Beyond general efforts to improve water quality, the city has additional requirements to improve impairments in local waterbodies. When waterbodies exceed water quality standards, as established by both the federal and state governments, a Total Maximum Daily Load (TMDL) may be required for that waterbody. A TMDL is a calculation of the total amount of a pollutant that a waterbody can receive to meet water quality standards; a TMDL also is the strategic plan and implementation requirements for how stakeholders will meet water quality standards.

The City of Riverside is named by EPA as responsible for three TMDLs:

Santa Ana River-Reach 3 for pathogens

The stretch of the Santa Ana River near the City of Riverside, called SAR Reach 3, is listed by US EPA as impaired for pathogens (bacteria). In 2006, a pathogen TMDL was approved to improve the water quality. Stakeholders, including the City of Riverside, are working as a task force to identify the sources of pollution and ways to mitigate the problem.

Lake Elsinore and Canyon Lake for nutrients

Lake Elsinore and Canyon Lake are named together in a nutrient TMDL that was approved in 2004. Stakeholders, including the City of Riverside, are working as a task force to identify the sources of pollution and ways to mitigate the problem.

Canyon Lake for pathogens

Canyon Lake is named as impaired for pathogens. A TMDL has not yet been approved.