Minnesota's Impaired Waters and TMDLs

Water Quality Assessment and Listing

The Clean Water Act requires states to monitor and assess their waters to determine if they are attaining water-quality standards.  The MPCA collects water-quality data from state, local and federal agencies, as well as citizens, and then conducts a rigorous process to complete this assessment. To best align resources, the MPCA is following the Intensive Watershed Monitoring approach for both monitoring (agency and local via grant funds) and assessments. 

Monitoring suggests that about 40 percent of Minnesota's lakes and streams are impaired for conventional pollutants, a rate comparable to what other states are finding. Impaired waters identified through the assessment process are placed on the Impaired Waters List.

More information is available on the MPCA Web site about environmental monitoring and water-quality standards.

Fact sheets and guidance documents

• Assessing and Listing Impaired Waters
• Guidance Manual for Assessing the Quality of Minnesota Surface Waters for Determination of Impairment: 305(b) Report and 303(d) List (wq-iw1-04)
• Natural Background and Water Quality - Guidance document for assessment of aquatic life use support
• Guidance for considering natural background when assessing lakes for eutrophication (wq-s1-63)

The MPCA provides access to assessment-related water quality information through its Assessment Water Quality viewer.

For assessment related questions, please contact Pam Anderson.