Dane County Water Report

Dane County earns a B grade for drinking water quality, scoring 65.0 out of 100. Over the past five years, EPA SDWIS records 17 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 16.2% of assessed waterways carry an impairment designation (91 of 562 water bodies) across Dane County's watersheds. The leading impairment causes are phosphorus, total 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 2026-05-14T14:00:00.000-05:00) puts YAHARA RIVER @ FORTON STREET BRIDGE @ STOUGHTON,WI at 254.0 cfs — running somewhat below its historical average at 69% 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. Dane County has extensive coverage with 362 active monitoring sites with 465,492 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.