Des Moines River IA 04-LDM-1004

from confluence with Indian Cr. (S35 T68N R8W Van Buren Co.) to confluence with Chequest Cr. in S27 T69N R10W Van Buren Co.

This is a DRAFT assessment

Draft assessments may change without notice

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 2022 - 2024
Stream/River Water Quality Data	CY 2022 - 2024
Lake Water Quality Data	CY 2020 - 2024
Biological Sampling Data	CY 2020 - 2024*
Fish Kill Data	CY 2020 - 2024
Fish Tissue Sampling Data	CY 2020 - 2024
Continuous Dissolved Oxygen Sampling Data	CY 2020 - 2024
*Biological sites sampled in both 2019 and 2023 were also assessed.

Open Segment Map
View 2026 assessment summary page

Cycle: 2026
Current Phase: Public Comment
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Stable
Created: 10/27/2025 3:09:44 PM
Updated: 1/26/2026 6:20:21 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

Low

Cycle Added

2020

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: Iowa DNR-rivers

TMDL Priority

Tier III

Class BWW1

Aquatic Life - Warm Water Type 1

Not Supported

Fish Kill: Due To Unknown Toxicity

Support Level

Not Supported

Impairment Code

5b - Biological impairment or pollutant-caused fish kill - unknown source. No administrative action.

Cause Magnitude

High

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Pollutant-caused fish kill

Data Source

Fish kill investigation: Iowa DNR

TMDL Priority

Tier IV

Class HH

Human Health -

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as "not supported" based on levels of indicator bacteria that exceeded state water quality criteria. The Class BWW1 use remains assessed as “not supported” based on fish kills in and upstream from this segment. The Class HH use was assessed as "fully supported" based on water quality monitoring data.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2022-2024	10890001	Des Moines River at Keosauqua
USGS	11	WQ	CY 2022-2024	5490500	Des Moines River at Keosauqua, IA
Iowa DNR	6	BIO	See Below	946	Des Moines River	Keosauqua
Iowa DNR	6	BIO	See Below	1258	Des Moines River	Bonaparte (REMAP #414)

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2022/ 2023/2024)

2022 Geometric Mean

2023 Geometric Mean

2024 Geometric Mean

Violates Annual Geometric Mean?

# 2022 SSM violations / SSM Violations needed for impairment

# 2023 SSM violations / SSM Violations needed for impairment

# 2024 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

10890001

8/8/8

135

182

YES

3 / 3

0 / 3

3 / 3

YES

MONITORED

NOT

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
10890001	6	35 / 3	7.5	9.6	8.5	2	7	NO	MONITORED	FULL
5490500	11	41 / 3	7.8	9.4	8.3	2	8	NO	MONITORED	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
10890001	6	Chloride	36 / 3	19	79	45	NA	0 / 0	7	NO	MONITORED	FULL
5490500	11	Chloride	40 / 3	20	88.7	41.8	NA	0 / 0	7	NO	MONITORED	FULL
10890001	6	Dissolved Oxygen	36 / 3	6.9	17.5	12	0	NA / NA	7	NO	MONITORED	FULL
5490500	11	Dissolved Oxygen	41 / 3	7.2	22.8	11.5	0	NA / NA	8	NO	MONITORED	FULL
10890001	6	pH	35 / 3	7.5	9.6	8.5	2	NA / NA	7	NO	MONITORED	FULL
5490500	11	pH	41 / 3	7.8	9.4	8.3	2	NA / NA	8	NO	MONITORED	FULL
10890001	6	Sulfate	36 / 3	34	120	71	0	NA / NA	7	NO	MONITORED	FULL
5490500	11	Sulfate	40 / 3	0.48	112	63.95	0	NA / NA	7	NO	MONITORED	FULL
10890001	6	Temperature	36 / 3	0	30.3	13.6	0	NA / NA	7	NO	MONITORED	FULL
5490500	11	Temperature	41 / 3	0.7	30.7	16.3	0	NA / NA	8	NO	MONITORED	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
10890001	6	Ammonia	35 / 3	0.54	0.05	0.02	0 / 0	NO	MONITORED	FULL
10890001	6	Cadmium	18 / 2	0.5	0.5	0.5	0 / 0	NO	MONITORED	FULL
10890001	6	Chromium	18 / 2	5	1.31	0.82	0 / 0	NO	MONITORED	FULL
10890001	6	Copper	18 / 2	3.2	2	2	0 / 0	NO	MONITORED	FULL
10890001	6	Lead	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10890001	6	Nickel	18 / 2	3.9	2.7	2.5	0 / 0	NO	MONITORED	FULL
10890001	6	Selenium	36 / 3	2.9	1.3	1.1	0 / 0	NO	MONITORED	FULL
10890001	6	Silver	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10890001	6	Zinc	18 / 2	9.4	1.7	0.8	0 / 0	NO	MONITORED	FULL

