waterbycounty
EPA SDWIS

Sioux County Water Quality

Sioux County, North Dakota

Water Grade

N/A

Water Score

N/A

Violations

N/A

State Rank

N/A

EPA SDWIS Compliance

Drinking Water Quality

Water Advisory: Sioux County

Water Verdict

Sioux County does not have sufficient EPA SDWIS water quality data to determine an overall assessment. Residents should contact their local water utility for the most recent Consumer Confidence Report.

Violation Context

Health-based violation data is not available for Sioux County. EPA health violations occur when water systems exceed allowable contaminant levels or fail to meet treatment requirements. Residents should request the latest Consumer Confidence Report from their water provider.

Consumer Guidance

Residents of Sioux County should obtain the annual Consumer Confidence Report from their water utility, which lists detected contaminants and any violations. Even without available data, using a NSF-certified water filter can provide additional peace of mind for drinking water.

Regional Context

State-level water quality comparison data is not available for Sioux County. When data is available, this section will show how the county's water quality compares to other counties in North Dakota.

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

29.4%

5 of 17 assessed

Some impairment

Top Impairment Causes

  • 1

    FECAL COLIFORM

  • 2

    ESCHERICHIA COLI (E. COLI)

Source: EPA ATTAINS · Reporting cycle 2022

Impairment is determined under the Clean Water Act §303(d): a water body is impaired when it fails to meet state-defined quality standards for designated uses (drinking, recreation, aquatic life). Assessment coverage varies by state — counties without assessed water bodies are not shown.

Past 5 years

Water Quality Monitoring

Monitoring Sites

8

Active in the past 5 years

Measurements Recorded

1.4K

1,436 total readings

Most Measured

  • Physical
  • Inorganics, Major, Non-metals
  • Organics, Other

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

50.3cfs

May 14, 6:00 PM UTC

vs Long-Term Average

54%

Well below typical

Primary Streamgage

CANNONBALL RIVER AT SOLEN, ND

USGS site
06354050
Drainage area
4,170 sq mi
Long-term mean
93.4 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 Sioux County, North Dakota?
Sioux County, North Dakota has a drinking-water quality grade of N/A with a score of N/A/100, based on EPA SDWIS compliance data. Compliance data is currently unavailable. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Sioux County?
Violation data for Sioux County is not currently available. Health-based violations indicate instances where contaminant levels exceeded EPA Maximum Contaminant Levels (MCLs).
How healthy are the watersheds in Sioux County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 29.4% of Sioux County's 17 assessed water bodies are classified as impaired (5 impaired). The top reported causes are FECAL COLIFORM, ESCHERICHIA COLI (E. COLI). Impairment means the water body fails to meet state quality standards for at least one designated use — drinking water source, recreation, aquatic life, or fish consumption. Note: watershed impairment doesn't always translate to tap-water issues; treatment plants can remove most regulated contaminants.
How much water-quality monitoring happens in Sioux County?
EPA's Water Quality Portal records 1,436 measurements from 8 monitoring sites in Sioux County over the past five years. The most frequently measured characteristic groups are Physical, Inorganics, Major, Non-metals, Organics, Other. 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 Sioux County right now?
Sioux County's primary USGS streamgage on the CANNONBALL RIVER is currently reading 50.3 cubic feet per second — 54% of the long-term mean of 93.4 cfs. This is well below typical — often a signal of drought stress on source water. For genuine real-time data, visit waterdata.usgs.gov.
How does Sioux County water compare to the North Dakota average?
Sioux County's SDWIS water quality score of N/A/100 is not available for comparison. The average water quality grade across North Dakota is C, based on data from 52 counties with available SDWIS data.
Is tap water safe to drink in Sioux County?
Based on EPA SDWIS data, Sioux County has a water quality grade of N/A (N/A/100). Insufficient data is available to fully assess compliance. 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 Sioux County have clean drinking water?
Sioux County has no reported health-based drinking water violations according to EPA records. With a water quality score of N/A/100 and grade N/A, 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 is water quality measured?
WaterByCounty layers four federal datasets per county. The A–F drinking-water grade comes from EPA SDWIS (Safe Drinking Water Act compliance, 5-year violation lookback). The Watershed Health zone surfaces EPA ATTAINS §303(d) impairment data. The Monitoring zone summarizes EPA Water Quality Portal records. The Streamflow zone reports the latest USGS NWIS reading from the county's primary streamgage. Each is reported separately so you can see where the water is actually weakest.

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.

Watershed health and impaired-waterway data from the EPA ATTAINS Clean Water Act §303(d) assessments — state-reported, EPA-finalized.

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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