Nebraska lake · state assessment record
Cottonwood Lake (Lake Yankton)
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.
- 322
- Assessed acres
- Lake
- Water type
This waterbody in one line
Cottonwood Lake (Lake Yankton), a lake in Nebraska, is assessed as not supporting one or more designated uses, with one listed impairment cause in the state's most recent Integrated Report cycle (2026), a cycle that is open for public comment. By assessed acreage it sits in the upper quartile by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (one listed cause vs 23,610 assessed lakes). Aquatic life is assessed as not supporting.
- Not Supporting
- overall status
- P87
- Assessed size nationally
- P20
- 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.
Reading Cottonwood Lake (Lake Yankton)'s filed record
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 Cottonwood Lake (Lake Yankton) nationally is assessed size: 322 acres, larger than 87% of the 38,628 lake-type units with an area on file.
Mixed use determinations
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.
Cottonwood Lake (Lake Yankton): Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Cottonwood Lake (Lake Yankton). 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 Cottonwood Lake (Lake Yankton) is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
Typical cause-list length
1 listed cause is a middle-tercile list length among assessed lake-type units. Look to IR category and use outcomes for the distinctive reading.
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 Cottonwood Lake (Lake Yankton) 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 |
Reading the record
Where Cottonwood Lake (Lake Yankton) sits among peers
86% of Nebraska's lakes assessed this deeply also came out mixed
Nebraska ruled definitively on 4 designated uses at Cottonwood Lake (Lake Yankton) 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: Cottonwood Lake (Lake Yankton). Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Cottonwood Lake (Lake Yankton) 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 322 assessed acres it ranks 5,087th 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 5,086 lakes with a larger one.
Awaiting a filing
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 Cottonwood Lake (Lake Yankton) 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
322 Top 13% larger than 87% 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
1 Longer than most more listed causes than 49% 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 Cottonwood Lake (Lake Yankton). 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, Cottonwood Lake (Lake Yankton) ranks 123rd by listed-cause count (one listed cause) and 32nd 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, which also appears 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 Cottonwood Lake (Lake Yankton)'s size or cause load
Similar assessed acres
Nearest filed extents (322 acres here).
- Deering Reservoir · 322 acres · NH
- Lake Yankton · 322 acres · SD
- Salmon Lake · 322 acres · NY
- Smith Mtn. Lake (Witcher Creek) · 322 acres · VA
Similar cause load
Nearest listed-cause counts (1 here). Peers already in the acreage column are omitted.
- Aaron · 1 causes · MN
- Aaron River Reservoir · 1 causes · MA
- Abbotts Creek (including Lexington-Thomasville Water Supply Reservoir at normal reservoir elevation, Tom-A-Lex Lake) · 1 causes · NC
- Abeniki Lake · 1 causes · NH
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-MT2-L0030. 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.