Missouri River IA 06-WEM-1707

from the Iowa/Missouri state line (Fremont Co.) to confluence with Platte R. west of Glenwood in Mills Co.

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 2020 - 2022
Stream/River Water Quality Data	CY 2020 - 2022
Lake Water Quality Data	CY 2018 - 2022
Biological Sampling Data	CY 2018 - 2022*
Fish Kill Data	CY 2018 - 2022
Fish Tissue Sampling Data	CY 2018 - 2022
Continuous Dissolved Oxygen Sampling Data	CY 2018 - 2022
*Biological sites sampled in both 2017 and 2021 were also assessed.

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Cycle: 2024
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 11/1/2023 8:13:14 AM
Updated: 1/12/2024 7:51:29 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

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

Flow Alteration

Support Level

Not Supported

Impairment Code

4c - Non-pollutant caused impairment. No TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Hydromodification: Flow Regulation/Modification

Source Confidence

Moderate

Cycle Added

2002

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Ambient monitoring: adjacent state

Habitat Alterations: Other

Support Level

Not Supported

Impairment Code

4c - Non-pollutant caused impairment. No TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Hydromodification: Channelization

Source Confidence

Moderate

Cycle Added

2002

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Ambient monitoring: adjacent state

Class HH

Human Health -

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use remains assessed as "not supported" due to high levels of indicator bacteria (E. coli) that exceeded state water quality criteria. 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. The Class HH (fish consumption) use was assessed as "fully supported" based on fish tissue sampling data.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
USACE	12	WQ	CY 2020-2022	99990118	Missouri River
USGS	11	WQ	CY 2020-2022	06807000	Missouri River at Nebraska City, NE
Iowa DNR	6	FT	See Below	1149	Missouri River at Nebraska City, NE

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2020/ 2021/2022)

2020 Geometric Mean

2021 Geometric Mean

2022 Geometric Mean

Violates Annual Geometric Mean?

# 2020 SSM violations / SSM Violations needed for impairment

# 2021 SSM violations / SSM Violations needed for impairment

# 2022 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

99990118

7/8/7

137

130

356

YES

2 / 3

4 / 3

YES

Mon

Not

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 A1 – pH:

Site ID	Data Source ID	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
99990118	12	35 / 3	6.6	8.7	8	0	7	NO	Mon	Full

Class BWW1 - Binomial Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	# Acute / Chronic Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
99990118	12	Chloride	36 / 3	15	43	26	NA	0 / 0	7	NO	Mon	Full
99990118	12	Dissolved Oxygen	36 / 3	6	14.28	10.48	0	NA / NA	7	NO	Mon	Full
99990118	12	pH	35 / 3	6.6	8.7	8	0	NA / NA	7	NO	Mon	Full
99990118	12	Sulfate	36 / 3	155	262	204	0	NA / NA	7	NO	Mon	Full
99990118	12	Temperature	36 / 3	0	28.97	13.07	0	NA / NA	7	NO	Mon	Full
06807000	11	Temperature	177 / 3	-0.1	30.5	16.72	0	NA / NA	24	NO	Mon	Full

Class BWW1 - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
99990118	12	Ammonia	34 / 3	0.49	0.13	0.09	0 / 0	NO	Mon	Full
99990118	12	Selenium	12 / 3	4	3	3	0 / 0	NO	Mon	Full

Class BWW1 – Historical Assessment:

The Class BWW1 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). The assessment was developed

in consultation with the Nebraska Missouri River fisheries biologist.

Class HH-F - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples per Year (2020/ 2021/2022)	2020 Mean	2021 Mean	2022 Mean	# Non-Detects per Year (2020/ 2021/2022)	Support Level per Year (2020/ 2021/2022)	Assessment Type	Support Level
99990118	12	Mercury	4/4/4	0.004	0.021	0.003	2/1/3	Full/Full/Full	Mon	Full
99990118	12	Selenium	4/4/4	3.5	3	2.5	0/0/0	Full/Full/Full	Mon	Full

Class HH - Fish Tissue Sampling:

Site ID	Biopart	Year	Species	# in sample / # of samples	Avg Length (cm)	(Avg) Hg (ppm)	Chlordane (ppm)	Sum PCBs (ppm)
1149	fillet	2015	common carp	3	50.6	0.11	0.02	0.06
1149	tissue plug	2015	flathead catfish	5	38.1	0.062
Support Level	Full

Monitoring and Methods

Assessment Key Dates

1/8/2020

Monitoring Start

12/12/2022

Monitoring End

8/19/2015

Fish Tissue Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

260

Fish tissue analysis

860

Other Agencies/Organizations provided monitoring data