2024 assessment for Lake Anita

Lake Anita IA 05-NSH-1435

Cass County S32T77NR34W 1/2 mi S Anita.

2024
Open Data Collection Period Modal

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2020 - 2022
Stream/River Water Quality Data	CY 2020 - 2022
Lake Water Quality Data	CY 2018 - 2022
Biological Sampling Data	CY 2018 - 2022*
Fish Kill Data	CY 2018 - 2022
Fish Tissue Sampling Data	CY 2018 - 2022
Continuous Dissolved Oxygen Sampling Data	CY 2018 - 2022
*Biological sites sampled in both 2017 and 2021 were also assessed.

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Overall IR

5 - Water is impaired or threatened and a TMDL is needed.

Trophic

Eutrophic

Trend

Stable

Created

11/1/2023 8:13:24 AM by

Updated

2/15/2024 7:14:41 AM by

Use Support

Class A1

Recreation - Primary contact

Not Supported

Turbidity: Secchi Disk Transparency

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

303(d) Listing Status

New

Source

Other: Sediment Resuspension

Source Confidence

Low

Cycle Added

2024

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier II

Class BLW

Aquatic Life - Lakes and wetlands

Fully Supported

Class HH

Human Health -

Fully Supported

303(d) Delistings for this Cycle

Cycle Added	Class	Cause	Data Source	Rationale
2010	Class A1	Algal Growth: Cyanobacteria	Ambient monitoring: Iowa DNR-lakes	New data: WQ improvement (chemical / physical / bacterial)

Documentation

Assessment Summary

The Class A1 use was assessed (monitored) as “not supported” due to non-algae turbidity that violated Iowa's narrative criteria protecting against aesthetically objectionable conditions. The Class BLW use was assessed (monitored) 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 algae at Lake Anita was prepared by DNR and approved by EPA in 2023.

Assessment Explanation

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2020-2022	21150001	Lake Anita Beach
Iowa DNR	6	WQ	CY 2018-2022	22150002	Lake Anita
Iowa DNR	6	FT	See Below	1100	Lake Anita	SW of Anita

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

21150001

13/12/15

0 / 4

1 / 4

0 / 4

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
22150002	6	15 / 5	7.7	8.5	8.2	0	4	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
22150002	6	Chlorophyll a TSI	15 / 5	26	76	60	NO	Mon	Full
22150002	6	Secchi TSI	15 / 5	49	72	67	YES	Mon	Not
22150002	6	Total Phosphorus TSI	15 / 5	37	73	60	NA	NA	NA
22150002	6	Inorganic suspended solids	15 / 5	0.6	9	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
22150002	6	Dissolved Oxygen	15 / 5	5.2	11.6	7.6	0	NA / NA	4	NO	Mon	Full
22150002	6	pH	15 / 5	7.7	8.5	8.2	0	NA / NA	4	NO	Mon	Full
22150002	6	Temperature	15 / 5	18.2	28	24	0	NA / NA	4	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
22150002	6	6	57.16733713	98%	4.306945477	64%	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
22150002	6	Ammonia	15 / 5	0.118	0.03	0.02	0 / 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)
1100	tissue plug	2019	black crappie	2	18.9	0.067
1100	tissue plug	2020	crappie spp.	8	27.5	0.167
1100	tissue plug	2019	largemouth bass	10	34.6	0.196
Support Level	Full

Monitoring and Methods

Assessment Key Dates

6/5/2018

Monitoring Start

9/20/2022

Monitoring End

7/1/2019

Fish Tissue Monitoring

7/1/2020

Fish Tissue Monitoring

4/13/2023

TMDL Completed

Methods

200

Physical/Chemical Monitoring

260

Fish tissue analysis

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)

420

Indicator bacteria monitoring