Updated Jul 2026
North Dakota Lake Water Quality
Water quality grades for 150 monitored lakes across 50 counties.
North Dakota has 150 graded lakes in our dataset, sampled across 50 counties, drawing on monitoring by the North Dakota Department of Environmental Quality plus federal and volunteer measurements. A-grade lakes are scarce in North Dakota: about 7% of the dataset. Most lakes here sit in C or D — productive, often shallow, frequently algal in late summer.
Eutrophic conditions dominate — nutrient-loaded, productive, with algal pressure that shows up most years in late summer. These lakes tend to be shallow, agricultural-watershed, and over-warmed by the time July ends. Benson ranks highest on average county grade (B). Ransom sits lowest. With only 50 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.
Grade Distribution
How North Dakota’s 150 graded lakes break down from A (excellent) to F.
Top-Graded North Dakota Lakes
The highest water-quality grades in North Dakota — clarity, depth, and A-F grade at a glance.
Wood Lake
Benson County, North Dakota
See grade for Wood Lake →Free Peoples Lake
Benson County, North Dakota
See grade for Free Peoples Lake →Fort Totten Bay Lake
Benson County, North Dakota
See grade for Fort Totten Bay Lake →Arnegard Dam Lake
McKenzie County, North Dakota
See grade for Arnegard Dam Lake →Epping-Springbrook Dam-Littoral Lake
Williams County, North Dakota
See grade for Epping-Springbrook Dam-Littoral Lake →Jarvis Beach Lake
Rolette County, North Dakota
See grade for Jarvis Beach Lake →Spiritwood Lake
Stutsman County, North Dakota
See grade for Spiritwood Lake →Lake Upsilon
Rolette County, North Dakota
See grade for Lake Upsilon →Twin Lakes
LaMoure County, North Dakota
See grade for Twin Lakes →Lake Map
Explore North Dakota Lakes
North Dakota reports, fishing & travel
North Dakota's cleanest and most-polluted lakes, ranked A–F
Fish species and top-graded lakes across North Dakota
Species activity outlook by water temperature and season
Where to stay at North Dakota's top lakes, each with its grade
Best-graded lakes within 50 miles of Fargo
Best-graded lakes within 50 miles of Bismarck
Best-graded lakes within 50 miles of Devils Lake
Reservoirs in North Dakota
View all 92 reservoirs →92 of 150 North Dakota lakes (61%) are man-made reservoirs in the USACE National Inventory of Dams. 55 carry a High or Significant hazard rating. The oldest matched dam dates to 1890.
EPA-Impaired Lakes in North Dakota
View all 41 impaired lakes →41 of 150 North Dakota lakes (27%) are officially listed as impaired under Clean Water Act §303(d) in the most recent EPA ATTAINS reporting cycle. 20 have an approved Total Maximum Daily Load (TMDL) restoration plan.
North Dakota Fishing & Recreation
Licenses, regulations, records, and where to fish across North Dakota.
Counties
All 50 North Dakota counties, ranked by average lake water quality. Compare them against every county nationwide in the county rankings, browse the full directory of graded lakes, or pick a different state.
North Dakota Lake Water Quality Dataset (2026)
Every graded North Dakota lake in one spreadsheet — A–F grade, water clarity, phosphorus, chlorophyll-a, trophic state, size, public access, and a link to each lake's report card.
