Skip to main content

Oregon State Flag An official website of the State of Oregon »

Temperature TMDL Replacement: Willamette River Mainstem and Major Tributaries

TMDL title: Temperature TMDLs for the Willamette Subbasin (excludes Tualatin and Yamhill Subbasins).
Water Quality Limited Parameters: Temperature

Schedule: DEQ will present the Willamette River Mainstem and Major Tributaries TMDL to the Environmental Quality Commission for proposed rule adoption in November 2024 to give EPA a minimum of 30 days for their action by Feb. 28, 2025.

Project area: 

  • Willamette River including all side channels and sloughs from the confluence of the Columbia River to the confluence of Coast Fork of the Willamette and Middle Fork of the Willamette Rivers (approximately river mile 187)
  • Multnomah Channel
  • Clackamas River downstream of River Mill Dam/Estacada Lake (approximately river mile 26)
  • Santiam River (all 12 miles)
  • North Santiam River downstream of Detroit Dam (approximately river mile 49)
  • South Santiam River downstream of Foster Dam (approximately river mile 38)
  • Long Tom River downstream of Fern Ridge Dam (approximately river mile 26)
  • Middle Fork Willamette River downstream of Dexter Dam (approximately river 17)
  • Fall Creek downstream of Fall Creek Dam (approximately river mile 7)
  • Coast Fork Willamette River downstream of Cottage Grove Dam (approximately river mile 30)
  • Row River downstream of Dorena Dam (approximately river mile 7.5)

The project schedule for all replacement temperature TMDLs is online. To stay informed of this possible schedule change and other project related information, please sign up for email updates on our main TMDL Replacement Project page

Project summary

In 2013, the United States Environmental Protection Agency disapproved the Natural Conditions Criterion contained in Oregon's water quality standard for temperature due to the 2012 U.S. District Court decision for NWEA v. EPA, 855 F. Supp. 2d 1199 (D. Or., 2012). This portion of the temperature water quality standard was used in most temperature TMDLs issued from 2003 through 2012. On Oct. 4, 2019, the U.S. District Court issued a judgment for NWEA v. EPA, No. 3:12-cv-01751-HZ (D. Or., Oct. 4, 2019) and required DEQ and USEPA to replace 15 Oregon temperature TMDLs that were based on the Natural Conditions Criterion and to reissue the temperature TMDLs based on the remaining elements of the temperature water quality standard.

A Total Maximum Daily Load is a water quality restoration plan and the calculation of the maximum amount of a pollutant that a waterbody can receive while still meeting water quality standards for that particular pollutant. The maximum amount of loading a waterbody can receive is called the loading capacity. Loading from all pollutant sources must not exceed the loading capacity of a waterbody, including an appropriate margin of safety. 

The temperature TMDLs for the Willamette Subbasins will be developed in two phases. Information on the first phase is on the Willamette Subbasin project web page. The second Willamette project phase includes the mainstem Willamette River and all the major tributaries downstream of the dams, except for the McKenzie River which is included in the Subbasins TMDL. The exact extents are described in the Quality Assurance Projects Plans listed below. The TMDL phasing considers the extent of the water quality models being used to support the TMDLs, requirements of the court order, and DEQ's available resources.

Quality Assurance Project Plan 

A Quality Assurance Project Plan is developed prior to writing the TMDL and does the following:
  • Define the issue and objectives of the TMDL, including the spatial and temporal extents of the water quality impairments. 
  • Provide a high-level description of the key processes and variables for temperature
  • Outlines the overarching technical approach for the TMDL, including the appropriate modeling and analytical tools to be used.
  • Provides the data sources for defining and creating inputs to the models, including data that were used in the modeling for the original TMDLs, if an original exists. 
Examples of these inputs can include meteorological data, stream flow and temperature, point sources and vegetation characteristics:
  • Describes how the analysis and modeling will be evaluated for acceptability
  • Describes potential scenarios for evaluating management strategies for reducing anthropogenic thermal loads
  • Provides various aspects for managing the TMDL development project, including documentation, the project team, data, and records management
View the Willamette Mainstem and Major Tributaries Quality Assurance Project Plan 
Willamette River Mainstem and Major Tributaries QAPP Interactive Map

Note:  McKenzie River to confluence with the South Fork McKenzie River (approximately river mile 56) , South Fork McKenzie River to Cougar Dam (approximately river mile 4) , and Blue River to Blue River Dam (approximately river mile 1.9) were moved from the Willamette Mainstem TMDL and added to the Willamette Subbasins TMDL.


Michele Martin
Project manager

Steve Mrazik
Watershed Management Manager

envelopeGreen.gifSign up for email updates on the TMDL Replacement Project web page


TMDL development and implementation is a public process. DEQ will develop this TMDL by rule per Oregon Administrative Rule Chapter 340 Division 42. During a rulemaking process, DEQ seeks public involvement by holding public hearings, establishing rule advisory committee meetings for technical and policy input, and for feedback regarding potential fiscal impacts related to the rule.

DEQ will hold two rule advisory committee meetings and a public hearing. DEQ will present the draft TMDL and Water Quality Management Plan to the Environmental Quality Commission, DEQ's formal policy and rulemaking body, for adoption before submitting the TMDL to EPA for approval or disapproval.

See the rulemaking web page for rule advisory committee meeting dates and information, draft project documents including the TMDL, Water Quality Management Plan, Technical Support Document, and Fiscal Impact Statement, and to sign up for email updates.