Indiana lake · state assessment record
Cook Lake
Assessment decisions reported by Indiana to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2008 reporting cycle.
- 93
- Assessed acres
- Lake, Freshwater
- Water type
This waterbody in one line
Cook Lake, a lake in Indiana, is assessed as not supporting one or more designated uses, with one listed impairment cause in the state's most recent Integrated Report cycle (2008). By assessed acreage it sits above the national median by assessed acreage (38,628 lakes); its impairment list is among the longest nationally (one listed cause vs 23,610 assessed lakes). Indiana assesses human health and wildlife as supported; it reported no verdict on fish consumption itself.
- Not Supporting
- overall status
- P68
- Assessed size nationally
- P20
- Shorter cause list
- Fully Supporting
- fish-consumption or fishery
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 Cook Lake 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 Cook Lake nationally is assessed size: 93 acres, larger than 68% of the 38,628 lake-type units with an area on file.
A split ruling across uses
This record splits: Not Supporting on recreation, Fully Supporting on fish consumption. The divergence is inside the designated-use matrix, not a single all-or-nothing label.
Cook Lake: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Cook Lake. 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 Cook Lake 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, Indiana carries 1,588 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Cook 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. Indiana filed its own confidence on the 2 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 |
|---|---|---|
| Full Body Contact | Recreation | Not Supporting Filer confidence: Excellent |
| Human Health and Wildlife | Fish-consumption or fishery | Fully Supporting Filer confidence: Good |
| Warm Water Aquatic Life | Aquatic-life or related | 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 |
|---|---|---|---|
| Phosphorus, Total | Full Body Contact | 2006 | TMDL priority: Medium |
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.
- Phosphorus, Total
- Non-Point Source (suspected)
Reading the record
Where Cook Lake sits among peers
55% of Indiana's lakes assessed this deeply also came out mixed
Indiana ruled definitively on 2 designated uses at Cook Lake and found 1 of 2 not supported. The dataset shows 69 Indiana lakes judged to that same depth.
Indiana's assessed lakes are most often judged on 1 use; this one was judged on 2.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 79 | 16 | 1 | 0 | 0 |
| Mixed | Not possible | 38 (this record) | 12 | 5 | 0 |
| None supported | 72 | 15 | 3 | 0 | 0 |
Ringed cell: Cook Lake. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Cook Lake is one of 1,588 lake-type waterbodies reported to EPA from Indiana, and one of 162 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 93 assessed acres it ranks 12,272nd 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 12,271 lakes with a larger one.
Open in the register
The state has not yet filed a definitive aquatic-life verdict for this record; that field populates when it reports it in a future Integrated Report cycle.
In context
Where Cook 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
93 Top 32% larger than 68% 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 Cook Lake. Hover or tap any bar for its full count and share.
In context
Indiana context
ATTAINS carries 1,588 lake-type waterbodies in Indiana, 145 assessed as not supporting at least one use and 96 fully supporting. Among the 162 indexed units there, Cook Lake ranks 87th by listed-cause count (one listed cause) and 84th by assessed size among the 156 with an area filed; it sits in the not-supporting set (145 statewide) . Its listed causes include Phosphorus, Total, which also appears among Indiana's most-filed impairment causes (led by PCBs in Fish Tissue).
| Other large assessed lakes in Indiana | Assessed acres |
|---|---|
| Lake Michigan (Not Indexed) (Salmonid) (Osrw) Not Supporting | 154,176 |
| Patoka Reservoir (Pws) Fully Supporting | 8,880 |
| Monroe Reservoir (Lower) (Pws) Not Supporting | 6,863 |
| Brookville Reservoir Not Supporting | 5,260 |
| Monroe Reservoir (Upper) (Pws) Not Supporting | 3,887 |
| Wawasee, Lake Not Supporting | 3,410 |
Peers near Cook Lake's size or cause load
Similar assessed acres
Nearest filed extents (93 acres here).
- Flint Pond · 93 acres · MA
- Lake George · 93 acres · MA
- Lake Wauwanoka · 93 acres · MO
- Lower Mystic Lake · 93 acres · MA
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 INK01P1040_00. 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.