East Nodaway River IA 05-NOD-1391

mouth (S6 T67N R36W Page Co.) to confluence with Long Branch Cr at S17-18 line T70N R35W Taylor 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 3:09:47 PM
Updated: 1/13/2026 3:15:07 PM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2008

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

Biological: low fish & invert IBIs- cause unknown

Support Level

Not Supported

Impairment Code

5b-v - Biological - verified

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2020

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

TMDL Priority

Tier IV

Class HH

Human Health -

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use remains assessed as "not supported" due to levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "not supported" based on biological sampling data. 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 2014-16, CY 2022-2024	10730002	East Nodaway River near Clarinda
Iowa DNR	6	BIO	See Below	150	East Nodaway River	Hawleyville
Iowa DNR	6	BIO	See Below	1147	East Nodaway River	State Highway 2 bridge 2.5 mi E of Clarinda

Presumptive Class A1 - Indicator Bacteria: 2014-2016

Site ID	Data Source ID	# Samples / # Years	2014 Geo. Mean	2015 Geo. Mean	2016 Geo. Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
10730002	6	24 / 3	467	789	544	Yes	16	67%	Yes	Evaluated	Not

Presumptive 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
10730002	6	36 / 3	7.2	8.5	8	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
10730002	6	Chloride	36 / 3	12	26	18	NA	0 / 0	7	NO	MONITORED	FULL
10730002	6	Dissolved Oxygen	36 / 3	7.6	14.4	10.1	0	NA / NA	7	NO	MONITORED	FULL
10730002	6	pH	36 / 3	7.2	8.5	8	0	NA / NA	7	NO	MONITORED	FULL
10730002	6	Sulfate	36 / 3	12	84	38	0	NA / NA	7	NO	MONITORED	FULL
10730002	6	Temperature	36 / 3	0	27	13	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
10730002	6	Ammonia	36 / 3	0.86	0.06	0.02	0 / 0	NO	MONITORED	FULL
10730002	6	Cadmium	17 / 2	0.5	0.5	0.5	0 / 0	NO	MONITORED	FULL
10730002	6	Chromium	17 / 2	12	1.59	0.86	0 / 1	NO	MONITORED	FULL
10730002	6	Copper	18 / 2	19	4	2.4	0 / 1	NO	MONITORED	FULL
10730002	6	Lead	17 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10730002	6	Nickel	17 / 2	5.5	2.5	2.3	0 / 0	NO	MONITORED	FULL
10730002	6	Selenium	36 / 3	3	1	0.8	0 / 0	NO	MONITORED	FULL
10730002	6	Silver	17 / 2	1	1	1	0 / 0	NO	MONITORED	FULL
10730002	6	Zinc	17 / 2	5.3	0.9	0.5	0 / 0	NO	MONITORED	FULL

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47f BMIBI BIT	BMIBI Pass/Fail
150	9/12/22	298.0	47f	MO	Surber	57	Good	54	Pass
1147	7/19/21	311.0	47f	MO	Floating Art Sub	56	Good	54	Pass

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	47f FIBI BIT	FIBI Pass/Fail
150	9/12/22	298.0	47f	MO	NA	38	Fair	31	Pass
150	7/30/18	298.0	47f	MO	NA	28	Fair	31	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Monitored	Pass (2/2)	Full
Fish	Evaluated	Fail (1/2)	Not		Assessment was evaluated because the FIBI assessment was inconclusive
Overall	Evaluated	Fail	Not	5bv	and included a sample not collected in a recent 5-year period.

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
10730002	6	Copper	18 / 2	19	4	2.4	0	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
10730002	6	Selenium	12/12/12	0.875	1.083	0.917	7/5/6	FS/FS/FS	MONITORED	FULL

Monitoring and Methods

Assessment Key Dates

1/7/2014

Monitoring Start

12/6/2016

Monitoring End

9/12/2022

Biological Monitoring

1/10/2022

Monitoring Start

12/3/2024

Monitoring End

7/19/2021

Biological Monitoring

7/30/2018

Biological Monitoring

Methods

150

Monitoring data more than 5 years old

200

Physical/Chemical Monitoring

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys

420

Indicator bacteria monitoring