Colorado multi-water assessment unit · state assessment record
East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries
The assessment record reported by Colorado to EPA under Clean Water Act sections 303(d) and 305(b).
- 46
- Acres of lake water
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries, a multi-water assessment unit in Colorado, was reported but not assessed in the state's most recent Integrated Report. By assessed acreage it sits above the national median by assessed acreage (38,628 lakes).
- Not Assessed
- overall status
- P53
- Assessed size nationally
The state agency files this as one assessment unit spanning 46.32 acres of lake water and 24.79 miles of stream and river. The verdicts and listed causes below are reported for the whole unit, not for the lake water alone. Assessment verdicts are the state agency's decisions as reported to EPA ATTAINS; PlainLakes renders them without modification.
Reading East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries'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
Assessed size is not the extreme here: 46.3 acres sits near the middle of the 38,628 units with an area filed (percentile 53).
IR category 3 on East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries
The Integrated Report category filed for East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries is 3. PlainLakes renders EPA's code without remapping it into a consumer grade.
Overall status: Not Assessed
ATTAINS overall status on this unit is “Not Assessed”. PlainLakes does not rewrite that vocabulary into a consumer score.
According to the U.S. Environmental Protection Agency's ATTAINS program, Colorado carries 344 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries 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 |
|---|---|---|
| Agriculture | Other | Not Assessed |
| Aquatic Life Cold Water-Class 2 | Aquatic-life or related | Not Assessed |
| Recreation | Recreation | Not Assessed |
The record
Listed impairment causes
The state reported this multi-water assessment unit in its most recent Integrated Report but reached no assessment determination, so no causes are listed. The unit is recorded under EPA integrated-reporting Category 3: reviewed, with insufficient information to determine whether it meets water-quality standards. An undetermined waterbody is neither confirmed clean nor confirmed impaired.
Reading the record
What this co-filed unit covers
24.79 miles of stream and river co-filed on this unit
The state agency files this as one assessment unit spanning 46.32 acres of lake water and 24.79 miles of stream and river. The verdicts and listed causes below are reported for the whole unit, not for the lake water alone.
This page is about the lake water in the unit; counts and verdicts below cover the whole multi-water assessment unit. How multi-water units are filed.
Scale and rank
East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries is one of 344 lake-type waterbodies reported to EPA from Colorado. It is not among the 122 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 46 assessed acres it ranks 18,224th 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 18,223 lakes with a larger one.
What this record holds
Colorado filed this multi-water assessment unit in its most recent Integrated Report but reached no determination, so the record holds that filing and its use rows, but no verdict, and with nothing judged, no impairment cause to track over time. The state has not yet filed a definitive fish-consumption verdict, a definitive recreation verdict, a definitive aquatic-life verdict, and 1 other for this record; those fields populate when it reports them in a future Integrated Report cycle.
In context
Where East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries 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
46 Top 47% larger than 53% 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
In both charts each bar is a band and taller bars hold more waterbodies; the dashed line and filled bar mark East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries. Hover or tap any bar for its full count and share.
In context
Colorado context
ATTAINS carries 344 lake-type waterbodies in Colorado, 89 assessed as not supporting at least one use and 74 fully supporting.
| Other large assessed lakes in Colorado | Assessed acres |
|---|---|
| John Martin Reservoir. Not Supporting | 17,147 |
| Blue Mesa Reservoir Fully Supporting | 8,957 |
| Lake Granby. Not Supporting | 7,036 |
| Two Buttes Reservoir, Two Buttes Pond, Hasty Lake, Holbrook Reservoir, Burchfield Lake, Nee-Skah (Queens) Reservoir, Neeso Pah Reservoir, Nee Noshe Reservoir. Fully Supporting | 6,123 |
| Lake and reserviors tributary to the South Platte River Not Assessed | 5,770 |
| Lake Meredith. Not Supporting | 5,531 |
Lakes near East and West Forks of Horsefly Creek and Happy Canyon Creek, mainstems and all tributaries's assessed acres
Similar assessed acres
Nearest filed extents (46 acres here).
- Rice Bed · 46 acres · MN
- Steel Lake · 46 acres · WA
- Long Lake · 46 acres · WI
- Black Earth · 46 acres · MN
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 COGUUN14_A. 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.