Flathead County Lake Quality

Montana, 80 lakes, average grade A (Excellent)

Flathead County has 80 graded lakes, enough that within-county variation matters as much as the county average. Some are deep glacial basins, others are shallow agricultural-watershed waters, and the grade distribution reflects that mix. The county's average grade is A — among the cleanest in {{stateName}}. 73 lakes pull an A on their own, and almost none fall into the D or F brackets.

Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Tally Lake (A) is the cleanest in the county.

Loading map…

Quick Answers for Flathead County

Cleanest lakes in Flathead County →Cleanest lakes in Montana →Safest swimming lakes in Montana →

Planning a trip? Check special fishing regulations for Tally Lake — or check the official Montana fishing regulations.

All Lakes in Flathead County

Rank	Lake	Grade	Clarity	Phosphorus
1	Tally Lake	A	15.2 ft	4.5 µg/L
2	Nla Lake	A	47.6 ft	1.1 µg/L
3	Nla Lake	A	20 ft	13.8 µg/L
4	Whitefish Lake	A	22 ft	3 µg/L
5	Whitefish Lake	A	23.5 ft	3.3 µg/L
6	Halfmoon Lake	A	17.8 ft	-
7	Bailey Lake	A	19.5 ft	-
8	Blanchard Lake	A	19 ft	-
9	Echo Lake	A	15.2 ft	-
10	Dickey Lake	A	17.7 ft	-
11	Little Bitterroot Lake	A	40.3 ft	-
12	Mcgilvray Lake	A	21 ft	-
13	Fish Lake	A	16.6 ft	-
14	Lower Stillwater Lake	A	21 ft	-
15	Skyles Lake	A	17 ft	-
16	Beaver Lake	A	18.8 ft	-
17	Whitefish Lake	A	26.3 ft	-
18	Upper Whitefish Lake	A	20.5 ft	-
19	Bootjack Lake	A	20.8 ft	-
20	Foy Lake	A	17.5 ft	-
21	Lake Blaine	A	17.1 ft	-
22	Ashley Lake	A	33.1 ft	-
23	Hanson-Doyle Lake	A	21.8 ft	-
24	Abbot Lake	A	15 ft	-
25	Peterson Lake	A	14.9 ft	-
26	Lake Five	A	16 ft	-
27	Murray Lake	A	22 ft	-
28	Dollar Lake	A	19.2 ft	-
29	Upper Stillwater Lake	A	21.9 ft	-
30	Tally Lake	A	16.1 ft	-
31	Hanson-Doyle Lake	A	-	7.3 µg/L
32	Lost Coon Lake	A	-	9.7 µg/L
33	Foys Lake	A	-	15.8 µg/L
34	Rogers Lake	A	-	11.6 µg/L
35	Beaver Lake	A	-	18.5 µg/L
36	Smith Lake	A	-	7.4 µg/L
37	Dollar Lake	A	-	7.2 µg/L
38	Lake Blaine	A	-	10 µg/L
39	Bailey Lake	A	-	7.1 µg/L
40	Flathead Lake	A	-	2.4 µg/L
41	Lake Five	A	-	10.6 µg/L
42	Spencer Lake	A	-	8.8 µg/L
43	Ashley Lake	A	-	9.8 µg/L
44	Peterson Lake	A	-	7.6 µg/L
45	Blanchard Lake	A	-	5.5 µg/L
46	Abbot Lake	A	-	9 µg/L
47	Murray Lake	A	-	13.4 µg/L
48	Halfmoon Lake	A	-	5.9 µg/L
49	Echo Lake	A	-	13.9 µg/L
50	Bootjack Lake	A	-	15.4 µg/L
51	Skyles Lake	A	-	6 µg/L
52	Flathead Lake	A	-	3 µg/L
53	Ashley Lake	A	-	9.5 µg/L
54	Little Bitterroot Lake	A	-	3.9 µg/L
55	Upper Whitefish Lake	A	-	4.1 µg/L
56	Lower Stillwater Lake	A	-	11 µg/L
57	Upper Stillwater Lake	A	-	5.7 µg/L
58	Mcgilvray Lake	A	-	6.9 µg/L
59	Lake Mcdonald	A	-	16 µg/L
60	Little Bitterroot Lake	A	-	3.5 µg/L
61	Little Bitterroot Lake Center	A	-	4 µg/L
62	Little Bitterroot Lake	A	-	4 µg/L
63	Lost Loon Lake	A	-	10.1 µg/L
64	Little Bitterroot Lake Southeast	A	-	2.5 µg/L
65	Little Bitterroot Lake Southwest	A	-	2.5 µg/L
66	Little Bitterroot Lake	A	-	2 µg/L
67	Little Bitterroot Lake	A	-	1.5 µg/L
68	Little Bitterroot Lake	A	-	3 µg/L
69	Little Bitterroot Lake South of Slaughter House Bay	A	-	1 µg/L
70	Little Bitterroot Lake	A	-	1 µg/L
71	Little Bitterroot Lake	A	-	3 µg/L
72	Nla Lake	A	21.2 ft	23.2 µg/L
73	Lake Mcdonald	A	-	20.5 µg/L
74	Spencer Lake	B	13.5 ft	-
75	Lost Coon Lake	B	11.8 ft	-
76	Rogers Lake	B	13.6 ft	-
77	Lake Mcdonald	B	-	39.5 µg/L
78	Lake Mcdonald	B	-	36.5 µg/L
79	Nla Lake	B	19.3 ft	9500 µg/L
80	Nla Lake	C	-	12000 µg/L