County water report

Yellowstone County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Yellowstone County, Montana.

Water grade

Water score

42.1

State rank

#28

of 55

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

0.0%

15 water bodies assessed

Monitoring sites

8,890 recent measurements

Live streamflow

217%

Yellowstone River at Billings MT

Water at a glance

Key Water Indicators for Yellowstone County

EPA SDWIS

Safety Grade

Score: 42.1 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

0% impaired

15 bodies assessed

USGS NWIS

Streamflow Snapshot

217% of mean

Yellowstone River at Billings MT

EPA WQP

Monitoring Sites

8,890 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

42.1/100

Health violations

Health-based violations

Violations per 100K served

28.5

Population-normalized SDWIS rate

Data center water stress

Yellowstone County has 1 facility in the DCWSI dataset.

ByCounty's DCWSI ranks this county #1793 nationally by combining its water score with mapped data center density.

DCWSI

25.3

0-100 index

Facility count

0.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

-7.9

Compared with US county median

Mapped facilities

Parsec Data Management
Facility details limited
OSM

See the Yellowstone County data-center report Review methodology

Data Center Water Budget Calculator

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

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayHigh Impact

Your facility would use 82.3% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

82.3% of county industrial baseline0.17 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 Yellowstone County’s Water

Drinking Water Quality Overview

EPA SDWIS

Yellowstone County's drinking water received a D grade, scoring 42.1 out of 100. Over the past five years, EPA SDWIS records 43 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). None of the assessed waterways are listed as impaired (0 of 15 water bodies) across Yellowstone County's watersheds. 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 2026-05-14T12:00:00.000-06:00) puts Yellowstone River at 15.2k cfs — running significantly above its long-term average at 217% 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. Yellowstone County has moderate coverage with 46 active monitoring sites with 8,890 recent measurements on record. Predominant monitoring categories include physical and biological, counts. 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 Yellowstone County

Water Verdict

Yellowstone County, Montana receives a below-average water quality assessment with a grade of D and a score of 42.1 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 track 15 water bodies in the county's watershed, none of which are currently listed as impaired under the Clean Water Act. At the most recent USGS reading, local streamflow was running above its historical mean at 216.9%.

Violation Context

EPA SDWIS records for Yellowstone County, Montana show 43 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 28.5 violations per 100,000 people served, this rate is high and signals significant water quality management issues. For independent context, 8,890 water-quality monitoring results have been recorded across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Yellowstone County's drinking-water compliance is below average with a Grade D, indicating repeated or unresolved violations in the recent record. Yellowstone County's drinking-water compliance score is 42.1 out of 100. The violation rate for Yellowstone County is 28.5 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. With 46 active water-quality monitoring sites in Yellowstone County, data coverage is strong. A pipeline streamflow snapshot from the Yellowstone River gauge is also available on this page.

Regional Context

Yellowstone County has poorer water quality than the average county in Montana. Its water score is 6.8 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 Yellowstone County's water environment

Official EPA Resources for Yellowstone County

EPA How's My Waterway

Interactive watershed health data for Yellowstone County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Yellowstone County

Consumer Confidence Reports (MT)

Annual water quality reports from utilities in Montana

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

0.0%

0 of 15 assessed

Mostly healthy

Top Impairment Causes

No specific impairment causes reported for the assessed water bodies in this county.

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

Active in the past 5 years

Measurements Recorded

8.9K

8,890 total readings

Most Measured

Physical
Biological, Counts
Organics, Other

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

15.2Kcfs

May 14, 6:00 PM UTC

vs Long-Term Average

217%

Well above typical

Primary Streamgage

Yellowstone River at Billings MT

USGS site: 06214500
Drainage area: 11,807 sq mi
Long-term mean: 7,008 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

Household size

3 people · ~225 gal/day

Filter type

Annual Total

$558

Monthly

$47

Water Bill

$558/yr

Filter Cost

$0/yr

Safety Grade for Yellowstone 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.

Try the full calculator →

Improve your water quality at home

Berkey filters remove 99.9%+ of contaminants from tap water.

Shop Berkey →

Test your tap water

Tap Score provides professional mail-in water testing.

Get Tested →

Frequently Asked Questions

What is the water quality in Yellowstone County, Montana?

Yellowstone County, Montana has a drinking-water quality grade of D with a score of 42.1/100, based on EPA SDWIS compliance data. The county has 43 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 Yellowstone County?

Yellowstone County has 43 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 Yellowstone County?

EPA ATTAINS assessments under Clean Water Act §303(d) indicate 0.0% of Yellowstone County's 15 assessed water bodies are classified as impaired (0 impaired). 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 Yellowstone County?

EPA's Water Quality Portal records 8,890 measurements from 46 monitoring sites in Yellowstone County over the past five years. The most frequently measured characteristic groups are Physical, Biological, Counts, Organics, Other. 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 Yellowstone County right now?

Yellowstone County's primary USGS streamgage on the Yellowstone River has a pipeline snapshot of 15,200 cubic feet per second — 217% of the long-term mean of 7,007.99 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 Yellowstone County water compare to the Montana average?

Yellowstone County's SDWIS water quality score of 42.1/100 is lower than the Montana state average of 48.9. The average water quality grade across Montana is D, based on data from 55 counties with available SDWIS data.

Is tap water safe to drink in Yellowstone County?

Based on EPA SDWIS data, Yellowstone County has a water quality grade of D (42.1/100). 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 Yellowstone County have so many water violations?

Yellowstone County has 43 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 Yellowstone County rank for water quality in Montana?

Yellowstone County ranks #28 out of 55 counties in Montana by SDWIS water quality score (1 = best). With a score of 42.1/100, it falls in the middle 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

Missoula County

Montana

40.6

Water score

Phillips County

Montana

36.7

Water score

Park County

Montana

47.9

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 May 14, 2026Reviewed by Evan Brooks, Data Editor

Explore more data for Yellowstone County

Property Tax Cost of Living Crime Rate Income Health Schools Disaster Risk Weather County Score