California reservoir · state assessment record
Upper San Leandro Reservoir
Assessment decisions reported by California to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2016 reporting cycle.
- 758
- Assessed acres
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
Upper San Leandro Reservoir, a reservoir in California, is assessed as not supporting one or more designated uses, with one listed impairment cause in the state's most recent Integrated Report cycle (2016). 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). California assesses commercial and sport fishing as not supported; it reported no verdict on fish consumption itself.
- Not Supporting
- overall status
- P93
- Assessed size nationally
- P20
- Shorter cause list
- Not Supporting
- fish-consumption or fishery
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 Upper San Leandro 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 Upper San Leandro Reservoir nationally is assessed size: 758.2 acres, larger than 93% of the 38,628 lake-type units with an area on file.
No ruled-on use clears the bar
On the uses this filer ruled on, fish consumption, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Upper San Leandro Reservoir: Category 5, TMDL still owed
Category 5 is the Integrated Report band where a TMDL (or equivalent) is still expected for Upper San Leandro Reservoir. 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 Upper San Leandro Reservoir 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, California carries 607 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Upper San Leandro 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.
| Designated use | Group | Verdict |
|---|---|---|
| Commercial and Sport Fishing | Fish-consumption or fishery | Not Supporting |
| Wildlife Habitat | Other | Not Supporting |
| Cold Freshwater Habitat | Aquatic-life or related | Insufficient Information |
| Municipal and Domestic Supply | Drinking-water supply designation | Insufficient Information |
| Warm Freshwater Habitat | Aquatic-life or related | Insufficient Information |
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 | Wildlife Habitat; Commercial and Sport Fishing | 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 Upper San Leandro Reservoir sits among peers
91% of California's lakes assessed this deeply also had no use supported (the standard result at this depth, not a distinction)
California ruled definitively on 2 designated uses at Upper San Leandro Reservoir and found none of them supported. The dataset shows 118 California lakes judged to that same depth.
California's assessed lakes are most often judged on 2 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 | 11 | 8 | 0 | 0 | 3 |
| Mixed | Not possible | 3 | 10 | 8 | 8 |
| None supported | 46 | 107 (this record) | 11 | 7 | 2 |
Ringed cell: Upper San Leandro Reservoir. Source: EPA ATTAINS, Reporting cycles 1987–2026.
Scale and rank
Upper San Leandro Reservoir 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 758 assessed acres it ranks 2,776th 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 2,775 lakes with a larger one.
Not yet on record
The state has not yet filed a definitive recreation verdict and a definitive aquatic-life verdict for this record; those fields populate when it reports them in a future Integrated Report cycle.
In context
Where Upper San Leandro 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
758 Top 7% larger than 93% 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 Upper San Leandro Reservoir. 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, Upper San Leandro Reservoir ranks 111th by listed-cause count (one listed cause) and 78th by assessed size among the 195 with an area filed; it sits in the not-supporting set (202 statewide) . Its listed causes include Mercury, which also appears among California's most-filed impairment causes (led by Mercury).
| 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 Upper San Leandro Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (758 acres here).
- Poplar · 758 acres · MN
- Contentnea Cr (Buckhorn Reservoir) · 758 acres · NC
- Umbagog Lake Drainage · 759 acres · ME
- Blackwater · 757 acres · MN
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 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 CAL2042001120091208102529. 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.