Jefferson County Water Report

Jefferson County's drinking water earned a C grade, scoring 54.0 out of 100. Over the past five years, EPA SDWIS records 62 health-based violations — a pattern that public water utilities are required to disclose and correct.

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 40.1% of assessed waterways are impaired (158 of 394 water bodies) across Jefferson 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.

USGS NWIS gauge data (as of 2026-05-14T12:45:00.000-06:00) puts CLEAR CREEK at 136.0 cfs — running somewhat below its historical average at 73% 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.

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Jefferson County has extensive coverage with 54 active monitoring sites with 13,505 recent measurements on record. Predominant monitoring categories include inorganics, minor, metals 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.