Nevada lake · state assessment record
Washoe Lakes
Assessment decisions reported by Nevada to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2022 reporting cycle.
- 5,545
- Assessed acres
- Lake
- Water type
This waterbody in one line
Washoe Lakes, a lake in Nevada, is assessed as not supporting one or more designated uses, with 4 listed impairment causes in the state's most recent Integrated Report cycle (2022). 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 (4 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting. Fish consumption is assessed as not supporting.
- Not Supporting
- overall status
- P99
- Assessed size nationally
- P3
- 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 Washoe Lakes 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 Washoe Lakes nationally is assessed size: 5,545 acres, larger than 99% of the 38,628 lake-type units with an area on file.
Longer than most cause lists
4 listed causes puts this unit above 95% 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.
The uses disagree
This record splits: Not Supporting on fish consumption, aquatic life, Fully Supporting on recreation. The divergence is inside the designated-use matrix, not a single all-or-nothing label.
Washoe Lakes: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Washoe Lakes. 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 Washoe Lakes 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, Nevada carries 69 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Washoe Lakes 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. Monitoring behind at least one of these designated-use verdicts ran through 2022, as Nevada filed it. Nevada filed its own confidence on the 9 definitive verdicts it rated: Low. 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 |
|---|---|---|
| Aquatic Life | Aquatic-life or related | Not Supporting Filer confidence: Low |
| Fish Consumption | Fish-consumption or fishery | Not Supporting Filer confidence: Low |
| Industrial Supply | Other | Fully Supporting Filer confidence: Low |
| Irrigation | Other | Fully Supporting Filer confidence: Low |
| Municipal or Domestic Supply | Drinking-water supply designation | Not Supporting Filer confidence: Low |
| Propagation of Wildlife | Other | Fully Supporting Filer confidence: Low |
| Recreation Involving Contact with the Water | Recreation | Fully Supporting Filer confidence: Low |
| Recreation Not Involving Contact with the Water | Recreation | Fully Supporting Filer confidence: Low |
| Watering of Livestock | Other | Fully Supporting Filer confidence: Low |
| Water and Organisms | 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 |
|---|---|---|---|
| Iron | Aquatic Life Also assessed as meeting: Irrigation | 2024 | TMDL priority: Low |
| Mercury in Fish Tissue | Fish Consumption | 2024 | TMDL priority: Low |
| Phosphorus | Aquatic Life | 2024 | TMDL priority: Low |
| Total Dissolved Solids (TDS) | Municipal or Domestic Supply | 2024 | TMDL priority: Low |
Reading the record
Where Washoe Lakes sits among peers
70% of Nevada's lakes assessed this deeply also came out mixed
Nevada ruled definitively on 9 designated uses at Washoe Lakes and found 3 of 9 not supported. The dataset shows 43 Nevada lakes judged to that same depth.
Nevada's assessed lakes are most often judged on 5 or more uses, as this one was.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 2 | 1 | 1 | 0 | 13 |
| Mixed | Not possible | 1 | 1 | 1 | 30 (this record) |
| None supported | 3 | 0 | 0 | 0 | 0 |
Ringed cell: Washoe Lakes. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Washoe Lakes is one of 69 lake-type waterbodies reported to EPA from Nevada, and one of 50 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 5,545 assessed acres it ranks 561st 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 560 lakes with a larger one.
In context
Where Washoe Lakes 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
5,545 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
4 Longer than most more listed causes than 95% 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 Washoe Lakes. Hover or tap any bar for its full count and share.
In context
Nevada context
ATTAINS carries 69 lake-type waterbodies in Nevada, 36 assessed as not supporting at least one use and 17 fully supporting. Among the 50 indexed units there, Washoe Lakes ranks 7th by listed-cause count (4 listed causes) and 7th by assessed size among the 50 with an area filed; it sits in the not-supporting set (36 statewide) . Its listed causes include Iron, Mercury in Fish Tissue, and Phosphorus, which also appear among Nevada's most-filed impairment causes (led by Phosphorus). It also lists Total Dissolved Solids (TDS), outside that top-five list.
| Other large assessed lakes in Nevada | Assessed acres |
|---|---|
| Lake Mead Fully Supporting | 147,392 |
| Lake Tahoe Not Supporting | 122,902 |
| Walker Lake Not Supporting | 35,521 |
| Lake Mohave Not Supporting | 27,001 |
| Rye Patch Reservoir Not Supporting | 16,001 |
| Lahontan Reservoir Not Supporting | 14,178 |
Peers near Washoe Lakes's size or cause load
Similar assessed acres
Nearest filed extents (5,545 acres here).
- Cobbosseecontee L · 5,543 acres · ME
- Keystone Lake, Cimarron River Arm, Upper · 5,550 acres · OK
- Martin Creek Reservoir · 5,539 acres · TX
- Green · 5,533 acres · MN
Similar cause load
Nearest listed-cause counts (4 here). Peers already in the acreage column are omitted.
- Agency Lake · 4 causes · OR
- Alachua Sink · 4 causes · FL
- Aldrich Pond · 4 causes · MA
- American Falls Reservoir (Snake River) · 4 causes · ID
What to do with this record
- The fish-consumption use is assessed as not supporting. Before eating fish from this lake, check your state fish-advisory program for species-specific meal limits. 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 NV06-SC-40-C_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.