Unnamed Tributary to Little Sioux River IA 06-LSR-6342

from mouth in S34 T94N R38W Clay Co. to headwaters in S14 T94N R38W Clay 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: 3 - Insufficient data exist to determine whether any designated uses are met.
Trend: Stable
Created: 10/27/2025 3:10:27 PM
Updated: 1/30/2026 11:35:02 AM

Use Support

Class A1

Presumptive Use

Recreation - Primary contact

Not Assessed

Class BWW1

Presumptive Use

Aquatic Life - Warm Water Type 1

WINOFI

Biological: low fish & invert IBIs- cause unknown

Support Level

Further Investigation Needed

Impairment Code

3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2012

Impairment Rationale

Potential Impairment

Data Source

Biological monitoring: Iowa DNR WQMA

Impairment Delistings

Cycle Added	Class	Cause	Data Source	Rationale
2014	Class BWW1	Fish Kill: Caused By Animal Waste	Biological monitoring: Iowa DNR fish kill follow-up	New data: recovery of fish community from pollutant-caused fish kill

Documentation

Assessment Summary

The presumptive Class BWW1 use was assessed as "WINOFI" based on biological sampling data. The previous 5b fish kill impairment was de-listed based on 2024 fish kill follow-up sampling that indicated fish community recovery from the fish kill. All other designated uses were "not assessed."

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	BIO	See Below	735	Unnamed Tributary to Little Sioux River	Bertram Reservation – Peterson – HW86

Presumptive Class A1 - No Data

Presumptive Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47a BMIBI BIT	BMIBI Pass/Fail
735	9/15/14	7.3	47a	MO	Surber	69	Good	54	Pass
735	9/15/14	7.3	47a	MO	Art Sub	33	Fair	54	Fail
735	8/4/14	7.3	47a	MO	Art Sub	26	Poor	54	Fail
735	8/4/14	7.3	47a	MO	Surber	50	Fair	54	Fail

Fish:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	47a FIBI BIT	FIBI Pass/Fail
735	9/15/14	7.3	47a	MO	NA	26	Fair	43	Fail
735	8/4/14	7.3	47a	MO	NA	13	Poor	43	Fail

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Evaluated	Fail (1/4)	WINOFI
Fish	Evaluated	Fail (0/2)	WINOFI		Assessment was evaluated because the drainage area
Overall	Evaluated	Fail	WINOFI	3bu	of the sample site was smaller than the calibrated range.

Fish Kill Assessment:

BioNet Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage/ Thermal	Fish per mile	47a REMAP 25 % fish per mile	>47a REMAP 25 % fish per mile?	47a expected fish taxa	Fish Taxa Present % (>50% to pass)
735	07/31/2024	7.3	47a	MO/WW	2513	496	Yes (Pass)	6/10	60% (Pass)
The presumptive Class BWW1 use previously resided in Category 5b based on a fish kill that occurred in 2011. This segment’s fish community was sampled in 2024 as part of the DNR fish kill follow-up sampling program. The results from this follow-up sampling and comparison to ecoregion averages suggest that the fish community of this segment is similar to non-fish kill impacted streams. Based on the fish kill follow-up sampling results, the Category for the fish kill assessment was changed from 5b to 3a (not assessed).

Details about the 2011 fish kill can be found here:https://programs.iowadnr.gov/fishkill/Events/831

Monitoring and Methods

Assessment Key Dates

8/4/2014

Biological Monitoring

9/15/2014

Biological Monitoring

9/19/2011

Fish Kill

7/31/2024

Biological Monitoring

Methods

140

Incidence of spills and/or fish kills

150

Monitoring data more than 5 years old

315

Regional reference site approach

320

Benthic macroinvertebrate surveys

330

Fish surveys