County Reservoir nationally is assessed size: 12,821 acres, larger than 99% of the 38,628 lake-type units with an area on file.
Longer than most cause lists
4 listed causes puts this unit above 95% 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.
A split ruling across uses
This record splits: Not Supporting on aquatic life, Fully Supporting on recreation. The divergence is inside the designated-use matrix, not a single all-or-nothing label.
Harlan County Reservoir: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Harlan County 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 Harlan County 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, Nebraska carries 554 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Harlan County 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 | Fully Supporting |
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 |
|---|---|---|---|
| Chlorophyll-a | Aquatic Life | 2026 | TMDL priority: Medium |
| Mercury in Fish Tissue | Aquatic Life | 2026 | TMDL priority: Medium |
| Nitrogen, Total | Aquatic Life | 2026 | TMDL priority: Medium |
| Phosphorus, Total | Aquatic Life | 2026 | TMDL priority: Medium |
Reading the record
Where Harlan County Reservoir sits among peers
86% of Nebraska's lakes assessed this deeply also came out mixed
Nebraska ruled definitively on 4 designated uses at Harlan County Reservoir and found 1 of 4 not supported. The dataset shows 113 Nebraska lakes judged to that same depth.
Nebraska's assessed lakes are most often judged on 4 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 | 41 | 34 | 45 | 16 | 2 |
| Mixed | Not possible | 35 | 62 | 97 (this record) | 3 |
| None supported | 21 | 1 | 0 | 0 | 0 |
Ringed cell: Harlan County Reservoir. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Harlan County 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 12,821 assessed acres it ranks 251st 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 250 lakes with a larger one.
Not yet on record
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 Harlan County 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
12,821 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
4 Longer than most more listed causes than 95% 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 Harlan County 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, Harlan County Reservoir ranks 34th by listed-cause count (4 listed causes) and 3rd by assessed size among the 247 with an area filed; it sits in the not-supporting set (219 statewide) . Its listed causes include Chlorophyll-a; Mercury in Fish Tissue; Nitrogen, Total; 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 |
| Calamus Reservoir Not Supporting | 5,028 |
| Swanson Reservoir Not Supporting | 4,660 |
| Sutherland Reservoir Fully Supporting | 2,954 |
| Merritt Reservoir Not Supporting | 2,543 |
Peers near Harlan County Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (12,821 acres here).
- Greers Ferry Lake · 12,883 acres · AR
- Lake Tenkiller · 12,900 acres · OK
- Bayou D'Arbonne Lake · 12,711 acres · LA
- Turtle Flambeau Flowage · 12,943 acres · WI
Similar cause load
Nearest listed-cause counts (4 here). Peers already in the acreage column are omitted.
- Agency Lake · 4 causes · OR
- Alachua Sink · 4 causes · FL
- Aldrich Pond · 4 causes · MA
- American Falls Reservoir (Snake River) · 4 causes · ID
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-RE2-L0010. 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.