Fresno County Water Report

Fresno County's drinking water earned a C grade, scoring 52.5 out of 100. Over the past five years, EPA SDWIS records 128 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 notable 24.7% of assessed waterways carry an impairment designation (23 of 93 water bodies) across Fresno County's watersheds. The leading impairment causes are toxicity and ph. 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 2021-12-09T00:00:00.000-08:00) puts SAN JOAQUIN R at 153.0 cfs — well below its long-term average at 20% 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. Fresno County has moderate coverage with 30 active monitoring sites with 5,568 recent measurements on record. Predominant monitoring categories include organics, pesticide and organics, other. 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.