Massachusetts lake · state assessment record
Reservoir (16 acres)
Assessment decisions reported by Massachusetts to EPA under Clean Water Act sections 303(d) and 305(b), last assessed in the 2026 reporting cycle, a cycle that is open for public comment.
- 16
- Assessed acres
- Lake, Freshwater
- Water type
This waterbody in one line
Reservoir, a lake in Massachusetts, is assessed as not supporting one or more designated uses, with one listed impairment cause in the state's most recent Integrated Report cycle (2026), a cycle that is open for public comment. By assessed acreage it sits below the national median by assessed acreage (38,628 lakes); its impairment list is among the longest nationally (one listed cause vs 23,610 assessed lakes). Aquatic life is assessed as not supporting.
- Not Supporting
- overall status
- P28
- Assessed size nationally
- P20
- 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.
Reservoir 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: in-state cause rank
Inside Massachusetts, this unit sits toward the short-list end: cause-list rank 591 of 678 indexed units.
No ruled-on use clears the bar
On the uses this filer ruled on, aquatic life, every determination is Not Supporting. That is a use-by-use reading of the filed record, not a single overall lake grade.
Reservoir: Category 4C reading
Category 4C marks impairment from pollution that is not a pollutant (for example habitat or flow alteration) on Reservoir. A classic TMDL load model often does not apply; the cause list should name the non-pollutant stressor.
Overall status: not supporting
The filer's overall status for Reservoir is Not Supporting. That tile summarizes the assessment unit; the designated-use rows and cause list are the evidence behind it.
Small within Massachusetts
State size rank 523 of 678 puts Reservoir toward the small end of Massachusetts's indexed lake-type units with an area.
According to the U.S. Environmental Protection Agency's ATTAINS program, Massachusetts carries 1,191 filed lake-type waterbodies in the August 2026 extract, and this page renders the assessment record EPA assigned to 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. For the one definitive verdict on this record, Massachusetts filed the assessment basis as Monitored Data. Those are EPA's own words, not PlainLakes' summary of them.
| Designated use | Group | Verdict |
|---|---|---|
| Fish, Other Aquatic Life and Wildlife | Aquatic-life or related | Not Supporting |
| Aesthetic | Other | Insufficient Information |
| Fish Consumption | Fish-consumption or fishery | Not Assessed |
| Primary Contact Recreation | Recreation | Insufficient Information |
| Secondary Contact Recreation | Recreation | Insufficient Information |
The record
Listed impairment causes
Causes the state listed as impairing designated uses of this lake, with the cycle each was first listed. None is a pollutant, so none carries a TMDL cleanup plan.
| Cause | Affected uses | First listed | Cleanup standing |
|---|---|---|---|
| Flow Regime Modification | Fish, Other Aquatic Life and Wildlife | 2002 | Not applicable (non-pollutant) |
Probable sources
Massachusetts 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
Reservoir: Category 4C reading
4C Category 4C: impaired by a non-pollutant; TMDL programme does not apply
Massachusetts filed this assessment unit as Category 4C: the impairment is not caused by a pollutant, so the Clean Water Act 303(d) cleanup-plan (TMDL) programme, which allocates pollutant loads, does not apply here.
A 4C listing is still an impairment finding about designated uses; it is not a clean bill of health. How listing and cleanup work.
Scale and rank
Reservoir is one of 1,191 lake-type waterbodies reported to EPA from Massachusetts, and one of 678 whose reported record carries enough populated assessment or gauge data for this site to list and index it. At 16 assessed acres it ranks 27,858th 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 27,857 lakes with a larger one.
Awaiting a filing
The state has not yet filed a definitive fish-consumption verdict and a definitive recreation verdict for this record; those fields populate when it reports them in a future Integrated Report cycle.
In context
Where 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
16 Top 72% larger than 28% 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 Reservoir. Hover or tap any bar for its full count and share.
In context
Massachusetts context
ATTAINS carries 1,191 lake-type waterbodies in Massachusetts, 678 assessed as not supporting at least one use and 40 fully supporting. Among the 678 indexed units there, Reservoir ranks 591st by listed-cause count (one listed cause) and 523rd by assessed size among the 678 with an area filed; it sits in the not-supporting set (678 statewide) . Its listed causes (Flow Regime Modification) sit outside Massachusetts's top-five list, which is led by Mercury in Fish Tissue.
| Other large assessed lakes in Massachusetts | Assessed acres |
|---|---|
| Quabbin Reservoir Not Supporting | 24,010 |
| Wachusett Reservoir Not Supporting | 3,962 |
| Assawompset Pond Not Assessed | 2,034 |
| North Watuppa Pond Not Supporting | 1,728 |
| Long Pond Not Supporting | 1,728 |
| South Watuppa Pond Not Supporting | 1,473 |
Peers near Reservoir's size or cause load
Similar assessed acres
Nearest filed extents (16 acres here).
- Baha Trail Lake · 16 acres · MO
- Banning Lake · 16 acres · IN
- Beards Creek · 16 acres · NH
- Beaver (Hydepk); · 16 acres · VT
Similar cause load
Nearest listed-cause counts (1 here). Peers already in the acreage column are omitted.
- Aaron · 1 causes · MN
- Abbotts Creek (including Lexington-Thomasville Water Supply Reservoir at normal reservoir elevation, Tom-A-Lex Lake) · 1 causes · NC
- Abeniki Lake · 1 causes · NH
- Academy Brook II Dam · 1 causes · NH
What to do with this record
- Assessment verdicts are cycle-based, not real-time. For fish-consumption decisions, your state advisory program is the binding source. 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 MA94127. 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.