Oligotrophic Lakes in Idaho

16 oligotrophic lakes in Idaho. Low nutrients, clear water, excellent for swimming.

An oligotrophic lake is what most people picture when they think of pristine northern lake country: clarity to depth, no algal scum, cold water that holds dissolved oxygen all the way to the bottom even in August. Across {{stateName}}, 16 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	Nla Lake	Gem	A	17.6 ft	-	39
2	Nla Lake	Valley	A	18.6 ft	-	33
3	Nla Lake	Blaine	A	29.9 ft	-	33
4	Nla Lake	Kootenai	A	19.2 ft	-	39
5	Nla Lake	Shoshone	A	-	-	35
6	Nla Lake	Custer	A	-	-	38
7	Deadwood Reservoir	Valley	A	17.2 ft	-	38
8	Bear Lake Off North Beach	Bear Lake	A	21.7 ft	-	36
9	Bear Lake	Bear Lake	A	19 ft	-	26
10	Bear Lake Se of St Charles Replicate of	Bear Lake	A	19 ft	-	26
11	Usgs Lake	Kootenai	A	-	-	30
12	Ideq Lake	Kootenai	A	-	-	30
13	Ideq Lake	Kootenai	A	-	-	27
14	Ideq Lake	Kootenai	A	-	-	26
15	Coeur D' Alene Lake	Kootenai	A	-	-	36
16	Nla Lake	Bonner	A	11 ft	-	38

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 →Montana version →New Mexico version →Tennessee version →Alabama version →Virginia version →Kentucky version →Utah version →Washington version →Wyoming version →All Idaho lakes →

Source: EPA National Aquatic Resource Surveys, 2026.