countyscore

Water Quality · Idaho

Best Water Quality Counties in Idaho 2026

Ranked by EPA drinking water health violations.

Top 10 — Water Quality in Idaho

Score reflects water quality only — not overall county quality.

1Adams County, ID
86
2Custer County, ID
86
3Oneida County, ID
86
4Shoshone County, ID
86
5Washington County, ID
86
6Nez Perce County, ID
61.5
7Ada County, ID
55.6
8Bannock County, ID
53.8
9Twin Falls County, ID
52.8
10Gem County, ID
51.2

All Idaho Counties — Water Quality Rankings

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

#CountyWater Quality ScoreOverall Score
1Adams County, ID
86
54.8
2Custer County, ID
86
59.8
3Oneida County, ID
86
59.3
4Shoshone County, ID
86
47.6
5Washington County, ID
86
56.8
6Nez Perce County, ID
61.5
40.3
7Ada County, ID
55.6
45.3
8Bannock County, ID
53.8
42.2
9Twin Falls County, ID
52.8
39.5
10Gem County, ID
51.2
54.9
11Bear Lake County, ID
48.5
63.3
12Minidoka County, ID
48.4
45.2
13Jerome County, ID
47.6
40.4
14Bonneville County, ID
44.7
41.4
15Gooding County, ID
38.3
47.5
16Caribou County, ID
36.7
65.4
17Lincoln County, ID
35.8
53.9
18Teton County, ID
35.7
61.4
19Kootenai County, ID
35.5
45.2
20Canyon County, ID
31.8
36.8
21Benewah County, ID
27.4
46.5
22Bingham County, ID
25.9
48.6
23Owyhee County, ID
19.8
49.3
24Bonner County, ID
19.7
50.6
25Butte County, ID
18.7
63.2
26Blaine County, ID
18.1
59.1
27Madison County, ID
17.5
53.7
28Jefferson County, ID
17.4
52.8
29Payette County, ID
16.4
49.3
30Latah County, ID
16.2
52.6
31Cassia County, ID
15.9
47.4
32Clearwater County, ID
15.9
58.8
33Elmore County, ID
14.8
42.5
34Camas County, ID
13.4
56.5
35Power County, ID
12.2
48
36Lemhi County, ID
9.2
54.5
37Lewis County, ID
9.1
55.5
38Clark County, ID
8.7
54.1
39Franklin County, ID
8
59.6
40Valley County, ID
6.3
54.3
41Boise County, ID
5.7
57.3
42Idaho County, ID
3.7
60
43Fremont County, ID
3.3
63.6
44Boundary County, ID
3.1
56.6

Explore More

Best overall counties in IdahoFull Water Quality data on WaterByCounty