PlainLakes

National ranking · Fully Supporting assessments

Largest lakes assessed as fully supporting

The biggest lake-type waterbodies whose most recent state assessment, filed with EPA ATTAINS under Clean Water Act sections 303(d) and 305(b) across reporting cycles 1987-2026, concluded that all evaluated designated uses are Fully Supporting. An assessment verdict is cycle-based and use-specific; it is not a guarantee of current conditions at any particular beach or fishing spot.

559,424
#1: Gilbert Bay (acres)
50
Ranked waterbodies
13,596
Fully Supporting nationally

This ranking in one line

Gilbert Bay in UT is the largest lake-type waterbody whose latest state assessment came back Fully Supporting, at 559,424 assessed acres.

#1
Gilbert Bay, UT
Assessed acres
559,424 assessed acres
Cycle
2022

Data updated 2026-08-17

According to the U.S. Environmental Protection Agency's ATTAINS program, 60,590 lake-type waterbodies carry filed assessment records nationwide, and this ranking orders the 50 largest whose latest overall status is Fully Supporting in the August 2026 extract. See our methodology for reporting-unit limits and refresh cadence.

Where the largest clean-verdict lakes are

The 12 states contributing most; 19 appear in the ranking overall

ranked units

What this shows ME contributes 11 of the 50 ranked units, and 19 states appear in total; a state reaches this list by assessing large lakes at all, not only by their condition.

Source EPA ATTAINS As of Reporting cycles 1987–2026

Every row

Full ranking

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# Name Assessed acres
1 Gilbert Bay (UT) Cycle: 2022 559,424
2 Lower Red Lake (MN) Cycle: 2022 164,689
3 Lake Powell (UT) Cycle: 2022 149,885
4 Lake Mead (NV) Cycle: 2022 147,392
5 Upper Red Lake (MN) Cycle: 2022 118,943
6 Kentucky Reservoir (TN) Assessment unit TN06040005020_1000 Cycle: 2022 99,500
7 Lake Superior (MN) Cycle: 2024 86,000
8 Moosehead Lake (ME) Cycle: 2002 79,454
9 Clarks Hill Lake (GA) Cycle: 2026 69,999
10 Lake Oahe (ND) Cycle: 2010 68,123
11 Lake Texoma (TX) Largest of 5 assessment units the state files for this water Cycle: 2024 49,400
12 Grand Lake Site 14 (OK) Cycle: 2017 46,500
12 Grand Lake Site 15 (OK) Cycle: 2017 46,500
14 Sebago Lake (ME) Cycle: 2002 45,624
15 Seneca Lake, Main Lake, Middle (NY) Cycle: 2022 40,290
16 International Falcon Reservoir (TX) Largest of 5 assessment units the state files for this water Cycle: 2024 36,817
17 Spednick Lake (ME) Cycle: 2002 35,904
18 Bear Lake (UT) Cycle: 2022 35,414
19 Chickamauga Reservoir (TN) Cycle: 2022 35,400
20 Chesuncook Lake (ME) Cycle: 2002 34,926
21 Dardanelle Lake (AR) Cycle: 2020 34,041
22 Cayuga Lake, Main Lake, Mid-South (NY) Cycle: 2022 33,083
23 Mooselookmeguntic Lake (ME) Cycle: 2002 32,243
24 West Grand Lake (ME) Cycle: 2002 31,174
25 Douglas Reservoir (TN) Cycle: 2024 30,400
26 Millwood Lake (AR) Largest of 2 assessment units the state files for this water Cycle: 2020 29,500
27 Old Hickory Reservoir (TN) Cycle: 2024 27,439
28 West Branch Penobscot River (3) (ME) Cycle: 2002 25,876
29 Lake C. W. McConaughy (NE) Cycle: 2026 24,868
30 Ouachita Lake (AR) Cycle: 2020 24,695
31 Stockton Lake (MO) Cycle: 2026 23,680
32 Hungry Horse Reservoir (MT) Cycle: 2006 23,596
33 Webster Brook (ME) Cycle: 2002 21,919
34 International Amistad Reservoir (TX) Largest of 4 assessment units the state files for this water Cycle: 2024 21,328
35 Ross Barnett Reservoir (MS) Cycle: 2024 20,737
36 Kentucky Reservoir (TN) Assessment unit TN06040001001_1000 Cycle: 2022 20,592
37 Barkley Reservoir (TN) Assessment unit TN05130205015_1000 Cycle: 2024 20,459
38 Tennessee River (Lake Guntersville) (AL) Cycle: 2022 20,440
39 Eagle Lake (ME) Cycle: 2002 20,281
40 Lake Tohopekaliga (FL) Cycle: 2024 19,006
41 Graham Lake (ME) Cycle: 2002 18,173
42 Greers Ferry Lake (AR) Cycle: 2022 18,151
43 Seminole Lake (GA) Cycle: 2026 16,924
44 Lake Audubon (ND) Cycle: 2008 16,610
45 Barkley Reservoir (TN) Assessment unit TN05130205015_2000 Cycle: 2024 16,541
46 Lake Verret and Grassy Lake (LA) Cycle: 2026 16,311
47 Phelps Lake (NC) Cycle: 2022 15,938
48 Tallapoosa River (Lake Martin) (AL) Cycle: 2022 15,867
49 Wright Patman Lake (TX) Largest of 15 assessment units the state files for this water Cycle: 2024 15,691
50 East Machias River (ME) Cycle: 2002 15,289

2 of the 50 rows in this table tie on the ranked value: 2 at 46,500 (rank 12). Tied rows share a rank and are listed in no meaningful order.

Filtered to overall status Fully Supporting in the latest reported cycle, ordered by assessed area. States file this figure in acres or in square miles; square-mile filings are converted at 640 acres per square mile and each record page shows the state’s own number. Units filed only as a shoreline length in miles are a different quantity and are not ranked here. Verdicts are the state's assessment decisions; a lake absent here may be unassessed rather than impaired. 3 of the 50 ranked lakes here carry verdicts their filers decided in Integrated Reports that have not been finalized, and those decisions can still change.

Reading this ranking

  • Fully Supporting is a use-attainment verdict from the reported cycle, not a real-time certification; check the lake page for which uses were evaluated. How verdicts work
  • For swimming decisions, current advisories from local health departments govern. Recreation safety
  • See the flip side: lakes carrying the most listed causes. Most-listed lakes

Rankings order reported source data; they are not endorsements or safety determinations.

Rankings are computed from state assessment decisions in EPA's ATTAINS system and USGS National Water Information System daily values; the ordering metric and any exclusion floor are stated above the table, no number is typed in by an editor. Ranking recomputed from the full ingested ATTAINS lake-type universe on every data refresh. 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.