Water Facts:

Impaired Waters

According to the Minnesota Pollution Control Agency, 40% of rivers and lakes tested in recent years are legally “impaired,” meaning pollution in them exceeds clean water standards. The list of impaired waters, then, is the closest thing to a complete list of Minnesota's polluted rivers and lakes. But many waters have not been recently tested.

The U.S. Clean Water Act requires states to publish and update a list of waters that are not meeting one or more water quality standards. The list, known as the Total Maximum Daily Load (TMDL) list, is updated every two years. Following assessment of water quality data and an extensive public participation process, the draft TMDL list is submitted to the U.S. EPA for final approval.

Minnesota's 2010 TMDL list contains 1,774 impairments on 388 rivers and 647 lakes. Minnesota’s 2008 list contained 1,475 impairments on 336 rivers and 510 lakes.

While the 2010 TMDL List has 1,774 impairments, the Inventory of all impaired waters contains 3,049 impairments. Waters in the Inventory of impaired waters will remain there until they meet water quality standards.

The inventory of impaired waters includes those needing a cleanup plan as noted above and those for which plans have already been developed and approved by US EPA but not fully implemented. The Inventory also includes waterbodies that are naturally impaired, such as the arsenic exceedances in the Red River of the North.

More information here.

Comments (3) Post a Comment

May. 11,2010 1:02 PM
Thank you for your observations. Actually, the definition of "impaired waters" used on this site is identical to that of the Clean Water Act and used by the Minnesota Pollution Control Agency.  Less than 5% of the state's impairments are caused by natural geologic conditions.  Also, sediment is a pollutant that degrades water quality, fishing and swimming and is typically caused in Minnesota waters by human activity.

Finally, it is the Minnesota Pollution Control Agency, not Conservation Minnesota, that tests Minnesota lakes.  The statement that 40% of lakes tested are polluted comes from the Agency and is accurate.


Oct. 29,2008 7:33 PM
Your website talks about impaired waters without providing a definition according to the Clean Water Act. Minnesota's lakes and rivers may be impaired only by natural geologic conditions or simply by excess sediment loading. Your general statements implying impaired lakes and rivers are very misleading and appear to strike fear into the general public in order to generate revenue for environmental programs. Please clarify your broad generalizations regarding this issue. 

Oct. 27,2008 10:56 PM
You state in your commercial that 40% of the lakes you tested were polluted.  That is a test which equals 510 lakes  and we have over 12,000 lakes in Minnesota.  Isn't your commercial a little misleading?