# AquaCensus

> The census of U.S. public water systems. AquaCensus catalogues every active public water system in the United States — population served, water source, system type, ownership and geography — from EPA SDWIS/ECHO public records, as free, indexable public-record pages. Dataset last updated July 2026.

AquaCensus (aquacensus.com) is operated by Hyder Media. The dataset is built from the U.S. EPA Safe Drinking Water Information System (SDWIS) via the EPA ECHO bulk data service, covering every active public water system regulated under the Safe Drinking Water Act.

## Key figures (national, updated 2026-07-08)
- 143,021 water systems catalogued
- Population served (reported, cumulative): 352M
- Community water systems (CWS): 49,389
- States + DC covered: 51
- Groundwater-sourced share: 90.4%
- Counties with 3+ active systems: 3,238

## Key pages
- [Water systems directory](https://aquacensus.com/water-systems): every active U.S. public water system, by state and county
- [Largest water systems](https://aquacensus.com/rankings/largest-water-systems): top 100 systems by population served
- [States by system count](https://aquacensus.com/rankings/states-by-system-count): all 50 states + DC ranked
- [Groundwater vs. surface water](https://aquacensus.com/rankings/groundwater-vs-surface-water): state-by-state source reliance
- [Methodology](https://aquacensus.com/methodology): sources, cadence, definitions, licensing

## Data & update cadence
EPA publishes the SDWA dataset quarterly; AquaCensus re-syncs on that cadence with id-stable upserts. Every page carries a machine-readable "Dataset updated" stamp and Dataset JSON-LD with dateModified.

## Contact & licensing
Contact: kenny@hyder.me. Content may be cited with attribution to "AquaCensus (aquacensus.com)". For bulk/API access see the site.