Basin Planning

About The Basin Plan

The Water Quality Control Plan for the Colorado River Basin (Basin Plan) is designed to preserve and enhance water quality in the Region and to protect the beneficial uses of all regional waters for the benefit of present and future generations. The Basin Plan contains the Region’s beneficial uses for ground and surface waters, water quality objectives to protect beneficial uses, and implementation programs to achieve water quality objectives. The Basin Plan fulfills state and federal statutory requirements for water quality planning, thereby preserving and protecting ground and surface waters of the Colorado River Basin Region.

Triennial Review

In accordance with state and federal laws, the Regional Water Board is obligated to keep the Region’s Basin Plan current and accurate via periodic review and to update it as appropriate. States are required to review their water quality standards at least once every three years – a process known as “triennial review” [33 U.S. Code Section 1313(c)]. The triennial review may result in amendments to the Basin Plan over the course of the three-year review cycle.

Amendments Under Development

  • Basin Plan Amendment to Establish Secondary Maximum Contaminant Levels as Groundwater Quality Objectives for Hydrologic Areas with Municipal and Domestic Supply Beneficial Use

      To ensure the protection of beneficial uses of groundwater and the prevention of nuisance, the Colorado River Basin Regional Water Quality Control Board (Regional Water Board) proposes amending Chapter 3 (Water Quality Objectives) of the Water Quality Control Plan for the Colorado River Basin Region (Basin Plan).

      Chapter 3 of the Basin Plan expressly incorporates by reference health-based drinking water standards known as Primary Maximum Contaminant Levels (MCLs), found in California Code of Regulations, title 22, sections 64431 (inorganic chemicals) and 64444 (organic chemicals), as water quality objectives for groundwater designated with the Municipal and Domestic Supply (MUN) beneficial use. The Basin Plan also expressly references the Primary MCLs found section 64426.1 for bacteria, as well as MCLs for radioactivity (§§ 64442, 64443) and copper and lead (§ 64678).

      Drinking water standards (known as MCLs) include primary (health-based) and secondary (aesthetics and/or nuisance-based) classifications. The proposed Basin Plan Amendment would establish regulatory limits in the Basin Plan for aesthetic and nuisance constituents by adding a reference to the Secondary MCLs found in California Code of Regulations, title 22, section 64449, as groundwater quality objectives. The proposed Basin Plan modification would be applicable to all groundwater basins within the region’s hydrologic units designated with the MUN beneficial use.

      CEQA Scoping


  • Basin Plan Amendment to Update Bacteria Water Quality Objectives for Waters Designated for Water Contact Recreation

      This is a non-regulatory update of the Basin Plan to incorporate State Water Board’s statewide bacteria objectives for coastal and non-coastal waters designated for water contact recreation (REC I). The amendment will update the numeric bacteria water quality objectives associated with REC I beneficial use to be consistent with the statewide objectives, which are already in effect. The amendment will also make other administrative, non-regulatory changes, including adding a new beneficial use definition for limited contact recreation (LREC I), and consolidating the site-specific objectives for the Colorado River.

      Regional Water Board Approval

Recent Fully Approved Amendments

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Basin Plan

Basin Plan Cover