Some of these decisions are EPA's. 3 of these 516 records carry a Clean Water Act cleanup plan EPA established rather than Pennsylvania. They are counted in every figure on this page, and each record page names which.
State water-quality picture · #19 by reported lake-type waterbodies
Pennsylvania lakes and reservoirs
Every figure on this page is computed from the assessment decisions Pennsylvania reported to the U.S. Environmental Protection Agency under Clean Water Act sections 303(d) and 305(b) (reporting cycles 1996–2026), plus daily water-level observations from the U.S. Geological Survey.
- 516
- Reported waterbodies
- 135
- Not supporting a use
- 62
- Fish use not supporting
- 0
- Gauged lakes
Pennsylvania in one line
516 lake-type waterbodies in Pennsylvania are reported to EPA ATTAINS across reporting cycles 1996–2026: 135 assessed as not supporting at least one designated use, 381 fully supporting, and 0 without a definitive overall verdict. The most-listed impairment cause is Mercury, on 60 waterbodies.
- 516
- reported waterbodies
- 135
- not supporting a use
- 381
- fully supporting
- 26%
- of definitive verdicts impaired
An unassessed waterbody is neither confirmed clean nor confirmed impaired; states assess on multi-year cycles.
Pennsylvania's mid-size register with a lighter not-supporting share
Pennsylvania sits in the middle third by inventory size (516 units) and in the lowest third for ruled not-supporting share (26%).
Data updated 2026-08-17
According to the U.S. Environmental Protection Agency's ATTAINS program, Pennsylvania reported 516 lake-type waterbodies in Pennsylvania in the August 2026 extract. See our methodology for filer attribution and multi-year reporting cycles.
Overall-status mix on Pennsylvania's mid-size inventory
Every reported lake-type unit in Pennsylvania falls into exactly one overall-status bucket. This bar is the inventory partition; the cause chart and national gauge below answer different questions.
Most-listed impairment causes in Pennsylvania
Waterbodies carrying each listed cause, most first
- Mercury
Mercury
60 waterbodies
- Nutrients
Nutrients
30 waterbodies
- pH
pH
26 waterbodies
- Organic Enrichment 20
Organic Enrichment
20 waterbodies
- Total Suspended Solids (TSS) 12
Total Suspended Solids (TSS)
12 waterbodies
What this shows Mercury is the most-listed impairment cause in Pennsylvania, on 60 of the lake-type waterbodies reported there.
Computed share from EPA ATTAINS filed records, not an official EPA rating or safety grade.
Pennsylvania: 26% of ruled verdicts are not-supporting, against a national share of 53%, 2.0× below the national rate.
Reporting practice
Pennsylvania's waterbodies mostly carry a definitive verdict
Each reporting authority decides how much of the water it files to EPA it actually assesses in a cycle. That decision sets the denominator behind every count on this page.
Pennsylvania holds the 19th-largest reported lake-type inventory in the country, 516 assessment units, carrying a definitive verdict on 100% of it. Every reported unit carries a verdict, so the counts above describe the whole reported inventory. Pennsylvania has also retired 3 lake-type assessment units, superseded filings that are kept on the site but not counted here.
The state reporting at the nearest rate is Vermont (100%).
Assessing more of an inventory is a reporting choice, set by cycle length, monitoring budget and how finely a state splits its waters into units. It is not a measure of water quality, and it is why a raw count from one state does not sit beside a raw count from another. How assessment coverage varies.
Pennsylvania against every comparable state
Share of reported lake-type waterbodies carrying a definitive verdict
100% 1st of 47 higher than 45 of 47 states
the 47 comparable states, by definitive-verdict share
Each bar is a band; taller bars hold more states. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count and share, and where it sits relative to this entry.
Source EPA ATTAINS · Reporting cycles 1987–2026
Each bar counts states whose definitive-verdict share falls in that 10-point band. The 47 states shown are those reporting at least 25 lake-type units; a share off a smaller inventory is precision the data does not have.
