Yellow River IA 01-YEL-437

from N. Fk. Yellow R. (S13 T96N R7W Allamakee Co.) to confluence with unnamed tributary in SE 1/4 S8 T96N R7W Winneshiek 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 3:09:32 PM
Updated: 1/12/2026 9:45:28 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

4a - Pollutant-caused impairment. TMDL has been completed.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2008

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Special project/study: Iowa DNR

Class BWW2

Aquatic Life - Warm Water Type 2

Not Supported

Biological: low fish IBI

Support Level

Not Supported

Impairment Code

5b-t - Biological - tentative

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2004

Impairment Rationale

Low Biotic Index

Data Source

Biological monitoring: Iowa DNR WQMA

TMDL Priority

Tier IV

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use was assessed as “not supported” due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BWW2 use was assessed as “not supported” based on biological sampling data. Note: A TMDL for the bacterial impairment for Yellow River basin streams was prepared by Iowa DNR in 2012 and was approved by U.S. EPA in February 2013. Due to TMDL completion, the Integrated Report category for the presumptive Class A1 recreational use was changed from 5p to 4a. The TMDL did not address the aquatic life use impairment; therefore, the Class BWW2 Category 5 impairment remains.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY2014 & CY2022	11960006	Yellow River near Castalia (Site YeRi3)
Iowa DNR	6	WQ	CY2014	15960002	Yellow River at 107 Ave
Iowa DNR	6	BIO	See Below	156	Yellow River	Site 1 – Most Upstream Site
Iowa DNR	6	BIO	See Below	1124	Yellow River	Corner of 120 Ave and 111 Ave

Presumptive Class A1 - Indicator Bacteria: 2014

Site ID	Data Source ID	# Samples / # Years	2014 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
11960006	6	20 / 1	601	Yes	15	75%	Yes	Evaluated	Not
15960002	6	20 / 1	1661	Yes	17	85%	Yes	Evaluated	Not

Presumptive Class A1 – pH: 2022

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
11960006	6	6 / 1	7.89	8.11	8	0	3	NO	EVALUATED	FULL

Class BWW2 - Binomial Parameters: 2022

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
11960006	6	Dissolved Oxygen	6 / 1	9.48	12.61	10.7	0	NA / NA	3	NO	EVALUATED	FULL
11960006	6	pH	6 / 1	7.89	8.11	8	0	NA / NA	3	NO	EVALUATED	FULL
11960006	6	Temperature	6 / 1	6.091	16.076	12.975	0	NA / NA	3	NO	EVALUATED	FULL

Class BWW2 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	52b BMIBI BIT	BMIBI Pass/Fail
156	9/26/22	18.7	52b	MS/WW	Hess	55	Fair	61	Fail
1124	9/26/22	14.6	52b	MS/WW	Hess	60	Good	61	Fail

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	52b FIBI BIT	FIBI Pass/Fail
156	9/26/22	18.7	52b	MS/WW	NA	58	Good	52	Pass
1124	9/27/22	14.6	52b	MS/WW	NA	59	Good	52	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (0/2)	Not
Fish	Evaluated	Pass (2/2)	Full		Assessment was evaluated because the samples included
Overall	Evaluated	Fail	Not	5bt	in the assessment were collected in the same year.

Monitoring and Methods

Assessment Key Dates

9/26/2022

Biological Monitoring

4/24/2014

Monitoring Start

10/8/2014

Monitoring End

9/27/2022

Biological Monitoring

2/1/2013

TMDL Completed

4/20/2022

Monitoring Start

9/12/2022

Monitoring End

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