Missouri River IA 06-WEM-1721

from confluence with Elm Cr. (S18 T83N R46W Monona Co. at river mile 691.0 at Decatur NE.) to confluence with Omaha Creek Ditch east of Homer NE at river mile 715.8 (=SW 1/4 S6 T86N R47W Woodbury Co. (near Browns Lake)).

Open Data Collection Period Modal

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2014 - 2016
Stream/River Water Quality Data	CY 2014 - 2016
Lake Water Quality Data	CY 2012 - 2016
Biological Sampling Data	CY 2012 - 2016*
Fish Kill Data	CY 2012 - 2016
Fish Tissue Sampling Data	CY 2012 - 2016
Continuous Dissolved Oxygen Sampling Data	CY 2012 - 2016
*Biological sites sampled in both 2011 and 2015 were also assessed.

Open Segment Map
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Cycle: 2018
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 7/30/2019 9:31:49 AM
Updated: 7/30/2019 9:32:39 AM

Use Support

Class A1

Recreation - Primary contact

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially 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

Partially Supported

Flow Alteration: Hydrologic Modification

Support Level

Partially 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

Habitat Alterations: Channel Modifications

Support Level

Partially 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

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 (primary contact recreation) uses are assessed (monitored) as "partially supported" based on the bacterial impairment of recreation uses identified by the Nebraska Department of Environmental Quality. The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially supported" based on information from local fisheries biologists on impacts related to flow modification and habitat alterations in this segment of the Missouri River. The human health/fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring in this river segment. The source of information for this assessment remains information from Nebraska fisheries biologists on habitat conditions in the Missouri River.

Assessment Explanation

The Class A1 (primary contact recreation) uses are assessed as "partially supporting" based on the bacterial impairment identifiedforthis assessment segment by the state of Nebraska. A TMDL forthe Nebraskaimpairmentin this segment of theMissouriRiver was approved by EPA in 2007. Because Iowa DNR did not participate in the preparation of this TMDL, this impairmentis appropriate forCategory 5a of Iowa's Integrated Report.

The Class B(WW1) aquatic life uses remain assessed (evaluated) as "partially 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.

Fish consumption uses remain “not assessed” due to the lack of recent fish contaminant monitoring in this river segment.

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

375

Qualitative physical habitat assessment

420

Indicator bacteria monitoring