Nevada reservoir · state assessment record
Topaz Lake
Assessment decisions reported by Nevada to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2022 reporting cycle.
- 987
- Assessed acres
- Reservoir
- Water type
- 91.3 ft
- Water Surface Elevation (provisional)
This waterbody in one line
Topaz Lake, a reservoir in Nevada, is assessed as not supporting one or more designated uses, with one listed impairment cause 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 among the longest nationally (one listed cause vs 23,610 assessed lakes). Aquatic life is assessed as fully supporting. Fish consumption is assessed as not supporting. A USGS gauge tracks its water surface elevation daily.
- Not Supporting
- overall status
- P94
- Assessed size nationally
- P20
- Shorter cause list
- Fully 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 Topaz Lake 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 Topaz Lake nationally is assessed size: 987.1 acres, larger than 94% of the 38,628 lake-type units with an area on file.
A split ruling across uses
This record splits: Not Supporting on fish consumption, Fully Supporting on recreation, aquatic life. The divergence is inside the designated-use matrix, not a single all-or-nothing label.
Topaz Lake: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Topaz Lake. 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 Topaz Lake is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
Typical cause-list length
1 listed cause is a middle-tercile list length among assessed lake-type units. Look to IR category and use outcomes for the distinctive reading.
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 Topaz 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. 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 | Fully 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 | Fully 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 reservoir, with the cycle each was first listed and the Clean Water Act action recorded against it.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Mercury in Fish Tissue | Fish Consumption | 2024 | TMDL priority: Low |
Reading the record
Where Topaz Lake sits among peers
70% of Nevada's lakes assessed this deeply also came out mixed
Nevada ruled definitively on 9 designated uses at Topaz Lake and found 1 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: Topaz Lake. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Topaz Lake 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 987 assessed acres it ranks 2,287th 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 2,286 lakes with a larger one.
Water level
A USGS gauge tracks this reservoir's water surface elevation daily, and the latest reading is 7.05 ft below the reading 30 days earlier, against a 365-day observed range of 20.2 ft.
Water level: 365-day record
Daily water surface elevation values, feet above a local project datum, not above sea level, from USGS gauge 10297000 (Topaz Lake Nr Topaz, Ca), 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
- 91.3 ft 7.049999999999997ft vs 30 days earlier
- 2026-08-15 · Provisional, subject to USGS revision
Water level: 365-day record
Subscribe to water level updates for Topaz Lake (RSS)
USGS files this series under its water surface elevation parameter, but the reading sits far below the 4,900 ft land-surface altitude USGS records for the gauge itself, which is how the local zero was identified. The figure tracks this reservoir’s own stage and is comparable with its own history alone, never with another lake’s reading.
68 of the 365 daily values in this window (19%) are provisional and subject to USGS revision; USGS has approved this gauge's record through 2026-06-08.
Full gauge record: USGS monitoring location 10297000
In context
Where Topaz 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
987 Top 6% larger than 94% 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
1 Longer than most more listed causes than 49% 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 Topaz Lake. 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, Topaz Lake ranks 28th by listed-cause count (one listed cause) and 11th by assessed size among the 50 with an area filed; it sits in the not-supporting set (36 statewide) . Its listed causes include Mercury in Fish Tissue, which also appears among Nevada's most-filed impairment causes (led by Phosphorus).
| 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 Topaz Lake's size or cause load
Similar assessed acres
Nearest filed extents (987 acres here).
- <Null> · 987 acres · OR
- Oconee Lake · 988 acres · GA
- Shaokatan · 986 acres · MN
- Mudd Lake · 989 acres · ND
Similar cause load
Nearest listed-cause counts (1 here). Peers already in the acreage column are omitted.
- Aaron · 1 causes · MN
- Aaron River Reservoir · 1 causes · MA
- Abbotts Creek (including Lexington-Thomasville Water Supply Reservoir at normal reservoir elevation, Tom-A-Lex Lake) · 1 causes · NC
- Abeniki Lake · 1 causes · NH
What to do with this record
- The fish-consumption use is assessed as not supporting. Before eating fish from this reservoir, check your state fish-advisory program for species-specific meal limits. 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 NV09-WR-02_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.