Water quality standards for surface waters

The surface water quality standards help protect and regulate the quality of fresh and marine waters in Washington. The standards protect the health of people, fish, shellfish, and wildlife.

Our standards have a three-part approach to protecting surface waters. The three-part approach covers:

Water quality standards are established to sustain public health and enjoyment of surface waters, and to propagate and protect fish, shellfish, and wildlife.

Our standards also support other water protection processes, and guide citizens, businesses, and other government agencies toward the goal of sustaining clean water for current and future use.

The standards implement portions of the federal Clean Water Act by specifying the designated and potential uses of waters in Washington. We set water quality criteria to protect those uses. The standards also contain policies to protect high quality waters and, in many cases, specify how to implement those standards.

Designated uses

We protect the state's waters for four groups of designated uses:

  • Aquatic life
  • Recreational
  • Water supply
  • Miscellaneous uses

Surface water quality criteria

Water quality criteria protects designated uses. We use them to assess the health of Washington surface waters and set pollution limits. The surface water quality standards contain numeric and narrative criteria for both marine and fresh waters.


Antidegradation helps us prevent unnecessary lowering of water quality. It provides a framework to identify waters we set as an “outstanding resource.” Our antidegradation standards follow federal regulation guides. 

Updates to the standards

Federal regulations require that we hold public hearings to review applicable surface water quality standards. This process is called a triennial review.

This review gives us an opportunity to discuss priorities and commitments to surface water quality standards. We then place activities (guidance, research, or rulemaking) on schedules that match their complexity. Sometimes, we may adopt new or changed standards.