• State Standards in Effect for CWA Purposes
• Federally Proposed or Promulgated Standards

State Standards in Effect for CWA Purposes

• [See The Basic Standards And Methodologies for Surface Water, Regulation No. 31 ]
  (Effective December 31, 2005) This regulation provides basic water quality standards, an antidegradation rule and implementation process, and a system for classifying state surface waters, for assigning water quality standards, for granting temporary modifications, and for periodic review of the classifications and standards.
• [See Colorado River Salinity Standards, Regulation No. 39 ]
  The regulation establishes water quality standards for salinity in the Colorado River Basin.
• [See Water Quality Standards for Salinity--Colorado River System, June 1999 ]
• [See Water Quality Standards for Salinity--Colorado River System, October 1999 ]

Classifications and Numeric Standards

The following regulations provide classifications and numeric water quality criteria for the indicated rivers and basins.

• [See Classifications And Numeric Standards for Arkansas River Basin, Regulation No. 32 (2006) ] and [See Tables ]
  (Effective March 2, 2006)
• [See Classifications And Numeric Standards for Upper Colorado River Basin And North Platte River, Regulation No. 33 (2006) ] and [See Tables ]
  (Effective March 2, 2006)
• [See Classifications And Numeric Standards for San Juan River And Dolores River Basins, Regulation No. 34 (2006) ] and [See Tables ]
  (Effective March 2, 2006)
• [See Classifications And Numeric Standards for San Juan Gunnison And Lower Dolores River Basins, Regulation No. 35 (2006) ]
  (Effective March 2, 2006)
• [See Classifications And Numeric Standards for Rio Grande Basin, Regulation No. 36 ] and [See Tables ]
  (Effective December 6, 2002)
• [See Classifications And Numeric Standards for Lower Colorado River Basin, Regulation No. 37 (2006) ] and [See Tables ]
  (Effective March 2, 2006)
• [See Classifications And Numeric Standards for South Platte River Basin, Laramie River Basin, Republican River Basin, Smoky Hill River Basin, Regulation No. 38 (2006) ] and [See Tables ]
  (Effective March 2, 2006)

Colorado's water quality standards are applicable to "waters of the State". In some limited instances, the definition adopted by Colorado for "waters of the State" as part of its water quality standards may result in water quality standards that are more comprehensive than required under section 303(c) of the Clean Water Act and the implementing federal regulations. EPA has included the State's water quality standards in their entirety here for context and as supplementary information for the reader.

Colorado water quality standards apply to all waters within the State of Colorado, with the exception of those waters that are within Indian Country, as defined in 18 U.S.C. Section 1151.

Federally Proposed or Promulgated Standards

None at this time.

Top of Page

• The Basic Standards And Methodologies for Surface Water, Regulation No. 31 (PDF)(178 pp, 2 MB)
• Colorado River Salinity Standards, Regulation No. 39 (PDF)(7 pp, 610 K)
• Water Quality Standards for Salinity--Colorado River System, June 1999 (PDF)(109 pp, 8 MB)
• Water Quality Standards for Salinity--Colorado River System, October 1999 (PDF)(49 pp, 3 MB)
• Classifications And Numeric Standards for Arkansas River Basin, Regulation No. 32 (2006) (PDF)(72 pp, 311 K)
• Tables (PDF)(16 pp, 244 K)
• Classifications And Numeric Standards for Upper Colorado River Basin And North Platte River, Regulation No. 33 (2006) (PDF)(83 pp, 187 K)
• Tables (PDF)(19 pp, 100 K)
• Classifications And Numeric Standards for San Juan River And Dolores River Basins, Regulation No. 34 (2006) (PDF)(46 pp, 342 K)
• Tables (PDF)(19 pp, 110 K)
• Classifications And Numeric Standards for San Juan Gunnison And Lower Dolores River Basins, Regulation No. 35 (2006) (PDF)(92 pp, 489 K)
• Classifications And Numeric Standards for Rio Grande Basin, Regulation No. 36 (PDF)(49 pp, 156 K)
• Tables (PDF)(11 pp, 116 K)
• Classifications And Numeric Standards for Lower Colorado River Basin, Regulation No. 37 (2006) (PDF)(62 pp, 501 K)
• Tables (PDF)(11 pp, 93 K)
• Classifications And Numeric Standards for South Platte River Basin, Laramie River Basin, Republican River Basin, Smoky Hill River Basin, Regulation No. 38 (2006) (PDF)(147 pp, 2 MB)
• Tables (PDF)(28 pp, 1 MB)