TMDL for Temperature in the Columbia and Lower Snake Rivers

Summary

On May 18, 2020, EPA established the Columbia and Lower Snake Rivers Temperature Total Maximum Daily Load (TMDL) as required by Section 303(d) of the Clean Water Act and its implementing regulations (Title 40 of the Code of Federal Regulations, Section 130.7).

Spanning almost 900 river miles, the TMDL examines sources of temperature impairments on the Columbia River from the Canadian border to the Pacific Ocean, and on the lower Snake River in Washington from its confluence with the Clearwater River at the Idaho border to its confluence with the Columbia River.

The TMDL is required under the federal Clean Water Act because significant portions of the Columbia and lower Snake Rivers are identified by the states of Washington and Oregon as impaired due to temperatures that exceed the numeric criteria portion of the states’ water quality standards at various locations and times of year.

EPA accepted public comments on the TMDL from May 21 through August 20, 2020. TMDL program regulations require that EPA consider comments, make necessary changes, and transmit the re-issued TMDL to the states for incorporation into their Water Quality Management Plans. 

On August 13, 2021, EPA transmitted the re-issued TMDL to the states of Oregon and Washington.

The TMDL document, EPA's responses to public comments, and appendices are available below.

For more information, contact John Palmer (palmer.john@epa.gov).

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Documents

Note: Appendices A, C, F and G did not change from the 2020 TMDL. Appendices B, D, E, H, and I were updated to reflect changes in the reissued TMDL. Appendix J is new.

• Columbia and Lower Snake Rivers Temperature Total Maximum Daily Load (TMDL) (pdf) (3.58 MB, August 13, 2021)
  Errata update version, May 10, 2022.
• Erratum for the Columbia and Lower Snake Rivers Temperature TMDL (pdf) (278.77 KB, October 7, 2021)
  EPA’s letter clarifying and correcting Table 1-1 in the TDML to identify an additional water quality limited segment to which the TMDL applies.
• Response to Public Comments on Columbia and Lower Snake Rivers Temperature TMDL (pdf) (2.02 MB, August 13, 2021)
  EPA's responses to comments received during the public comment period from May 21 through August 20, 2020.
• Appendix A: Temperature Water Quality Standards for the Columbia and Lower Snake Rivers (pdf) (1.09 MB)
  Existing temperature water quality standards for the Columbia and Lower Snake Rivers within the geographic scope of the TMDL.
• Appendix B: Temperature Data Compilation, Quality Assurance and Analysis (pdf) (5.03 MB)
  Existing conditions and water quality criteria exceedances for temperature.
• Appendix C: RBM10 Model Development Report (pdf) (19.79 MB)
  Update of the RBM10 Temperature Model of the Columbia and Snake Rivers.
• Appendix D: RBM10 Model Scenario Report (pdf) (3.97 MB)
  Assessment of impacts to Columbia and Snake River temperatures using the RBM10 Model.
• Appendix E: Tributary Assessment Methods and Results (pdf) (2.33 MB)
  Temperature analysis for tributaries discharging into the Columbia River.
• Appendix F: ORD Technical Memorandum on Tributary Restoration (pdf) (2.58 MB)
  Stream temperature predictions under varying shade and climate scenarios in the Columbia River Basin.
• Appendix G: Climate Change (pdf) (1.76 MB)
  Assessment and synthesis of the literature on climate change impacts on temperatures of the Columbia and Snake Rivers.
• Appendix H: Temperature Metric Analysis (pdf) (463.07 KB)
  Comparing Daily Maximum, Daily Average and 7-Day Average of the daily maximum temperature averaging periods on the Columbia and Snake Rivers.
• Appendix I: Temperature Heat Loads (pdf) (364.43 KB)
  Calculated head loads for loading capacity and allocations.
• Appendix J: Considerations for Permit Writers on Wasteload Allocations (pdf) (233.53 KB, August 10, 2021)
  Evaluation of point source discharges in the Columbia and Snake River Temperature TMDL and considerations for permit writers.