waterbycounty
Federal water data

County water report

Modoc County Water Report

Drinking-water compliance, watershed health, monitoring records, and river conditions for Modoc County, California.

Water grade

F

Water score

31.1

State rank

#42

of 58

Health violations

3

EPA SDWIS, 5-year lookback

Watershed impaired

22.1%

68 water bodies assessed

Monitoring sites

16

1,017 recent measurements

Live streamflow

1%

PIT R NR CANBY CA

Water at a glance

Key Water Indicators for Modoc County

EPA SDWIS

Safety Grade

F

Score: 31.1 / 100

EPA SDWIS

Active Violations

3

5-year health-based lookback

EPA ATTAINS

Watershed Health

22% impaired

68 bodies assessed

USGS NWIS

Streamflow Snapshot

1% of mean

PIT R NR CANBY CA

EPA WQP

Monitoring Sites

16

1,017 recent readings

Source: EPA SDWIS · Safe Drinking Water Information System

Drinking Water Compliance

Compliance grade

F

Based on EPA SDWIS compliance history.

Water score

Higher scores indicate cleaner recent compliance records.

31.1/100

Health violations

3

Health-based violations

Violations per 100K served

61.0

Population-normalized SDWIS rate

Editorial analysis

Understanding Modoc County’s Water

Drinking Water Quality Overview

EPA SDWIS

Modoc County's water systems carry a failing grade, scoring 31.1 out of 100. Over the past five years, EPA SDWIS records 3 health-based violations — a small cluster that warrants attention.

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 22.1% of assessed waterways carry an impairment designation (15 of 68 water bodies) across Modoc County's watersheds. The leading impairment causes are ph and total dissolved solids (tds). 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 2026-05-14T11:45:00.000-07:00) puts PIT R at 1.1 cfs — well below its long-term average at 1% of mean — low-flow conditions worth noting for water-dependent ecosystems. 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. Modoc County has moderate coverage with 16 active monitoring sites with 1,017 recent measurements on record. Predominant monitoring categories include organics, pesticide and organics, other. 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 Modoc County

Water Verdict

Modoc County receives a poor water quality assessment with a grade of F and a score of 31.1 out of 100. The water supply has documented quality issues. Residents are strongly encouraged to use filtered or bottled water for drinking and to stay informed about utility improvement plans.

Violation Context

Modoc County has recorded 3 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 61.0 violations per 100,000 people served, this rate is high and signals significant water quality management issues.

Consumer Guidance

Drinking-water compliance in Modoc County is rated Grade F, reflecting significant health-based violations in the recent reporting period. Modoc County's drinking-water compliance score is 31.1 out of 100. The violation rate for Modoc County is 61.0 per 100,000 people served. An NSF 53 or NSF 58-certified filter is recommended for drinking and cooking water. Check the Consumer Confidence Report from your utility to identify the specific contaminants and required corrective actions — utilities are legally required to notify customers of violations. pH is the leading impairment cause in Modoc County's watershed. With 16 active water-quality monitoring sites in Modoc County, data coverage is strong. A pipeline streamflow snapshot from the PIT R gauge is also available on this page.

Regional Context

Modoc County has poorer water quality than the average county in California. Its water score is 13.5 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 Modoc County's water environment

Watershed Impairment Causes (EPA ATTAINS)

  • 1

    pH imbalance

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

  • 2

    Total Dissolved Solids (Tds)

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

  • 3

    Low dissolved oxygen

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

Source: EPA ATTAINS · Reporting cycle 2022

Official EPA Resources for Modoc County

EPA How's My Waterway

Interactive watershed health data for Modoc County

EPA ECHO: Drinking Water Systems

Search water utilities and violation records for Modoc County

Consumer Confidence Reports (CA)

Annual water quality reports from utilities in California

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

22.1%

15 of 68 assessed

Some impairment

Top Impairment Causes

  • 1

    PH

  • 2

    TOTAL DISSOLVED SOLIDS (TDS)

  • 3

    DISSOLVED OXYGEN

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

16

Active in the past 5 years

Measurements Recorded

1.0K

1,017 total readings

Most Measured

  • Organics, Pesticide
  • Organics, Other
  • 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

1.08cfs

May 14, 6:45 PM UTC

vs Long-Term Average

1%

Well below typical

Primary Streamgage

PIT R NR CANBY CA

USGS site
11348500
Drainage area
1,431 sq mi
Long-term mean
230 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 Modoc 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 →

Sponsored

Test your tap water

Tap Score provides professional mail-in water testing.

Get Tested →

Frequently Asked Questions

What is the water quality in Modoc County, California?
Modoc County, California has a drinking-water quality grade of F with a score of 31.1/100, based on EPA SDWIS compliance data. The county has 3 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 Modoc County?
Modoc County has 3 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 Modoc County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 22.1% of Modoc County's 68 assessed water bodies are classified as impaired (15 impaired). The top reported causes are PH, TOTAL DISSOLVED SOLIDS (TDS), DISSOLVED OXYGEN. 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 Modoc County?
EPA's Water Quality Portal records 1,017 measurements from 16 monitoring sites in Modoc County over the past five years. The most frequently measured characteristic groups are Organics, Pesticide, Organics, Other, 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 Modoc County right now?
Modoc County's primary USGS streamgage on the PIT R has a pipeline snapshot of 1.08 cubic feet per second — 1% of the long-term mean of 230.11 cfs. This is well below typical — often a signal of drought stress on source water. For the latest gauge feed, visit waterdata.usgs.gov.
How does Modoc County water compare to the California average?
Modoc County's SDWIS water quality score of 31.1/100 is lower than the California state average of 44.6. The average water quality grade across California is D, based on data from 58 counties with available SDWIS data.
Is tap water safe to drink in Modoc County?
Based on EPA SDWIS data, Modoc County has a water quality grade of F (31.1/100). 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).
Does Modoc County have clean drinking water?
Modoc County has 3 health-based drinking water violations according to EPA records. With a water quality score of 31.1/100 and grade F, 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 Modoc County rank for water quality in California?
Modoc County ranks #42 out of 58 counties in California by SDWIS water quality score (1 = best). With a score of 31.1/100, it falls in the bottom 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

Kern County

California

F

30.0

Water score

Napa County

California

F

33.4

Water score

Tuolumne County

California

F

34.0

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 Reviewed by Evan Brooks, Data Editor

Explore more data for Modoc County

Property TaxCost of LivingCrime RateIncomeHealthSchoolsDisaster RiskWeatherCounty Score