Monitoring, Assessment and TMDLs: California
California's Water Resources Control Board and nine Regional Water Quality Control Boards are responsible for conducting monitoring, assessment, reporting under CWA Sections 303(d) and 305(b) and Total Maximum Daily Loads (TMDLs) development for the State of California. The State Board and Regional Boards cooperate in developing Section 305(b) and Section 303(d) listing reports. TMDLs are normally developed by Regional Boards, and then approved by the State Board and State Office of Administrative Law before being submitted for EPA approval.
- Monitoring, Assessment and Integrated Reporting in California
- Section 303(d) Listing in California
- TMDLs in California
- State-Adopted TMDLs in California
Monitoring, Assessment and Integrated Reporting in California
More information about California's monitoring and assessment programs may be found at State Water Resources Control Board's Water Issues site.
The State Water Resources Control Board also includes a comprehensive range of water quality monitoring and assessment data that can be viewed across space and time: visit My Water Quality for further information.
Section 303(d) Listing in California
California’s 2024 Section 303(d) List of Impaired Waters
On December 12, 2024, EPA issued its decision to partially approve and partially disapprove California’s 2024 List of Impaired Waters.
EPA found California’s decision not to list 44 waterbodies for benthic community effects inconsistent with California’s water quality standards. These standards protect freshwater ecosystems including the preservation or enhancement of aquatic habitats, vegetation, fish, or wildlife, including invertebrates. EPA has identified the 44 waterbodies as impaired for benthic community effects and as requiring Total Maximum Daily Loads (TMDLs) under CWA 303(d).
EPA found nine waterbody-pollutant combinations that were erroneously classified as having an approved regulatory alternative to a TMDL, however these impairments still require TMDLs and must be included on the 2024 List. EPA has identified the 9 waterbody-pollutant combinations as still requiring a TMDL.
- Partial Approval and Partial Disapproval of California’s 2024 List of Impaired Waters (pdf)
- Erratum to Partial Approval and Partial Disapproval of California’s 2024 List of Impaired Waters (pdf)
California’s 2012 Section 303(d) List of Impaired Waters
On June 26, 2015, EPA approved California's 2012 Section 303(d) list of impaired waters in three Regional Water Quality Control Boards (the North Coast, the Lahontan and the Colorado River Boards) and disapproved the omission of the mercury impairment at Topaz Lake which met the federal listing requirements. EPA provided public notice of its proposed action to place Topaz Lake on California's 303(d) list and provided opportunity for public comment on the proposed addition. The public comment period closed on July 26, 2015 and no comments were received. On July 30, 2015, EPA issued its final decision to add Topaz Lake to the State's 303(d) list. See EPA's final decision letter.
California's 2012 Integrated Report is available at the California State Water Resources Control Board.
California's 2008-2010 Integrated Report
On November 12, 2010, EPA approved California’s 2008-2010 Section 303(d) list of impaired waters and disapproved the omission of several water bodies and associated pollutants that meet federal listing requirements. EPA identified additional water bodies and pollutants for inclusion on the State’s 303(d) list. EPA provided public notice and the opportunity for public comment on our proposed additions which ended December 23, 2010. On October 11, 2011, EPA issued its final decision regarding the waters EPA added to the State’s 303(d) list. See final transmittal letter with enclosures and responsiveness summary below.
California’s 2008-2010 Integrated Report which serves as both their Section 303(d) list and Section 305(b) report is available on their website in report form and as a searchable map.
California's 2004-2006 Integrated Report
On May 29, 2008, EPA revised its previous decision to add microcystin toxins as an additional cause of impairment to one Klamath River segment (Middle Hydrologic Area: Oregon to Iron Gate) previously listed by California in its 2006 Clean Water Act Section 303(d) List. EPA solicited public comment on its action and has now completed its review of the comments received. Based on comments from the North Coast Regional Board, EPA agreed to revise the description of the segment which EPA is listing as impaired due to “microcystin toxins.” EPA identified this impaired portion as “the reach of the Klamath River including the Copco and Iron Gate Reservoirs.” Accordingly, this segment does not include Klamath River upstream of Copco I Reservoir to Oregon.
On March 13, 2008, EPA reconsidered its prior approval of the omission of microcystin toxins listings for three Klamath River segments and determined to add a listing for microcystin toxin for one of these three segments, “Klamath River HU, Middle HA, Oregon to Iron Gate”. California’s 2006 Section 303(d) List already identifies each segment of the Klamath River within California as impaired due to Nutrients, Organic Enrichment/Low Dissolved Oxygen, and Temperature. EPA’s reconsideration of its decisions related to microcystin toxins and the Klamath River, and its determination to add a listing for microcystin toxins for one of the river’s segments, do not affect EPA’s determinations regarding any other portion of California’s Section 303(d) List. Neither EPA’s approval of the State’s listings for the Klamath River listings, nor EPA’s determination to add the listing for microcystin toxins, extends to any water bodies located within Indian country, as defined in 18 U.S.C. 1151.
On Nov. 30, 2006, EPA partially approved California's 2004-2006 303(d) list submission. In summary, this action approved the State's list of impaired waters. On March 8, 2007, EPA partially disapproved California's 2004-2006 303(d) List; that is, we disapproved the State's omission of impaired waters that met federal listing regulations or guidance. EPA identified 36 additional waters bodies and associated pollutants for 34 waters to be added to the State's 303(d) list. EPA provided public notice and the opportunity for public comment on our proposed additions which ended April 16, 2007.
On June 28, 2007, EPA issued its final decision regarding the waters EPA added to the State’s List. See final transmittal letter with enclosures and responsiveness summary below.
California Regional and State Boards are currently working on developing the 2008 Integrated Report for submittal in 2010.
TMDLs in California
More information about California's TMDL program, including the State's Proposed Impaired Waters Guidance and Regional Board TMDL programs, can be found at the State Water Resources Control Board's Total Maximum Daily Load Program site or by contacting California TMDL Program Manager.
State-Adopted TMDLs in California
Lake Tahoe TMDL
Information on the status of TMDLs being developed or previously developed by the State of California can be found at California's State Water Resources Control Board's Total Maximum Daily Load Program page.