Chapter 173-201A WAC (Natural Conditions)

The Washington State Department of Ecology is considering revising Chapter 173-201A WAC, Water Quality Standards for Surface Waters of the State of Washington.

We are considering revisions to several natural conditions provisions in our surface water quality standards. We have natural conditions provisions in our rule because conditions in some surface waters naturally do not meet water quality criteria. For example, a naturally low-flowing stream in a natural prairie without any human alteration may have seasonally higher temperatures than the limit set to protect fish. These inconsistencies may be due to natural processes or seasonal conditions that prevent a water body from meeting the applicable aquatic life criteria.

Our goal is to refine the natural conditions criteria to protect characteristics unique to a specific water. 

We will evaluate the latest scientific data, methods, modeling tools, and approaches to update natural conditions provisions necessary for refining aquatic life protection in our surface waters. As part of this process, we will consider the Environmental Protection Agency’s recommended approaches for natural conditions in water quality standards. 

Specifically, we are considering amendments to:

  • WAC 173-201A-200(1)(c), Aquatic life temperature criteria, including, but not limited to, subsection (i).
  • WAC 173-201A-200(1)(d), Aquatic life dissolved oxygen (D.O.) criteria including, but not limited to, subsection (i)
  • WAC 173-201A-210(1)(c), Aquatic life temperature criteria including, but not limited to, subsection (i).
  • WAC 173-201A-210(1)(d), Aquatic life dissolved oxygen (D.O.) including, but not limited to, criteria subsection (i).
  • WAC 173-201A-260(1), Natural and irreversible human conditions.
  • WAC 173-201A-310(3), Tier I – Protection and maintenance of existing and designed uses.

We may amend other sections of Chapter 173-201A WAC as necessary to be consistent with or provide support to any revisions to the sections noted above.

Rulemaking timeline


Announcement phase (CR-101)

Filing date:
Sept. 27, 2022

Announcement documents

Rule development phase

Sept. 27, 2022 - early 2024

Public input & involvement

March 1 and 2, 2023 – Public Informational Webinars

We invite you to attend an informational webinar for the rulemaking to update our natural conditions provisions in the surface water quality standards, chapter 173-201A WAC. During this webinar, we will provide an overview of:

  • Natural conditions provisions – what they are and what they protect
  • Importance of natural conditions in Washington
  • Options and scope of the rulemaking
  • Timelines and opportunities for public participation

View presentation slides (pdf)

Webinar details

This webinar will be offered via Zoom at the following dates and times:

Wednesday, March 1, 2023 – 1:30 p.m.
Register for the afternoon webinar
Join by phone only - 1- 253-205-0468
Meeting ID - 892 9541 6854

Thursday, March 2, 2023 5:30 p.m.
Register for the evening webinar
Join by phone only - 1- 253-215-8782
Meeting ID - 820 4253 3399

Workshops offered via webinar allow individuals to view the presentation and ask questions via computer or mobile device.

Additional languages

Español (Spanish) 中文 (Chinese) Tiếng Việt (Vietnamese) 한국어 (Korean)


To request ADA accommodation for disabilities, or printed materials in a format for the visually impaired, contact Ecology's ADA Coordinator by email at, or call 360-407-6831. People with impaired hearing may call Washington Relay Service at 711. People with speech disability may call TTY at 877-833-6341.