Iowa River IA 02-IOW-622

from south corporate limit of Wapello (S35 T74N R3W Louisa Co.) to Long Cr (S1 T74N R4W Louisa 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: 2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
Trend: Stable
Created: 10/27/2025 3:09:42 PM
Updated: 1/12/2026 11:44:46 AM

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

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2010

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Class HH

Human Health -

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed as “fully supported” based on E. coli and pH sampling data. The Class BWW1 use was assessed as "WINOFI" based on biological sampling data. The Class HH (fish consumption) use was assessed as "fully supported" based on fish tissue sampling data and water quality monitoring data. Note: A TMDL covering the bacteria impairments for all segments, with the segment code prefix "IA 02-IOW" in the Iowa River Basin, was approved by EPA in 2018.

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	10580003	Iowa River at Wapello
USGS	11	WQ	CY 2022-2024	5465500	Iowa River at Wapello, IA
Iowa DNR	6	BIO	See Below	337	Iowa River	Wapello (REMAP #45)
Iowa DNR	6	BIO	See Below	939	Iowa River	Wapello
Iowa DNR	6	FT	See Below	1167	Iowa River	E of Wapello

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

10580003

8/8/8

2 / 3

0 / 3

2 / 3

MONITORED

FULL

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
10580003	6	35 / 3	7.5	9.3	8.5	5	7	NO	MONITORED	FULL
5465500	11	40 / 3	7.8	9	8.2	0	7	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
10580003	6	Chloride	36 / 3	15	60	40	NA	0 / 0	7	NO	MONITORED	FULL
5465500	11	Chloride	40 / 3	15.3	57.4	35.5	NA	0 / 0	7	NO	MONITORED	FULL
10580003	6	Dissolved Oxygen	36 / 3	7	14.7	11.2	0	NA / NA	7	NO	MONITORED	FULL
5465500	11	Dissolved Oxygen	40 / 3	6.8	15.2	10.5	0	NA / NA	7	NO	MONITORED	FULL
10580003	6	pH	35 / 3	7.5	9.3	8.5	5	NA / NA	7	NO	MONITORED	FULL
5465500	11	pH	40 / 3	7.8	9	8.2	0	NA / NA	7	NO	MONITORED	FULL
10580003	6	Sulfate	36 / 3	15	52	35	0	NA / NA	7	NO	MONITORED	FULL
5465500	11	Sulfate	40 / 3	13.6	57.2	32.2	0	NA / NA	7	NO	MONITORED	FULL
10580003	6	Temperature	36 / 3	0.1	26.7	13.2	0	NA / NA	7	NO	MONITORED	FULL
5465500	11	Temperature	40 / 3	0	30.2	16.2	0	NA / NA	7	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
10580003	6	Ammonia	35 / 3	0.55	0.09	0.02	0 / 0	NO	MONITORED	FULL
10580003	6	Cadmium	18 / 2	0.5	0.5	0.5	0 / 0	NO	MONITORED	FULL
10580003	6	Chromium	18 / 2	11	1.9	0.99	0 / 0	NO	MONITORED	FULL
10580003	6	Copper	18 / 2	4	2	2	0 / 0	NO	MONITORED	FULL
10580003	6	Lead	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10580003	6	Nickel	18 / 2	2.1	1.4	1.4	0 / 0	NO	MONITORED	FULL
10580003	6	Selenium	36 / 3	2	0.9	0.8	0 / 0	NO	MONITORED	FULL
10580003	6	Silver	18 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10580003	6	Zinc	18 / 2	5	1.2	0.5	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	72d BMIBI BIT	BMIBI Pass/Fail
939	9/15/21	12499.0	72d	MS	Floating Art Sub	37	Fair	51	Fail
337	9/16/19	12490.1	72d	MS	Floating Art Sub	22	Poor	51	Fail

Fish:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	72d FIBI BIT	FIBI Pass/Fail
337	9/16/19	12490	72d	MS	NA	43	Fair	36	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (0/2)	WINOFI
Fish	Evaluated	Pass (1/1)	Full		Assessment was evaluated because the drainage areas of
Overall	Evaluated	Fail	WINOFI	3bu	the sample sites were greater than the calibrated range.

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)
1167	fillet	2024	common carp	3	55.7	0.11	<0.05	J0.0297
1167	whole	2024	common carp	3	53.1	0.068	<0.05	0.0832
Support Level	Full

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
10580003	6	Copper	18 / 2	4	2	2	2	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
10580003	6	Selenium	12/12/12	1.083	0.625	1.033	4/9/5	FS/FS/FS	MONITORED	FULL

Monitoring and Methods

Assessment Key Dates

1/10/2022

Monitoring Start

12/11/2024

Monitoring End

9/16/2019

Biological Monitoring

3/9/2018

TMDL Completed

9/15/2021

Biological Monitoring

9/12/2024

Fish Tissue Monitoring

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

260

Fish tissue analysis

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring

860

Other Agencies/Organizations provided monitoring data