A loaded canoe on the shore of the Big River

Water quality standards are the foundation for a wide range of programs under the federal Clean Water Act (CWA). The goal for water quality standards is protecting water uses through applying criteria. The department continually works to improve Missouri’s water quality standards to best reflect the most recent science and regulatory obligations extended to Missouri’s waters. For information about variances from the water quality standards, which allow deviation from meeting a water quality-based effluent limit for dischargers for a limited time, visit Water Quality Standards Variances

Section 303(c)(1) of the Clean Water Act and the regulations EPA developed to implement that section, located in Code of Federal Regulations 40 C.F.R. § 131.20, require that states from time to time, but at least once every three years, hold public hearings to review applicable water quality standards and, as appropriate, modify and adopt water quality standards. Any new or revised water quality standards resulting from the standards review are required to be submitted to EPA for review and approval.

The Water Quality Standards Workgroup provides input and assistance to the department in developing and refining appropriate water quality standards for protecting Missouri’s streams, lakes and wetlands. If you have a question or want to reach department Water Quality Standards team members, email us at wqs@dnr.mo.gov

Public Notices/ Public Comments

There are no currently active Water Quality Standards Review Public Notices/ Public Comments.

Department Review

Information about the status of any proposed changes to the water quality standards will be available on the department's Laws, Rules and Regulations webpage. To filter out proposed changes, choose "Rules in Development" in the "Type" field in the search box.

Petition for Developing Recreational Criteria for Cyanotoxins

On March 29, 2022, the department received a petition from the Missouri Coalition for the Environment to amend the water quality standards to establish water quality criteria for cyanotoxins, specifically microcystin and cylindrospermopsin, to protect recreational use of Missouri lakes and reservoirs. The documents below include the submitted petition, reference documents and a letter to the Joint Committee on Administrative Rules requesting an extension to respond.

Reference Documents

EPA Actions