Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Little Sioux River IA 06-LSR-1565

from confluence with Maple R. (S17 T83N R44W Monona Co.) to confluence with Big Cr. in Anthon in S4 T87N R43W Woodbury Co.

Assessment Cycle
2024
Release Status
Pending
Data Collection Period
Overall IR Category
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Stable
Created
11/1/2023 8:13:03 AM
Updated
12/22/2023 9:28:52 AM
Assessment conducted in accordance with Iowa's 2024 IR methodology.
Use Support
Class A1
Recreation
Primary contact
Not Supported
Impairments
Support Level
Not Supported
Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2008
Impairment Rationale
Geometric mean criterion exceeded
Data Source
Ambient monitoring: Iowa DNR-rivers
TMDL Priority
Tier III
Class BWW1
Aquatic Life
Warm Water Type 1
WINOFI
Support Level
Water in Need of Further Investigation (WINOFI)
Impairment Code
3b-u - Use potentially biologically impaired based on uncalibrated IBI metrics.
Cause Magnitude
Moderate
Status
New
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2024
Impairment Rationale
Low Biotic Index
Data Source
Biological monitoring: Iowa DNR WQMA
Class HH
Human Health
Fully Supported
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 use was assessed as "not supported" due to levels of indicator bacteria (E. coli) that violated state water quality criteria. The Class BWW1 use was assessed as "WINOFI" based on biological sampling data. The Class HH 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 2020-2022

10970001

Little Sioux River near Smithland

Iowa DNR

6

BIO

See Below

845

Little Sioux River

Smithland


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

10970001

6

8/8/8

457

140

130

YES

5 / 3

3 / 3

2 / 3

YES

Mon

Not


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

10970001

6

36 / 3

7.3

8.5

8.1

0

7

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

10970001

6

Chloride

36 / 3

15

30

22

NA

0 / 0

7

NO

Mon

Full

10970001

6

Dissolved Oxygen

36 / 3

6.7

13.7

10.6

0

NA / NA

7

NO

Mon

Full

10970001

6

pH

36 / 3

7.3

8.5

8.1

0

NA / NA

7

NO

Mon

Full

10970001

6

Sulfate

36 / 3

35

120

80

0

NA / NA

7

NO

Mon

Full

10970001

6

Temperature

36 / 3

0

27.5

12.4

0

NA / NA

7

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

10970001

6

Ammonia

36 / 3

0.45

0.05

0.02

0 / 0

NO

Mon

Full

10970001

6

Cadmium

20 / 3

0.5

0.5

0.5

0 / 0

NO

Mon

Full

10970001

6

Chromium

20 / 3

6

1.09

0.66

0 / 0

NO

Mon

Full

10970001

6

Lead

20 / 3

1

0.91

1

0 / 0

NO

Mon

Full

10970001

6

Nickel

20 / 3

4.4

2.2

2.1

0 / 0

NO

Mon

Full

10970001

6

Selenium

18 / 2

4

3

3

0 / 0

NO

Mon

Full

10970001

6

Silver

20 / 3

1

0.902

1

0 / 0

NO

Mon

Full

10970001

6

Zinc

20 / 3

7

1.1

0.5

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

47m BMIBI BIT

BMIBI Pass/Fail

845

8/24/21

2686.7

47m

MO

Floating Art Sub

24

Poor

54

Fail

845

8/14/18

2686.7

47m

MO

Floating Art Sub

54

Good

54

Pass


Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Evaluated

Fail (1/2)

WINOFI

Assessment was evaluated because the drainage area

Overall

Evaluated

Fail

WINOFI

3bu

of the site was greater than the calibrated range.


Class HH-F - Toxic Parameters:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Maximum Value

Mean Value

Median Value

Number of Non - Detects

Mean Value > Criterion or MCL

Assessment Type

Support Level

10970001

6

Selenium

18 / 2

4

3

3

0

NO

Mon

Full

Monitoring and Methods
Assessment Key Dates
8/8/2018
Biological Monitoring
1/7/2020
Monitoring Start
12/13/2022
Monitoring End
8/24/2021
Biological Monitoring
Methods
200
Physical/Chemical Monitoring
315
Regional reference site approach
320
Benthic macroinvertebrate surveys
420
Indicator bacteria monitoring