303(d) Listing Methodology

Person holding glass bottle with brown water

Every two years, the state of Colorado creates the 303(d) List of waterbodies that do not meet water quality standards, as required by the Federal Clean Water Act. The Environmental Protection Agency defined these waterbodies as impaired waters. Waterbodies with pollution levels that exceed water quality standards do not support one or more of their intended uses, such as agriculture, wildlife habitat, recreation, and public drinking water supply. 

The 303(d) Listing Methodology provides guidance for determining if a waterbody meets water quality standards and whether it supports its designated use. This helps provide information about the water quality status of all surface waters in Colorado. 


The 303(d) Listing Methodology workgroup considers revisions to this document every two years to support the development of the 303(d) List of Impaired Waters and the Monitoring & Evaluation List. Revisions or additions often come from issues raised during the previous 303(d) listing cycle.

How to get involved



303(d) Listing Methodology stakeholder meetings will occur monthly from September through November 2023. At the end of these meetings, the division will propose revisions to the listing methodology that the Water Quality Control Commission will consider through an administrative action hearing. The administrative action hearing is scheduled for March 2024.

Sign up to receive notifications about this effort. 

The division launched this stakeholder effort with a virtual kickoff on September 20, 2023.  A copy of the meeting recording, chat, presentation, and other meeting materials are stored in this public folder

Workgroup meetings

  • Wednesday, September 20, 2023 | 9 - 11 a.m.
  • Wednesday, October 18, 2023 | 1 - 3 p.m.
  • Wednesday, November 15, 2023  | 9 - 11 a.m.

Temperature training session


For more information, please contact: