Dissolved Oxygen Amendment

Approved Amendment

The revised water quality objectives for dissolved oxygen have been approved by OAL and are now in effect under state law. To comply with the Federal Clean Water Act (CWA), and before the surface water objectives become fully effective under the CWA, they must first be approved by the Unites State Environmental Protection Agency (U.S. EPA).  


The Regional Water Board directed staff in its 2007 Triennial Review of the Basin Plan to develop a proposal for the revision of the water quality objectives (objective) for dissolved oxygen (DO). The DO objectives as contained in the Basin Plan at that time were divided into two categories: waterbody specific DO objectives defining daily minimums and annual means (Table 3-1) and aquatic life objectives defining daily minimum requirements for those waterbodies without waterbody specific objectives. Revisions to these objectives were developed and have been adopted by the Regional Water Board. Revisions include:

  • Revisions to the aquatic life objectives to update the daily minimum requirements to protect against acute DO impairment.
  • Revisions to the aquatic life objectives to include weekly and/or monthly average requirements to protect against chronic DO impairment.
  • Deletion of waterbody specific DO objectives, based on day time grab samples and inappropriate as 24-hour daily minimums.
  • Description of a process for calculating natural background DO conditions as daily minimum requirements in those waterbodies that cannot meet aquatic life objectives, due to natural conditions.

Project History

Two California Environmental Quality Act (CEQA) scoping meetings were held in the fall of 2008, one in Santa Rosa and one in Weaverville. A scoping document was presented and public comments solicited.
In the March 2009, a Peer Review Draft Staff Report was written, based in part on scoping comments received. It was submitted to 2 peer reviewers for their scientific review and comment. The Regional Water Board received peer review comments later in the spring of 2009 and began revision of the document for public review.
In the meantime, the schedule for the Klamath River Total Maximum Daily Load (TMDL) for DO (and other parameters) required the immediate review of the waterbody specific objectives for DO in the Klamath mainstem. Staff turned its attention to revision of the Klamath DO objectives, based on the scientific peer reviewed proposed revisions and the waterbody-specific analyses conducted as part of TMDL development. A Public Review Draft Staff Report was released for public review in 2009. The Klamath River-specific DO objectives was adopted by the Regional Water Board in March 2010, adopted by the State Water Resources Control Board in September 2010, and approved by USEPA Region 9 in December 2010.
A basin planning project to make revisions to other water quality objectives (Water Quality Objective Update Amendment) was altered to include regionwide revisions of DO objectives, as well. This combined planning project was brought before the Regional Water Board in June 2015 and adopted. It was approved by the State Water Board in February 2016.  

Available Documents

June 18, 2015 Materials as Adopted

The following documents were adopted by the Regional Water Board during the June 18, 2015 hearing. Minor changes to the documents were made during the hearing and have been incorporated in the versions present below.

Final Staff Report

Staff Report for the proposed Water Quality Objectives Update Amendment, June 18, 2015. Individual Sections of the Staff Report are available for ease of downloading:

DO Objectives for the Klamath River (March 2010)

Scientific Peer Reviews (March 2009)

CEQA Scoping (2008)

Mailing List

We encourage users interested in the DO Amendment and other basin planning issues to subscribe to the Basin Planning email list.

If you would like to be added to the hard-copy mailing list, please contact Lisa Bernard at 707-576-2677 or 5550 Skylane Blvd, Suite A, Santa Rosa, CA 95403

Contact Us

For information, comments, or questions concerning the DO Amendment please contact:

Lisa Bernard

  (Page last updated 7/5/23)