Iowa DNR
Iowa DNR
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Water Quality Assessments
Impaired Waters List

2022 305(b) Assessment Summary

2022 Integrated Report including the 2022 Impaired Waters List: Approved by U.S. EPA on April 29, 2022:

Iowa DNR submitted the 2022 Integrated Report which includes the 2022 Impaired Waters List to the U.S. EPA as required by Sections 305(b) and 303(d) of the federal Clean Water Act for approval on April 1, 2022. Iowa DNR received final approval of this submittal from the U.S. EPA on April 29, 2022.

Public comments were sought on Iowa’s draft 2022 list of impaired waters from February 18, 2022, through March 19, 2022. Iowa DNR prepared a summary of responses to the 15 comments received on the draft 2022 list of Impaired Waters Iowa’s draft list was updated following the public comment period and Iowa's final 2022 Impaired Waters list, as submitted to U.S. EPA, contained 597 waterbodies with a total of 786 impairments.

Materials for review

Background

Iowa's Section 303(d) lists and Integrated Reports are prepared according to Iowa DNR's assessment and listing methodology and follow U.S. EPA guidelines for "integrated reporting" that combine requirements of Sections 305(b), 303(d), and 314 of the federal Clean Water Act. These U.S. EPA guidelines suggest that states place all their waters into one of the following categories that comprise a state's Integrated Report:

  • Supported: The designated uses* of these waterbodies were assessed as fully supported. Waters with all their designated uses assessed as fully supported are in Category 1 of the Integrated Report. Those waters where some of the designated uses were met but insufficient information exists to determine whether the remaining uses were met are placed in Category 2 of the Integrated Report.
  • Uses Not Assessed: These are designated uses for which insufficient information exists to determine whether that designated use was met. Other designated uses for that waterbody, however, may have been assessed as either "supported" or "impaired".

  • Waterbodies Not Assessed: Insufficient information exists to determine whether any beneficial uses designated for that waterbody were met. These waterbodies are placed into Category 3 of the Integrated Report.

  • Category 4: The waterbody is impaired but a TMDL is not required; the waterbody is not included on the state's section 303(d) list of impaired waters (Category 5 of the Integrated Report).

  • Category 5: The states Section 303(d) list of impaired waters. The waterbody is impaired and a total maximum daily load (TMDL) is needed.

  • WINOFI: As provided for in Iowa's credible data law, the Department is to maintain a separate list of waters that require further investigative monitoring. As specified in the credible data law, this list is not part of the Section 303(d)/impaired waters process in Iowa and includes waterbodies where limited information suggests, but does not conclusively (credibly) demonstrate, a water quality impairment. If the results of further investigative monitoring demonstrate, with data of sufficient quality and quantity, that a water quality impairment exists, the affected waterbody can be added to Iowa's Section 303(d) list.

  • Delistings: These waters are proposed for removal from Iowa's previous (2020) list of impaired waters. A rationale for each proposed delisting is provided.

[*Designated uses are beneficial uses applied to specific Iowa surface waters (streams, rivers, lakes, and wetlands) in the Iowa Water Quality Standards. Examples of beneficial uses are uses for primary contact recreation (for example, swimming-type uses), aquatic life protection, and as a source of water for a public water supply. Beneficial uses designated for Iowa's surface waters are protected by narrative and numeric water quality criteria. For a more detailed description of designated uses applied to Iowa surface waters, see pages 9 and 10 [Surface Water Quality Criteria, Designated Use Segments] of the Iowa Water Quality Standards. For a list of the Iowa surface waters and their respective designated uses, see Iowa's Surface Water Classification.]

Assessment Results

Healthy Waters

Healthy waters are those segments in Integrated Report Categories 1 and 2.

  • Category 1: All designated uses are met
  • Category 2: One or more designated uses are met, but there are insufficient data to determine if the remaining designated uses are met.

Waters In Need of Further Investigation (WINOFI)

As provided for in Iowa's Credible Data Law, the Department is to maintain a separate list of waters that require further investigative monitoring. This list is not part of the Section 303(d)/impaired waters process in Iowa and includes segments where limited information suggests, but does not conclusively (credibly) demonstrate, a water quality impairment. If the results of further investigative monitoring demonstrate, with data of sufficient quality and quantity, that a water quality impairment exists, the affected segment can be added to Iowa's Section 303(d) list.

Impaired Waters

Impaired waters are those segments in Integrated Report Categories 4 and 5.

  • Category 4: The segment is impaired but a TMDL is not required; the segment is not included on the state's section 303(d) list of impaired waters (Category 5 of the Integrated Report).
  • Category 5: Iowa's Section 303(d) List of Impaired Waters. The segment is impaired and a total maximum daily load (TMDL) is needed.

Not Assessed

The number of assessments the Iowa DNR can make in a given cycle are limited by budgets and staffing resources.

  • Category 3: Insufficient data to determine whether any designated uses are met.
Rivers and Streams
Lakes and Reservoirs
Wetlands

Summary Statistics

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Category 5 Impaired Waters List

Total number of impaired waterbody segments
597
Total number of impaired uses
785

Overall Integrated Report Categories

Category - Description Waterbody Segments
1 - All designated uses are met. 15
2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met. 321
3 - Insufficient data exist to determine whether any designated uses are met.
EPA Category 3 and WINOFIs

Iowa maintains a separate list, per the Credible Data Law, of segments with insufficient information (WINOFI). Because these segments do not have enough information to determine use support, EPA considers these "Not Assessed". Therefore, for the purpose of reporting the Integrated Report to EPA, these WINOFI segments are grouped into the EPA's Category 3.

For this cycle, there are a total of 295 WINOFI segments and 1235 "Not Assessed" segments.

1530
4 - Water is impaired or threatened and a TMDL has been completed or is not needed. 154
5 - Water is impaired or threatened and a TMDL is needed. 597
TMDL information and documentation for finalized TMDLs can be found at Iowa DNR Water Improvement Plans