Well water hardness in South Dakota
Across 40 counties of South Dakota, the median well sampled by the USGS has 18 gpg of hardness. Counties range from 0.5 gpg (Ziebach County) to 28.6 gpg (Clay County).
Millions of American households drink water from their own well. No utility tests that water and no water quality report covers it. These pages summarise the hardness the U.S. Geological Survey measured in wells county by county, so you know what to expect before you test your own well.
Counties, hardest first
| gpg | mg/L | wells | ||
|---|---|---|---|---|
| Clay County | 28.6 | 490 | 22 | very hard |
| Brookings County | 28.3 | 485 | 315 | very hard |
| Day County | 26.9 | 460 | 16 | very hard |
| Hughes County | 26.9 | 460 | 204 | very hard |
| Jerauld County | 26.9 | 460 | 19 | very hard |
| Hamlin County | 26.3 | 450 | 27 | very hard |
| Hand County | 26 | 445 | 18 | very hard |
| Union County | 25.7 | 440 | 253 | very hard |
| Clark County | 25.1 | 430 | 20 | very hard |
| Deuel County | 24.5 | 420 | 11 | very hard |
| Kingsbury County | 24.5 | 420 | 239 | very hard |
| Minnehaha County | 23.9 | 410 | 432 | very hard |
| Douglas County | 23.4 | 400 | 13 | very hard |
| Charles Mix County | 22.4 | 384 | 14 | very hard |
| Fall River County | 21.6 | 371 | 20 | very hard |
| Lincoln County | 21.5 | 368 | 130 | very hard |
| Brown County | 20.2 | 345 | 32 | very hard |
| Campbell County | 19.3 | 330 | 15 | very hard |
| Davison County | 19.3 | 330 | 25 | very hard |
| McPherson County | 18.7 | 320 | 12 | very hard |
| Meade County | 17.3 | 297 | 59 | very hard |
| Lawrence County | 16.7 | 286 | 75 | very hard |
| Butte County | 16.1 | 276 | 20 | very hard |
| Beadle County | 15.8 | 270 | 125 | very hard |
| Marshall County | 15.2 | 260 | 25 | very hard |
| Gregory County | 14.2 | 243 | 22 | very hard |
| Mellette County | 13.7 | 235 | 51 | very hard |
| Custer County | 13.4 | 230 | 74 | very hard |
| Lyman County | 12.9 | 220 | 19 | very hard |
| Pennington County | 12.5 | 214 | 154 | very hard |
| Spink County | 12.3 | 210 | 699 | very hard |
| Tripp County | 8.8 | 150 | 18 | hard |
| Aurora County | 8.7 | 149 | 19 | hard |
| Oglala Lakota County | 8.3 | 142 | 58 | hard |
| Todd County | 8.2 | 141 | 140 | hard |
| Bennett County | 7.6 | 130 | 49 | hard |
| Jackson County | 1.9 | 33 | 14 | soft |
| Corson County | 1.2 | 21 | 17 | soft |
| Harding County | 0.9 | 15 | 18 | soft |
| Ziebach County | 0.5 | 8 | 13 | soft |
Counties with fewer than 10 sampled wells, or a median outside 5–500 mg/L, are not shown until the figure is reviewed.