2020 assessment for Des Moines River

Des Moines River IA 04-LDM-1011

from Ottumwa dam (S24 T72N R14W Wapello Co.) to confluence with Cedar Cr in S33 T75N R17W Mahaska Co.

2020
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 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 were also assessed.

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Overall IR

2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.

Trend

Unknown

Created

6/9/2020 1:19:50 PM by

Updated

10/6/2026 10:18:43 AM by

Use Support

Class A1

Recreation - Primary contact

Fully Supported

Class BWW1

Aquatic Life - Warm Water Type 1

WINOFI

Biological: low aquatic macroinvertebrate IBI

Support Level

Further Investigation Needed

Impairment Code

3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.

Cause Magnitude

Slight

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2014

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

Fish Kill: Cause Unknown

Support Level

Further Investigation Needed

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Moderate

303(d) Listing Status

Continuing

Source

Hydromodification: Low Flow

Source Confidence

Moderate

Cycle Added

2018

Impairment Rationale

Non Pollutant-caused fish kill

Data Source

Fish kill investigation: Iowa DNR

Class C

Drinking Water -

Fully Supported

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

303(d) Delistings for this Cycle

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use remains assessed as “fully supported” based on water quality monitoring data. The Class BWW1 use was assessed as "partially supported” based on biological sampling data and based on the results of a fish kill investigation. The Class C use remains assessed as "fully supported" based on water quality monitoring data. All other designated uses were "not assessed". Note: The Site ID for the data tables in the Assessment Explanation sections Class A1, BWW1, and Class C have all been updated to Site ID 10900003. From 2020 IR to 2024 IR, DNR inadvertently put Site IDs 10900002 and 10620001 in the data tables. The results for Site ID #10900003 were correctly assessed in the data tables for this segment from 2020-2024; however, the sites in the site ID column were incorrect. This update occurred on 10-6-2026.

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2012-2014	10900003	Des Moines River US of Ottumwa at Co Rd T67 Bridge at Chillicothe
Iowa DNR	6	BIO	See Below	955	Des Moines River – Ottumwa - US
Iowa DNR	6	BIO	See Below	1156	Des Moines River – Chillicothe REMAP #454

Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2012 Geometric Mean	2013 Geometric Mean	2014 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10900002	6	22 / 3	86	40	100	No	3	14%	No	Evaluated	Full

Class A1 - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10900002	6	33 / 3	8.7	8.2	8.2	0	0%	No	Evaluated	Full

Class BWW1 - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	Significantly >10% Violations	Assessment Type	Support Level
10900002	6	Ammonia	33 / 3	0.45	0.1	0.05	0 / 0	0% / 0%	No	Evaluated	Full
10900002	6	Chloride	33 / 3	91	49	43	0 / 0	0% / 0%	No	Evaluated	Full
10900002	6	Dissolved oxygen	33 / 3	17	10.6	10.1	NA / 0	NA / 0%	No	Evaluated	Full
10900002	6	pH	33 / 3	8.7	8.2	8.2	0 / NA	0% / NA	No	Evaluated	Full
10900002	6	Sulfate	33 / 3	130	78	82	0 / NA	0% / NA	No	Evaluated	Full
10900002	6	Temperature	33 / 3	29.1	12.8	11.8	0 / 0	0% / 0%	No	Evaluated	Full

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	BM Sample Gear	BMIBI score	BMIBI Class	BMIBI BIT	BMIBI Pass/ Fail
1156	8/22/17	13200	40a	MS/WW	Float ArtSub	64	Good	41	Pass
955	10/8/12	13257	47f	MS/WW	ArtSub	15	Poor	51	Fail

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/Thermal	Riffle Stream?	FIBI score	FIBI Class	40a FIBI BIT	FIBI Pass/ Fail
1156	8/22/17	13200	40a	MS/WW	NA	32	Fair	33	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	Earned IR Category	Actual IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (1/2)	Partial
Fish	Evaluated	Pass (1/1)	Full			FIBI passed with 7 point FIBI UAV applied to single samples.
Overall	Evaluated	Fail	Partial	3bu	3bu	Assessment is evaluated because the drainage areas of the sample sites were larger than the calibrated range.

Class BWW1 – Fishkill Assessment:

The Class BWW1 use assessment based on the 2017 fish kill placed this segment in Category 3b. Because the cause of the fish kill was not identified, or the fish kill was attributed to a non-pollutant cause (e.g., winterkill), the assessment type is “evaluated.” Segments assessed using “evaluated” assessments are placed in Category 3b and are added to the state list of waters in need of further investigation. If no additional fish kills are reported in the segment for a 10 year period (2027), the Category will be changed from 3b to 3a (water not assessed).

Details about the 2016 fish kill can be found here:https://programs.iowadnr.gov/fishkill/Events/944

Class C - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10620001	6	Chloride	33 / 3	91	49	43	0	0%	No	Evaluated	Full
10620001	6	Inorganic nitrogen (nitrate and nitrite)	33 / 3	14	4	3.4	2	6%	No	Evaluated	Full

Class C - 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
10620001	6	Alachlor	32 / 3	0.1	0.04	0.025	NA	No	Evaluated	Full
10620001	6	Atrazine	26 / 3	2	0.43	0.2	NA	No	Evaluated	Full
10620001	6	Carbofuran	26 / 3	0.1	0.1	0.1	NA	No	Evaluated	Full
10620001	6	Cyanazine	26 / 3	0.1	0.1	0.1	NA	No	Evaluated	Full

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

10/8/2012

Biological Monitoring

1/5/2012

Fixed Monitoring Start Date

9/14/2014

Fixed Monitoring End Date

8/4/2017

Fish Kill

8/22/2017

Biological Monitoring

Methods

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

230

Fixed station physical/chemical (conventional plus toxic pollutants)

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring