countyscore

Water Quality · Montana

Best Water Quality Counties in Montana 2026

Ranked by EPA drinking water health violations.

Top 10 — Water Quality in Montana

Score reflects water quality only — not overall county quality.

1Big Horn County, MT
86
2Broadwater County, MT
86
3Carter County, MT
86
4Daniels County, MT
86
5Deer Lodge County, MT
86
6Fallon County, MT
86
7Garfield County, MT
86
8Glacier County, MT
86
9Judith Basin County, MT
86
10McCone County, MT
86

All Montana Counties — Water Quality Rankings

55 counties ranked by water quality score. Overall Score shown for context.

#CountyWater Quality ScoreOverall Score
1Big Horn County, MT
86
42.9
2Broadwater County, MT
86
54.5
3Carter County, MT
86
72.7
4Daniels County, MT
86
67.8
5Deer Lodge County, MT
86
48.9
6Fallon County, MT
86
72.4
7Garfield County, MT
86
67.7
8Glacier County, MT
86
52.6
9Judith Basin County, MT
86
77.5
10McCone County, MT
86
75.3
11Meagher County, MT
86
65.5
12Musselshell County, MT
86
59.7
13Petroleum County, MT
86
80.1
14Powder River County, MT
86
67.7
15Powell County, MT
86
59.5
16Roosevelt County, MT
86
46.6
17Sanders County, MT
86
60.6
18Sheridan County, MT
86
49.4
19Silver Bow County, MT
86
36.4
20Stillwater County, MT
86
58.9
21Sweet Grass County, MT
86
64.6
22Wheatland County, MT
86
63.2
23Ravalli County, MT
56.9
58.4
24Flathead County, MT
55
39.8
25Cascade County, MT
54.3
33.5
26Gallatin County, MT
54.3
44.2
27Park County, MT
47.9
48.9
28Yellowstone County, MT
42.1
32.6
29Missoula County, MT
40.6
35.1
30Phillips County, MT
36.7
62.3
31Teton County, MT
33.5
62.9
32Beaverhead County, MT
32.9
63
33Valley County, MT
32.7
56.1
34Lake County, MT
30.7
40.5
35Madison County, MT
28.6
65.6
36Toole County, MT
27.2
49.1
37Hill County, MT
26.5
34.1
38Carbon County, MT
26.3
64.8
39Lewis and Clark County, MT
26.1
38.4
40Mineral County, MT
24.1
54.1
41Lincoln County, MT
22.9
57.7
42Chouteau County, MT
21.1
65.7
43Pondera County, MT
15.1
51.5
44Custer County, MT
13.5
48
45Dawson County, MT
13.2
47.7
46Wibaux County, MT
9.4
63.2
47Richland County, MT
8.6
52.7
48Rosebud County, MT
5.5
60.2
49Jefferson County, MT
3.7
58
50Golden Valley County, MT
2.2
69.9
51Liberty County, MT
2.2
57.1
52Granite County, MT
1.9
57.4
53Fergus County, MT
1.5
56.6
54Blaine County, MT
0.9
54.1
55Treasure County, MT
0.2
69.5

Explore More

Best overall counties in MontanaFull Water Quality data on WaterByCounty