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EPA SDWIS

Minidoka County Water Quality

Minidoka County, Idaho

Water Grade

D

Water Score

48.4

Violations

2

State Rank

#12

of 44 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

D

Based on EPA compliance history and violation data

Water Score

48.4/100

Higher = better quality

Health Violations

2

Health-based violations

Violation Rate

18.5%

Systems with violations

Water Advisory: Minidoka County

Water Verdict

Minidoka County receives a below-average water quality assessment with a grade of D and a score of 48.4 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Minidoka County has recorded 2 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 18.5 violations per 1,000 residents, this rate is high and signals significant water quality management issues.

Consumer Guidance

Residents of Minidoka 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 2 recorded health violations, 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

Minidoka County has better water quality than the average county in Idaho. Its water score is 15.8 points higher than the state average, indicating stronger water system performance relative to neighboring counties.

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

55.6%

60 of 108 assessed

Moderate concern

Top Impairment Causes

  • 1

    TOTAL SUSPENDED SOLIDS (TSS)

  • 2

    PHOSPHORUS, TOTAL

  • 3

    FLOW REGIME MODIFICATION

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

171

Active in the past 5 years

Measurements Recorded

5.5K

5,512 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

10.7Kcfs

May 14, 7:00 PM UTC

vs Long-Term Average

168%

Well above typical

Primary Streamgage

SNAKE R NR MINIDOKA ID AT HOWELLS FERRY

USGS site
13081500
Drainage area
15,700 sq mi
Long-term mean
6,380 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 Minidoka County, Idaho?
Minidoka County, Idaho has a drinking-water quality grade of D with a score of 48.4/100, based on EPA SDWIS compliance data. The county has 2 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Minidoka County?
Minidoka County has 2 health-based drinking water violations 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 healthy are the watersheds in Minidoka County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 55.6% of Minidoka County's 108 assessed water bodies are classified as impaired (60 impaired). The top reported causes are TOTAL SUSPENDED SOLIDS (TSS), PHOSPHORUS, TOTAL, FLOW REGIME MODIFICATION. 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 Minidoka County?
EPA's Water Quality Portal records 5,512 measurements from 171 monitoring sites in Minidoka 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 Minidoka County right now?
Minidoka County's primary USGS streamgage on the SNAKE R is currently reading 10,700 cubic feet per second — 168% of the long-term mean of 6,379.68 cfs. This is well above typical — often a signal of recent precipitation or storm runoff. For genuine real-time data, visit waterdata.usgs.gov.
How does Minidoka County water compare to the Idaho average?
Minidoka County's SDWIS water quality score of 48.4/100 is higher than the Idaho state average of 32.6. The average water quality grade across Idaho is F, based on data from 44 counties with available SDWIS data.
Is tap water safe to drink in Minidoka County?
Based on EPA SDWIS data, Minidoka County has a water quality grade of D (48.4/100). 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 Minidoka County have clean drinking water?
Minidoka County has 2 health-based drinking water violations according to EPA records. With a water quality score of 48.4/100 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 Minidoka County rank for water quality in Idaho?
Minidoka County ranks #12 out of 44 counties in Idaho by SDWIS water quality score (1 = best). With a score of 48.4/100, it falls in the top 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

Bear Lake County

Idaho

D

48.5

Water score

Jerome County

Idaho

D

47.6

Water score

Gem County

Idaho

C

51.2

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.

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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