Iowa lake · state assessment record
Big Creek Lake
Assessment decisions reported by Iowa to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2024 reporting cycle, a cycle that carries an interim EPA action.
- 883
- Assessed acres
- Lake
- Water type
- Eutrophic
- Reported trophic class
This waterbody in one line
Big Creek Lake, a lake in Iowa, 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), a cycle that carries an interim EPA action. By assessed acreage it sits among the largest 10% by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (2 listed causes vs 23,610 assessed lakes).
- Not Supporting
- overall status
- P94
- Assessed size nationally
- P10
- Shorter cause list
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 Big Creek Lake 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 Big Creek Lake nationally is assessed size: 883 acres, larger than 94% of the 38,628 lake-type units with an area on file.
No ruled-on use clears the bar
On the uses this filer ruled on, recreation, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Big Creek Lake: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Big Creek Lake. 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 Big Creek Lake 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, Iowa carries 371 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Big Creek Lake 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 |
|---|---|---|
| Human Health | Recreation | Fully Supporting |
| Primary Contact Recreation | Recreation | Not Supporting |
| Aquatic Life | Aquatic-life or related | Insufficient Information |
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 |
|---|---|---|---|
| Escherichia coli (E. coli) | Primary Contact Recreation | 2006 | TMDL approved |
| Chlorophyll-a | Primary Contact Recreation | 2020 | TMDL priority: High |
Probable sources
Iowa listed the source of the impairment as unknown. That is the state's own filed value, not a gap in this record: the cause has been identified, the origin has not.
Reading the record
Cleanup queue for Big Creek Lake
1 listed cause ranked High in the TMDL queue, still without a plan
Iowa ranked Chlorophyll-a high in its TMDL development queue, and no cleanup plan is on file for that listing yet. That queue rank is the state's own scheduling signal, not an EPA national rule.
A High ranking names a position in the state's plan-writing queue; it is not a measure of how impaired the water is. How listing and cleanup work.
Scale and rank
Big Creek Lake is one of 371 lake-type waterbodies reported to EPA from Iowa, and one of 167 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 883 assessed acres it ranks 2,460th 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 2,459 lakes with a larger one.
Open in the register
The state has not yet filed a definitive fish-consumption verdict and a definitive aquatic-life verdict for this record; those fields populate when it reports them in a future Integrated Report cycle.
Reported trophic class
Eutrophic is the trophic class the filing agency reported to EPA ATTAINS for this assessment unit. It describes nutrient enrichment, not whether the water is safe, and it is not a PlainLakes inference. What the trophic scale measures.
In context
Where Big Creek Lake 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
883 Top 6% larger than 94% 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 Big Creek Lake. Hover or tap any bar for its full count and share.
In context
Iowa context
ATTAINS carries 371 lake-type waterbodies in Iowa, 137 assessed as not supporting at least one use and 66 fully supporting. Among the 167 indexed units there, Big Creek Lake ranks 36th by listed-cause count (2 listed causes) and 18th by assessed size among the 167 with an area filed; it sits in the not-supporting set (137 statewide) . Its listed causes include Escherichia coli (E. coli) and Chlorophyll-a, which also appear among Iowa's most-filed impairment causes (led by Chlorophyll-a).
| Other large assessed lakes in Iowa | Assessed acres |
|---|---|
| Red Rock Reservoir Not Supporting | 19,000 |
| Rathbun Reservoir - Main Basin Fully Supporting | 6,330 |
| Saylorville Reservoir Not Supporting | 5,950 |
| Coralville Reservoir Not Supporting | 4,900 |
| Big Spirit Lake Fully Supporting | 4,169 |
| Clear Lake Not Supporting | 3,684 |
Peers near Big Creek Lake's size or cause load
Similar assessed acres
Nearest filed extents (883 acres here).
- Lake Penchant · 883 acres · LA
- Dexter Reservoir · 884 acres · OR
- Austin Stream · 882 acres · ME
- Humphreys Lake · 882 acres · OK
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 IA 04-UDM-1242. 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.