Little Spirit Lake IA 06-LSR-1659

Dickinson County S8T100NR36W 5 mi. NE of Montgomery.

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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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 8:13:35 AM
Updated: 5/8/2024 10:51:57 AM

Use Support

Class A1

Recreation - Primary contact

Fully Supported

Class BLW

Aquatic Life - Lakes and wetlands

Not Supported

Toxic Inorganics: Ammonia

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

New

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2024

Impairment Rationale

Violations of chronic criterion

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier II

Class HH

Human Health -

Not Assessed

Impairment Delistings

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 (monitored) as “not supported” due to chronic violations of ammonia criteria. All other designated uses were “not assessed.” Note: A TMDL for turbidity and algae at Little Spirit Lake was prepared by DNR and approved by EPA in 2005. Because not all of the Section 303(d) impairments were identified for the 2016 assessment/listing cycle (Ammonia) are addressed by the TMDL, this waterbody is placed in IR Category 5a (impaired; TMDL needed).

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2018-2022	270630001	Little Spirit Lake

Class A1 - 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
270630001	6	16 / 4	7.75	9.72	8.38	1	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
270630001	6	Chlorophyll a TSI	16 / 4	37	89	56	NO	Mon	Full
270630001	6	Secchi TSI	16 / 4	47	89	62	NO	Mon	Full
270630001	6	Total Phosphorus TSI	16 / 4	68	109	84	NA	NA	NA
270630001	6	Inorganic suspended solids	12 / 4	0.6	24	2.8	NA	NA	NA

DNR's assessment methodology indicates that a TSI value less than or equal to 63 are necessary to suggest de-listing of an impairment. The Secchi depth TSI value for the 2002 assessment listing cycle was 74, which based on DNR's assessment/listing methodology indicated an impairment based on the narrative criteria protecting against aesthetically objectionable conditions. Because the TSI value for the 2024 assessment/listing cycle is less than or equal to the delisting trigger of 63 (median TSI value for Secchi depth was 62), based on DNR's methodology, these values suggest "full support" of the Class A1 uses protecting against aesthetically objectionable conditions and the impairment (4a) for Secchi depth is suggested for removal for the 2024 assessment/listing cycle.

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
270630001	6	Dissolved Oxygen	15 / 4	4.8	12.4	7.6	1	NA / NA	4	NO	Mon	Full
270630001	6	pH	16 / 4	7.75	9.72	8.38	1	NA / NA	4	NO	Mon	Full
270630001	6	Temperature	16 / 4	16.4	28.1	23.8	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
270630001	6	3	22.25208383	99%	16.225613	89%	YES	Evaluated	WINOFI

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
270630001	6	Ammonia	16 / 4	1.72	0.54	0.32	0 / 3	YES	Mon	Not

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

5/30/2018

Monitoring Start

9/20/2022

Monitoring End

1/13/2005

TMDL Completed

Methods

200

Physical/Chemical Monitoring

260

Fish tissue analysis

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)