Arizona lake · state assessment record
Stoneman Lake
Assessment decisions reported by Arizona to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2026 reporting cycle.
- 125
- Assessed acres
- Lake, Freshwater
- Water type
- Eutrophic
- Reported trophic class
This waterbody in one line
Stoneman Lake, a lake in Arizona, is assessed as not supporting one or more designated uses, with 2 listed impairment causes in the state's most recent Integrated Report cycle (2026). By assessed acreage it sits above the national median by assessed acreage (38,628 lakes); its impairment list is among the longest nationally (2 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting.
- Not Supporting
- overall status
- P74
- 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.
Stoneman Lake against the ATTAINS 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: in-state cause rank
Inside Arizona, cause-list rank is the local separator: Stoneman Lake is 8 of 44 indexed units by listed-cause count, toward the top of that state's filed lists.
Every filed use falls short
On the uses this filer ruled on, recreation, aquatic life, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Stoneman Lake: Category 4A reading
Category 4A means a TMDL (or equivalent) is already approved for the impairment on Stoneman Lake. The remaining work is implementation and tracking, read the cleanup-standing and cause rows for what the state already committed to address.
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 Stoneman 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, Arizona carries 78 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Stoneman 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 |
|---|---|---|
| Agricultural Irrigation | Other | Not Supporting |
| Agricultural Livestock Watering | Other | Not Supporting |
| Aquatic and Wildlife (Coldwater Fishery) | Aquatic-life or related | Not Supporting |
| Full Body Contact | Recreation | Not Supporting |
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 |
|---|---|---|---|
| Dissolved Oxygen | Aquatic and Wildlife (Coldwater Fishery) | 1998 | TMDL approved |
| pH | Full Body Contact; Agricultural Irrigation; Aquatic and Wildlife (Coldwater Fishery); Agricultural Livestock Watering | 1998 | TMDL approved |
Reading the record
Stoneman Lake: Category 4A reading
4A Category 4A: impaired, TMDL completed
Arizona filed this assessment unit as Category 4A: impaired, with a pollutant-budget TMDL already completed under 303(d). The listing remains an impairment finding; the plan is on file rather than still awaiting write-up.
Scale and rank
Stoneman Lake is one of 78 lake-type waterbodies reported to EPA from Arizona, and one of 44 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 125 assessed acres it ranks 10,084th 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 10,083 lakes with a larger one.
Open in the register
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.
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 Stoneman 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
125 Top 26% larger than 74% 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 Stoneman Lake. Hover or tap any bar for its full count and share.
In context
Arizona context
ATTAINS carries 78 lake-type waterbodies in Arizona, 34 assessed as not supporting at least one use and 20 fully supporting. Among the 44 indexed units there, Stoneman Lake ranks 8th by listed-cause count (2 listed causes) and 26th by assessed size among the 44 with an area filed; it sits in the not-supporting set (34 statewide) . Its listed causes include Dissolved Oxygen and pH, which also appear among Arizona's most-filed impairment causes (led by Mercury in Fish Tissue).
| Other large assessed lakes in Arizona | Assessed acres |
|---|---|
| Lake Mohave Not Supporting | 27,044 |
| Lake Havasu Not Supporting | 19,780 |
| Roosevelt Lake Not Supporting | 18,345 |
| Lake Powell Not Supporting | 9,770 |
| Lake Pleasant Not Supporting | 8,000 |
| Topock Marsh Not Assessed | 4,870 |
Peers near Stoneman Lake's size or cause load
Similar assessed acres
Nearest filed extents (125 acres here).
- Bayles · 125 acres · IL
- Campbell Lake · 125 acres · AK
- Farm Pond · 125 acres · MA
- Glass Lake · 125 acres · NY
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 AZL15060202-1490_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.