waterbycounty
Federal water data

County water report

Ada County Water Report

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

Water grade

C

Water score

55.6

State rank

#7

of 44

Health violations

50

EPA SDWIS, 5-year lookback

Watershed impaired

46.1%

219 water bodies assessed

Monitoring sites

3

943 recent measurements

Live streamflow

No gauge

Snake River blw Swan Falls Dam, ID

Water at a glance

Key Water Indicators for Ada County

EPA SDWIS

Safety Grade

C

Score: 55.6 / 100

EPA SDWIS

Active Violations

50

5-year health-based lookback

EPA ATTAINS

Watershed Health

46% impaired

219 bodies assessed

USGS NWIS

Streamflow Snapshot

No gauge

Snake River blw Swan Falls Dam, ID

EPA WQP

Monitoring Sites

3

943 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.

55.6/100

Health violations

50

Health-based violations

Violations per 100K served

9.9

Population-normalized SDWIS rate

Data center water stress

Ada County has 4 facilities in the DCWSI dataset.

ByCounty's DCWSI ranks this county #122 nationally by combining its water score with mapped data center density.

DCWSIThe Data Center Water Stress Index: 60% the county's water-system stress plus 40% how concentrated data centers already are, scored 0-100. Higher means data-center density and water pressure overlap more here.

60.5

0-100 index

Facility count

4

67.8 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+5.6

Compared with US county median

Named operators

Meta

Mapped facilities

  • BRISBIE LLC

    KUNA

    EPA ECHO

  • Meta Kuna Data Center

    Meta

    OSM

  • OpenStreetMap data center 1455915217

    Facility details limited

    OSM

  • OpenStreetMap data center 1455915218

    Facility details limited

    OSM
See the Ada County data-center reportReview methodology

Data Center Water Budget Calculator

Estimate daily water use for a hypothetical facility in Ada County.

1 MW1,000 MW
40%100%
799K gallons/dayHigh Impact

Your facility would use 72.2% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

72.2% of county industrial baseline0.31 Mgal/day remaining headroom

Based on USGS 2020 water-use data and EPA-standard cooling intensity constants. Not a substitute for site-specific water rights analysis.

Editorial analysis

Understanding Ada County’s Water

Drinking Water Quality Overview

EPA SDWIS

Ada County's drinking water earned a C grade, scoring 55.6 out of 100. Over the past five years, EPA SDWIS records 50 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 substantial 46.1% of assessed waterways are impaired (101 of 219 water bodies) across Ada 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.

Monitoring Network

EPA WQP

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Ada County has limited coverage with 3 active monitoring sites with 943 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 Ada County

Water Verdict

Ada County receives a fair water quality assessment with a grade of C and a score of 55.6 out of 100. The water supply meets baseline federal standards, but there may be periods of elevated contaminant levels or infrastructure concerns worth monitoring.

Violation Context

Ada County has recorded 50 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 9.9 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Tap water in Ada County meets baseline standards but the compliance record shows room for improvement, with a Grade C rating. Ada County's drinking-water compliance score is 55.6 out of 100. The violation rate for Ada County is 9.9 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 Ada County's watershed. There are 3 active water-quality monitoring sites in Ada County. A pipeline streamflow snapshot from the Snake River blw Swan Falls Dam, ID gauge is also available on this page.

Regional Context

Ada County has better water quality than the average county in Idaho. Its water score is 23 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 Ada 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 Ada County

EPA How's My Waterway

Interactive watershed health data for Ada County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Ada County

Consumer Confidence Reports (ID)

Annual water quality reports from utilities in Idaho

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

46.1%

101 of 219 assessed

Moderate concern

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

3

Active in the past 5 years

Measurements Recorded

943

943 total readings

Most Measured

  • Physical
  • Nutrient
  • Inorganics, Major, Non-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).

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 Ada 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 Ada County, Idaho?
Ada County, Idaho has a drinking-water quality grade of C with a score of 55.6/100, based on EPA SDWIS compliance data. The county has 50 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 Ada County?
Ada County has 50 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 Ada County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 46.1% of Ada County's 219 assessed water bodies are classified as impaired (101 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 Ada County?
EPA's Water Quality Portal records 943 measurements from 3 monitoring sites in Ada County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Inorganics, Major, Non-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.
How does Ada County water compare to the Idaho average?
Ada County's SDWIS water quality score of 55.6/100 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 Ada County?
Based on EPA SDWIS data, Ada County has a water quality grade of C (55.6/100). 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).
Why does Ada County have so many water violations?
Ada County has 50 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 Ada County rank for water quality in Idaho?
Ada County ranks #7 out of 44 counties in Idaho by SDWIS water quality score (1 = best). With a score of 55.6/100, 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

Bannock County

Idaho

C

53.8

Water score

Twin Falls County

Idaho

C

52.8

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.

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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