White Oak Conservation Area Lake IA 03-SSK-929

Mahaska County S28T75NR14W 4 mi SSW of Rose Hill.

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 2018 - 2020
Stream/River Water Quality Data	CY 2018 - 2020
Lake Water Quality Data	CY 2016 - 2020
Biological Sampling Data	CY 2016 - 2020*
Fish Kill Data	CY 2016 - 2020
Fish Tissue Sampling Data	CY 2016 - 2020
Continuous Dissolved Oxygen Sampling Data	CY 2016 - 2020
*Biological sites sampled in both 2015 and 2019 were also assessed.

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Cycle: 2022
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Eutrophic
Trend: Stable
Created: 12/27/2021 9:16:06 AM
Updated: 2/4/2022 7:14:36 AM

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

Status

Continuing

Source

Agriculture

Source Confidence

Low

Cycle Added

2020

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 HH

Human Health -

Not Assessed

Impairment Delistings

Cycle Added	Class	Cause	Data Source	Rationale
2004	Class A1	Algal Growth: Chlorophyll a	Ambient monitoring: Iowa DNR-lakes	New data: WQ improvement (chemical / physical / bacterial)

Documentation

Assessment Summary

The Class A1 use was assessed as “not supported” due to turbidity levels that violated Iowa’s narrative criteria protecting against aesthetically objectionable conditions. The Class BLW use was assessed as “fully supported.” 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 2016-2020	22620003	White Oak 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
22620003	6	15 / 5	7.2	9.2	8.3	1	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
22620003	6	Chlorophyll a TSI	15 / 5	36	83	61	NO	Monitored	Full
22620003	6	Secchi TSI	15 / 5	54	77	70	YES	Monitored	Not
22620003	6	Total Phosphorus TSI	15 / 5	56	78	74	NA	NA	NA
22620003	6	Inorganic suspended solids	15 / 5	0.3	17	3.4	NA	NA	NA

DNR's assessment methodology indicates that at least two assessment/listing cycles with a TSI value less than or equal to 63 are necessary to suggest de-listing of an impairment. The chlorophyll a TSI value for the 2004 assessment listing cycle was 64, 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 2020 assessment/listing cycle was less than the trigger of 65 (2020 listing for chlorophyll a was 63), and because the TSI value for the current listing cycle is 61, based on DNR's methodology, these values suggest "full support" of the Class A1 use protecting against aesthetically objectionable conditions and the impairment (5a) for chlorophyll a is suggested for delisting for the 2022 assessment/listing cycle.

Class BLW - Conventional 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
22620003	6	Ammonia	15 / 5	0.0003	0.6504	0.1	NA	0 / 0	4	NO	Monitored	Full
22620003	6	Dissolved Oxygen	14 / 5	4	13.2	7.7	1	NA / NA	4	NO	Monitored	Full
22620003	6	pH	15 / 5	7.2	9.2	8.3	1	NA / NA	4	NO	Monitored	Full
22620003	6	Temperature	15 / 5	19.1	29	23.9	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
22620003	6	6	103.09	91.6%	14.14	69.5%	NO	Evaluated	NA

Class HH: No Data

Monitoring and Methods

Assessment Key Dates

6/22/2016

Non-fixed Monitoring Start Date

9/9/2020

Non-fixed Monitoring End Date

Methods

120

Surveys of fish and game biologists/other professionals

222

Non-fixed-station monitoring (conventional during key seasons and flows)

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)