Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Little Turkey River IA 01-TRK-162

from the Clayton/Delaware county line to south line of S11 T90N R3W in Delaware 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 8:12:31 AM
Updated
12/14/2023 9:16:04 AM
Use Support
Class A1
Recreation - Primary contact
Not Supported
Support Level
Not Supported
Impairment Code
5p - Impairment occurs on a waterbody with a presumptive A1 or B(WW1) use.
Cause Magnitude
High
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2012
Impairment Rationale
Geometric mean criterion exceeded
Data Source
TMDL monitoring: Iowa DNR
TMDL Priority
Tier III
Class A2
Recreation - Secondary contact
Not Supported
Support Level
Not Supported
Impairment Code
5a - Pollutant-caused impairment. TMDL needed.
Cause Magnitude
High
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
N/A
Cycle Added
2012
Impairment Rationale
Geometric mean criterion exceeded
Data Source
TMDL monitoring: Iowa DNR
TMDL Priority
Tier III
Class BCW1
Aquatic Life - Cold Water Type 1
Not Supported
Support Level
Not Supported
Impairment Code
5b-t - Biological - tentative
Cause Magnitude
Slight
Status
Continuing
Source
Unknown: Source Unknown
Source Confidence
Low
Cycle Added
2008
Impairment Rationale
Low Biotic Index
Data Source
Special project/study
TMDL Priority
Tier IV
Class HH
Human Health -
Not Assessed
Impairment Delistings
No delistings for this assessment cycle.
Documentation
Assessment Summary

The presumptive Class A1 use and Class A2 use was assessed as "not supported” due to high levels of indicator bacteria (E. coli) that exceeded state water quality criteria. The Class BCW1 use was assessed as "not supported" based on biological sampling data. 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

WQ

CY 2010

11280002

Little Turkey River

Near Colesburg (Site LTR1)

Iowa DNR

6

BIO

See Below

631

Little Turkey River

Colesburg (DS)


Presumptive Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples / # Years

2010 Geometric Mean

Annual Geometric Mean Violation

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

11280002

6

16 / 1

2523

Yes

14

88%

Yes

Evaluated

Not


Presumptive Class A2 - Indicator Bacteria:

Site ID

Data Source ID

# Samples / # Years

2010 Geometric Mean

Annual Geometric Mean Violation

# Violations

% Violations

Significantly >10% Violations

Assessment Type

Support Level

11280002

6

16 / 1

2523

Yes

9

56%

Yes

Evaluated

Not


Class BCW1 - Biological Sampling:

Benthic Macroinvertebrates:

BioNet Site ID

Date

Drainage Area (mi2)

Ecoregion

Major Drainage/Thermal

BM Sample Gear

CBI score

CBI Class

CBI BIT

CBI Pass/ Fail

631

7/18/12

7

52b

MS/CW

Hess

34

NA

60

Fail


Overall Assessment:

Community

Assessment Type

Assessment Result

Support Level

IR Category

Reason

Benthic Macroinvertebrates

Evaluated

Fail (0/1)

Not

5bv

Assessment was evaluated because it was based on a single sample.


Class BCW1 - Trout Natural Reproduction:

In contrast to the benthic macroinvertebrate data, based on the January 2024 trout reproduction in Iowa streams summary prepared by the DNR Fisheries Bureau, the Class BCW1 coldwater aquatic life use of the Little Turkey River was assessed as "fully supported." According to the updated summary, this stream was placed in Category II: streams that exhibit recent but inconsistent reproductive success and occasional stocking may be needed to maintain the trout population(s).


Class HH - No Data

Monitoring and Methods
Assessment Key Dates
3/10/2010
Monitoring Start
7/26/2010
Monitoring End
1/1/2024
Biological Monitoring
7/18/2012
Biological Monitoring
Methods
120
Surveys of fish and game biologists/other professionals
150
Monitoring data more than 5 years old
315
Regional reference site approach
320
Benthic macroinvertebrate surveys
330
Fish surveys
420
Indicator bacteria monitoring