County water report

Larimer County Water Report

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

Water grade

Water score

46.6

State rank

#26

of 64

Health violations

105

EPA SDWIS, 5-year lookback

Watershed impaired

44.7%

217 water bodies assessed

Monitoring sites

168

69,840 recent measurements

Live streamflow

196%

CACHE LA POUDRE RIV AB BOXELDER CRK NR TIMNATH, CO

Water at a glance

Key Water Indicators for Larimer County

EPA SDWIS

Safety Grade

Score: 46.6 / 100

EPA SDWIS

Active Violations

105

5-year health-based lookback

EPA ATTAINS

Watershed Health

45% impaired

217 bodies assessed

USGS NWIS

Streamflow Snapshot

196% of mean

CACHE LA POUDRE RIV AB BOXELDER CRK NR TIMNATH, CO

EPA WQP

Monitoring Sites

168

69,840 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.

46.6/100

Health violations

105

Health-based violations

Violations per 100K served

21.3

Population-normalized SDWIS rate

Data center water stress

Larimer County has 1 facility in the DCWSI dataset.

ByCounty's DCWSI ranks this county #1660 nationally by combining its water score with mapped data center density.

DCWSI

28.0

0-100 index

Facility count

0.0 density percentile

Discharge estimate

Not reported

EPA CWA fields where available

Water vs median

-3.4

Compared with US county median

Mapped facilities

CELESTICA CORPORATION
FORT COLLINS
EPA ECHO

See the Larimer County data-center report Review methodology

Data Center Water Budget Calculator

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

Facility size: 100 MW

1 MW1,000 MW

Cooling type

Utilization: 70%

40%100%

799K gallons/dayHigh Impact

Your facility would use 38.9% of this county's industrial water baseline. Verify water rights and long-term drought projections before committing.

38.9% of county industrial baseline1.25 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 Larimer County’s Water

Drinking Water Quality Overview

EPA SDWIS

Larimer County's drinking water received a D grade, scoring 46.6 out of 100. Over the past five years, EPA SDWIS records 105 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 44.7% of assessed waterways are impaired (97 of 217 water bodies) across Larimer County's watersheds. The leading impairment causes are arsenic and escherichia coli (e. coli). 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 2026-05-14T13:00:00.000-06:00) puts CACHE LA POUDRE RIV AB BOXELDER CRK at 303.0 cfs — running significantly above its long-term average at 196% 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. Larimer County has extensive coverage with 168 active monitoring sites with 69,840 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 Larimer County

Water Verdict

Larimer County receives a below-average water quality assessment with a grade of D and a score of 46.6 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Larimer County has recorded 105 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 21.3 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Larimer County's drinking-water compliance is below average with a Grade D, indicating repeated or unresolved violations in the recent record. Larimer County's drinking-water compliance score is 46.6 out of 100. The violation rate for Larimer County is 21.3 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. Arsenic is the leading impairment cause in Larimer County's watershed. With 168 active water-quality monitoring sites in Larimer County, data coverage is strong. A pipeline streamflow snapshot from the CACHE LA POUDRE RIV AB BOXELDER CRK gauge is also available on this page.

Regional Context

Larimer County has better water quality than the average county in Colorado. Its water score is 7.9 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 Larimer County's water environment

Watershed Impairment Causes (EPA ATTAINS)

1
Arsenic
Impairment cause per EPA Clean Water Act §303(d) assessment
2
E. coli (bacteria)
Impairment cause per EPA Clean Water Act §303(d) assessment
3
Elevated temperature
Impairment cause per EPA Clean Water Act §303(d) assessment

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Larimer County

EPA How's My Waterway

Interactive watershed health data for Larimer County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Larimer County

Consumer Confidence Reports (CO)

Annual water quality reports from utilities in Colorado

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

44.7%

97 of 217 assessed

Moderate concern

Top Impairment Causes

1
ARSENIC
2
ESCHERICHIA COLI (E. COLI)
3
TEMPERATURE

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

168

Active in the past 5 years

Measurements Recorded

70K

69,840 total readings

Most Measured

Physical
Nutrient
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

303cfs

May 14, 7:00 PM UTC

vs Long-Term Average

196%

Well above typical

Primary Streamgage

CACHE LA POUDRE RIV AB BOXELDER CRK NR TIMNATH, CO

USGS site: 06752280
Drainage area: 1,244 sq mi
Long-term mean: 154 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 Larimer 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 →

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Frequently Asked Questions

What is the water quality in Larimer County, Colorado?

Larimer County, Colorado has a drinking-water quality grade of D with a score of 46.6/100, based on EPA SDWIS compliance data. The county has 105 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 Larimer County?

Larimer County has 105 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 Larimer County?

EPA ATTAINS assessments under Clean Water Act §303(d) indicate 44.7% of Larimer County's 217 assessed water bodies are classified as impaired (97 impaired). The top reported causes are ARSENIC, ESCHERICHIA COLI (E. COLI), TEMPERATURE. 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 Larimer County?

EPA's Water Quality Portal records 69,840 measurements from 168 monitoring sites in Larimer County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, 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 Larimer County right now?

Larimer County's primary USGS streamgage on the CACHE LA POUDRE RIV AB BOXELDER CRK has a pipeline snapshot of 303 cubic feet per second — 196% of the long-term mean of 154.32 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 Larimer County water compare to the Colorado average?

Larimer County's SDWIS water quality score of 46.6/100 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 Larimer County?

Based on EPA SDWIS data, Larimer County has a water quality grade of D (46.6/100). 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 Larimer County have so many water violations?

Larimer County has 105 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 Larimer County rank for water quality in Colorado?

Larimer County ranks #26 out of 64 counties in Colorado by SDWIS water quality score (1 = best). With a score of 46.6/100, 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

Moffat County

Colorado

47.7

Water score

Grand County

Colorado

43.5

Water score

Pitkin County

Colorado

49.7

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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