Iowa DNR

Water Quality Assessments

Impaired Waters List

Ioway Creek IA 03-SSK-6459

from unnamed tributary (T85N R25W Sec9 NW Boone Co.) to headwaters (T87N R26W Sec34 Hamilton Co.)

Assessment Cycle
Release Status
Data Collection Period
Overall IR Category
3 - Insufficient data exist to determine whether any designated uses are met.
6/9/2020 1:41:57 PM
10/15/2020 9:34:10 AM
Assessment conducted in accordance with Iowa's 2020 IR methodology
Use Support
Class A1
Not Assessed
Class BWW1
Fish Kill: Caused By Animal Waste
Support Level
Water in Need of Further Investigation (WINOFI)
Impairment Code
3b - Use potentially impaired based on an evaluated assessment.
Cause Magnitude
Agriculture: Animal Feeding Operations
Source Confidence
Cycle Added
Impairment Rationale
Pollutant-caused fish kill
Data Source
Fish kill investigation: Iowa DNR
General Use
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Assessment Summary

The presumptive Class BWW1 use remains assessed as "partially supported" due to a fish kill investigation. All other designated uses were "not assessed". 

Assessment Explanation

Presumptive Class A1 - No Data

Presumptive Class BWW1 - Fish kill Assessment:

The presumptive Class BWW1 aquatic life use previously resided in Category 4d based on the assessment developed for the 2011 fish kill. Because no additional fish kills were reported in this segment for at least five years post fish kill (2016), the Category for the fish kill assessment was changed from 4d to 3b (potentially impaired). DNR believes that any impact from the fish kill from which the impairment was based has likely dissipated. If no additional fish kills are reported in the segment for an additional five-year period (2021), the Category will be changed from 3b to 3a (water not assessed).

Details about the 2011 fish kill can be found here:

Monitoring and Methods
Assessment Key Dates
8/20/2011 Fish Kill
120 Surveys of fish and game biologists/other professionals
140 Incidence of spills and/or fish kills
150 Monitoring data more than 5 years old