California Water Boards' Annual Performance Report - Fiscal Year  2019-20 


  • Data Source: TMDL Planner/Tracker Database. Period: July 1,  2019 to June 30,  2020 .
    • California TMDL Program Status Summary Report Fiscal Year  19-20 .
  • Unit of Measure: Number of TMDL projects adopted, or under development, during the fiscal year, and the number of 303(d) listings associated with the TMDL projects.
  • Data Definitions: TMDL Projects Adopted: The number of TMDL projects adopted by the Regional Water Board during the FY. TMDL Projects include new USEPA approved TMDLs, or USEPA approved alternatives to TMDLs (category 4b projects), or reconsideration of existing USEPA approved TMDLs, or USEPA approved alternatives to TMDLs, that will enact the necessary control actions to restore water quality. Listings Addressed by TMDL Project Adoptions: The number of waterbody-pollutant combinations associated with the TMDL projects adopted during the FY.
  • References: Information on the Water Boards' TMDL activities
    Water Boards' 2010 Clean Water Act Section 303(d) List of Impaired Waterbodies (303(d) List)


303(d) Listing (Impaired Water)
A 303(d) listings is a waterbody-pollutant combination that is responsible for the impairment as specified on the Clean Water Act Section 303(d) List of Impaired Waterbodies (i.e., each waterbody-pollutant combination is called a listing). If a single waterbody is impaired by multiple pollutants, the waterbody will have multiple listings, one for each pollutant. The geographic extent of a listing may vary from a small segment of a stream to an entire watershed. The current TMDL projects and listings are documented in the Water Boards' 2010 Clean Water Act Section 303(d) List of Impaired Waterbodies.

A pollutant is a waste or substance that, at certain levels, can cause waterbody impairment. The monitoring programs of the Water Boards and others provide information on the levels of pollutants in the State's waters.

A mathematical calculation of the assimilative capacity of a specific waterbody for a specific pollutant, and the allocation of acceptable levels of the pollutant load to the sources of the pollutants.

TMDL Project
A TMDL project is a planned strategy to reduce pollution in an impaired waterbody so that its water quality standards are met. A TMDL project may address more than one or more waterbody-pollutant combinations for a given waterbody or segment of waterbody (known as 303(d) listings). A TMDL project includes the development of the TMDL, and TMDL implementation plan, or a USEPA approved alternatives to TMDLs, category 4b projects. A TMDL is comprised of a calculation of the maximum amount of a pollutant that the waterbody can receive and still meet water quality standards (i.e., waterbody's assimilative capacity); an allocation of acceptable pollutant loading to the various sources of the pollutant; and in California, an implementation plan for restoring water quality. A category 4b project is an alternative approach that implements pollution control requirements (e.g., best management practices) that is stringent enough to implement applicable water quality standards within a reasonable period of time.