Iowa DNR
Iowa DNR

ADBNet

Water Quality Assessments
Impaired Waters List

Lost Island Lake IA 06-LSR-1632

Palo Alto County S31T97NR34W 3 mi N of Ruthven.

This is a DRAFT assessment
Draft assessments may change without notice
Overall IR
1 - All designated uses are met.
Trophic
Eutrophic
Trend
Stable
Current Phase
Public Comment
Created
10/27/2025 3:10:25 PM by
Updated
11/24/2025 9:03:28 AM by
Use Support
Class A1
Recreation - Primary contact
Fully Supported
Class BLW
Aquatic Life - Lakes and wetlands
Fully Supported
Class HH
Human Health -
Fully Supported
No delistings for this assessment cycle.
Documentation
Assessment Summary

The Class A1 use was assessed (monitored) as "fully supported." The Class BLW use was assessed (evaluated)as "fully supported." The Class HH (fish consumption) use was assessed (monitored) as "fully supported" based on fish tissue sampling data. Note: A TMDL for turbidity at Lost Island Lake was prepared by DNR and approved by EPA in 2009.

Assessment Explanation

Data Sources:

Data Source

Data Source ID

Data Type

Data Age

Site ID

Site Name

Site Description

Iowa DNR

6

WQ

CY 2020-2024

22740002

Lost Island Lake

Iowa DNR

6

FT

See Below

1072

Lost Island Lake

Class A - Indicator Bacteria: No Data

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

22740002

6

12 / 4

8.35

8.76

8.52

0

4

NO

MONITORED

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

22740002

6

Chlorophyll a TSI

15 / 5

27

81

60

NO

MONITORED

FULL

22740002

6

Secchi TSI

15 / 5

46

75

63

NO

MONITORED

FULL

22740002

6

Total Phosphorus TSI

15 / 5

37

72

62

NA

NA

NA

22740002

6

Fixed suspended solids

15 / 5

0.7

18

3

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

22740002

6

Dissolved Oxygen

13 / 5

7

10.5

8.4

0

NA / NA

4

NO

MONITORED

FULL

22740002

6

pH

12 / 4

8.35

8.76

8.52

0

NA / NA

4

NO

MONITORED

FULL

22740002

6

Temperature

13 / 5

19.2

25.5

23.1

0

NA / NA

4

NO

MONITORED

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

22740002

6

5

85.94183166

95.43%

11.91168815

75.28%

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

22740002

6

Ammonia

12 / 4

0.034

0.02

0.02

0 / 0

NO

MONITORED

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)

1072

tissue plug

2020

northern pike

10

67.6

0.065

Support Level

Full


Monitoring and Methods
Assessment Key Dates
6/23/2020
Monitoring Start
9/11/2024
Monitoring End
2/5/2009
TMDL Completed
7/1/2020
Fish Tissue Monitoring
Methods
140
Incidence of spills and/or fish kills
200
Physical/Chemical Monitoring
260
Fish tissue analysis
340
Primary producer surveys (phytoplankton/periphyton/macrophyton)