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	40a BMIBI BIT	BMIBI Pass/Fail
946	10/9/24	14038	40a	MS	Hess	56	Good	41	Pass
946	7/27/20	14038	40a	MS	Floating Art Sub	60	Good	41	Pass
1258	7/27/20	14100	40a	MS	Hess	58	Good	41	Pass

Fish:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	40a FIBI BIT	FIBI Pass/Fail
1258	7/28/20	14100	40a	MS	NA	30	Fair	33	Pass*

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Pass (3/3)	Full		*The FIBI score passed after the 7 point UAV was applied to single sample.
Fish	Evaluated	Pass (1/1)	Full		The assessment was evaluated because the drainage areas of the sites were
Overall	Evaluated	Pass	Full	1	greater than the calibrated range.

Class BWW1 – Fishkill Assessment:

The Class BWW1 aquatic life use remains assessed as “not supported” due to 2012, 2023, and 2024 fish kills. These kills are in a series of kills that have occurred over the last 25 years that appear to involve primarily shovelnose sturgeon (Scaphirhynchus platorynchus). Although the cause(s) of the fish kills remains unknown, low flow conditions, flow alterations, and very high water temperatures are believed to have contributed to the kills. Other possible causes include: elevated pH levels caused ambient levels of ammonia in the river toxic to the ammonia-intolerant shovelnose sturgeon and the kills were caused by a virus specific to shovelnose sturgeon.

The aquatic life use was placed in Category 5b based on the best professional judgement of the IR and DNR fisheries staff responsible for this region of the river and because there were multiple fish kills in this segment in the last five years. DNR believes that: (1) the repeated occurrence of these kills over the last 25 years from the Ottumwa dam to the Mississippi River, (2) the large numbers of sturgeon killed (thousands), and (3) the likelihood that these fish kills could be addressed by a TMDL provide overwhelming evidence that this impairment should reside in IR Category 5b and on the Impaired Waters List.

Due to uncertainty regarding the recovery of the aquatic life following fish kills, any existing fish kill 5b impairment will remain in Category 5b until more recent sampling has shown recovery of the aquatic community, the responsible party has paid restitution for all the historic fish kills, or a TMDL has been completed addressing the impairment.

Details about the 2012 fish kill can be found here: https://programs.iowadnr.gov/fishkill/Events/867

Details about the 2023 fish kill can be found here: https://programs.iowadnr.gov/fishkill/Events/1046

Details about the 2024 fish kill can be found here: https://programs.iowadnr.gov/fishkill/Events/1060

Class HH-F - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	Number of Non - Detects	Mean Value > Criterion or MCL	Assessment Type	Support Level
10890001	6	Copper	18 / 2	3.2	2	2	1	NO	MONITORED	FULL
Site ID	Data Source ID	Parameter Name	# Samples per Year (2022/ 2023/2024)	2022 Mean	2023 Mean	2024 Mean	# Non-Detects per Year (2022/ 2023/2024)	Support Level per Year (2022/ 2023/2024)	Assessment Type	Support Level
10890001	6	Selenium	12/12/12	1.25	1.175	1.408	4/6/3	FS/FS/FS	MONITORED	FULL

Monitoring and Methods

Assessment Key Dates

7/10/2006

Fish Kill

7/12/2012

Fish Kill

1/4/2022

Monitoring Start

12/10/2024

Monitoring End

7/27/2020

Biological Monitoring

7/28/2020

Biological Monitoring

10/9/2024

Biological Monitoring

7/10/2023

Fish Kill

8/28/2024

Fish Kill

Methods

140

Incidence of spills and/or fish kills

200

Physical/Chemical Monitoring

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring