IMPAIRED WATERS


A stream or lake is considered impaired when it fails to meet Water Quality Standards established by the Clean Water Commission. The federal Clean Water Act requires states to identify and list all impaired waters.

Missouri has established acceptable standards for drinking water, fishing, swimming, aquatic life and other designated uses. Waters that don't meet these standards are placed on a special list called the 303(d) list. Different standards must be met for different uses. For example, water quality requirements for drinking water would be different from those for livestock watering.

If a waterbody is determined to be impaired, a watershed management plan will be developed that will include the Total Maximum Daily Load (TMDL) calculation. The Department of Natural Resources is currently required to develop TMDLs for impaired water bodies for approval by the US Environmental Protection Agency.  The TMDL process is a tool used to restore and protect water quality in streams, rivers, and lakes.

Information contained in a TMDL document includes:

  • Location of the impaired waterbody
  • Identification of the pollutants(s)
  • Sources of the pollutants(s)
  • A calculation of the pollutant "load" that the water can absorb without becoming impaired
  • A plan to reduce the pollutant "load" and restore the waterbody to meet the standards for its designated use

Not every water body on the 303(d) list has a TMDL approved by the EPA.  Current TMDLs can be found at the MDNR TMDL website.

The TMDL process works best when local people work together to understand and identify problems in their watershed. That way they can help develop the most effective solution for reducing water pollution. Citizen participation and cooperation is crucial for successful watershed management. Inclusive, community-based, public stewardship is the key to protecting our natural resources.  For information on which impaired waterbodies are currently being studied by MDNR go to Impaired Waters and Total Maximum Daily Loads- TMDL Under Developments.

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