Iowa DNR

Water Quality Assessments

Impaired Waters List

2008 305(b) Assessment Summary

Legacy Assessment Summary

Beginning with the 2016 assessment cycle, the format of assessments was changed from assessing the overall status of a waterbody segment to a more detailed assessment of individual use attainment for each segment. This change implemented US EPA's guidelines for assessments and required a change in database structure to support the new assessment methodology. These pre-2016 assessments are referred to as "Legacy Assessments", and their format is preserved as that was the official submission for those Integrated Reports. Assessments for the 2016 and later use the current EPA guidelines.

Due to this change in assessment format, summary information for legacy assessment cycles is limited.

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

Summary Statistics

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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. 352
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 199 WINOFI segments and 1029 "Not Assessed" segments.

4 - Water is impaired or threatened and a TMDL has been completed or is not needed. 107
5 - Water is impaired or threatened and a TMDL is needed. 435