Denver County Water Report

Denver County earns an A grade for drinking water quality, scoring 71.8 out of 100. Over the past five years, EPA SDWIS records 2 health-based violations — a small cluster that warrants attention.

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 39.1% of assessed waterways are impaired (95 of 243 water bodies) across Denver 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 2026-05-14T12:55:00.000-06:00) puts CHERRY CREEK at 40.8 cfs — flowing above its historical average at 145% 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. Denver County has extensive coverage with 59 active monitoring sites with 28,462 recent measurements on record. Predominant monitoring categories include organics, pesticide 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.