2024 assessment for West Fork Little Sioux River

West Fork Little Sioux River IA 06-LSR-1834

confluence with unnamed tributary (T91N R42W Sec3 Cherokee County) to confluence with unnamed tributary (T92N R42W Sec1)

2024
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
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Overall IR

3 - Insufficient data exist to determine whether any designated uses are met.

Trend

Unknown

Created

12/8/2023 10:46:33 AM by

Updated

1/9/2024 7:47:51 AM by

Use Support

Class A2

Recreation - Secondary contact

Not Assessed

Class BWW2

Aquatic Life - Warm Water Type 2

Not Assessed

303(d) Delistings for this Cycle

Cycle Added	Class	Cause	Data Source	Rationale
2006	Class BWW2	Fish Kill: Due To Unknown Toxicity	Biological monitoring: Iowa DNR fish kill follow-up	New data: recovery of fish community from pollutant-caused fish kill

Documentation

Assessment Summary

The Class BWW2 use was "not assessed" based on biological sampling data collected in 2022 that showed recovery of the fish community in this segment from the fish kill. Based on the 2022 fish sampling data, the 5b fish kill impairment was de-listed. All other designated uses were "not assessed."

Assessment Explanation

Class A2 - No Data

Class BWW2 – Fishkill 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?	2024 IR 47a expected fish taxa	Fish Taxa Present % (>50% to pass)
1388	09/28/22	26.0	47a	MO/WW	9831	496	Yes (Pass)	6/10	60% (Pass)
The Class BWW2 use previously resided in Category 5b based on a fish kill that occurred in 2004. This segment’s fish community was sampled in 2022 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 2004 fish kill can be found here: https://programs.iowadnr.gov/fishkill/Events/625

Monitoring and Methods

Assessment Key Dates

8/24/2004

Fish Kill

9/28/2022

Biological Monitoring

Methods

140

Incidence of spills and/or fish kills

150

Monitoring data more than 5 years old

330

Fish surveys