County water report

Boulder County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Boulder County, Colorado.

Water grade

Water score

56.1

State rank

#15

of 64

Health violations

EPA SDWIS, 5-year lookback

Watershed impaired

46.0%

252 water bodies assessed

Monitoring sites

32,082 recent measurements

Live streamflow

60%

BOULDER CREEK AT NORTH 75TH ST. NEAR BOULDER, CO

Water at a glance

Key Water Indicators for Boulder County

EPA SDWIS

Safety Grade

Score: 56.1 / 100

EPA SDWIS

Active Violations

5-year health-based lookback

EPA ATTAINS

Watershed Health

46% impaired

252 bodies assessed

USGS NWIS

Streamflow Snapshot

60% of mean

BOULDER CREEK AT NORTH 75TH ST. NEAR BOULDER, CO

EPA WQP

Monitoring Sites

32,082 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.

56.1/100

Health violations

Health-based violations

Violations per 100K served

9.5

Population-normalized SDWIS rate

Data center water stress

Boulder County has 1 facility in the DCWSI dataset.

ByCounty's DCWSI ranks this county #1385 nationally by combining its water score with mapped data center density.

DCWSI

33.7

0-100 index

Facility count

0.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

+6.1

Compared with US county median

Mapped facilities

NORTHROP GRUMMAN ELECTRONICS SYSTEMS
BOULDER
EPA ECHO

See the Boulder County data-center report Review methodology

Data Center Water Budget Calculator

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

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayHigh Impact

Your facility would use 48.5% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

48.5% of county industrial baseline0.85 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 Boulder County’s Water

Drinking Water Quality Overview

EPA SDWIS

Boulder County's drinking water earned a C grade, scoring 56.1 out of 100. Over the past five years, EPA SDWIS records 40 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 46.0% of assessed waterways are impaired (116 of 252 water bodies) across Boulder County's watersheds. The leading impairment causes are arsenic and copper. 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 2026-05-14T12:15:00.000-06:00) puts BOULDER CREEK at 55.4 cfs — running somewhat below its historical average at 60% of mean. 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. Boulder County has extensive coverage with 85 active monitoring sites with 32,082 recent measurements on record. Predominant monitoring categories include inorganics, minor, metals 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 Boulder County

Water Verdict

Boulder County, Colorado receives a fair water quality assessment with a grade of C and a score of 56.1 out of 100. The water supply meets baseline federal standards, but there may be periods of elevated contaminant levels or infrastructure concerns worth monitoring. Separately, EPA ATTAINS assessments cover 252 water bodies in the county's watershed, with 46.0% 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 below its historical mean at 60.1% — worth watching in drier seasons.

Violation Context

EPA SDWIS records for Boulder County, Colorado show 40 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 9.5 violations per 100,000 people served, this rate is high and signals significant water quality management issues. This compliance record sits alongside an unusually deep monitoring archive: 32,082 water-quality results have been logged across the county in the EPA Water Quality Portal over the past five years.

Consumer Guidance

Residents of Boulder County should be aware that arsenic has been identified as a watershed impairment cause, and drinking-water compliance is at a C-grade level. Boulder County's drinking-water compliance score is 56.1 out of 100. Long-term low-level arsenic exposure is a health concern; an NSF 58-certified reverse-osmosis filter is the most effective point-of-use option for arsenic removal. Reviewing your utility's Consumer Confidence Report will show whether treated water meets the EPA's 10 ppb MCL. The violation rate for Boulder County is 9.5 per 100,000 people served. With 85 active water-quality monitoring sites in Boulder County, data coverage is strong. A pipeline streamflow snapshot from the BOULDER CREEK gauge is also available on this page.

Regional Context

Boulder County has better water quality than the average county in Colorado. Its water score is 17.4 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 Boulder County's water environment

Watershed Impairment Causes (EPA ATTAINS)

1
Arsenic
Impairment cause per EPA Clean Water Act §303(d) assessment
2
Copper
Impairment cause per EPA Clean Water Act §303(d) assessment
3
Zinc
Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Boulder County

EPA How's My Waterway

Interactive watershed health data for Boulder County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Boulder County

Consumer Confidence Reports (CO)

Annual water quality reports from utilities in Colorado

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

46.0%

116 of 252 assessed

Moderate concern

Top Impairment Causes

1
ARSENIC
2
COPPER
3
ZINC

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

32K

32,082 total readings

Most Measured

Inorganics, Minor, Metals
Physical
Nutrient

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

55.4cfs

May 14, 6:15 PM UTC

vs Long-Term Average

60%

Below typical

Primary Streamgage

BOULDER CREEK AT NORTH 75TH ST. NEAR BOULDER, CO

USGS site: 06730200
Drainage area: 307 sq mi
Long-term mean: 92.1 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 Boulder 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 Boulder County, Colorado?

Boulder County, Colorado has a drinking-water quality grade of C with a score of 56.1/100, based on EPA SDWIS compliance data. The county has 40 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 Boulder County?

Boulder County has 40 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 Boulder County?

EPA ATTAINS assessments under Clean Water Act §303(d) indicate 46.0% of Boulder County's 252 assessed water bodies are classified as impaired (116 impaired). The top reported causes are ARSENIC, COPPER, ZINC. 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 Boulder County?

EPA's Water Quality Portal records 32,082 measurements from 85 monitoring sites in Boulder County over the past five years. The most frequently measured characteristic groups are Inorganics, Minor, Metals, Physical, Nutrient. 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 Boulder County right now?

Boulder County's primary USGS streamgage on the BOULDER CREEK has a pipeline snapshot of 55.4 cubic feet per second — 60% of the long-term mean of 92.11 cfs. Flow is within typical range for this gauge. For the latest gauge feed, visit waterdata.usgs.gov.

How does Boulder County water compare to the Colorado average?

Boulder County's SDWIS water quality score of 56.1/100 is higher than the Colorado state average of 38.7. The average water quality grade across Colorado is F, based on data from 64 counties with available SDWIS data.

Is tap water safe to drink in Boulder County?

Based on EPA SDWIS data, Boulder County has a water quality grade of C (56.1/100). 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 Boulder County have so many water violations?

Boulder County has 40 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 Boulder County rank for water quality in Colorado?

Boulder County ranks #15 out of 64 counties in Colorado by SDWIS water quality score (1 = best). With a score of 56.1/100, 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

Weld County

Colorado

55.2

Water score

Montezuma County

Colorado

54.6

Water score

Jefferson County

Colorado

54.0

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 May 14, 2026Reviewed by Evan Brooks, Data Editor

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