Iowa DNR

Water Quality Assessments

Impaired Waters List

ADBNet Documentation

Presumptive Use Designations

Due to changes in the Iowa Water Quality Standards that became effective at the state level in March 2006, all perennially-flowing streams and intermittent streams with perennial pools are now presumed to be capable to supporting the highest level of primary contact recreation use (Class A1) and the highest level of aquatic life use (Class B(WW1)).

These changes to the Iowa Water Quality Standards were approved by U.S. EPA in February 2008. A “use attainability analysis” or UAA must be conducted, including field investigations, to determine whether a presumptively-applied use is, in fact, the appropriate designated use for the stream segment in question. In order to keep impairments of presumptive designated uses separate from impairments of appropriate designated uses, DNR created IR Subcategory 5p. Impairments that occur on a waterbody presumptively designated for Class A1 primary contact recreation use or Class B(WW1) aquatic life use will be placed in this state-defined subcategory. Following completion of a UAA and the application and approval of the appropriate designated uses, the 5p impairments will be re-assessed using the applicable water quality criteria and will be moved to the appropriate category or subcategory of Iowa’s future Integrated Reports.

This page was created 3/23/2021 1:51:03 PM and was last updated 11/17/2021 12:20:18 PM