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Water Quality Assessment

Lahontan Region Integrated Report – 303(d) list of water quality limited segments and 305(b) surface water quality assessments

California has integrated the 303(d) List of Impaired Waters and the 305(b) Water Quality Assessment Report into a single report (Integrated Report). The Integrated Report satisfies the requirements of both Clean Water Act (CWA) Sections 303(d) and 305(b).

CWA Section 303(d) and 40 CFR §130.7 require states to identify waterbodies that do not meet water quality standards and are not supporting their designated beneficial uses. Waters which do not meet water quality standards are placed on the Section 303(d) List of Water Quality Limited Segments (also known as the list of impaired waterbodies, or the 303(d) list). Decisions to place waterbodies on the 303(d) list are governed by the Water Quality Control Policy for developing California’s Clean Water Act Section 303(d) List. U.S. EPA must approve the 303(d) list before it is considered final.

The 303(d) list identifies the pollutant or stressor causing impairment and establishes a schedule for developing a water pollution control plan to restore and maintain water quality. In most cases, water quality impairments are addressed by development of a Total Maximum Daily Load (TMDL), although in some cases other regulatory programs will address the impairment instead of a TMDL. Adoption and implementation of a TMDL or alternative regulatory program serves to attain and maintain water quality standards for the impaired waterbody. To learn more about the Integrated Report evaluation process please visit the State Water Board's Surface Water Quality Assessment website.

If you would like to receive announcements and notices pertaining to the Integrated Report by e-mail, please visit our e-mail subscriptions page.


2018 Integrated Report

  • On November 20th, 2019 the Lahontan Water Board adopted Resolution R6T-2019-0276 to transmit the regions' recommended updates to the 303(d) List to the State Water Board.
  • On October 20, 2021, the State Water Board approved the 2018 California Integrated Report, which included updates to the 303(d) List for the Lahontan Region.
  • On June 9, 2021, U.S. EPA approved the 2018 California Integrated Report.

The Current (2018) California Integrated Report and 303(d) List https://www.waterboards.ca.gov/water_issues/programs/water_quality_assessment/2018_integrated_report.html



2012 Integrated Report

On July 30, 2015, the U.S. EPA issued its final decision regarding the waterbodies and pollutants added to California's 303(d) List. This replaces the 2010 California Clean Water Act section 303(d) List as California's current 303(d) List.


2010 Integrated Report

(CWA Section 303(d) list/ 305(b) Report) On October 11, 2011, the U.S.EPA issued its final decision regarding the water bodies and pollutants added to California's 303(d) List. This replaces the 2006 California Clean Water Act 303(d) List as California's current 303(d) List.


Previous 303(d) lists and 305(b) reports

The 2010 Integrated Report is the first Integrated Report developed for the State of California. Previous assessments were developed by the State Water Board in separate documents and can be found on the State Water Board’s Integrated Report Cycles website.