By size
Largest assessed lakes in Pennsylvania
By assessed acreage as reported in ATTAINS. Acreage is the assessed unit's size, which can differ from a lake's full surface area.
| # | Waterbody | Assessed acres |
|---|---|---|
| 1 | Pymatuning Reservoir-05030102001826 Not Supporting | 15,995 |
| 2 | Allegheny Reservoir-05010001002698 Not Supporting | 12,211 |
| 3 | Raystown Lake-02050303001006 Fully Supporting | 8,127 |
| 4 | Lake Clark-02050306012077 Fully Supporting | 8,117 |
| 5 | Lake Wallenpaupack-02040103001053 Not Supporting | 5,461 |
| 6 | Presque Isle Bay-04120101000933 Not Supporting | 3,655 |
| 7 | Shenango River Lake (Res)-05030102001670 Fully Supporting | 3,417 |
| 8 | Lake Arthur-05030105001146 Fully Supporting | 3,075 |
| 9 | Youghiogheny River Lake-05020006001912 Not Supporting | 2,916 |
| 10 | Foster Joseph Sayers Lake-02050204002478 Fully Supporting | 2,083 |
| 11 | Pymatuning Reservoir-05030102001484 Not Supporting | 1,772 |
| 12 | Glendale Lake-02050201001384 Not Supporting | 1,585 |
By cause count
Most-listed waterbodies in Pennsylvania
Waterbodies carrying the most listed impairment causes among the lake-type units reported by Pennsylvania.
| # | Waterbody | Listed causes |
|---|---|---|
| 1 | Lake Towhee-02040105001730 Not Supporting | 5 |
| 1 | Meadow Lake-02040203002090 Not Supporting | 5 |
| 3 | Lake Luxembourg-02040201003565 Not Supporting | 4 |
| 3 | Lake Winola-02050106002864 Not Supporting | 4 |
| 3 | Magnolia Lake-02040201000968 Not Supporting | 4 |
| 3 | Pymatuning Reservoir-05030102001484 Not Supporting | 4 |
| 3 | Pymatuning Reservoir-05030102001826 Not Supporting | 4 |
| 3 | Shawnee Lake-02050303001015 Not Supporting | 4 |
| 3 | Warrington Lake-02040201000836 Not Supporting | 4 |
| 10 | Blue Marsh Lake-02040203008645 Not Supporting | 3 |
9 of the 10 rows in this table tie on the ranked value: 2 at 5 (rank 1), 7 at 4 (rank 3). Tied rows share a rank and are listed in no meaningful order; where a tie reaches the top the medal is shared, because nothing separates those rows.
States near Pennsylvania's lighter not-supporting load
Two EPA ATTAINS peer sets outside Pennsylvania. The reporting-practice chart above stays on definitive-verdict share; these neighborhoods highlight register-size and not-supporting peers while Pennsylvania's ruled impairment share sits in the lowest third.
Similar reported inventory
Nearest states by lake-type units on the register (516 here).
- Texas · 489 units · 27 off
- Nebraska · 554 units · 38 off
- Oklahoma · 456 units · 60 off
- West Virginia · 434 units · 82 off
States with a similar not-supporting load
Nearest states by units assessed not supporting a use (135 here). Inventory peers above are omitted.
- Iowa · 137 not supporting · 2 off
- Alabama · 143 not supporting · 8 off
- Indiana · 145 not supporting · 10 off
- South Dakota · 145 not supporting · 10 off
Peers are nearest-neighbor matches on EPA ATTAINS register size and not-supporting counts among states with at least 25 reported units. Impairment peers skip states already listed in the inventory column so the two link sets stay distinct.
Using this state picture
- Comparisons across states hold on shares, not counts: 100% of the inventory reported from Pennsylvania carries a definitive verdict, 1st of 47 comparable states. National rankings
- Fish-consumption verdicts here are assessment decisions. Species-level meal advice comes from the state fish-advisory program. Consumption guide
- Browse every named Pennsylvania waterbody with a populated record. Browse waterbodies
PlainLakes renders state assessment decisions and federal gauge observations without modification.
Figures on this page are computed from the assessment decisions Pennsylvania reported to EPA's ATTAINS system and from USGS National Water Information System daily values, no number is typed in by an editor. State counts aggregate every lake-type assessment unit reported by Pennsylvania, including unnamed units that never receive their own page. 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.