Gustafson Lake IA 06-LSR-1625

Buena Vista County S18T93NR36W 1 mi S of Sioux Rapids.

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.

Open Segment Map
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Cycle: 2024
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Unknown
Trend: Unknown
Created: 11/1/2023 8:13:30 AM
Updated: 12/22/2023 2:52:06 PM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5* - 303(d)-impaired last cycle; fully supporting this cycle; potential de-listing.

Cause Magnitude

Slight

Status

Continuing

Source

Hydromodification: Erosion and Sedimentation

Source Confidence

Low

Cycle Added

2014

Impairment Rationale

Single-sample maximum criterion exceeded in significantly > 10% of samples

Data Source

Beach monitoring: Iowa DNR city/county

TMDL Priority

Tier II

Turbidity: Secchi Disk Transparency

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Slight

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

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

Not Assessed

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 "not supported" due to violations of the state's criteria for indicator bacteria based on historical results of the county beach monitoring program at Gabrielson Park beach and due to poor water transparency caused by non-algal turbidity. 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 2018-2022	22110002	Gustafson Lake

Class A1 - Indicator Bacteria: No Data. For historical assessment see the 2018 Class A1 assessment.

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
22110002	6	12 / 4	7.9	8.6	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
22110002	6	Chlorophyll a TSI	15 / 5	26	81	61	NO	Mon	Full
22110002	6	Secchi TSI	15 / 5	59	73	65	YES	Mon	Not
22110002	6	Total Phosphorus TSI	15 / 5	58	75	62	NA	NA	NA
22110002	6	Inorganic suspended solids	15 / 5	0.6	12	3.3	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
22110002	6	Dissolved Oxygen	15 / 5	6.4	14.7	9.9	0	NA / NA	4	NO	Mon	Full
22110002	6	pH	12 / 4	7.9	8.6	8.2	0	NA / NA	4	NO	Mon	Full
22110002	6	Temperature	15 / 5	17.4	27.3	22.7	0	NA / NA	4	NO	Mon	Full

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
22110002	6	Ammonia	12 / 4	0.252	0.07	0.04	0 / 0	NO	Mon	Full

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

9/12/2022

Monitoring End

6/4/2018

Monitoring Start

Methods

200

Physical/Chemical Monitoring

420

Indicator bacteria monitoring