Some of these decisions are EPA's. 1 of these 77 records carries a Clean Water Act cleanup plan EPA established rather than Alaska. They are counted in every figure on this page, and each record page names which.
State water-quality picture · #42 by reported lake-type waterbodies
Alaska lakes and reservoirs
Every figure on this page is computed from the assessment decisions Alaska reported to the U.S. Environmental Protection Agency under Clean Water Act sections 303(d) and 305(b) (reporting cycles 1989–2024), plus daily water-level observations from the U.S. Geological Survey.
- 77
- Reported waterbodies
- 7
- Not supporting a use
- Not reported
- Fish use assessments
- 0
- Gauged lakes
Alaska in one line
77 lake-type waterbodies in Alaska are reported to EPA ATTAINS across reporting cycles 1989–2024: 7 assessed as not supporting at least one designated use, 9 fully supporting, and 61 without a definitive overall verdict. The most-listed impairment cause is Fecal Coliform, on 3 waterbodies.
- 77
- reported waterbodies
- 7
- not supporting a use
- 9
- fully supporting
- 0
- lakes with a linked USGS gauge
An unassessed waterbody is neither confirmed clean nor confirmed impaired; states assess on multi-year cycles.
Alaska's smaller reported lake-type inventory
At 77 units, Alaska is in the lowest third of state lake-type registers. The charts below describe that compact filing set, not a national-scale inventory.
Data updated 2026-08-17
According to the U.S. Environmental Protection Agency's ATTAINS program, Alaska reported 77 lake-type waterbodies in Alaska in the August 2026 extract. See our methodology for filer attribution and multi-year reporting cycles.
Overall-status split on Alaska's compact register
Every reported lake-type unit in this smaller Alaska filing set falls into exactly one overall-status bucket. The bar partitions 77 units; cause and gauge panels below stay separate.
Most-listed impairment causes in Alaska
Waterbodies carrying each listed cause, most first
- Fecal Coliform
Fecal Coliform
3 waterbodies
- Contaminated Sediments (PAHs) 1
Contaminated Sediments (PAHs)
1 waterbodies
- Dissolved Oxygen 1
Dissolved Oxygen
1 waterbodies
- Iron 1
Iron
1 waterbodies
- Lead in Sediment 1
Lead in Sediment
1 waterbodies
What this shows Fecal Coliform is the most-listed impairment cause in Alaska, on 3 of the lake-type waterbodies reported there.
Assessment outcomes in Alaska
Overall-status mix across reported lake-type waterbodies
- Not supporting a use 7
Not supporting a use
7 waterbodies
- Fully supporting 9
Fully supporting
9 waterbodies
- No definitive verdict
No definitive verdict
61 waterbodies
What this shows Most reported waterbodies in Alaska do not yet carry a definitive overall verdict.
Reporting practice
A definitive verdict is still missing for most of Alaska's inventory
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.
Alaska holds the 42nd-largest reported lake-type inventory in the country, 77 assessment units, carrying a definitive verdict on 20.8% of it. The counts above describe the 16 units carrying a verdict, not all 77 reported. Alaska has also retired 73 lake-type assessment units, superseded filings that are kept on the site but not counted here.
The states reporting at the nearest rates are Wisconsin (23.7%) and West Virginia (17.1%).
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.
Alaska against every comparable state
Share of reported lake-type waterbodies carrying a definitive verdict
20.8% 44th of 47 higher than 3 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 Alaska
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 | Iliamna Lake Not Assessed | 960,000 |
| 2 | Kenai Lake Not Assessed | 57,618 |
| 3 | Whitefish Lake Not Assessed | 18,726 |
| 4 | Lower Fire Lake Not Assessed | 4,480 |
| 5 | Redoubt Lake Not Assessed | 3,209 |
| 6 | Harding Lake Fully Supporting | 2,659 |
| 7 | Nancy Lake Not Assessed | 2,240 |
| 8 | Quartz Lake Not Assessed | 1,600 |
| 9 | Big Lake Not Supporting | 1,250 |
| 10 | Troutman Lake Not Assessed | 800 |
| 10 | Birch Lake Fully Supporting | 800 |
| 12 | Robe Lake Not Assessed | 682 |
2 of the 12 rows in this table tie on the ranked value: 2 at 800 (rank 10). Tied rows share a rank and are listed in no meaningful order.
By cause count
Most-listed waterbodies in Alaska
Waterbodies carrying the most listed impairment causes among the lake-type units reported by Alaska.
| # | Waterbody | Listed causes |
|---|---|---|
| 1 | Lucile Lake (stormwater outfalls) Not Supporting | 3 |
| 2 | Red Lake-Anton Road Pond Not Supporting | 2 |
| 3 | Big Lake Not Supporting | 1 |
| 3 | Campbell Lake Not Supporting | 1 |
| 3 | Lucile Lake Not Supporting | 1 |
| 3 | University Lake Not Supporting | 1 |
| 3 | Westchester Lagoon Not Supporting | 1 |
5 of the 7 rows in this table tie on the ranked value: 5 at 1 (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 with similar inventory scale or impairment load
Two EPA ATTAINS peer sets outside Alaska. The reporting-practice chart above stays on definitive-verdict share; these neighborhoods are cross-state nearest neighbors on register size and not-supporting counts.
States with a similar reported inventory
Nearest states by lake-type units on the register (77 here).
States with a similar not-supporting load
Nearest states by units assessed not supporting a use (7 here). Inventory peers above are omitted.
- Mississippi · 14 not supporting · 7 off
- Maine · 31 not supporting · 24 off
- Maryland · 32 not supporting · 25 off
- Delaware · 40 not supporting · 33 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: 20.8% of the inventory reported from Alaska carries a definitive verdict, 44th 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 Alaska 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 Alaska 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 Alaska, 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.