Duval County Water Report

Duval 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 notable 29.9% of assessed waterways carry an impairment designation (259 of 865 water bodies) across Duval County's watersheds. The leading impairment causes are mercury in fish tissue and iron. 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 2026-05-14T14:30:00.000-04:00) puts ST. JOHNS RIVER at 153.0k cfs — running significantly above its long-term average at 2892% 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.

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Duval County has extensive coverage with 406 active monitoring sites with 119,762 recent measurements on record. Predominant monitoring categories include physical and inorganics, minor, metals. 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.