Understanding Iowa's Impaired Waters Lists

Clear Creek in eastern Iowa.You've likely heard of Iowa's many "impaired" waters. But what makes a water impaired and what can we do to take streams and lakes off the list?

3-Step Process for Impaired Waters Study
How does a stream/river/lake get on the impaired waters list?

Fact sheet on impaired waters
Full impaired waters list and details
2018 Interactive Map of Impaired Waters
2018 Impaired Waters Map 

Each lake and stretch of stream or river in Iowa is designated for a specific use, like for contact recreation such as swimming or fishing; for drinking water; or for maintaining a healthy population of fish and other aquatic life. If the water quality in the stream or lake does not allow it to meet its designated use, it does not meet Iowa's water quality standards and is considered "impaired."

The waterbody is then placed on the "303(d)" list, commonly known as the "impaired waters list." This is named after section 303(d) of the federal Clean Water Act and means that the stream or lake needs a water quality improvement plan written.

Once on the 303(d) list, a water quality improvement plan is written. The plan outlines water quality problems, identifies needed reductions in pollutants and offers possible solutions. Waters that have a water quality improvement plan written for them move off the 303(d) list, or impaired waters list.

Even though it's off the 303(d) list, the waterbody is still considered impaired until water quality improves. Local groups need to take action and work with the DNR to improve their stream or lake. The water quality improvement plan can offer ideas for solutions, and the DNR can provide additional assistance for Iowans looking to organize a watershed improvement project.

Local action can lead to improved water quality, which can help the stream or lake meet state water quality standards again. When the waterbody meets those standards, it may be able to come off the impaired waters list.


Impaired waters step-by-step

  1. Water quality in a waterbody (lake or stream segment) falls below state water quality standards
  2. Waterbody placed on 303(d) list
  3. Water quality improvement plan written
  4. Waterbody remains impaired but moves off 303(d) list
  5. Local citizens come together to improve waterbody
  6. Local efforts lead to improved water quality that meets state standards
  7. Waterbody determined by DNR and U.S. Environmental Protection Agency to no longer be considered "impaired"

DNR Contacts
Dan Kendall 
DNR Ambient Lake Monitoring Coordinator