Top 25 Cleanest Lakes
| Rank | Lake | County | Grade | Clarity | Max Depth |
|---|---|---|---|---|---|
| 1 | Wood Lake | Benson | A | - | 26.2 ft |
| 2 | Free Peoples Lake | Benson | A | - | 54 ft |
| 3 | Fort Totten Bay Lake | Benson | A | - | - |
| 4 | Arnegard Dam Lake | McKenzie | A | - | 12.2 ft |
| 5 | Epping-Springbrook Dam-Littoral Lake | Williams | A | - | 25.4 ft |
| 6 | Jarvis Beach Lake | Rolette | A | - | 26.3 ft |
| 7 | Spiritwood Lake | Stutsman | A | 31 ft | 54.7 ft |
| 8 | Lake Upsilon | Rolette | A | 11.2 ft | 25 ft |
| 9 | Twin Lakes | LaMoure | A | 14.1 ft | 40.3 ft |
| 10 | Round Lake | McHenry | A | 12.1 ft | 16.7 ft |
| 11 | Qacmainstfbk Lake | Mercer | A | - | - |
| 12 | Velva Sportsmans Dam Lake | Ward | B | 13.6 ft | 23.2 ft |
| 13 | Davis Dam Lake | Slope | B | 7.5 ft | 5.8 ft |
| 14 | Arroda Lake | Oliver | B | 6.7 ft | 36.7 ft |
| 15 | Kota Ray Dam Lake | Williams | B | 7.7 ft | 26.2 ft |
| 16 | Skjermo Lake | Divide | B | 7.7 ft | 19 ft |
| 17 | Hooker Lake | Rolette | B | 12.2 ft | 25.4 ft |
| 18 | Whitman Dam Lake | Nelson | B | 12 ft | 20.8 ft |
| 19 | Qacmainstdup Lake | Mercer | B | - | - |
| 20 | Patterson Lake | Stark | B | - | 24.8 ft |
| 21 | Lake Ashtabula | Barnes | B | 3.4 ft | 42.8 ft |
| 22 | Lake Ashtabula | Barnes | B | 6.6 ft | 42.8 ft |
| 23 | Mt Carmel Dam Lake | Cavalier | B | 7.9 ft | 31.2 ft |
| 24 | Gordon Center Lake | Rolette | B | 8.2 ft | 28.3 ft |
| 25 | Wheaton Lake | Rolette | B | 8.5 ft | 25.6 ft |
25 Lakes Needing Attention
| Rank | Lake | County | Grade | Clarity |
|---|---|---|---|---|
| 1 | Harmon Lake | Morton | F | - |
| 2 | Niagara Dam Lake | Grand Forks | F | 1 ft |
| 3 | Kolding Dam Lake | Grand Forks | F | 1.7 ft |
| 4 | Mirror Lake | Adams | F | 2.1 ft |
| 5 | Cedar Lake | Slope | F | 1.3 ft |
| 6 | Belcourt Lake Beach | Rolette | F | 1 ft |
| 7 | Sweet Briar Dam-Mid Reservoir | Morton | F | 3 ft |
| 8 | Sweetbriar Dam Lake | Morton | F | 3 ft |
| 9 | Gordon Beach Lake | Rolette | F | 1 ft |
| 10 | Kalmbach Lake | LaMoure | F | 0.7 ft |
| 11 | Juanita Lake | Foster | F | 1 ft |
| 12 | Dead Colt Creek Dam Lake | Ransom | F | 3.3 ft |
| 13 | Sprague Lake | Sargent | F | 1.6 ft |
| 14 | Buffalo Lake | Pierce | F | 0.3 ft |
| 15 | Mchugh Slough Lake | Nelson | F | 1.6 ft |
| 16 | Morrison Lake | Ramsey | F | 1.9 ft |
| 17 | Eastern Stump Lake | Nelson | F | 4.7 ft |
| 18 | Western Stump Lake | Nelson | F | 4.3 ft |
| 19 | Tioga Dam Lake | Williams | D | 2.2 ft |
| 20 | Odland Dam Lake | Golden Valley | D | 1.5 ft |
| 21 | Froelich Dam Lake | Sioux | D | 3.9 ft |
| 22 | Nelson Lake | Oliver | D | 1.3 ft |
| 23 | Nygren Dam Lake | Morton | D | 2.6 ft |
| 24 | Warsing Dam Lake | Eddy | D | 2.3 ft |
| 25 | Antelope Lake | Pierce | D | 3.5 ft |
Where to stay near North Dakota
Top-rated places to stay near North Dakota
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Source: EPA National Aquatic Resource Surveys, 2026.