Quick answer
About 122,000 people in South Dakota (15.0% of residents) got their water from private wells in 2010, according to USGS estimates. South Dakota Department of Agriculture and Natural Resources runs the state’s private well guidance. DANR's private well page links to the Midwest Assistance Program's free private well assessment, which includes water testing with lab results while funding is available.
- People on private wells
- 122,202
- Share of residents
- 15.0%
- Rank among states
- 43rd
- Well users modeled above 10 µg/L arsenic
- 4.1%
Where to get your well tested in South Dakota
- South Dakota Department of Agriculture and Natural Resources: Private Well Sampling, the state’s guidance for private well owners.
- Well water testing in South Dakota: what to test for and how to collect a sample.
- Certified laboratories in South Dakota. Use a lab certified for drinking water, so results are reliable.
Free or low-cost testing
DANR's private well page links to the Midwest Assistance Program's free private well assessment, which includes water testing with lab results while funding is available. (source)
Mail-in lab kits are another option when no local lab is convenient. See well water test kits for what home kits can and can’t tell you.
What to test for
- Every year: total coliform bacteria and nitrate.
- Before buying equipment: pH, hardness, iron, manganese and, if there’s a smell, hydrogen sulfide.
- Based on location: arsenic, uranium and radon, PFAS, and lead in older plumbing.
Private wells by county
Estimated people relying on private wells in each South Dakota county in 2010, the share of residents that represents, and the modeled share of well users with arsenic above 10 µg/L. These are USGS model estimates (2010 population), not measurements of any well. Arsenic is hidden for counties with fewer than 500 well users.
| County | People on wells | Share | Arsenic >10 µg/L |
|---|---|---|---|
| Pennington County | 11,431 | 11.3% | 2.9% |
| Minnehaha County | 9,161 | 5.4% | 5.2% |
| Meade County | 8,266 | 32.5% | 2.7% |
| Lawrence County | 7,230 | 30.0% | 2.3% |
| Oglala Lakota County | 5,699 | 41.9% | 4.2% |
| Custer County | 4,757 | 57.9% | 3.0% |
| Beadle County | 4,636 | 26.6% | 3.1% |
| Roberts County | 4,099 | 40.4% | 6.3% |
| Brown County | 3,416 | 9.4% | 9.5% |
| Codington County | 3,347 | 12.3% | 5.4% |
| Todd County | 3,134 | 32.6% | 3.0% |
| Brookings County | 3,044 | 9.5% | 4.0% |
Show all 66 counties
| Union County | 2,950 | 20.5% | 4.8% |
| Spink County | 2,207 | 34.4% | 6.1% |
| Fall River County | 1,884 | 26.6% | 4.4% |
| Corson County | 1,774 | 43.8% | 4.5% |
| Bennett County | 1,747 | 50.9% | 4.1% |
| Butte County | 1,702 | 16.8% | 3.0% |
| Davison County | 1,680 | 8.6% | 2.8% |
| Lincoln County | 1,616 | 3.6% | 6.4% |
| Marshall County | 1,519 | 32.6% | 8.0% |
| Perkins County | 1,506 | 50.5% | 4.0% |
| Turner County | 1,504 | 18.0% | 5.0% |
| Sanborn County | 1,446 | 61.4% | 3.0% |
| Grant County | 1,441 | 19.6% | 7.0% |
| Hand County | 1,436 | 41.9% | 5.0% |
| Jackson County | 1,434 | 47.3% | 3.0% |
| Hughes County | 1,281 | 7.5% | 3.0% |
| Lake County | 1,272 | 11.4% | 3.4% |
| Day County | 1,111 | 19.5% | 3.0% |
| McCook County | 1,009 | 18.0% | 3.5% |
| Yankton County | 986 | 4.4% | 4.7% |
| Hutchinson County | 938 | 12.8% | 4.4% |
| Hamlin County | 915 | 15.5% | 5.0% |
| Moody County | 905 | 14.0% | 5.0% |
| Gregory County | 882 | 20.7% | 2.0% |
| Tripp County | 867 | 15.4% | 2.0% |
| Aurora County | 856 | 31.6% | 3.0% |
| Douglas County | 854 | 28.5% | 3.0% |
| Lyman County | 852 | 22.7% | 2.4% |
| Harding County | 832 | 66.3% | 5.0% |
| Charles Mix County | 821 | 9.0% | 2.6% |
| McPherson County | 807 | 32.8% | 7.0% |
| Faulk County | 775 | 32.8% | 5.0% |
| Miner County | 772 | 32.3% | 3.0% |
| Jerauld County | 756 | 36.5% | 4.0% |
| Deuel County | 746 | 17.1% | 6.0% |
| Dewey County | 733 | 13.8% | 3.0% |
| Clark County | 723 | 19.6% | 3.0% |
| Kingsbury County | 718 | 14.0% | 4.6% |
| Edmunds County | 706 | 17.4% | 5.4% |
| Mellette County | 705 | 34.4% | 3.0% |
| Clay County | 703 | 5.1% | 4.2% |
| Bon Homme County | 606 | 8.6% | 3.3% |
| Haakon County | 588 | 30.3% | 3.0% |
| Sully County | 570 | 41.5% | 4.0% |
| Ziebach County | 567 | 20.2% | 4.0% |
| Potter County | 479 | 20.6% | – |
| Campbell County | 476 | 32.5% | – |
| Hyde County | 473 | 33.3% | – |
| Hanson County | 469 | 14.1% | – |
| Stanley County | 415 | 14.0% | – |
| Buffalo County | 366 | 19.1% | – |
| Walworth County | 323 | 5.9% | – |
| Jones County | 144 | 14.4% | – |
| Brule County | 135 | 2.6% | – |
Counties with the highest modeled arsenic share: Brown County (9.5%), Marshall County (8.0%), Grant County (7.0%), McPherson County (7.0%), Lincoln County (6.4%).
After you get results
Enter your numbers in the test results tool to see what needs treating and in what order. The guide to reading a well water test explains units and limits.
Common questions
Does South Dakota offer free well water testing?
DANR's private well page links to the Midwest Assistance Program's free private well assessment, which includes water testing with lab results while funding is available.
Who oversees private wells in South Dakota?
South Dakota Department of Agriculture and Natural Resources (Private Well Sampling) publishes guidance for private well owners. Private wells aren’t covered by the federal Safe Drinking Water Act, so testing and treatment are up to the owner.
How many people use private wells in South Dakota?
USGS estimates about 122,000 people, or 15.0% of the population in 2010. That ranks 43rd of the states covered by the estimate.
What should I test my well for in South Dakota?
Test every year for total coliform bacteria and nitrate, plus pH, hardness, iron and manganese before buying equipment. Ask the state program or a certified lab about local concerns such as arsenic, uranium or PFAS.
Sources
- South Dakota Department of Agriculture and Natural Resources: Private Well Sampling
- South Dakota Department of Agriculture and Natural Resources: well water testing
- South Dakota certified laboratories
- South Dakota free or low-cost testing
- USGS data release: domestic well locations and populations served, 2000 and 2010 (Johnson, Belitz and Lombard, 2019)
- CDC Environmental Public Health Tracking: private well water data (from USGS)