waterbycounty
EPA SDWIS

Grant County Water Quality

Grant County, South Dakota

Water Grade

D

Water Score

44.5

Violations

1

State Rank

#38

of 63 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

D

Based on EPA compliance history and violation data

Water Score

44.5/100

Higher = better quality

Health Violations

1

Health-based violations

Violation Rate

24.6%

Systems with violations

Water Advisory: Grant County

Water Verdict

Grant County receives a below-average water quality assessment with a grade of D and a score of 44.5 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Grant County has recorded 1 health-based violation, meaning the water system experienced at least one exceedance of federal contaminant limits or treatment requirements. At 24.6 violations per 1,000 residents, this rate is high and signals significant water quality management issues.

Consumer Guidance

Residents of Grant County are advised to use filtered or bottled water for drinking and cooking until water quality improves. A reverse-osmosis or activated-carbon filter certified to remove the contaminants listed in the utility's Consumer Confidence Report is recommended. With 1 recorded health violation, staying informed about utility communications and boil-water notices is especially important. For long-term peace of mind, request your utility's latest Consumer Confidence Report and consider independent water testing if you have specific health concerns.

Regional Context

Grant County has poorer water quality than the average county in South Dakota. Its water score is 12.3 points lower than the state average, suggesting more challenges with contamination control or infrastructure than neighboring counties.

Past 5 years

Water Quality Monitoring

Monitoring Sites

23

Active in the past 5 years

Measurements Recorded

1.3K

1,337 total readings

Most Measured

  • Physical
  • Nutrient
  • Microbiological

Categories measured most frequently

Data from the EPA Water Quality Portal (WQP), aggregating monitoring records from federal, state, and tribal sources. Each measurement represents a single sample analyzed for a specific characteristic (e.g., E. coli, pH, dissolved oxygen, nitrogen).

Live USGS Streamgage

River & Stream Conditions

Current Discharge

58.9cfs

May 14, 7:00 PM UTC

vs Long-Term Average

82%

Below typical

Primary Streamgage

WHETSTONE RIVER NEAR BIG STONE CITY, SD

USGS site
05291000
Drainage area
398 sq mi
Long-term mean
72.0 cfs

One representative streamgage (the one with the largest drainage area in the county). Many counties have multiple gauges — this view summarizes the primary one. The long-term mean is the full-record annual average; "% of typical" compares the latest reading against that average.

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Frequently Asked Questions

What is the water quality in Grant County, South Dakota?
Grant County, South Dakota has a drinking-water quality grade of D with a score of 44.5/100, based on EPA SDWIS compliance data. The county has 1 health-based drinking water violation over the past 5 years. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Grant County?
Grant County has 1 health-based drinking water violation recorded by the EPA over the past 5 years. Health-based violations indicate instances where contaminant levels exceeded EPA Maximum Contaminant Levels (MCLs). Violations may have been resolved — check with your local water utility for current status.
How much water-quality monitoring happens in Grant County?
EPA's Water Quality Portal records 1,337 measurements from 23 monitoring sites in Grant County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Microbiological. Each measurement is a single sample analyzed for one characteristic (E. coli, pH, dissolved oxygen, etc.). High monitoring density means more scientific evidence behind any reported signal — it does not by itself indicate water quality.
What's happening with rivers in Grant County right now?
Grant County's primary USGS streamgage on the WHETSTONE RIVER is currently reading 58.9 cubic feet per second — 82% of the long-term mean of 72.02 cfs. Flow is within typical range for this gauge. For genuine real-time data, visit waterdata.usgs.gov.
How does Grant County water compare to the South Dakota average?
Grant County's SDWIS water quality score of 44.5/100 is lower than the South Dakota state average of 56.8. The average water quality grade across South Dakota is D, based on data from 63 counties with available SDWIS data.
Is tap water safe to drink in Grant County?
Based on EPA SDWIS data, Grant County has a water quality grade of D (44.5/100). This indicates below-average compliance with significant violations. Residents may want to consider home water filtration or independent testing. The grade speaks to the public water system, not the watershed — for watershed-level concerns, see the Watershed Health zone. For the most up-to-date information, contact your local water utility or review your Consumer Confidence Report (CCR).
Does Grant County have clean drinking water?
Grant County has 1 health-based drinking water violation according to EPA records. With a water quality score of 44.5/100 and grade D, the county's drinking water has had some compliance issues but continues to be monitored. Note: drinking-water compliance speaks to the public water system, not necessarily to the watershed itself — check the Watershed Health zone for ATTAINS §303(d) data.
How does Grant County rank for water quality in South Dakota?
Grant County ranks #38 out of 63 counties in South Dakota by SDWIS water quality score (1 = best). With a score of 44.5/100, it falls in the middle third of counties statewide. The ranking reflects EPA SDWIS compliance only — not watershed impairment, monitoring density, or streamflow, which are tracked separately on this page.

Counties with Similar Water Quality

Turner County

South Dakota

D

45.4

Water score

Dewey County

South Dakota

D

46.9

Water score

Beadle County

South Dakota

D

47.6

Water score

Data Sources

Drinking-water compliance data from the EPA Safe Drinking Water Information System (SDWIS) via the ECHO enforcement database. Scores reflect compliance history and health-based violation counts.

Water-quality monitoring counts from the EPA Water Quality Portal (WQP) — federated USGS, EPA, and state agency sampling records over a rolling 5-year window.

Live streamflow from the USGS National Water Information System (NWIS) — continuous discharge measurements from the largest-drainage gauge in each county, compared against the full-record long-term annual mean.

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.

By Logan Johnson, Founder & Data EditorUpdated Reviewed by Logan Johnson, Founder & Data Editor

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