South Fork Iowa River IA 02-IOW-746

mouth (S4 T86N R19W Hardin Co.) to confluence with Tipton Cr. in S21 T87N R20W Hardin 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
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Cycle: 2024
Release Status: Final
Overall IR: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trend: Unknown
Created: 11/1/2023 8:12:56 AM
Updated: 12/15/2023 10:22:08 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

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2010

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Ambient monitoring: USDA/National Lab for Ag. and Environment

Class BWW1

Aquatic Life - Warm Water Type 1

Fully Supported

Class HH

Human Health -

Not Assessed

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 BWW1 use was assessed as "fully supported" based on biological sampling data and water quality monitoring data. All other designated uses were "not assessed." Note: A TMDL covering the bacteria impairments for all segments, with the segment code prefix "IA 02-IOW" in the Iowa River Basin, was approved by EPA in 2018. Due to the completion of the TMDL, the IR category for the Class A1 use was changed from 5p (impaired; TMDL needed) to 4a (impaired; TMDL approved).

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2020-2022	10420002	S. Fork Iowa River at R Ave
USGS	11	WQ	CY 2020-2022	5451210	South Fork Iowa River NE of New Providence, IA
Iowa DNR	6	BIO	See Below	1195	South Fork Iowa River	N of New Providence at R Ave – SFI-4
NLAE	20	WQ	CY 2014-2015	SF450	South Fork Iowa River	NE of New Providence, IA

Presumptive Class A1 – Indicator Bacteria: 2014-2015

Site ID	Data Source ID	# Samples / # Years	2014 Geometric mean	2015 Geometric mean	Annual Geomean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
SF450	20	16 / 2	194	695	Yes	10	63%	Yes	Evaluated	Not

Presumptive Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2020/ 2021/2022)

2020 Geometric Mean

2021 Geometric Mean

2022 Geometric Mean

Violates Annual Geometric Mean?

# 2020 SSM violations / SSM Violations needed for impairment

# 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

10420002

0/4/6

640

398

YES

4 / NA

5 / NA

YES

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
10420002	6	14 / 3	7.86	8.36	8.13	0	4	NO	Mon	Full
5451210	11	133 / 3	7.6	8.6	8.2	0	19	NO	Mon	Full

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
5451210	11	Chloride	61 / 3	12.5	36.6	22.6	NA	0 / 0	10	NO	Mon	Full
10420002	6	Dissolved Oxygen	14 / 3	4.73	12.14	9.35	1	NA / NA	4	NO	Mon	Full
5451210	11	Dissolved Oxygen	71 / 3	5.9	14.5	10.3	0	NA / NA	11	NO	Mon	Full
10420002	6	pH	14 / 3	7.86	8.36	8.13	0	NA / NA	4	NO	Mon	Full
5451210	11	pH	133 / 3	7.6	8.6	8.2	0	NA / NA	19	NO	Mon	Full
5451210	11	Sulfate	61 / 3	10.7	44.4	22.9	0	NA / NA	10	NO	Mon	Full
10420002	6	Temperature	14 / 3	12.435	29.646	21.268	0	NA / NA	4	NO	Mon	Full
5451210	11	Temperature	71 / 3	0	28.1	14.1	0	NA / NA	11	NO	Mon	Full

Class BWW1 - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
5451210	11	Ammonia	68 / 3	0.59	0.06	0.02	0 / 0	NO	Mon	Full

Class BWW1 - Biological Sampling:

Benthic Macroinvertebrates:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	BM Sample Gear	BMIBI score	BMIBI Class	47b BMIBI BIT	BMIBI Pass/Fail
1195	8/24/22	225.0	47b	MS	Surber	65	Good	62	Pass
1195	7/19/22	225.0	47b	MS	Hess	77	Excellent	62	Pass
1195	8/26/21	225.0	47b	MS	Surber	54	Fair	62	Fail
1195	7/19/21	225.0	47b	MS	Hess	66	Good	62	Pass
1195	8/26/20	225.0	47b	MS	Surber	72	Good	62	Pass
1195	7/22/20	225.0	47b	MS	Hess	65	Good	62	Pass
1195	8/15/19	225.0	47b	MS	Floating Art Sub	52	Fair	62	Fail

Fish:

Site ID	Date	Drainage Area (mi2)	Ecoregion	Major Drainage	Riffle Stream?	FIBI score	FIBI Class	47b FIBI BIT	FIBI Pass/Fail
1195	8/24/22	225.0	47b	MS	Yes	65	Good	53	Pass
1195	8/26/21	225.0	47b	MS	Yes	65	Good	53	Pass
1195	8/26/20	225.0	47b	MS	Yes	67	Good	53	Pass
1195	8/15/19	225.0	47b	MS	Yes	77	Excellent	53	Pass

Overall:

Community	Assessment Type	Assessment Result	Support Level	IR Category	Reason
Benthic Macroinvertebrates	Monitored	Pass (5/7)	Full
Fish	Monitored	Pass (4/4)	Full		Assessment was monitored because the samples used to complete
Overall	Monitored	Pass	Full	1	the assessment were collected in a recent five year period.

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

12/5/2022

Monitoring End

1/13/2020

Monitoring Start

4/9/2014

Monitoring Start

11/3/2015

Monitoring End

3/9/2018

TMDL Completed

8/15/2019

Biological Monitoring

7/22/2020

Biological Monitoring

8/26/2020

Biological Monitoring

7/29/2021

Biological Monitoring

8/26/2021

Biological Monitoring

7/19/2022

Biological Monitoring

8/24/2022

Biological Monitoring

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