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County water report

Mellette County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Mellette County, South Dakota.

Water grade

F

Water score

15.7

State rank

#60

of 63

Health violations

1

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

1

109 recent measurements

Live streamflow

65%

LITTLE WHITE RIVER BELOW WHITE RIVER,SD

Water at a glance

Key Water Indicators for Mellette County

EPA SDWIS

Safety Grade

F

Score: 15.7 / 100

EPA SDWIS

Active Violations

1

5-year health-based lookback

EPA ATTAINS

Watershed Health

Not reported

Coverage varies by state

USGS NWIS

Streamflow Snapshot

65% of mean

LITTLE WHITE RIVER BELOW WHITE RIVER,SD

EPA WQP

Monitoring Sites

1

109 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

F

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

15.7/100

Health violations

1

Health-based violations

Violations per 100K served

187.6

Population-normalized SDWIS rate

Editorial analysis

Understanding Mellette County’s Water

Drinking Water Quality Overview

EPA SDWIS

Mellette County's water systems carry a failing grade, scoring 15.7 out of 100. Over the past five years, EPA SDWIS records 1 health-based violation — a single incident worth monitoring.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T13:00:00.000-05:00) puts LITTLE WHITE RIVER BELOW WHITE RIVER,SD at 99.1 cfs — running somewhat below its historical average at 65% of mean. Streamflow is a leading indicator of drought stress, sediment load, and dilution capacity: low flows concentrate pollutants and warm water temperatures, stressing aquatic life and, in surface-water-dependent systems, the source water quality for treatment plants.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Mellette County has limited coverage with 1 active monitoring site with 109 recent measurements on record. Predominant monitoring categories include physical and nutrient. More monitoring sites generally indicate greater scientific attention to local water conditions — and provide the baseline data that regulators use to set future impairment listings.

Editorial advisory

What the data suggests for Mellette County

Water Verdict

Mellette County receives a poor water quality assessment with a grade of F and a score of 15.7 out of 100. The water supply has documented quality issues. Residents are strongly encouraged to use filtered or bottled water for drinking and to stay informed about utility improvement plans.

Violation Context

Mellette County has recorded 1 health-based violation, meaning the water system experienced at least one exceedance of federal contaminant limits or treatment requirements. At 187.6 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Drinking-water compliance in Mellette County is rated Grade F, reflecting significant health-based violations in the recent reporting period. Mellette County's drinking-water compliance score is 15.7 out of 100. An NSF 53 or NSF 58-certified filter is recommended for drinking and cooking water. Check the Consumer Confidence Report from your utility to identify the specific contaminants and required corrective actions — utilities are legally required to notify customers of violations. There is 1 active water-quality monitoring site in Mellette County. A pipeline streamflow snapshot from the LITTLE WHITE RIVER BELOW WHITE RIVER,SD gauge is also available on this page.

Regional Context

Mellette County has poorer water quality than the average county in South Dakota. Its water score is 41.1 points lower than the state average, suggesting more challenges with contamination control or infrastructure than neighboring counties.

Advisory text summarizes county-level public records and is not a replacement for your utility's current Consumer Confidence Report or direct local notices.

Contaminants & Resources

Key issues flagged in Mellette County's water environment

Official EPA Resources for Mellette County

EPA How's My Waterway

Interactive watershed health data for Mellette County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Mellette County

Consumer Confidence Reports (SD)

Annual water quality reports from utilities in South Dakota

Past 5 years

Water Quality Monitoring

Monitoring Sites

1

Active in the past 5 years

Measurements Recorded

109

109 total readings

Most Measured

  • Physical
  • Nutrient
  • Inorganics, Major, Metals

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

99.1cfs

May 14, 6:00 PM UTC

vs Long-Term Average

65%

Below typical

Primary Streamgage

LITTLE WHITE RIVER BELOW WHITE RIVER,SD

USGS site
06450500
Drainage area
1,549 sq mi
Long-term mean
153 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; the percent-of-typical value compares the latest reading against that average.

Free tool

Estimate Your Water Costs

Water Cost Estimate

3

3 people  ·  ~225 gal/day

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Mellette County:F — Failing

High violation count or severe watershed conditions.

Estimates use the national average residential water rate ($0.0068/gal, EPA/AWWA 2023) and EPA WaterSense per-person consumption baseline (75 gal/person/day). Actual bills vary by utility, usage tier, and local infrastructure fees. For informational purposes only.

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Frequently Asked Questions

What is the water quality in Mellette County, South Dakota?
Mellette County, South Dakota has a drinking-water quality grade of F with a score of 15.7/100, 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 streamflow snapshots are reported separately on this page.
Are there any water violations in Mellette County?
Mellette 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 Mellette County?
EPA's Water Quality Portal records 109 measurements from 1 monitoring sites in Mellette County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Inorganics, Major, Metals. 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 Mellette County right now?
Mellette County's primary USGS streamgage on the LITTLE WHITE RIVER BELOW WHITE RIVER,SD has a pipeline snapshot of 99.1 cubic feet per second — 65% of the long-term mean of 152.73 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.
How does Mellette County water compare to the South Dakota average?
Mellette County's SDWIS water quality score of 15.7/100 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 Mellette County?
Based on EPA SDWIS data, Mellette County has a water quality grade of F (15.7/100). 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 Mellette County have clean drinking water?
Mellette County has 1 health-based drinking water violation according to EPA records. With a water quality score of 15.7/100 and grade F, 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 Mellette County rank for water quality in South Dakota?
Mellette County ranks #60 out of 63 counties in South Dakota by SDWIS water quality score (1 = best). With a score of 15.7/100, it falls in the bottom 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

Spink County

South Dakota

F

16.5

Water score

Custer County

South Dakota

F

17.0

Water score

Campbell County

South Dakota

F

17.8

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 Evan Brooks, Data EditorUpdated Reviewed by Evan Brooks, Data Editor

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