countyscore

Best Water Quality Counties in Idaho

EPA drinking water health violations and safety grades Compare rankings across all 44 counties.

Average Water Quality Score
33/100
Top County
Adams County
Counties Ranked
44

Top 10

#1
Adams County
ID
86/100
#2
Custer County
ID
86/100
#3
Oneida County
ID
86/100
#4
Shoshone County
ID
86/100
#5
Washington County
ID
86/100
#6
Nez Perce County
ID
62/100
#7
Ada County
ID
56/100
#8
Bannock County
ID
54/100
#9
Twin Falls County
ID
53/100
#10
Gem County
ID
51/100

All Idaho Counties Ranked

#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
54
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
55.6
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

Data Source

Water Quality data from WaterByCounty. See full details at WaterByCounty. Data updated February 2026.