Unnamed Tributary to Unnamed Tributary to Yellow River IA 01-YEL-6575

from mouth (T96N R7W Sec15) to headwaters (T96N R7W Sec21) Winneshiek Co.

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 2020 - 2022
Stream/River Water Quality Data	CY 2020 - 2022
Lake Water Quality Data	CY 2018 - 2022
Biological Sampling Data	CY 2018 - 2022*
Fish Kill Data	CY 2018 - 2022
Fish Tissue Sampling Data	CY 2018 - 2022
Continuous Dissolved Oxygen Sampling Data	CY 2018 - 2022
*Biological sites sampled in both 2017 and 2021 were also assessed.

Open Segment Map
View assessment methodology in new window

Cycle: 2024
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown
Created: 11/1/2023 8:14:01 AM
Updated: 1/30/2024 7:13:51 AM

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

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2014

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Watershed project monitoring

TMDL Priority

Tier III

Class BWW1

Presumptive Use

Aquatic Life - Warm Water Type 1

Fully Supported

Impairment Delistings

Cycle Added	Class	Cause	Data Source	Rationale
2014	Class A1	pH	Ambient monitoring: Iowa DNR-rivers	New data: WQ improvement (chemical / physical / bacterial)
2014	Class BWW1	pH	Ambient monitoring: Iowa DNR-rivers	New data: WQ improvement (chemical / physical / bacterial)

Documentation

Assessment Summary

The Class A1 use remains assessed as "not supported" due to levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The presumptive Class BWW1 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 2021-2022	15960038	Unnamed Tributary to Yellow River at 130th Ave (Site 6)

Presumptive Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples per Year (2021/2022)	2021 Geometric Mean	2022 Geometric Mean	Violates Annual Geometric Mean?	# 2021 SSM violations / SSM Violations needed for impairment	# 2022 SSM violations / SSM Violations needed for impairment	Violates Annual SSM Significantly >10% Rule?	Assessment Type	Support Level
15960038	6	4/6	589	235	YES	3 / NA	4 / NA	NA	Eval	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
15960038	6	10 / 2	7.85	8.21	8	0	3	NO	Mon	Full

Presumptive 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
15960038	6	Dissolved Oxygen	10 / 2	9.34	12.78	10.61	0	NA / NA	3	NO	Mon	Full
15960038	6	pH	10 / 2	7.85	8.21	8	0	NA / NA	3	NO	Mon	Full
15960038	6	Temperature	10 / 2	3.143	17.102	12.192	0	NA / NA	3	NO	Mon	Full

Monitoring and Methods

Assessment Key Dates

5/20/2021

Monitoring Start

10/18/2022

Monitoring End

Methods

200

Physical/Chemical Monitoring

420

Indicator bacteria monitoring