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EPA SDWIS

Del Norte County Water Quality

Del Norte County, California

Water Grade

F

Water Score

40.5

Violations

8

State Rank

#35

of 58 (1 = best)

EPA SDWIS Compliance

Drinking Water Quality

Water Quality Grade

F

Based on EPA compliance history and violation data

Water Score

40.5/100

Higher = better quality

Health Violations

8

Health-based violations

Violation Rate

31.6%

Systems with violations

Water Advisory: Del Norte County

Water Verdict

Del Norte County receives a below-average water quality assessment with a grade of F and a score of 40.5 out of 100. Residents should review their utility's Consumer Confidence Report and may want to consider additional water filtration for drinking.

Violation Context

Del Norte County has recorded 8 health-based violations, indicating multiple instances where federal contaminant limits or treatment requirements were not met. At 31.6 violations per 1,000 residents, this rate is high and signals significant water quality management issues.

Consumer Guidance

Residents of Del Norte County are advised to use filtered or bottled water for drinking and cooking until water quality improves. A reverse-osmosis or activated-carbon filter certified to remove the contaminants listed in the utility's Consumer Confidence Report is recommended. With 8 recorded health violations, staying informed about utility communications and boil-water notices is especially important. For long-term peace of mind, request your utility's latest Consumer Confidence Report and consider independent water testing if you have specific health concerns.

Regional Context

Del Norte County has water quality close to the average county in California. Its water score is within 4.1 points of the state average, meaning its overall water system performance is broadly representative of California as a whole.

Clean Water Act §303(d)

Watershed Health

Impaired Water Bodies

25.0%

7 of 28 assessed

Some impairment

Top Impairment Causes

  • 1

    COPPER

  • 2

    DISSOLVED OXYGEN

  • 3

    ORGANIC ENRICHMENT

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

78

Active in the past 5 years

Measurements Recorded

17K

16,696 total readings

Most Measured

  • Physical
  • Nutrient
  • Microbiological

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

7,320cfs

May 14, 6:30 PM UTC

vs Long-Term Average

44%

Well below typical

Primary Streamgage

KLAMATH R NR KLAMATH CA

USGS site
11530500
Drainage area
12,100 sq mi
Long-term mean
16.6K 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; "% of typical" compares the latest reading against that average.

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Frequently Asked Questions

What is the water quality in Del Norte County, California?
Del Norte County, California has a drinking-water quality grade of F with a score of 40.5/100, based on EPA SDWIS compliance data. The county has 8 health-based drinking water violations over the past 5 years. Watershed health, monitoring records, and live streamflow are reported separately on this page.
Are there any water violations in Del Norte County?
Del Norte County has 8 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 Del Norte County?
EPA ATTAINS assessments under Clean Water Act §303(d) indicate 25.0% of Del Norte County's 28 assessed water bodies are classified as impaired (7 impaired). The top reported causes are COPPER, DISSOLVED OXYGEN, ORGANIC ENRICHMENT. 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 Del Norte County?
EPA's Water Quality Portal records 16,696 measurements from 78 monitoring sites in Del Norte County over the past five years. The most frequently measured characteristic groups are Physical, Nutrient, Microbiological. 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 Del Norte County right now?
Del Norte County's primary USGS streamgage on the KLAMATH R is currently reading 7,320 cubic feet per second — 44% of the long-term mean of 16,590.53 cfs. This is well below typical — often a signal of drought stress on source water. For genuine real-time data, visit waterdata.usgs.gov.
How does Del Norte County water compare to the California average?
Del Norte County's SDWIS water quality score of 40.5/100 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 Del Norte County?
Based on EPA SDWIS data, Del Norte County has a water quality grade of F (40.5/100). 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 Del Norte County have so many water violations?
Del Norte County has 8 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 Del Norte County rank for water quality in California?
Del Norte County ranks #35 out of 58 counties in California by SDWIS water quality score (1 = best). With a score of 40.5/100, 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

Calaveras County

California

F

40.6

Water score

San Benito County

California

F

38.6

Water score

Stanislaus County

California

D

42.9

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, 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 Logan Johnson, Founder & Data EditorUpdated Reviewed by Logan Johnson, Founder & Data Editor

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