Sequoyah County Water Report

Sequoyah County's water systems carry a failing grade, scoring 18.3 out of 100. Over the past five years, EPA SDWIS records 60 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 large majority — 100.0% — of assessed waterways are impaired (4 of 4 water bodies) across Sequoyah County's watersheds. The leading impairment causes are mercury and phosphorus, total. 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 2026-05-14T13:30:00.000-05:00) puts Illinois River at 73.0 cfs — well below its long-term average at 4% 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. Sequoyah County has moderate coverage with 17 active monitoring sites with 14,927 recent measurements on record. Predominant monitoring categories include physical and not assigned. 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.