Methodology & data sources
What our numbers mean, where they come from, and — just as important — what they don't claim to be.
AGUACYCLE covers 51 states and D.C., 709 cities, 48,769 community water systems, 22 water-issue explainers, 22 analysis pieces, and 45 glossary terms.
Drinking-water quality (EPA SDWIS)
Our water-quality figures come directly from the U.S. EPA's Safe Drinking Water Information System (SDWIS), via the ECHO national SDWA data download — the federal system of record for drinking-water compliance. We process the full national dataset (every public water system and every violation) and focus on active Community Water Systems (CWS), the systems that deliver year-round tap water to residents.
For each state, county, and matched city we count: community water systems, population served, systems with a health-based violation (an EPA-flagged MCL, MRDL, or treatment-technique violation) since 2016, systems with unresolved violations, the contaminants and rules driving those violations, and systems exceeding EPA's 0.015 mg/L lead action level based on their most recent 90th-percentile lead sample. Violations are de-duplicated by violation ID. The data reflects the 2026 Q1 SDWIS refresh.
Water use (USGS)
Per-capita use, total withdrawals, the groundwater/surface split, and sector shares come from the U.S. Geological Survey's Estimated Use of Water in the United States, 2015 (the most recent comprehensive county-level compilation). Per-capita figures are public-supply withdrawals divided by the population served — a withdrawal measure, not consumptive use.
Drought (U.S. Drought Monitor)
Current drought status and the annual drought-history charts come from the U.S. Drought Monitor (a partnership of the National Drought Mitigation Center, USDA, and NOAA), updated weekly. We record the share of each state's area in each drought category (D0–D4) and chart the late-summer severe-drought (D2+) extent each year.
What's a real measurement vs. an estimate
Water-quality, water-use, and drought figures above are real, sourced, and dated. The one curated estimate we still show is each state's wastewater reuse share — there is no clean federal per-state reuse figure, so we label it as an estimate wherever it appears. Editorial narrative on each profile is written by our team for context.
City profiles outside our hand-written marquee set are generated from a structured template that combines each city's real population, its matched water utility's real EPA record, and its county's real water-quality rollup with its state's water context. We are transparent that the prose is programmatically assembled while the underlying numbers are real.
Other primary sources
We also draw on and link to the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Bureau of Reclamation for Colorado River and reservoir operations, and EPA's National Primary Drinking Water Regulations for contaminant limits and health effects. City names, populations, and coordinates are derived from open geographic datasets (GeoNames).
Corrections
We treat accuracy as a process. Federal data carries reporting lags and gaps, and a system's mailing city does not always equal the community it serves. If you spot an error or have better data, please get in touch through our contact page. We refresh the underlying datasets as new federal releases become available.