Anne Arundel County Water Report

Anne Arundel County earns a B grade for drinking water quality, scoring 67.5 out of 100. Over the past five years, EPA SDWIS records 11 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 48.8% of assessed waterways are impaired (60 of 123 water bodies) across Anne Arundel County's watersheds. The leading impairment causes are fecal coliform and total suspended solids (tss). 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 PATUXENT RIVER at 335.0 cfs — running somewhat below its historical average at 86% 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. Anne Arundel County has extensive coverage with 237 active monitoring sites with 63,231 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.