Oligotrophic Lakes in Oregon

18 oligotrophic lakes in Oregon. 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}}, 18 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	Odell Lake	Klamath	A	22.3 ft	-	32
2	Crescent Lake	Klamath	A	42.2 ft	-	25
3	Odell Lake	Klamath	A	18.7 ft	-	34
4	Crescent Lake	Klamath	A	51.7 ft	-	22
5	Blue River Lake	Lane	A	-	-	37
6	Cougar Lake	Lane	A	-	-	24
7	Odell Lake	Klamath	A	-	-	32
8	Crescent Lake	Klamath	A	-	-	19
9	Applegate Lake	Jackson	A	-	-	27
10	Lake of the Woods	Klamath	A	-	-	32
11	Galesville Reservoir	Douglas	A	-	-	34
12	Fourmile Lake	Klamath	A	-	-	23
13	Wallowa Lake	Wallowa	A	-	-	25
14	Willow Lake	Jackson	A	-	-	38
15	Henry Hagg Lake	Washington	A	-	-	35
16	Green Peter Lake	Linn	A	-	-	34
17	Timothy Lake	Clackamas	A	-	-	32
18	Wickiup Reservoir Davis Cr Arm	Deschutes	A	-	-	27

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 →Arkansas version →Oklahoma version →Kansas version →Nebraska version →Nevada version →Arizona version →Idaho version →Montana version →New Mexico version →All Oregon lakes →

Source: EPA National Aquatic Resource Surveys, 2026.