Oligotrophic Lakes in Washington

24 oligotrophic lakes in Washington. Low nutrients, clear water, excellent for swimming.

Oligotrophic lakes are the clear, cold, nutrient-poor end of the trophic scale. The Carlson Trophic State Index measures this as TSI below 40 — water transparent enough to see 15+ feet down, total phosphorus under 12 µg/L, chlorophyll-a barely registering. Across {{stateName}}, 24 lakes register as oligotrophic — 0% of them break 50 feet of depth, which is the structural condition that underwrites the trophic class. Without depth and a low-nutrient watershed, oligotrophy is hard to sustain.

On the LakeGrade rubric, oligotrophic lakes almost always pull an A or B — the same low-nutrient conditions that produce the trophic class also produce the high grade.

#	Lake	County	Grade	Clarity	Depth	TSI
1	Ross Lake	Whatcom	A	18.8 ft	-	30
2	Nla Lake	Skamania	A	26.3 ft	-	34
3	Nla Lake	King	A	77.4 ft	-	16
4	Nla Lake	Chelan	A	42.8 ft	-	23
5	Nla Lake	Snohomish	A	22.6 ft	-	37
6	Nla Lake	Pierce	A	-	-	33
7	Fdr Lake	Lincoln	A	16.2 ft	-	38
8	Fdr Lake	Okanogan	A	21.5 ft	-	35
9	Gravelly Lake	Pierce	A	25.4 ft	-	30
10	Banks Lake	Grant	A	19.4 ft	-	36
11	American Lake	Pierce	A	19.7 ft	-	34
12	Steilacoom Lake	Pierce	A	17.4 ft	-	36
13	Lake Roesiger	Snohomish	A	17.1 ft	-	36
14	Angle Lake	King	A	20 ft	-	34
15	Fdr Lake	Grant	A	28.2 ft	-	29
16	Lake Louise	Pierce	A	17.1 ft	-	36
17	Billy Clapp Lake	Grant	A	16.4 ft	-	37
18	Lake: Summit Lake	Thurston	A	-	-	32
19	Lake: Deep Lake	Thurston	A	-	-	38
20	Nla Upper Lake	Grays Harbor	A	-	-	35
21	Rimrock Reservoir	Yakima	A	-	-	40
22	Fdr Lake	Ferry	A	13.5 ft	-	40
23	Fdr Lake	Ferry	A	19 ft	-	38
24	Nla Lower Lake	Grays Harbor	B	-	-	39

All oligotrophic lakes →Minnesota version →Wisconsin version →Illinois version →Michigan version →Iowa version →Ohio version →Pennsylvania version →New York version →Missouri version →Indiana version →North Dakota version →South Dakota version →Florida version →Colorado version →North Carolina version →Vermont version →Texas version →Oregon version →Arkansas version →Oklahoma version →Kansas version →Nebraska version →Nevada version →Arizona version →Idaho version →Montana version →New Mexico version →Tennessee version →Alabama version →Virginia version →Kentucky version →Utah version →Wyoming version →All Washington lakes →

Source: EPA National Aquatic Resource Surveys, 2026.