Colorado reservoir · state assessment record
Ridgway Reservoir.
Assessment decisions reported by Colorado to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2022 reporting cycle.
- 528
- Assessed acres
- Lake / Reservoir / Pond
- Water type
- 69,820.0 acre-ft
- Reservoir Storage (provisional)
This waterbody in one line
Ridgway Reservoir., a reservoir in Colorado, is assessed as fully supporting its designated uses, with no impairment causes listed in the state's most recent Integrated Report cycle (2022). By assessed acreage it sits among the largest 10% by assessed acreage nationally (38,628 lakes); its impairment list is shorter than on half of assessed lakes (0 listed causes). A USGS gauge tracks its reservoir storage daily.
- Fully Supporting
- overall status
- P91
- Assessed size nationally
- P51
- 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 Ridgway Reservoir. 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: cause-list length
The standout filed fact is a short cause list: 0 causes, shorter than 51% of assessed lake-type units. A short list can mean a focused impairment, or a shallow assessment.
Large assessed unit
At 528 acres, Ridgway Reservoir. clears the upper tercile of assessed lake-type units with an area on file (3,594 still larger). Size comparisons use the portal's deduplicated lake ranking population, not raw ATTAINS row counts.
All ruled-on uses pass
The filed use determinations for recreation are all Fully Supporting. Where an overall IR category still flags the unit, look at the cause list and report standing rather than treating the use row as empty.
IR category in the supporting band
EPA's Integrated Report category for Ridgway Reservoir. is 2. In ATTAINS that band means the assessed uses are supporting (or supporting with other waters in the unit), so the narrative weight shifts to how deep the assessment went and whether monitoring is current, not to a restoration plan.
Overall status: fully supporting
Overall status is Fully Supporting. If an IR category or cause row still appears, it usually reflects a prior listing path or a use the overall rollup does not collapse, read those sections rather than stopping at the tile.
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 Ridgway 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. Colorado filed 2019 as the year this waterbody was last monitored.
| Designated use | Group | Verdict |
|---|---|---|
| Agriculture | Other | Fully Supporting |
| Recreation | Recreation | Fully Supporting |
| Aquatic Life Cold Water-Class 1 | Aquatic-life or related | Insufficient Information |
The record
Listed impairment causes
The state's reported assessment lists no impairment causes for this reservoir.
Reading the record
Ridgway Reservoir.: Category 2 reading
2 Category 2: some uses supported, others not assessed
Colorado filed this assessment unit as Category 2: some designated uses are supported and others were not assessed in this cycle. Absence of a failing verdict is not the same as a full Category 1 finding.
Scale and rank
Ridgway Reservoir. is one of 344 lake-type waterbodies reported to EPA from Colorado, and one of 122 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 528 assessed acres it ranks 3,595th 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 3,594 lakes with a larger one.
Reservoir storage
A USGS gauge tracks this reservoir's storage daily, and the latest reading is 4,620.00 acre-ft less than the reading 30 days earlier, against a 365-day observed range of 20,570.0 acre-ft. 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.
Reservoir storage: 365-day record
Daily reservoir storage values from USGS gauge 09147022 (Ridgway Reservoir Near Ridgway, Co), shown weekly. Readings are daily-batch snapshots, not real-time conditions.
- Latest reading
- 69,820.0 acre-ft 4620acre-ft vs 30 days earlier
- 2026-08-15 · Provisional, subject to USGS revision
Reservoir storage: 365-day record
Subscribe to reservoir storage updates for Ridgway Reservoir. (RSS)
105 of the 360 daily values in this window (29%) are provisional and subject to USGS revision; USGS has approved this gauge's record through 2026-04-27.
Of the 360 daily values in this record, 2 were estimated by USGS rather than measured. USGS marks these individually; approval and estimation are separate judgements and a value can carry both.
Full gauge record: USGS monitoring location 09147022
In context
Where Ridgway 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
528 Top 9% larger than 91% 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
0 Among the shortest cause lists fewer listed causes than 51% 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 Ridgway Reservoir.. 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. Among the 122 indexed units there, Ridgway Reservoir. ranks 97th by listed-cause count (no listed causes) and 44th by assessed size among the 122 with an area filed; it is one of the 74 fully-supporting indexed records in the state .
| 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 |
Peers near Ridgway Reservoir.'s size or cause load
Similar assessed acres
Nearest filed extents (528 acres here).
- Hauff Lake · 528 acres · ND
- Garrison Lake · 528 acres · OR
- Marion · 528 acres · MN
- Clear Lake · 528 acres · SD
Similar cause load
Nearest listed-cause counts (0 here). Peers already in the acreage column are omitted.
- 31st Street Harbor · 0 causes · IL
- 42nd Avenue East Beach · 0 causes · MN
- 59th Street Harbor · 0 causes · IL
- 657 Dunleavy (Beach) · 0 causes · MI
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
- Storage is a volume in acre-feet, not a water level, and it moves with seasonal drawdown and release schedules as well as inflow. How to read gauge data
- 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 COGUUN19_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.