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DNR Releases Latest Draft of Impaired Waters List

  • 3/19/2024 10:50:00 AM
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DES MOINES -- The Iowa Department of Natural Resources is seeking public comment on the newly released draft impaired waters list (303(d) list). Data released by the Iowa DNR today shows a reduction in 96 impairments relative to the 2022 303d impairment list, once the 2024 list is approved by the EPA.

Iowa’s 2024 303(d) list includes waterbody segments that are not meeting all applicable state water quality standards for their designated uses. A water on the 303(d) list is referred to as an impaired water. Once the DNR creates a water quality improvement plan for the segment (called Total Maximum Daily Loads, or TMDLs), the segment does not need to be included on future 303(d) lists. Additionally, more current data may show that a previously included segment is no longer impaired and can be excluded from the list, subject to conditions contained in the reporting methodology. The DNR and the EPA refer to either of these scenarios as delisting an impaired water. 

The 303(d) list and associated methodology can be found on the DNR’s website, at: A list of waters delisted relative to the 2022 303(d) list that are not included in the 2024 303(d) list can also be found at the DNR’s webpage.

The DNR analyzed 1,428 waterbody segments for the 2024 303(d) list, which include portions of rivers, streams, lakes, reservoirs and wetlands. In total, the 2024 303(d) list shows a net reduction in 21 impaired segments from the 2022 303(d) list.

“The assessment of Iowa’s waters is an always-changing story, one that can only be properly told with quality data. I’m happy to report that increased monitoring and availability of data was a key driver in the reduced number of impaired segments this cycle,” said Noah Poppelreiter, supervisor of the DNR’s Water Quality Monitoring and Assessment section. “We hope to continue increasing the DNR’s monitoring capacity throughout the state in 2024 and 2025.” 

Process for Impaired Waters Study

The DNR uses all credible data that is readily available to assess waterbody segments. To start, the DNR maintains sampling programs that collect data through fixed station river monitoring, ambient lake monitoring, beach monitoring, wadeable stream biological monitoring, fish tissue monitoring, and wetland/shallow lakes monitoring. Other data is also analyzed before assessing a segment, including data from sources such as the DNR’s Supplemental Streams Monitoring program; data collected by DNR Fisheries and stored in the DNR’s Fish Kill Database; data collected by federal partners such as the US Geological Survey; data collected by municipalities; and data collected on the border rivers by adjacent states. 

The DNR then compiles all available credible data collected within the correct time frame. The data is reviewed and assembled into a standard format. Then, these results are compared to appropriate criteria for each designated use. The final assessment for each segment is a compilation of all these results. The 2024 303(d) list is a collection of 2,440 use assessments. 

Most Iowa waters are designated for both aquatic life protection and water contact recreation. Others also may include one or both designations for drinking water or human health protection. 

Success stories: Get involved!

To keep the positive momentum moving forward to improve water quality in Iowa, the DNR is encouraging citizens to get involved. The DNR Watershed Improvement program provides assistance on how to start a water quality effort and seek grant opportunities.

Iowa has several water quality success stories including watershed improvements. To qualify as a success, there must be evidence of water quality improvement that led to a deslisting. 

Public comment is welcomed now through April 12, 2024, and should be sent to:



Postal mail:

Iowa Department of Natural Resources
Attn: Impaired Waters/Segment List
Water Quality Monitoring & Assessment Section
Wallace State Office Building
502 E. Ninth St.
Des Moines, IA 50319