Safe Drinking Water Information System (SDWIS)

Years Available
2013 to present
Mode of Collection
Census: reports on all public water systems.
The Safe Drinking Water Information System (SDWIS) databases store information about drinking water. The federal version (SDWIS/FED) stores the information the U.S. Environmental Protection Agency (EPA) needs to monitor approximately 156,000 public water systems.
Selected Content
The following types of data are included for each water system: basic information (such as name, location, type of system, number of people served); violation information (such as compliance with monitoring and treatment schedules, etc.); enforcement information (such as actions taken to return system to compliance); and sampling information (for unregulated and regulated contaminants).
Population Covered
Persons served by community water systems (CWS).
Of the 156,000 public water systems, approximately 51,000 are community water systems (CWS) that serve most people in the United States (a little less than 300 million). Of these water systems, 4,221 or 8 percent, serve more than 246 million people, or 82 percent, of the total population. Similarly, more water systems use ground water rather than surface water as a source, but more people receive their water from a system supplied by surface water. The state version (SDWIS/STATE) is a database designed to help states run their drinking water programs. These databases contain information submitted by states, EPA regions, and public water systems in conformance with reporting requirements established by the Safe Drinking Water Act (SDWA) and related regulations. EPA uses these data to address non-compliant systems, oversee state drinking water systems, track contaminant levels, respond to public inquiries, and prepare national reports (such as the Annual Potable Water Systems Compliance Report 2). States supervise the public water systems within their jurisdictions to ensure that each system meets state and EPA standards for safe drinking water. The Safe Drinking Water Act requires states to report drinking water information periodically to EPA. This information is maintained in a federal database, the SDWIS Fed Data Warehouse.
Interpretation Issues
Quarterly reporting, lag in reporting.
There are some inaccuracies and underreporting of some data. EPA is working to improve data quality