California reservoir · state assessment record
Pyramid Lake
Assessment decisions reported by California to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2022 reporting cycle.
- 1,177
- Assessed acres
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
Pyramid Lake, a reservoir in California, is assessed as not supporting one or more designated uses, with 7 listed impairment causes in the state's most recent Integrated Report cycle (2022). By assessed acreage it sits among the largest 5% by assessed acreage nationally (38,628 lakes); its impairment list is among the longest nationally (7 listed causes vs 23,610 assessed lakes). Aquatic life is assessed as not supporting. California assesses commercial and sport fishing as not supported; it reported no verdict on fish consumption itself.
- Not Supporting
- overall status
- P95
- Assessed size nationally
- P1
- 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.
Pyramid 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: cause-list length
The standout filed fact is cause-list length: 7 listed impairment causes, a longer list than 99% of assessed lake-type units (n=23,610). List length tracks how states sample and code, not a severity score.
Large assessed unit
At 1,177 acres, Pyramid Lake clears the upper tercile of assessed lake-type units with an area on file (2,023 still larger). Size comparisons use the portal's deduplicated lake ranking population, not raw ATTAINS row counts.
Every filed use falls short
On the uses this filer ruled on, fish consumption, aquatic life, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Pyramid Lake: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Pyramid 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 Pyramid 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, California carries 607 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Pyramid 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 Supply | Other | Fully Supporting |
| Cold Freshwater Habitat | Aquatic-life or related | Not Supporting |
| Commercial and Sport Fishing | Fish-consumption or fishery | Not Supporting |
| Municipal and Domestic Supply | Drinking-water supply designation | Not Supporting |
| Warm Freshwater Habitat | Aquatic-life or related | Not Supporting |
| Wildlife Habitat | Other | 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 |
|---|---|---|---|
| DDT (Dichlorodiphenyltrichloroethane) | Commercial and Sport Fishing Also assessed as meeting: Cold Freshwater Habitat, Warm Freshwater Habitat | 2024 | None reported |
| Dieldrin | Commercial and Sport Fishing Also assessed as meeting: Cold Freshwater Habitat, Warm Freshwater Habitat | 2024 | None reported |
| Mercury | Commercial and Sport Fishing; Wildlife Habitat Also assessed as meeting: Cold Freshwater Habitat, Warm Freshwater Habitat | 2024 | None reported |
| Polychlorinated Biphenyls (PCBs) | Commercial and Sport Fishing Also assessed as meeting: Cold Freshwater Habitat, Warm Freshwater Habitat | 2024 | None reported |
| Sodium | Municipal and Domestic Supply Also assessed as meeting: Agricultural Supply | 2024 | None reported |
| Temperature | Cold Freshwater Habitat Also assessed as meeting: Warm Freshwater Habitat | 2024 | None reported |
| pH | Cold Freshwater Habitat; Municipal and Domestic Supply; Warm Freshwater Habitat | 2024 | None reported |
Probable sources
California listed the source of the impairment as unknown. That is the state's own filed value, not a gap in this record: the cause has been identified, the origin has not.
Reading the record
Where Pyramid Lake sits among peers
8 of 13 California lakes assessed this deeply also came out mixed
California ruled definitively on 6 designated uses at Pyramid Lake and found 5 of 6 not supported. The dataset shows 13 California lakes judged to that same depth.
California's assessed lakes are most often judged on 2 uses; this one was judged on 6.
| 1 | 2 | 3 | 4 | 5+ | |
|---|---|---|---|---|---|
| All supported | 11 | 8 | 0 | 0 | 3 |
| Mixed | Not possible | 3 | 10 | 8 | 8 (this record) |
| None supported | 46 | 107 | 11 | 7 | 2 |
Ringed cell: Pyramid Lake. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Pyramid Lake is one of 607 lake-type waterbodies reported to EPA from California, and one of 195 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 1,177 assessed acres it ranks 2,024th 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 2,023 lakes with a larger one.
Still unfiled
The state has not yet filed a definitive recreation verdict for this record; that field populates when it reports it in a future Integrated Report cycle.
In context
Where Pyramid 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
1,177 Top 5% larger than 95% 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
7 Longer than most more listed causes than 99% 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 Pyramid Lake. Hover or tap any bar for its full count and share.
In context
California context
ATTAINS carries 607 lake-type waterbodies in California, 202 assessed as not supporting at least one use and 22 fully supporting. Among the 195 indexed units there, Pyramid Lake ranks 4th by listed-cause count (7 listed causes) and 55th by assessed size among the 195 with an area filed; it sits in the not-supporting set (202 statewide) . Its listed causes include DDT (Dichlorodiphenyltrichloroethane), Mercury, Polychlorinated Biphenyls (PCBs), and pH, which also appear among California's most-filed impairment causes (led by Mercury). It also lists Dieldrin, Sodium, and Temperature, outside that top-five list.
| Other large assessed lakes in California | Assessed acres |
|---|---|
| Salton Sea Not Supporting | 233,045 |
| Tahoe, Lake Not Supporting | 84,092 |
| Goose Lake (Modoc County) Not reported | 62,385 |
| Honey Lake Not Supporting | 55,526 |
| Klamath River HU, Tule Lake and Lower Klamath Lake National Wildlife Refuge Not Supporting | 48,791 |
| Mono Lake Not Supporting | 45,299 |
Peers near Pyramid Lake's size or cause load
Similar assessed acres
Nearest filed extents (1,177 acres here).
- Lake Henry. · 1,178 acres · CO
- Whitewater · 1,177 acres · MN
- John Flannagan Reservoir · 1,177 acres · VA
- Big Black River · 1,178 acres · ME
Similar cause load
Nearest listed-cause counts (7 here). Peers already in the acreage column are omitted.
- Adder Pond · 7 causes · NH
- Arrow Lake · 7 causes · TN
- Barton Cove · 7 causes · MA
- Blue Heron Lagoon · 7 causes · MI
What to do with this record
- The listing here is on a fishery use, not on fish consumption, and this state reported no consumption verdict for this reservoir. Your state fish-advisory program is the source for whether the catch is safe to eat. 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 CAL4034200020091208113257. 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.