The Water Quality Portal (WQP) is a cooperative service sponsored by the United States Geological Survey (USGS), the Environmental Protection Agency (EPA) and the National Water Quality Monitoring Council (NWQMC) that integrates publicly available water quality data from the USGS National Water Information System (NWIS) the EPA STOrage and RETrieval (STORET) Data Warehouse, and the USDA ARS Sustaining The Earth’s Watersheds - Agricultural Research Database System (STEWARDS) .

The EPA water quality data originate from the STORET Data Warehouse, which is the EPA's repository of water quality monitoring data collected by water resource management groups across the country. Organizations, including states, tribes, watershed groups, other federal agencies, volunteer groups and universities, submit data to the STORET Warehouse in order to make their data publicly accessible. For more information about STORET, see the  STORET Home Page.

The USGS water quality data originate from the NWISWeb Database. The database contains current and historical water data from more than 1.5 million sites across the nation and is used by state and local governments, public and private utilities, private citizens, and other federal agencies involved with managing our water resources. For more information on what data are available and how NWIS data are mapped to the Water Quality Exchange (WQX) format, visit  NWIS Water Quality Web Services.

The ARS water quality data originate from the STEWARDS (Sustaining The Earth’s Watersheds - Agricultural Research Database System) database and were developed as part of the Conservation Effects Assessment Program (CEAP). STEWARDS contains long-term hydrologic, weather, and water quality data from 17 ARS benchmark research watersheds. For more information about STEWARDS, see the STEWARDS Home Page.