Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Missouri River IA 06-WEM-1720

from confluence with Little Sioux R. (Harrison Co.) to confluence with Elm Cr. at river mile 691.0 at Decatur NE (=S18 T83N R46W Monona Co.).

Cycle
2024
Release Status
Final
Overall IR
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Unknown
Created
11/1/2023 8:13:45 AM
Updated
1/31/2024 2:03:59 PM
Use Support
Class A1
Recreation - Primary contact
Not Supported
Support Level
Not Supported
Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
Moderate
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2016
Impairment Rationale
Listing by adjacent state
Data Source
Ambient monitoring: adjacent state
TMDL Priority
Tier III
Class BWW1
Aquatic Life - Warm Water Type 1
Not Supported
Support Level
Not Supported
Impairment Code
4c - Non-pollutant caused impairment. No TMDL needed.
Cause Magnitude
Moderate
Status
Continuing
Source
Hydromodification: Dam Release
Source Confidence
Moderate
Cycle Added
1992
Impairment Rationale
Adverse impacts on plant/animal communities
Data Source
Special project/study
Support Level
Not Supported
Impairment Code
4c - Non-pollutant caused impairment. No TMDL needed.
Cause Magnitude
Moderate
Status
Continuing
Source
Hydromodification: Habitat Modification
Source Confidence
Moderate
Cycle Added
1992
Impairment Rationale
Adverse impacts on plant/animal communities
Data Source
Special project/study
Class HH
Human Health -
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 use remains assessed as "not supported" based on the bacteria impairment of recreational use identified by the Nebraska Department of Environmental Quality. The Class BWW1 use remains assessed as "not supported" based on information from local fisheries biologists on impacts related to flow modification and habitat alterations in this segment of the Missouri River. All other designated uses are “not assessed.”

Assessment Explanation

Class A1: Historical Assessment

The Class A1 primary contact recreation use remains assessed as "not supported" based on the bacteria impairment identified for this assessment segment by the state of Nebraska. A TMDL for the Nebraska impairment in this segment of the Missouri River was approved by EPA in 2007. Because Iowa DNR did not participate in the preparation of this TMDL, this impairment is appropriate for Category 5a of Iowa's Integrated Report.

Class BWW1: Historical Assessment

The Class BWW1 aquatic life use remains assessed as "not supported" (IR Category 4c, non-pollutant stressor) based on the assessment developed for the 1998, 2000, and 2002 reports (i.e., habitat alterations and flow modifications that resulted from development of the river for navigation uses in the mid-Twentieth Century). This assessment was developed in consultation with the Missouri River fisheries biologist for the state of Nebraska.

Class HH - No Data

Monitoring and Methods
Assessment Key Dates

None listed

Methods
120
Surveys of fish and game biologists/other professionals
150
Monitoring data more than 5 years old
860
Other Agencies/Organizations provided monitoring data