Oligotrophic Lakes in Montana

161 oligotrophic lakes in Montana. 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}}, 161 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	Big Sky Lake South Hole	Missoula	A	17.7 ft	-	36
2	Tally Lake	Flathead	A	15.2 ft	-	31
3	Nla Lake	Granite	A	28.4 ft	-	29
4	Nla Lake	Missoula	A	41.9 ft	-	23
5	Nla Lake	Flathead	A	47.6 ft	-	17
6	Nla Lake	Flathead	A	20 ft	-	36
7	Nla Lake	Lewis and Clark	A	15.9 ft	-	35
8	Nla Lake	Lincoln	A	16.9 ft	-	39
9	Nla Lake	Lincoln	A	25.4 ft	-	35
10	Nla Lake	Lake	A	32.3 ft	-	30
11	Nla Lake	Ravalli	A	18 ft	-	32
12	Lake Alva Mid-Lake Deep	Missoula	A	21.6 ft	-	32
13	Salmon Lake South Basin	Missoula	A	16.6 ft	-	37
14	Seeley Lake Middle Basin	Missoula	A	15.4 ft	-	36
15	Whitefish Lake	Flathead	A	22 ft	-	28
16	Whitefish Lake	Flathead	A	23.5 ft	-	29
17	Placid Lake North Finger Outlet Hole	Missoula	A	16.8 ft	-	36
18	Placid Lake Midlake Hole	Missoula	A	16.5 ft	-	35
19	Lake Inez North Hole	Missoula	A	17.4 ft	-	36
20	Salmon Lake Mid-South Basin	Missoula	A	16.4 ft	-	37
21	Lake Inez South Hole	Missoula	A	17.8 ft	-	38
22	Seeley Lake North Basin	Missoula	A	16.8 ft	-	37
23	Clearwater Lake Deep	Missoula	A	28.6 ft	-	29
24	Lake Koocanusa	Lincoln	A	-	-	31
25	Lake Koocanusa	Lincoln	A	-	-	30
26	Rainy Lake Deep	Missoula	A	18.9 ft	-	35
27	Salmon Lake Mid-North Basin	Missoula	A	17 ft	-	38
28	Halfmoon Lake	Flathead	A	17.8 ft	-	36
29	Lake Mary Ronan East Location	Lake	A	15.1 ft	-	40
30	Bailey Lake	Flathead	A	19.5 ft	-	34
31	Big Therriault Lake	Lincoln	A	37.3 ft	-	25
32	Tetrault Lake	Lincoln	A	21.8 ft	-	33
33	Blanchard Lake	Flathead	A	19 ft	-	35
34	Lindbergh Lake	Missoula	A	26.5 ft	-	30
35	Murphy Lake	Lincoln	A	15 ft	-	38
36	Echo Lake	Flathead	A	15.2 ft	-	38
37	Swan Lake	Lake	A	23.3 ft	-	32
38	Dickey Lake	Flathead	A	17.7 ft	-	36
39	Sophie Lake	Lincoln	A	21.1 ft	-	33
40	Little Bitterroot Lake	Flathead	A	40.3 ft	-	24
41	Mcgilvray Lake	Flathead	A	21 ft	-	33
42	Fish Lake	Flathead	A	16.6 ft	-	37
43	Glen Lake	Lincoln	A	19.9 ft	-	34
44	Lower Stillwater Lake	Flathead	A	21 ft	-	33
45	Skyles Lake	Flathead	A	17 ft	-	36
46	Beaver Lake	Flathead	A	18.8 ft	-	35
47	Whitefish Lake	Flathead	A	26.3 ft	-	30
48	Upper Whitefish Lake	Flathead	A	20.5 ft	-	34
49	Bootjack Lake	Flathead	A	20.8 ft	-	33
50	Foy Lake	Flathead	A	17.5 ft	-	36
51	Lake Blaine	Flathead	A	17.1 ft	-	36
52	Ashley Lake	Flathead	A	33.1 ft	-	27
53	Lake Mary Ronan	Lake	A	16.8 ft	-	36
54	Hanson-Doyle Lake	Flathead	A	21.8 ft	-	33
55	Abbot Lake	Flathead	A	15 ft	-	38
56	Peterson Lake	Flathead	A	14.9 ft	-	38
57	Lake Five	Flathead	A	16 ft	-	37
58	Murray Lake	Flathead	A	22 ft	-	33
59	Dollar Lake	Flathead	A	19.2 ft	-	35
60	Holland Lake	Missoula	A	30.5 ft	-	28
61	Upper Stillwater Lake	Flathead	A	21.9 ft	-	33
62	Jette Lake	Lake	A	15.8 ft	-	37
63	Tally Lake	Flathead	A	16.1 ft	-	37
64	Hauser Lake	Lewis and Clark	A	15.6 ft	-	38
65	Hauser Lake D	Lewis and Clark	A	21.8 ft	-	33
66	Holter Reservoir	Lewis and Clark	A	19 ft	-	35
67	Holter Reservoir	Lewis and Clark	A	15.4 ft	-	38
68	Holter Reservoir	Lewis and Clark	A	26.2 ft	-	30
69	Swan Lake South End	Lake	A	-	-	28
70	Hanson-Doyle Lake	Flathead	A	-	-	36
71	Loon Lake	Lake	A	-	-	35
72	Sophie Lake	Lincoln	A	-	-	39
73	Lost Coon Lake	Flathead	A	-	-	38
74	Swan Lake North End	Lake	A	-	-	27
75	Rogers Lake	Flathead	A	-	-	40
76	Smith Lake	Flathead	A	-	-	33
77	Tetrault Lake	Lincoln	A	-	-	38
78	Dollar Lake	Flathead	A	-	-	37
79	Lake Blaine	Flathead	A	-	-	38
80	Bailey Lake	Flathead	A	-	-	35
81	Dickey Lake	Lincoln	A	-	-	39
82	Flathead Lake	Flathead	A	-	-	21
83	Flathead Lake	Lake	A	-	-	25
84	Spencer Lake	Flathead	A	-	-	38
85	Ashley Lake	Flathead	A	-	-	37
86	Fish Lake	Lincoln	A	-	-	38
87	Peterson Lake	Flathead	A	-	-	34
88	Flathead Lake	Lake	A	-	-	22
89	Blanchard Lake	Flathead	A	-	-	31
90	Abbot Lake	Flathead	A	-	-	37
91	Murphy Lake	Lincoln	A	-	-	34
92	Halfmoon Lake	Flathead	A	-	-	33
93	Skyles Lake	Flathead	A	-	-	34
94	Flathead Lake	Lake	A	-	-	25
95	Flathead Lake	Flathead	A	-	-	24
96	Ashley Lake	Flathead	A	-	-	37
97	Flathead Lake	Lake	A	-	-	23
98	Little Bitterroot Lake	Flathead	A	-	-	28
99	Upper Whitefish Lake	Flathead	A	-	-	26
100	Lower Stillwater Lake	Flathead	A	-	-	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 →Idaho version →New Mexico version →Tennessee version →Alabama version →Virginia version →Kentucky version →Utah version →Washington version →Wyoming version →All Montana lakes →

Source: EPA National Aquatic Resource Surveys, 2026.