Cleanest Lakes in Washington
Ross Lake in Whatcom County leads the rankings with a water quality grade of A and 18.8 ft of clarity. Below are the top 50 cleanest monitored lakes in Washington, ranked by EPA water quality score.
Ranked List
| # | Lake | County | Grade | Clarity | Phosphorus | Algae |
|---|---|---|---|---|---|---|
| 1 | Ross Lake | Whatcom | A | 18.8 ft | 4.5 µg/L | - |
| 2 | Nla Lake | Skamania | A | 26.3 ft | 10.5 µg/L | 1.3 µg/L |
| 3 | Nla Lake | King | A | 77.4 ft | 1.9 µg/L | 0.4 µg/L |
| 4 | Nla Lake | Chelan | A | 42.8 ft | 3.9 µg/L | 0.5 µg/L |
| 5 | Nla Lake | Snohomish | A | 22.6 ft | 13.5 µg/L | 2 µg/L |
| 6 | Nla Lake | Pierce | A | - | 19.6 µg/L | 0.3 µg/L |
| 7 | Fdr Lake | Lincoln | A | 16.2 ft | 10 µg/L | 2.3 µg/L |
| 8 | Fdr Lake | Okanogan | A | 21.5 ft | 11 µg/L | 1.3 µg/L |
| 9 | Banks Lake | Grant | A | 19.4 ft | 13 µg/L | 1.3 µg/L |
| 10 | Lake: Ward Lake | Thurston | A | - | 10.5 µg/L | 3.2 µg/L |
| 11 | Lake: Summit Lake | Thurston | A | - | 6 µg/L | 1.3 µg/L |
| 12 | Lake: Deep Lake | Thurston | A | - | 7 µg/L | 3.8 µg/L |
| 13 | Nla Upper Lake | Grays Harbor | A | - | 12.4 µg/L | 0.9 µg/L |
| 14 | Rimrock Reservoir | Yakima | A | - | 15 µg/L | 1.8 µg/L |
| 15 | Nla Lake | Grant | A | 12.8 ft | 15.7 µg/L | 2 µg/L |
| 16 | Fdr Lake | Ferry | A | 13.5 ft | 12 µg/L | 2.6 µg/L |
| 17 | Fdr Lake | Ferry | A | 19 ft | 20 µg/L | 1.3 µg/L |
| 18 | Nla Lake | Mason | A | - | 14.1 µg/L | 8 µg/L |
| 19 | Spearhead Lake | Skagit | A | 10.8 ft | 14 µg/L | - |
| 20 | Lake: Hicks Lake | Thurston | A | - | 16 µg/L | 8.5 µg/L |
| 21 | Nla Lake | Douglas | B | 13 ft | 55.9 µg/L | 4.4 µg/L |
| 22 | Nla Lower Lake | Grays Harbor | B | - | 38.9 µg/L | 0.4 µg/L |
| 23 | Nla Lake | Kitsap | B | 18.8 ft | 9506.1 µg/L | 1.7 µg/L |
| 24 | Nla Lake | Okanogan | B | 22.7 ft | 20518.3 µg/L | 2.7 µg/L |
| 25 | Nla Lake | Grant | B | 16.4 ft | 39517.1 µg/L | 1.5 µg/L |
| 26 | Nla Lake | Whatcom | B | 16.4 ft | 7502.8 µg/L | 0.4 µg/L |
| 27 | Nla Lake | Pierce | B | 16.4 ft | 4504.1 µg/L | 1.8 µg/L |
| 28 | Nla Lake | Okanogan | B | 14.9 ft | 47515.6 µg/L | 2.2 µg/L |
| 29 | Nla Lake | Stevens | B | 18.7 ft | 50000 µg/L | 1.5 µg/L |
| 30 | Nla Lake | Ferry | B | 20.9 ft | 50000 µg/L | 1.6 µg/L |
| 31 | Nla Lake | Jefferson | B | 9.7 ft | 27.4 µg/L | 8.1 µg/L |
| 32 | Lake: Pattison Lake | Thurston | B | - | 26.5 µg/L | 10.5 µg/L |
| 33 | Lake: Barnes Lake | Thurston | B | - | 27 µg/L | 11.6 µg/L |
| 34 | Lake: Offutt Lake | Thurston | B | - | 23 µg/L | 11 µg/L |
| 35 | Nla Lake | Pend Oreille | C | 11.3 ft | 19019.2 µg/L | 3.7 µg/L |
| 36 | Nla Lake | Pierce | C | 10.9 ft | 11510.7 µg/L | 3.6 µg/L |
| 37 | Nla Lake | King | C | 12 ft | 14011.8 µg/L | 3.8 µg/L |
| 38 | Nla Lake | Grant | C | 12.1 ft | 69000 µg/L | 2.8 µg/L |
| 39 | Nla Lake | Grant | C | 11.6 ft | 20000 µg/L | 4.4 µg/L |
| 40 | Nla Lake | Yakima | C | 9.4 ft | 34.8 µg/L | 7.8 µg/L |
| 41 | Nla Lake | Whatcom | C | 10.2 ft | 7508 µg/L | 3.7 µg/L |
| 42 | Nla Lake | Pend Oreille | C | 14.7 ft | 40000 µg/L | 4.2 µg/L |
| 43 | Nla Lake | Grays Harbor | C | 10.6 ft | 36011.4 µg/L | 4 µg/L |
| 44 | Nla Lake | Chelan | C | 13.7 ft | 8004.8 µg/L | 1.6 µg/L |
| 45 | Nla Lake | Snohomish | C | 13.8 ft | 9000 µg/L | 4.8 µg/L |
| 46 | Nla Lake | Okanogan | C | 14 ft | 12516.3 µg/L | 4 µg/L |
| 47 | Nla Lake | King | C | 7.7 ft | 6024.7 µg/L | 3.1 µg/L |
| 48 | Nla Lake | Lewis | C | - | 34000 µg/L | 1.5 µg/L |
| 49 | Nla Lake | Skamania | C | - | 85000 µg/L | 2.1 µg/L |
| 50 | Nla Lake | Whatcom | C | - | 8000 µg/L | 1.5 µg/L |