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Water: Water Quality Standards

Basic Information

out of date Note: EPA no longer updates this information, but it may be useful as a reference or resource.

This is the final release of the WQSDB—it will not be updated. (For future plans, see the Release 9 Fact Sheet.) You can see the WQS documents upon which the WQSDB information was based and access state WQS program webpages. You are also able to download pre-formatted reports, and copies of the database.

If you have any questions, please contact us.

The Water Quality Standards Database (WQSDB) displays and compares the water quality standards (WQS) which protect the Nation’s surface waters.


The project began as a prototype in 1998 and has evolved into the National WQSDB containing an online library of approved state, territory and tribal WQS documents as well as use information that can be viewed in tabular form or spatially in EnviroMapper for WATERS. Work is progressing to include numeric criteria tables that can be compared between jurisdictions and to integrate water quality data into EPA's geographic cross-program platform — WATERS (Watershed Assessment, Tracking & Environmental Results).

For an explanation of the role of WQS in protecting water quality, explore the Introduction to WQS.

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WQS Database Components

  • Water Quality Standards Regulations. — Each jurisdiction provides the full text of their WQS regulations as source information for the WQSDB. These easily accessed documents are stored as PDF in the Water Quality Standards Document Repository (WQSDR). The lists of new or revised WQS are updated periodically.
  • Designated Use Information. — Designated Use (DU) classifications are narrative statements describing appropriate intended human and/or aquatic life and other quality objectives for waterbodies. Although jurisdictions define their DUs uniquely, the WQSDB links together the DUs from different jurisdictions into a consistent format, through national comparison values.
  • Waterbody Attributes. — Waterbody Attributes, in addition to Uses, include the jurisdictional (e.g., EPA Region, Consortium, State, County) and geophysical (e.g., Hydrologic Unit Code) locational elements, as well as waterbody types and characteristics of a waterbody segment. These attributes can be used to locate related water quality information.
  • Criteria Data. — Water quality criteria are descriptions (e.g. narrative, numeric andequations) of chemical, physical and biological conditions necessary to achieve and protect DUs. Future inclusion of data will enable users to view and compare narrative and numeric criteria across jurisdictions. Florida, Illinois, Mississippi and Missouri are the criteria pilot states. The WQSDB includes the EPA numeric criteria in tabular reports for easy comparison to each jurisdiction's numeric criteria.
  • Documentation. — This information describes the standard operating procedures for operation and maintenance of the WQSDB, or a copy administered by a jurisdiction. (Zip file 1.68MB)

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  • WATERS — This cross program integrating framework unifies geography-specific water quality information previously available only on individual state web sites and various EPA web sites. Components of WATERS utilizing WQSDB data include:
    • WebRIT — This Web Reach Indexing Tool is used to identify the segments of waterbodies that may have DUs, criteria or other water quality or attributes assigned to them.
    • RAD. — The spatial data are stored in this Reach Address Database, which is based on the National Hydrography Dataset (NHD). The data link to WQSDB is through the waterbody segment identifier, Entity ID.
    • EnviroMapper for Water. — This web-based Geographic Information System (GIS) application dynamically displays information about waterbodies in the United States.
    • Ask WATERS. — A flexible query tool in which the data sources can be correlated toanswer questions about the health of and threats to water resources.

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