Colorado reservoir · state assessment record
John Martin Reservoir.
Assessment decisions reported by Colorado to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2018 reporting cycle.
- 17,147
- Assessed acres
- Lake / Reservoir / Pond
- Water type
- 3,802.2 ft
- Water Surface Elevation (provisional)
This waterbody in one line
John Martin Reservoir., a reservoir in Colorado, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (2018). By assessed acreage it sits among the largest 1% of assessed lakes nationally (38,628 lakes with a filed area); its impairment list is among the longest nationally (2 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting. A USGS gauge tracks its water surface elevation daily.
- Not Supporting
- overall status
- P100
- Assessed size nationally
- P10
- 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.
How John Martin Reservoir. 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 John Martin Reservoir. nationally is assessed size: 17,147 acres, larger than 100% of the 38,628 lake-type units with an area on file.
The uses disagree
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.
John Martin Reservoir.: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for John Martin Reservoir.. 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 John Martin Reservoir. 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, Colorado carries 344 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to John Martin 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 2015 as the year this waterbody was last monitored.
| Designated use | Group | Verdict |
|---|---|---|
| Agriculture | Other | Fully Supporting |
| Aquatic Life Warm Water-Class 1 | Aquatic-life or related | Not Supporting |
| Recreation | Recreation | Fully Supporting |
| Water Supply | Drinking-water supply designation | Not Supporting |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this reservoir, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Arsenic | Water Supply | 2006 | TMDL priority: High |
| Selenium | Aquatic Life Warm Water-Class 1 | 2006 | TMDL priority: Low |
Reading the record
Cleanup queue for John Martin Reservoir.
1 listed cause ranked High in the TMDL queue, still without a plan
Colorado ranked Arsenic 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
John Martin 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 17,147 assessed acres it ranks 176th 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 175 lakes with a larger one.
Water level
A USGS gauge tracks this reservoir's water surface elevation daily, and the latest reading is 1.28 ft below the reading 30 days earlier, against a 365-day observed range of 12.5 ft. 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.
Water level: 365-day record
Daily water surface elevation values, feet above the National Geodetic Vertical Datum of 1929 (NGVD 29), from USGS gauge 07130000 (John Martin Reservoir at Caddoa, Co), shown weekly. Readings are daily-batch snapshots, not real-time conditions. Each daily value is a single reading taken at 24:00, not a daily mean. It is the only daily statistic USGS files for this gauge.
- Latest reading
- 3,802.2 ft 1.2800000000002ft vs 30 days earlier
- 2026-08-15 · Provisional, subject to USGS revision
Water level: 365-day record
Subscribe to water level updates for John Martin Reservoir. (RSS)
116 of the 365 daily values in this window (32%) are provisional and subject to USGS revision; USGS has approved this gauge's record through 2026-04-21.
Of the 365 daily values in this record, 24 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 07130000
In context
Where John Martin 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
17,147 Top 1% larger than 99%+ 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 John Martin 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, John Martin Reservoir. ranks 10th by listed-cause count (2 listed causes) and 1st by assessed size among the 122 with an area filed; it sits in the not-supporting set (89 statewide) . Its listed causes include Arsenic and Selenium, which also appear among Colorado's most-filed impairment causes (led by Arsenic).
| Other large assessed lakes in Colorado | Assessed acres |
|---|---|
| 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 |
| Adobe Creek Reservoir. Not Supporting | 4,784 |
Peers near John Martin Reservoir.'s size or cause load
Similar assessed acres
Nearest filed extents (17,147 acres here).
- Lake Texoma · 17,140 acres · TX
- Crescent Lake · 17,072 acres · FL
- Long Lake Refuge · 16,990 acres · ND
- Lake Charlevoix · 17,324 acres · MI
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
- Water levels shown are daily snapshots. Seasonal drawdown and datum conventions matter when comparing levels. How to read level 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 COARLA11_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.