Culpeper County Water Report

Culpeper County earns a B grade for drinking water quality, scoring 64.8 out of 100. Over the past five years, EPA SDWIS records 1 health-based violation — a single incident worth monitoring.

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 50.6% of assessed waterways are impaired (43 of 85 water bodies) across Culpeper County's watersheds. The leading impairment causes are escherichia coli (e. coli) and benthic macroinvertebrates bioassessments. 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 RAPIDAN RIVER at 144.0 cfs — well below its long-term average at 26% 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. Culpeper County has moderate coverage with 39 active monitoring sites with 18,381 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.