New Hampshire reservoir · state assessment record
Lake Winnipesaukee
Assessment decisions reported by New Hampshire to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2024 reporting cycle.
- 44,315
- Assessed acres
- Lake / Reservoir / Pond
- Water type
This waterbody in one line
Lake Winnipesaukee, a reservoir in New Hampshire, is assessed as not supporting one or more designated uses, with 3 listed impairment causes in the state's most recent Integrated Report cycle (2024). 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 (3 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
- P100
- Assessed size nationally
- P5
- 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.
Where Lake Winnipesaukee stands in 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 Lake Winnipesaukee nationally is assessed size: 44,315 acres, larger than 100% of the 38,628 lake-type units with an area on file.
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.
Longer than most cause lists
3 listed causes puts this unit above 90% 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.
Lake Winnipesaukee: Category 4A reading
Category 4A means a TMDL (or equivalent) is already approved for the impairment on Lake Winnipesaukee. The remaining work is implementation and tracking, read the cleanup-standing and cause rows for what the state already committed to address.
Overall status: not supporting
The filer's overall status for Lake Winnipesaukee 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, New Hampshire carries 2,786 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to Lake Winnipesaukee 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. The latest monitoring New Hampshire filed against this record runs through 2023. For the definitive verdicts on this record, New Hampshire filed the assessment basis as Monitored Data. Those are EPA's own words, not PlainLakes' summary of them.
| Designated use | Group | Verdict |
|---|---|---|
| Aquatic Life Integrity | Aquatic-life or related | Not Supporting |
| Fish Consumption | Fish-consumption or fishery | Not Supporting |
| Potential Drinking Water Supply | Drinking-water supply designation | Fully Supporting |
| Primary Contact Recreation | Recreation | Fully Supporting |
| Secondary Contact Recreation | Recreation | Fully 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 |
|---|---|---|---|
| Mercury - Fish Consumption Advisory | Fish Consumption | 2002 | TMDL approved |
| Non-Native Aquatic Plants | Aquatic Life Integrity | 2002 | None reported |
| pH | Aquatic Life Integrity | 2006 | TMDL approved |
Reading the record
Lake Winnipesaukee: Category 4A reading
4A Category 4A: impaired, TMDL completed
New Hampshire 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
Lake Winnipesaukee is one of 2,786 lake-type waterbodies reported to EPA from New Hampshire, and one of 2,233 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 44,315 assessed acres it ranks 71st 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 70 lakes with a larger one.
Why no water-level record
Lake Winnipesaukee has no daily USGS water-level or reservoir-storage series on this page because NWIS lists a lake monitoring site named for the waterbody, but the site is not active, and PlainLakes ingests only the active inventory, so there is no series to attach. How PlainLakes links gauges.
In context
Where Lake Winnipesaukee 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
44,315 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
3 Longer than most more listed causes than 90% 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 Lake Winnipesaukee. Hover or tap any bar for its full count and share.
In context
New Hampshire context
ATTAINS carries 2,786 lake-type waterbodies in New Hampshire, 2,783 assessed as not supporting at least one use and 0 fully supporting. Among the 2,233 indexed units there, Lake Winnipesaukee ranks 129th by listed-cause count (3 listed causes) and 1st by assessed size among the 2,233 with an area filed; it sits in the not-supporting set (2,783 statewide) . Its listed causes include Mercury - Fish Consumption Advisory and pH, which also appear among New Hampshire's most-filed impairment causes (led by Mercury - Fish Consumption Advisory). It also lists Non-Native Aquatic Plants, outside that top-five list.
| Other large assessed lakes in New Hampshire | Assessed acres |
|---|---|
| Squam Lake Not Supporting | 6,774 |
| Lake Umbagog Not Supporting | 4,639 |
| Newfound Lake Not Supporting | 4,440 |
| Lake Winnisquam Not Supporting | 4,203 |
| Sunapee Lake Not Supporting | 4,115 |
| Connecticut River - Gilman Dam Pond Not Supporting | 3,800 |
Peers near Lake Winnipesaukee's size or cause load
Similar assessed acres
Nearest filed extents (44,315 acres here).
- Lake Abert · 44,751 acres · OR
- Lake George · 43,576 acres · FL
- Lake Erie Sandusky Basin Shoreline (<=3m) · 43,526 acres · OH
- Robert S. Kerr Lake · 43,380 acres · OK
Similar cause load
Nearest listed-cause counts (3 here). Peers already in the acreage column are omitted.
- 67th St. Beach · 3 causes · IL
- Abiquiu Reservoir · 3 causes · NM
- Absecon Creek (AC Reserviors) (gage to SB) · 3 causes · NJ
- Absecon Creek (below gage) · 3 causes · NJ
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
- 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 NHLAK700020110-02-19. 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.