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County water report

Minidoka County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Minidoka County, Idaho.

Water grade

D

Water score

48.4

State rank

#12

of 44

Health violations

2

EPA SDWIS, 5-year lookback

Watershed impaired

55.6%

108 water bodies assessed

Monitoring sites

171

5,512 recent measurements

Live streamflow

168%

SNAKE R NR MINIDOKA ID AT HOWELLS FERRY

Water at a glance

Key Water Indicators for Minidoka County

EPA SDWIS

Safety Grade

D

Score: 48.4 / 100

EPA SDWIS

Active Violations

2

5-year health-based lookback

EPA ATTAINS

Watershed Health

56% impaired

108 bodies assessed

USGS NWIS

Streamflow Snapshot

168% of mean

SNAKE R NR MINIDOKA ID AT HOWELLS FERRY

EPA WQP

Monitoring Sites

171

5,512 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

D

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

48.4/100

Health violations

2

Health-based violations

Violations per 100K served

18.5

Population-normalized SDWIS rate

Editorial analysis

Understanding Minidoka County’s Water

Drinking Water Quality Overview

EPA SDWIS

Minidoka County's drinking water received a D grade, scoring 48.4 out of 100. Over the past five years, EPA SDWIS records 2 health-based violations — a small cluster that warrants attention.

Watershed Conditions

EPA ATTAINS

Under the Clean Water Act §303(d), EPA ATTAINS tracks whether waterways meet quality standards for drinking, recreation, and aquatic life (reporting cycle: 2022). A substantial 55.6% of assessed waterways are impaired (60 of 108 water bodies) across Minidoka County's watersheds. The leading impairment causes are total suspended solids (tss) and phosphorus, total. Impairment does not mean tap water is unsafe — it measures ambient waterway conditions upstream of treatment, not finished drinking water.

River & Streamflow Status

USGS NWIS

USGS NWIS gauge data (as of 2026-05-14T13:00:00.000-06:00) puts SNAKE R at 10.7k cfs — running significantly above its long-term average at 168% of mean flow. 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. Minidoka County has extensive coverage with 171 active monitoring sites with 5,512 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 Minidoka County

Water Verdict

Minidoka County, Idaho 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. Separately, EPA ATTAINS assessments cover 108 water bodies in the county's watershed, with 55.6% listed as impaired under the Clean Water Act — a source-water measure that is tracked independently of tap-water compliance. At the most recent USGS reading, local streamflow was running above its historical mean at 167.7%.

Violation Context

EPA SDWIS records for Minidoka County, Idaho show 2 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 18.5 violations per 100,000 people served, this rate is high and signals significant water quality management issues. For independent context, 5,512 water-quality monitoring results have been recorded across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Minidoka County's drinking-water compliance is below average with a Grade D, indicating repeated or unresolved violations in the recent record. Minidoka County's drinking-water compliance score is 48.4 out of 100. The violation rate for Minidoka County is 18.5 per 100,000 people served. Residents are encouraged to use an NSF 53 or NSF 58-certified filter for drinking and cooking water until the underlying violations are resolved. Running tap water for 30 seconds before use and avoiding older lead-pipe connections can also reduce exposure risk. The current Consumer Confidence Report from your utility will specify the contaminants of concern. Total Suspended Solids (Tss) is the leading impairment cause in Minidoka County's watershed. With 171 active water-quality monitoring sites in Minidoka County, data coverage is strong. A pipeline streamflow snapshot from the SNAKE R gauge is also available on this page.

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.

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 Minidoka County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Total Suspended Solids (Tss)

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 2

    Phosphorus (excess nutrients)

    Impairment cause per EPA Clean Water Act §303(d) assessment

  • 3

    Flow Regime Modification

    Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Minidoka County

EPA How's My Waterway

Interactive watershed health data for Minidoka County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Minidoka County

Consumer Confidence Reports (ID)

Annual water quality reports from utilities in Idaho

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; the percent-of-typical value compares the latest reading against that average.

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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 Minidoka County:D — Poor

Elevated violations or significant watershed impairment.

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 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 streamflow snapshots 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 has a pipeline snapshot of 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 the latest gauge feed, 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 and 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 Evan Brooks, Data EditorUpdated Reviewed by Evan Brooks, Data Editor

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