Miami-Dade County Water Report

Miami-Dade County earns an A grade for drinking water quality, scoring 70.4 out of 100. Over the past five years, EPA SDWIS records 25 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 large majority — 60.1% — of assessed waterways are impaired (304 of 506 water bodies) across Miami-Dade County's watersheds. The leading impairment causes are mercury in fish tissue and dissolved oxygen. 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 2026-05-14T14:45:00.000-04:00) puts N.W. WELLFIELD CANAL at 1.8 cfs — well below its long-term average at 2% 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.

EPA's Water Quality Portal (WQP) aggregates monitoring data from federal, state, and tribal agencies. Miami-Dade County has extensive coverage with 485 active monitoring sites with 298,206 recent measurements on record. Predominant monitoring categories include physical 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.