waterbycounty
Compiled federal source snapshot

South Dakota Water Quality

Drinking water data for all 53 counties.

Avg SDWIS Compliance Index

51.6

Most Common Five-Year SDWIS Compliance Band

A

Counties with Data

53

of 53 total

County water atlas

South Dakota water signals by county

A state-level 2.5D view across drinking-water compliance, watershed impairment, monitoring density, and streamflow snapshot context. Pin any county, switch layers, then use the lens controls to compare index ranges, recorded violation rates, or impaired watersheds without leaving the page.

Counties

53

Avg SDWIS index

51.6

Watersheds

0

ATTAINS counties

Monitoring

53

32 fresh USGS snapshots

State atlas layers combine EPA SDWIS health-based violations, EPA ATTAINS 303(d) impairment assessments, EPA Water Quality Portal monitoring sites, and representative USGS NWIS streamflow gauges. Streamflow values appear only for fresh pipeline snapshots, not as a continuously updated stream. County pages include the observation time and year.

Prepared by ByCounty Editorial TeamPublished by WaterByCounty

Multi-source coverage in South Dakota

Beyond Drinking Water

EPA SDWIS

53/ 53

counties with drinking-water compliance data

88 health violations statewide (5yr)

EPA ATTAINS

—

No §303(d) assessments yet for South Dakota

EPA WQP

704

monitoring sites across 53 counties

70,678 total readings (5yr window)

USGS NWIS

32

counties with a fresh pipeline snapshot

1 above28 below

State atlas notes

What stands out in South Dakota

County water quality is not one number. The strongest read comes from comparing drinking-water compliance against watershed impairment, monitoring density, and streamflow context. Use these signals as a starting point, then open any county profile for source-level detail.

Compliance spread

Bennett County has the highest value in the published state SDWIS Compliance Index table at 86.2/100, while Mellette County has the lowest at 8.0/100. That is a 78.2 point gap inside one state.

Zero health violations

20

3+ health violations

8

Monitoring hubs

Pennington County91 sitesBrookings County39 sitesDeuel County38 sites

Lowest flow reads

Davison County0%Stanley County0%Charles Mix County1%

Highest fresh streamflow pipeline snapshots: Hanson County (144%, observation 2026), Spink County (106%, observation 2026), Roberts County (103%, observation 2026). These are source-data observations, not household tap-water conclusions.

All South Dakota Counties

CountySDWIS Compliance Index
Bennett County86.2
Brookings County86.2
Charles Mix County86.2
Clark County86.2
Davison County86.2
Faulk County86.2
Gregory County86.2
Harding County86.2
Hughes County86.2
Jackson County86.2
Jones County86.2
Kingsbury County86.2
Lake County86.2
Lyman County86.2
Marshall County86.2
McCook County86.2
Perkins County86.2
Stanley County86.2
Union County86.2
Ziebach County86.2
Minnehaha County69.8
Codington County60.3
Lincoln County60.3
Beadle County54.5
Clay County51.6
Lawrence County45.2
Meade County44.0
Yankton County40.3
Pennington County39.1
Dewey County37.7
Turner County36.0
Hutchinson County35.2
Grant County35.0
Butte County33.9
Moody County33.1
Tripp County31.4
Brown County31.3
Hamlin County29.1
Day County29.0
Bon Homme County26.6
Spink County20.8
Brule County20.1
Deuel County18.5
Roberts County17.7
Edmunds County17.4
McPherson County15.9
Hanson County14.6
Haakon County12.2
Fall River County11.9
Corson County10.2
Campbell County9.3
Custer County8.9
Mellette County8.0

Frequently Asked Questions

Which South Dakota county has the highest SDWIS Compliance Index?
Bennett County has the highest SDWIS Compliance Index in the published South Dakota cohort at 86.2/100. This WaterByCounty relative comparison is not an EPA score and does not establish current conditions for a utility or address.
What does the Five-Year SDWIS Compliance Band mean?
The band is derived only from each county aggregation's recorded health-violation rate per 100,000 people served for the stated five-year source window. It is separate from the relative SDWIS Compliance Index and is not a current determination for a specific utility or address.
Which USGS streamflow records are shown across South Dakota?
WaterByCounty has 32 fresh USGS pipeline snapshots in the published South Dakota cohort. Each county page shows its observation timestamp and year. A pipeline snapshot is not a continuously updated reading or a tap-water safety measure.
Where can South Dakota residents find current official information?
Review the applicable utility's Consumer Confidence Report, active notices, and the state drinking-water agency. WaterByCounty's county-level historical aggregations do not establish the current status of a specific utility, address, private well, or household plumbing system.
What does Water Quality Portal monitoring volume show in South Dakota?
The published county records contain 70,678 results from 704 monitoring locations in the site's five-year aggregation. Monitoring volume does not by itself indicate better or worse water quality.

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. The WaterByCounty SDWIS Compliance Index reflects the recorded rate and is not an EPA score.

Disclaimer: This data is informational only. It is not health, legal, or professional advice. For concerns about your specific water supply, contact your local water utility.

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