Dry Branch IA 01-TRK-2002

confluence with unnamed tributary in the N 1/2 S4 T95N R8W Fayette Co. to headwaters in SW1/4 S33 T97N R8W Winneshiek Co.

Assessment Cycle

2024

Release Status

Final

Data Collection Period

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.

Overall IR Category: 5 - Water is impaired or threatened and a TMDL is needed.
Trend: Unknown

Created: 11/1/2023 8:14:11 AM
Updated: 1/22/2024 1:36:45 PM

Assessment conducted in accordance with Iowa's 2024 IR methodology

Use Support

Class A1

Recreation

Primary contact

Presumptive Use

Not Supported

Impairments

Support Level

Not Supported

Impairment Code

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

Cause Magnitude

High

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

Aquatic Life

Warm Water Type 1

Presumptive Use

WINOFI

Further Investigation Needed

Support Level

Water in Need of Further Investigation (WINOFI)

Impairment Code

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

Cause Magnitude

Moderate

Status

New

Source

Agriculture: Subsurface Drainage

Source Confidence

Low

Cycle Added

2024

Impairment Rationale

Potential Impairment

Data Source

Fish kill investigation: Iowa DNR

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The presumptive Class A1 use remains assessed as “not supported” due to violations of Iowa water quality criteria for indicator bacteria (E. coli). The presumptive Class BWW1 use was assessed as "WINOFI" based on the occurrence of a single fish kill in this segment.

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2012-2014	15960015	Dry Branch at 110 St	DBR30

Presumptive 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
15960015	6	25 / 3	1700	3702	183	Yes	18	72%	Yes	Evaluated	Not

Presumptive 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
15960015	6	23 / 3	8.7	8.2	8.2	0	0%	No	Evaluated	Full

Presumptive Class BWW1 - Binomial 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
15960015	6	Ammonia	15 / 2	0.66	0.18	0.05	0 / 0	0% / 0%	No	Evaluated	Full
15960015	6	Chloride	16 / 2	34	32	33	0 / 0	0% / 0%	No	Evaluated	Full
15960015	6	Dissolved oxygen	24 / 3	11	8.3	8	NA / 0	NA / 0%	No	Evaluated	Full
15960015	6	pH	23 / 3	8.7	8.2	8.2	0 / NA	0% / NA	No	Evaluated	Full
15960015	6	Temperature	24 / 3	28.1	16.7	18.4	0 / 0	0% / 0%	No	Evaluated	Full

Presumptive Class BWW1 – Fish kill Assessment:

The presumptive Class BWW1 aquatic life use assessment based on the 2021 fish kill placed this segment in Category 3b. This assessment was “evaluated” because there was a single fish kill on this segment in the last five years. Segments assessed using “evaluated” assessments are placed in Category 3b and are added to the state list of Waters In Need Of Further Investigation (WINOFI). If no additional fish kills are reported in this segment for a 5-year period (2026), the Category will be changed from 3b to 3a (not assessed).

Details about the 2021 fish kill can be found here: https://programs.iowadnr.gov/fishkill/Events/1014

Monitoring and Methods

Assessment Key Dates

4/4/2012

Monitoring Start

11/5/2014

Monitoring End

7/9/2021

Fish Kill

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

200

Physical/Chemical Monitoring

330

Fish surveys

420

Indicator bacteria monitoring