Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Winnebago River IA 02-WIN-826

mouth (Floyd Co.) to confluence with Calmus Cr. at Mason City in S34 T97N R20W Cerro Gordo Co.

Cycle
2024
Release Status
Final
Overall IR
5 - Water is impaired or threatened and a TMDL is needed.
Trend
Unknown
Created
11/1/2023 8:12:36 AM
Updated
1/12/2024 12:47:42 PM
Use Support
Class A1
Recreation - Primary contact
Not Supported
Support Level
Not Supported
Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
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
Fully Supported
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 "fully supported” based on biological sampling data and water quality monitoring data. The Class HH use was assessed as "fully supported" based on fish tissue sampling data.

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

1035

Winnebago River

Winnebago near Fossil Rock Park

Iowa DNR

6

WQ

CY 2012-2014

10170003

Winnebago River

Downstream of Mason City (DS1)

Iowa DNR

6

FT

See Below

1134

Winnebago River

E of Mason City


Presumptive Class A1 - Indicator Bacteria: 2012-2014

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

10170003

6

22 / 3

387

222

371

Yes

13

59%

Yes

Evaluated

Not


Presumptive Class A1 - pH: 2012-2014

Site ID

Data Source ID

# Samples / # Years

Maximum Value

Mean Value

Median Value

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

10170003

6

33 / 3

8.5

8.1

8.2

0

0%

No

Evaluated

Full


Class BWW1 - Binomial Parameters: 2012-2014

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

10170003

6

Ammonia

33 / 3

0.49

0.11

0.05

0 / 0

0% / 0%

No

Evaluated

Full

10170003

6

Chloride

33 / 3

150

50

41

0 / 0

0% / 0%

No

Evaluated

Full

10170003

6

Dissolved oxygen

33 / 3

15.4

10.8

11.1

NA / 0

NA / 0%

No

Evaluated

Full

10170003

6

pH

33 / 3

8.5

8.1

8.2

0 / NA

0% / NA

No

Evaluated

Full

10170003

6

Sulfate

33 / 3

110

70

74

0 / NA

0% / NA

No

Evaluated

Full

10170003

6

Temperature

33 / 3

26.8

11.5

14.7

0 / 0

0% / 0%

No

Evaluated

Full


Class BWW1 - Biological Sampling:


Fish:

Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage

Riffle Stream?

FIBI score

FIBI Class

47c FIBI BIT

FIBI Pass/Fail

1035

8/1/19

695

47c

MS

Undetermined

59

Good

44

Pass

1035

8/13/18

695

47c

MS

Undetermined

54

Good

44

Pass

1035

7/12/17

695

47c

MS

Undetermined

44

Fair

44

Pass


Overall:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Fish

Evaluated

Pass (3/3)

Full

Assessment was evaluated because the drainage area of the site

Overall

Evaluated

Pass

Full

1

used for the assessment was greater than the calibrated range.


Class HH - Fish Tissue Sampling:

Site ID

Biopart

Year

Species

# in sample / # of samples

Avg Length (cm)

(Avg) Hg (ppm)

Chlordane (ppm)

Sum PCBs (ppm)

1134

tissue plug

2015

walleye

5

41.9

0.092

Support Level

Full

Monitoring and Methods
Assessment Key Dates
1/3/2012
Monitoring Start
9/8/2014
Monitoring End
8/21/2015
Fish Tissue Monitoring
7/12/2017
Biological Monitoring
8/13/2018
Biological Monitoring
8/1/2019
Biological Monitoring
Methods
150
Monitoring data more than 5 years old
200
Physical/Chemical Monitoring
260
Fish tissue analysis
315
Regional reference site approach
330
Fish surveys
420
Indicator bacteria monitoring