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County water report

Lemhi County Water Report

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

Water grade

F

Water score

9.2

State rank

#36

of 44

Health violations

13

EPA SDWIS, 5-year lookback

Watershed impaired

25.1%

838 water bodies assessed

Monitoring sites

79

4,206 recent measurements

Live streamflow

281%

SALMON RIVER NR SHOUP ID

Water at a glance

Key Water Indicators for Lemhi County

EPA SDWIS

Safety Grade

F

Score: 9.2 / 100

EPA SDWIS

Active Violations

13

5-year health-based lookback

EPA ATTAINS

Watershed Health

25% impaired

838 bodies assessed

USGS NWIS

Streamflow Snapshot

281% of mean

SALMON RIVER NR SHOUP ID

EPA WQP

Monitoring Sites

79

4,206 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.

9.2/100

Health violations

13

Health-based violations

Violations per 100K served

367.8

Population-normalized SDWIS rate

Editorial analysis

Understanding Lemhi County’s Water

Drinking Water Quality Overview

EPA SDWIS

Lemhi County's water systems carry a failing grade, scoring 9.2 out of 100. Over the past five years, EPA SDWIS records 13 health-based violations — a pattern that public water utilities are required to disclose and correct.

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 notable 25.1% of assessed waterways carry an impairment designation (210 of 838 water bodies) across Lemhi County's watersheds. The leading impairment causes are temperature and sedimentation/siltation. 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 2026-05-14T12:30:00.000-06:00) puts SALMON RIVER at 8.1k cfs — running significantly above its long-term average at 281% 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. Lemhi County has extensive coverage with 79 active monitoring sites with 4,206 recent measurements on record. Predominant monitoring categories include biological, counts and biological, fish. 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 Lemhi County

Water Verdict

Lemhi County, Idaho receives a poor water quality assessment with a grade of F and a score of 9.2 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. Separately, EPA ATTAINS assessments cover 838 water bodies in the county's watershed, with 25.1% 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 281.4%.

Violation Context

EPA SDWIS records for Lemhi County, Idaho show 13 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 367.8 violations per 100,000 people served, this rate is high and signals significant water quality management issues. For independent context, 4,206 water-quality monitoring results have been recorded across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Drinking-water compliance in Lemhi County is rated Grade F, reflecting significant health-based violations in the recent reporting period. Lemhi County's drinking-water compliance score is 9.2 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. Temperature is the leading impairment cause in Lemhi County's watershed. With 79 active water-quality monitoring sites in Lemhi County, data coverage is strong. A pipeline streamflow snapshot from the SALMON RIVER gauge is also available on this page.

Regional Context

Lemhi County has poorer water quality than the average county in Idaho. Its water score is 23.4 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 Lemhi County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Elevated temperature

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

  • 2

    Sedimentation and siltation

    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 Lemhi County

EPA How's My Waterway

Interactive watershed health data for Lemhi County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Lemhi County

Consumer Confidence Reports (ID)

Annual water quality reports from utilities in Idaho

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

25.1%

210 of 838 assessed

Some impairment

Top Impairment Causes

  • 1

    TEMPERATURE

  • 2

    SEDIMENTATION/SILTATION

  • 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

79

Active in the past 5 years

Measurements Recorded

4.2K

4,206 total readings

Most Measured

  • Biological, Counts
  • Biological, Fish
  • Physical

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

8,120cfs

May 14, 6:30 PM UTC

vs Long-Term Average

281%

Well above typical

Primary Streamgage

SALMON RIVER NR SHOUP ID

USGS site
13307000
Drainage area
6,239 sq mi
Long-term mean
2,886 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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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 Lemhi County:C — Moderate

Some violations or watershed impairment detected.

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 Lemhi County, Idaho?
Lemhi County, Idaho has a drinking-water quality grade of F with a score of 9.2/100, based on EPA SDWIS compliance data. The county has 13 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 Lemhi County?
Lemhi County has 13 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 Lemhi County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 25.1% of Lemhi County's 838 assessed water bodies are classified as impaired (210 impaired). The top reported causes are TEMPERATURE, SEDIMENTATION/SILTATION, 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 Lemhi County?
EPA's Water Quality Portal records 4,206 measurements from 79 monitoring sites in Lemhi County over the past five years. The most frequently measured characteristic groups are Biological, Counts, Biological, Fish, Physical. 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 Lemhi County right now?
Lemhi County's primary USGS streamgage on the SALMON RIVER has a pipeline snapshot of 8,120 cubic feet per second — 281% of the long-term mean of 2,885.52 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 Lemhi County water compare to the Idaho average?
Lemhi County's SDWIS water quality score of 9.2/100 is lower 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 Lemhi County?
Based on EPA SDWIS data, Lemhi County has a water quality grade of F (9.2/100). 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).
Why does Lemhi County have so many water violations?
Lemhi County has 13 health-based drinking water violations on record from the EPA SDWIS database. A higher violation count can result from aging infrastructure, underfunded water utilities, agricultural runoff contamination, or industrial pollution. Counties with more water systems may also see more violations simply due to scale. Residents concerned about water quality should consider independent water testing and home filtration systems.
How does Lemhi County rank for water quality in Idaho?
Lemhi County ranks #36 out of 44 counties in Idaho by SDWIS water quality score (1 = best). With a score of 9.2/100, 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

Lewis County

Idaho

F

9.1

Water score

Clark County

Idaho

F

8.7

Water score

Franklin County

Idaho

F

8.0

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.

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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