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Federal water data

County water report

Corson County Water Report

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

Water grade

F

Water score

19.3

State rank

#56

of 63

Health violations

1

EPA SDWIS, 5-year lookback

Watershed impaired

Not reported

EPA ATTAINS coverage varies by state

Monitoring sites

17

2,333 recent measurements

Live streamflow

16%

GRAND RIVER AT LITTLE EAGLE,SD

Water at a glance

Key Water Indicators for Corson County

EPA SDWIS

Safety Grade

F

Score: 19.3 / 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

16% of mean

GRAND RIVER AT LITTLE EAGLE,SD

EPA WQP

Monitoring Sites

17

2,333 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.

19.3/100

Health violations

1

Health-based violations

Violations per 100K served

137.6

Population-normalized SDWIS rate

Editorial analysis

Understanding Corson County’s Water

Drinking Water Quality Overview

EPA SDWIS

Corson County's water systems carry a failing grade, scoring 19.3 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 2026-05-14T12:15:00.000-06:00) puts GRAND RIVER at 43.3 cfs — well below its long-term average at 16% of mean — low-flow conditions worth noting for water-dependent ecosystems. 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. Corson County has moderate coverage with 17 active monitoring sites with 2,333 recent measurements on record. Predominant monitoring categories include physical and inorganics, major, non-metals. 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 Corson County

Water Verdict

Corson County receives a poor water quality assessment with a grade of F and a score of 19.3 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

Corson County has recorded 1 health-based violation, meaning the water system experienced at least one exceedance of federal contaminant limits or treatment requirements. At 137.6 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Drinking-water compliance in Corson County is rated Grade F, reflecting significant health-based violations in the recent reporting period. Corson County's drinking-water compliance score is 19.3 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. With 17 active water-quality monitoring sites in Corson County, data coverage is strong. A pipeline streamflow snapshot from the GRAND RIVER gauge is also available on this page.

Regional Context

Corson County has poorer water quality than the average county in South Dakota. Its water score is 37.5 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 Corson County's water environment

Official EPA Resources for Corson County

EPA How's My Waterway

Interactive watershed health data for Corson County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Corson County

Consumer Confidence Reports (SD)

Annual water quality reports from utilities in South Dakota

Past 5 years

Water Quality Monitoring

Monitoring Sites

17

Active in the past 5 years

Measurements Recorded

2.3K

2,333 total readings

Most Measured

  • Physical
  • Inorganics, Major, Non-metals
  • Nutrient

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

43.3cfs

May 14, 6:15 PM UTC

vs Long-Term Average

16%

Well below typical

Primary Streamgage

GRAND RIVER AT LITTLE EAGLE,SD

USGS site
06357800
Drainage area
5,316 sq mi
Long-term mean
267 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

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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 Corson 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 Corson County, South Dakota?
Corson County, South Dakota has a drinking-water quality grade of F with a score of 19.3/100, 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 Corson County?
Corson 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 Corson County?
EPA's Water Quality Portal records 2,333 measurements from 17 monitoring sites in Corson County over the past five years. The most frequently measured characteristic groups are Physical, Inorganics, Major, Non-metals, Nutrient. 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 Corson County right now?
Corson County's primary USGS streamgage on the GRAND RIVER has a pipeline snapshot of 43.3 cubic feet per second — 16% of the long-term mean of 267.41 cfs. This is well below typical — often a signal of drought stress on source water. For the latest gauge feed, visit waterdata.usgs.gov.
How does Corson County water compare to the South Dakota average?
Corson County's SDWIS water quality score of 19.3/100 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 Corson County?
Based on EPA SDWIS data, Corson County has a water quality grade of F (19.3/100). 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 Corson County have clean drinking water?
Corson County has 1 health-based drinking water violation according to EPA records. With a water quality score of 19.3/100 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 Corson County rank for water quality in South Dakota?
Corson County ranks #56 out of 63 counties in South Dakota by SDWIS water quality score (1 = best). With a score of 19.3/100, 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

Deuel County

South Dakota

F

19.4

Water score

Campbell County

South Dakota

F

17.8

Water score

Brule County

South Dakota

F

21.0

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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