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County water report

Gem County Water Report

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

Water grade

C

Water score

51.2

State rank

#10

of 44

Health violations

1

EPA SDWIS, 5-year lookback

Watershed impaired

29.3%

157 water bodies assessed

Monitoring sites

27

4,292 recent measurements

Live streamflow

282%

PAYETTE RIVER NR LETHA ID

Water at a glance

Key Water Indicators for Gem County

EPA SDWIS

Safety Grade

C

Score: 51.2 / 100

EPA SDWIS

Active Violations

1

5-year health-based lookback

EPA ATTAINS

Watershed Health

29% impaired

157 bodies assessed

USGS NWIS

Streamflow Snapshot

282% of mean

PAYETTE RIVER NR LETHA ID

EPA WQP

Monitoring Sites

27

4,292 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

C

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

51.2/100

Health violations

1

Health-based violations

Violations per 100K served

14.5

Population-normalized SDWIS rate

Editorial analysis

Understanding Gem County’s Water

Drinking Water Quality Overview

EPA SDWIS

Gem County's drinking water earned a C grade, scoring 51.2 out of 100. Over the past five years, EPA SDWIS records 1 health-based violation — a single incident worth monitoring.

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 29.3% of assessed waterways carry an impairment designation (46 of 157 water bodies) across Gem County's watersheds. The leading impairment causes are sedimentation/siltation and temperature. 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 PAYETTE RIVER at 7.0k cfs — running significantly above its long-term average at 282% 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. Gem County has moderate coverage with 27 active monitoring sites with 4,292 recent measurements on record. Predominant monitoring categories include organics, other and physical. 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 Gem County

Water Verdict

Gem County, Idaho receives a below-average water quality assessment with a grade of C and a score of 51.2 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 157 water bodies in the county's watershed, with 29.3% 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 281.6%.

Violation Context

EPA SDWIS records for Gem County, Idaho show 1 health-based violation, meaning a water system experienced at least one exceedance of federal contaminant limits or treatment requirements. At 14.5 violations per 100,000 people served, this rate is high and signals significant water quality management issues. For independent context, 4,292 water-quality monitoring results have been recorded across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Tap water in Gem County meets baseline standards but the compliance record shows room for improvement, with a Grade C rating. Gem County's drinking-water compliance score is 51.2 out of 100. The violation rate for Gem County is 14.5 per 100,000 people served. Residents who are immunocompromised, pregnant, or have young children may benefit from using an NSF 53-certified filter. Contacting your local utility for the current Consumer Confidence Report will confirm which specific violations were recorded and whether they have been resolved. Sedimentation/Siltation is the leading impairment cause in Gem County's watershed. With 27 active water-quality monitoring sites in Gem County, data coverage is strong. A pipeline streamflow snapshot from the PAYETTE RIVER gauge is also available on this page.

Regional Context

Gem County has better water quality than the average county in Idaho. Its water score is 18.6 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 Gem County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    Sedimentation and siltation

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

  • 2

    Elevated temperature

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

  • 3

    E. coli (bacteria)

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

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Gem County

EPA How's My Waterway

Interactive watershed health data for Gem County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Gem County

Consumer Confidence Reports (ID)

Annual water quality reports from utilities in Idaho

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

29.3%

46 of 157 assessed

Some impairment

Top Impairment Causes

  • 1

    SEDIMENTATION/SILTATION

  • 2

    TEMPERATURE

  • 3

    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

27

Active in the past 5 years

Measurements Recorded

4.3K

4,292 total readings

Most Measured

  • Organics, Other
  • Physical
  • Inorganics, Minor, Metals

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

7,040cfs

May 14, 6:30 PM UTC

vs Long-Term Average

282%

Well above typical

Primary Streamgage

PAYETTE RIVER NR LETHA ID

USGS site
13250000
Drainage area
2,760 sq mi
Long-term mean
2,500 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

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 Gem 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 Gem County, Idaho?
Gem County, Idaho has a drinking-water quality grade of C with a score of 51.2/100, 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 Gem County?
Gem 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 healthy are the watersheds in Gem County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 29.3% of Gem County's 157 assessed water bodies are classified as impaired (46 impaired). The top reported causes are SEDIMENTATION/SILTATION, TEMPERATURE, 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 Gem County?
EPA's Water Quality Portal records 4,292 measurements from 27 monitoring sites in Gem County over the past five years. The most frequently measured characteristic groups are Organics, Other, Physical, Inorganics, Minor, Metals. 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 Gem County right now?
Gem County's primary USGS streamgage on the PAYETTE RIVER has a pipeline snapshot of 7,040 cubic feet per second — 282% of the long-term mean of 2,499.66 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 Gem County water compare to the Idaho average?
Gem County's SDWIS water quality score of 51.2/100 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 Gem County?
Based on EPA SDWIS data, Gem County has a water quality grade of C (51.2/100). This indicates moderate compliance. Some violations have been recorded but overall standards are maintained. 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 Gem County have clean drinking water?
Gem County has 1 health-based drinking water violation according to EPA records. With a water quality score of 51.2/100 and grade C, 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 Gem County rank for water quality in Idaho?
Gem County ranks #10 out of 44 counties in Idaho by SDWIS water quality score (1 = best). With a score of 51.2/100, 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

Twin Falls County

Idaho

C

52.8

Water score

Bannock County

Idaho

C

53.8

Water score

Bear Lake County

Idaho

D

48.5

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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