water flowing in a stream

The objective of the Clean Water Act is to restore and maintain the chemical, physical and biological integrity of the nation’s waters.

Missouri’s Water Quality Standards (WQS) [10 CSR 20-7.031] are provisions in state regulations that describe the desired condition of a body of water and the means by which that condition will be protected or achieved.

Three Core Components of WQS:

  1. Designated uses of a body of water
  2. Criteria to protect designated uses
  3. Antidegradation requirements to protect existing uses

The objective of WQS is the protection of uses through the application of criteria. Water quality criteria are expressed as concentrations, loads or narrative statements. The level of protection given to a stream, river or lake is dependent on the expected, or "designated use(s)," of that water. Once we assign designated uses to a water body, it is considered “classified” and is listed in Missouri’s WQS as such. Finally, antidegradation policy requires actions to maintain and protect high quality waters and existing water quality.

Search for classification and designated uses of any body of water in the state using the department's Water Quality Standards Map Viewer.

We are continually working to improve Missouri’s WQS to best reflect the most recent science and regulatory obligations extended to Missouri’s waters.

Triennial Review

Section 303(c)(1) of the Clean Water Act and the EPA’s implementing regulations at 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. Visit the Program Rule Development page for up-to-date information on the status of the 10 CSR 20-7.031 – Water Quality Standards rule.

Public Notices/ Public Comments

Get Involved

Discussions of Water Quality Standards topics are conducted through meetings of the Water Quality Standards Workgroup. This workgroup provides input and assistance to the department in developing and refining appropriate water quality standards for the protection of Missouri’s streams, lakes and wetlands. 

Do you have a question or want to reach Water Quality Standards staff, email us at wqs@dnr.mo.gov. We would love to hear from you!

Water Quality Standards General Resources

Numeric Nutrient Criteria for Lakes Resources

Recent EPA Actions on Water Quality Standards

Additional Information