Water Quality by County
3,254 counties with public water systems.
| County | State | Systems | Population | Violations |
|---|---|---|---|---|
| Dickey | North Dakota | 8 | 4,858 | 562 |
| Ransom | North Dakota | 5 | 4,835 | 57 |
| Perry | Arkansas | 5 | 4,831 | 689 |
| Ouray | Colorado | 8 | 4,816 | 776 |
| Kearney | Nebraska | 10 | 4,814 | 342 |
| County 10031 | 10 | 3 | 4,805 | 1,849 |
| Antelope | Nebraska | 15 | 4,785 | 735 |
| County 09103 | 09 | 1 | 4,782 | 49 |
| Oregon | Missouri | 7 | 4,746 | 412 |
| Moca Municipio | Puerto Rico | 3 | 4,744 | 579 |
| Schuyler | Missouri | 4 | 4,740 | 113 |
| Lynn | Texas | 6 | 4,736 | 3,009 |
| Merrick | Nebraska | 9 | 4,718 | 410 |
| Randolph | Georgia | 5 | 4,714 | 373 |
| Union | New Mexico | 8 | 4,699 | 434 |
| Lake | Oregon | 19 | 4,699 | 1,186 |
| Lake | Tennessee | 2 | 4,686 | 125 |
| Cumberland | Illinois | 4 | 4,683 | 314 |
| Lanier | Georgia | 8 | 4,679 | 168 |
| Pondera | Montana | 12 | 4,664 | 3,462 |
| Sherman | Kansas | 3 | 4,630 | 220 |
| Norman | Minnesota | 21 | 4,630 | 284 |
| Gallatin | Illinois | 7 | 4,629 | 306 |
| Caswell | North Carolina | 36 | 4,614 | 3,202 |
| Mathews | Virginia | 39 | 4,608 | 1,282 |
| Cavalier | North Dakota | 5 | 4,570 | 205 |
| Grant | Oregon | 13 | 4,568 | 940 |
| Wilkin | Minnesota | 12 | 4,567 | 182 |
| Fisher | Texas | 4 | 4,546 | 822 |
| Columbia | Washington | 12 | 4,546 | 369 |
| Wayne | Utah | 18 | 4,533 | 2,003 |
| Dade | Missouri | 20 | 4,521 | 908 |
| Roosevelt | Montana | 4 | 4,519 | 801 |
| Treutlen | Georgia | 3 | 4,518 | 52 |
| Harper | Kansas | 8 | 4,510 | 777 |
| Alfalfa | Oklahoma | 11 | 4,497 | 2,822 |
| Hansford | Texas | 4 | 4,467 | 273 |
| Reynolds | Missouri | 30 | 4,465 | 1,774 |
| Bacon | Georgia | 6 | 4,461 | 57 |
| Fillmore | Nebraska | 12 | 4,458 | 263 |
| Scott | Illinois | 7 | 4,447 | 247 |
| Hot Springs | Wyoming | 8 | 4,429 | 261 |
| Norton | Kansas | 8 | 4,426 | 1,144 |
| Aleutians East Borough | Alaska | 8 | 4,402 | 4,617 |
| Ritchie | West Virginia | 5 | 4,397 | 630 |
| Twiggs | Georgia | 14 | 4,374 | 634 |
| Kingman | Kansas | 6 | 4,365 | 1,028 |
| Eureka | Nevada | 14 | 4,364 | 385 |
| Johnson | Nebraska | 6 | 4,345 | 210 |
| Mora | New Mexico | 21 | 4,341 | 5,016 |
| Grant | Minnesota | 20 | 4,335 | 379 |
| Pierce | Nebraska | 9 | 4,334 | 542 |
| Cameron | Pennsylvania | 14 | 4,333 | 3,675 |
| Adams | Iowa | 2 | 4,320 | 922 |
| Ozark | Missouri | 26 | 4,318 | 3,177 |
| Wheeler | Texas | 5 | 4,317 | 837 |
| County 10057 | 10 | 6 | 4,309 | 239 |
| Turner | South Dakota | 6 | 4,296 | 448 |
| Atchison | Missouri | 6 | 4,290 | 191 |
| Hidalgo | New Mexico | 9 | 4,264 | 2,378 |
| Chariton | Missouri | 5 | 4,263 | 163 |
| Johnson | Georgia | 3 | 4,262 | 121 |
| Grayson | Virginia | 28 | 4,254 | 1,335 |
| Monroe | Missouri | 4 | 4,240 | 167 |
| County 09023 | 09 | 8 | 4,233 | 2,869 |
| Culberson | Texas | 12 | 4,216 | 464 |
| Aurora | South Dakota | 4 | 4,212 | 173 |
| Atkinson | Georgia | 6 | 4,211 | 230 |
| Nelson | North Dakota | 6 | 4,204 | 159 |
| Richmond | Virginia | 14 | 4,196 | 391 |
| Monroe | Iowa | 2 | 4,193 | 97 |
| Lee | South Carolina | 2 | 4,183 | 285 |
| Tyrrell | North Carolina | 3 | 4,168 | 590 |
| Essex | Virginia | 20 | 4,164 | 631 |
| Furnas | Nebraska | 8 | 4,158 | 532 |
| Madison | Virginia | 28 | 4,157 | 2,063 |
| Stanton | Nebraska | 7 | 4,143 | 174 |
| Webster | West Virginia | 8 | 4,131 | 1,690 |
| Clay | North Carolina | 28 | 4,115 | 2,363 |
| Jasper | South Carolina | 17 | 4,111 | 283 |
| Dixon | Nebraska | 15 | 4,108 | 819 |
| Pepin | Wisconsin | 22 | 4,102 | 511 |
| Grant | Oklahoma | 10 | 4,090 | 3,596 |
| Hutchinson | South Dakota | 4 | 4,085 | 315 |
| Big Stone | Minnesota | 17 | 4,078 | 304 |
| Clark | South Dakota | 7 | 4,073 | 919 |
| Rooks | Kansas | 9 | 4,062 | 1,019 |
| Hardeman | Texas | 7 | 4,053 | 566 |
| Hardin | Illinois | 5 | 4,051 | 900 |
| Stevens | Kansas | 2 | 4,038 | 329 |
| Walworth | South Dakota | 3 | 4,027 | 154 |
| Maries | Missouri | 11 | 4,013 | 1,272 |
| Coal | Oklahoma | 8 | 4,013 | 1,205 |
| Thayer | Nebraska | 11 | 4,010 | 633 |
| Pierce | North Dakota | 3 | 3,994 | 69 |
| Clinch | Georgia | 6 | 3,988 | 290 |
| Clearwater | Minnesota | 29 | 3,978 | 192 |
| Mineral | Nevada | 7 | 3,971 | 566 |
| Custer | Colorado | 16 | 3,964 | 959 |
| Niobrara | Wyoming | 5 | 3,918 | 842 |