Iowa DNR
Iowa DNR
ADBNet
Water Quality Assessments
Impaired Waters List

Lake Ahquabi IA 04-LDM-1080

Warren County S14T75NR24W 4 mi SSW of Indianola.

Cycle
2024
Release Status
Final
Overall IR
5 - Water is impaired or threatened and a TMDL is needed.
Trophic
Eutrophic
Trend
Stable
Created
11/1/2023 8:13:06 AM
Updated
2/5/2024 8:21:54 AM
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
Other: Sediment Resuspension
Source Confidence
Low
Cycle Added
2022
Impairment Rationale
Narrative criteria violation: aesthetically objectionable conditions
Data Source
Ambient monitoring: Iowa DNR-lakes
TMDL Priority
Tier I
Class BLW
Aquatic Life - Lakes and wetlands
Fully Supported
Class C
Drinking Water -
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 (monitored) as “not supported” due to aesthetically objectionable conditions caused by non-algal turbidity. The Class BLW use was assessed (monitored) as “fully supported.” The Class C use was assessed (monitored) as “fully supported.” The Class HH (fish consumption) 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

WQ

CY 2020-2021

21910001

Lake Ahquabi Beach

Iowa DNR

6

WQ

CY 2018-2021

22910002

Lake Ahquabi

Iowa DNR

6

FT

See Below

1071

Lake Ahquabi

S of Indianola

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

21910001

6

8/7/0

31

59

NA

NO

2 / 3

1 / 3

NA

NO

Mon

Full

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

22910002

6

11 / 4

7

8.73

8.18

0

3

NO

Mon

Full

Class A1 - Lake TSI's:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Minimum Value

Maximum Value

Median Value

Median TSI Violation?

Assessment Type

Support Level

22910002

6

Chlorophyll a TSI

11 / 4

15

71

61

NO

Mon

Full

22910002

6

Secchi TSI

11 / 4

41

73

68

YES

Mon

Not

22910002

6

Total Phosphorus TSI

11 / 4

57

70

64

NA

NA

NA

22910002

6

Inorganic suspended solids

11 / 4

0.6

7.5

1.9

NA

NA

NA

Class BLW - 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

22910002

6

Dissolved Oxygen

10 / 4

4.1

11.3

7.6

1

NA / NA

3

NO

Mon

Full

22910002

6

pH

11 / 4

7

8.73

8.18

0

NA / NA

3

NO

Mon

Full

22910002

6

Temperature

11 / 4

22.1

29.3

25.2

0

NA / NA

3

NO

Mon

Full

Class BLW - Lake Planktonic Cyanobacteria:

Site ID

Data Source ID

# Samples

Maximum Cyanobacteria Wet Mass

Maximum Cyanobacteria % Composition

Median Cyanobacteria Wet Mass

Median Cyanobacteria % Composition

Median Cyanobacteria Concentration = 75th Percentile

Assessment Type

Support Level

22910002

6

4

8.450481068

95%

4.796588552

41%

NO

Evaluated

NA

Class BLW - 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

22910002

6

Ammonia

11 / 4

0.142

0.06

0.04

0 / 0

NO

Mon

Full

Class C - Binomial Parameters:

Site ID

Data Source ID

Parameter Name

# Samples / # Years

Minimum Value

Maximum Value

Mean Value

Median Value

# Violations

Violates Significantly >10% Rule?

Assessment Type

Support Level

22910002

6

Inorganic nitrogen (nitrate and nitrite)

11 / 4

0.02

0.63

0.14

0.03

0

NO

Mon

Full

22910002

6

pH

11 / 4

7

8.73

8.18

8.2

0

NO

Mon

Full

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)

1071

tissue plug

2019

largemouth bass

10

34

0.218

Support Level

Full


Monitoring and Methods
Assessment Key Dates
5/22/2018
Monitoring Start
7/13/2021
Monitoring End
7/1/2019
Fish Tissue Monitoring
Methods
200
Physical/Chemical Monitoring
260
Fish tissue analysis
340
Primary producer surveys (phytoplankton/periphyton/macrophyton)
420
Indicator bacteria monitoring