La Paz County Water Report

La Paz County's water systems carry a failing grade, scoring 9.8 out of 100. Over the past five years, EPA SDWIS records 47 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 small share — 5.9% — of assessed waterways are impaired (1 of 17 water bodies) across La Paz County's watersheds. The leading impairment cause is ammonia-nitrogen. 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 2026-04-28T09:30:00.000-07:00) puts BILL WILLIAMS RIVER at 4.7 cfs — well below its long-term average at 7% 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. La Paz County has extensive coverage with 65 active monitoring sites with 25,243 recent measurements on record. Predominant monitoring categories include organics, other and organics, pesticide. 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.