Bob White Lake IA 05-CHA-1338

Wayne County S4T68NR22W 1 mi W of Allerton.

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 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 were also assessed.

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Cycle: 2020
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Hypereutrophic
Trend: Stable
Created: 8/20/2020 2:25:09 PM
Updated: 10/14/2020 2:43:01 PM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Algal Growth: Chlorophyll a

Support Level

Not Supported

Impairment Code

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

Cause Magnitude

High

Status

Continuing

Source

Natural: Internal Nutrient Recycling (Primarily Lakes)

Source Confidence

Moderate

Cycle Added

2008

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier I

Bacteria: Indicator Bacteria- E. coli

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

High

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2004

Impairment Rationale

Geometric mean criterion exceeded

Data Source

Beach monitoring: Iowa DNR city/county

TMDL Priority

Tier I

Turbidity

Support Level

Not Supported

Impairment Code

4a - Pollutant-caused impairment. TMDL has been completed.

Cause Magnitude

High

Status

Continuing

Source

Other: Sediment Resuspension

Source Confidence

Moderate

Cycle Added

2004

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

Class BLW

Aquatic Life - Lakes and wetlands

Partially Supported

Turbidity

Support Level

Further Investigation Needed

Impairment Code

3b - Use potentially impaired based on an evaluated assessment.

Cause Magnitude

Slight

Status

Continuing

Source

Other: Sediment Resuspension

Source Confidence

Moderate

Cycle Added

2004

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Biological monitoring: Iowa DNR Fisheries

Organic Enrichment: Low Dissolved Oxygen

Support Level

Partially Supported

Impairment Code

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

Cause Magnitude

Moderate

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Low

Cycle Added

2014

Impairment Rationale

Significantly > 10% of samples fail to meet criterion

Data Source

Ambient monitoring: Iowa DNR-lakes

TMDL Priority

Tier I

Class C

Drinking Water -

Fully Supported

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use is assessed (monitored) as “not supported” due to poor water transparency primarily due to large amounts of suspended sediment, but also due to algae blooms that violate Iowa's narrative criterion protecting against nuisance aquatic life. Violations of the state water quality standard for indicator bacteria also contribute to the impairment at this lake. The Class BLW use is assessed (monitored) as "not supported" due to violations of the Class BLW criterion for DO. The Class C (drinking water) use is assessed (monitored) as “fully supported.” All other designated uses are “not assessed.” Note: A TMDL for siltation at Bob White Lake was prepared by DNR and approved by EPA in 2002. Because the Section 303(d) impairments for indicator bacteria, algal Growth/Chlorophyll a, and dissolved oxygen were not addressed in the TMDL, this waterbody was placed into IR Category 5a (impaired; TMDL required.)

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2000-2002	21930001	Bob White Beach
Iowa DNR	6	WQ	CY 2014-2018	22930001	Bob White Lake
Iowa DNR	6	WQ	CY 2014-2014	14000143	Bob White 1

Class A1 - Indicator Bacteria: Historical data, form 2018 Assessment cycle

Site ID	Data Source ID	# Samples / # Years	2000 Geometric Mean	2001 Geometric Mean	2002 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
21930001	6	63 / 3	42.6	137.4	15.87	YES	12	19%	YES	Evaluated	Full

Class A1 - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
22930001	6	15 / 5	8.8	7.89	7.9	0	0%	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
14000143	6	Chlorophyll a TSI	13 / 1	41	77	62	NO	Monitored	Full
22930001	6	Chlorophyll a TSI	28 / 5	31	88	56	NO	Monitored	Full
22930001	6	Secchi TSI	15 / 5	59	93	83	YES	Monitored	Not
14000143	6	Total Phosphorus TSI	13 / 1	75	92	83	NA	NA	NA
22930001	6	Total Phosphorus TSI	28 / 5	69	95	84	NA	NA	NA
22930001	6	Inorganic suspended solids	15 / 5	3	76.5	27	NA	NA	NA

Although the index value for Chlorophyll a is below the impairment trigger of 65 for this assessment cycle, Bob White Lake was listed as partially supporting its Class A1 uses due to aesthetically objectionable conditions. Based on DNR's methodology, the median TSI value for Chlorophyll a must be 63 or less for two consecutive assessment/listing cycles before a lake can be removed from the state's Section 303(d) list (IR Category 5). Therefore, Bob White Lakewill remain listed as "not supported" for the 2020 assessment/listing cycle.

Class BLW - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	Significantly >10% Violations	Assessment Type	Support Level
22930001	6	Ammonia	15 / 5	0.683	0.22	0.13	0 / 0	0% / 0%	NO	Monitored	Full
22930001	6	Dissolved oxygen	15 / 5	11.1	6.87	7.2	NA / 3	NA / 20%	NO	Monitored	Full
22930001	6	pH	15 / 5	8.8	7.89	7.9	0 / NA	0% / NA	NO	Monitored	Full
22930001	6	Temperature	15 / 5	30.6	24.1	24.7	0 / 0	0% / 0%	NO	Monitored	Full

According to DNR's methodology, a lake must meet water quality standards for two consecutive cycles to suggest de-listing.Therefore, Bob White Lake will remain listed for the 2020 cycle as "not supported" its Class B(LW) uses due to dissolved oxygen.

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 Wet Mass = 75th Percentile	Assessment Type	Support Level
22930001	6	11	133.147	98.5 %	0.371	33.5 %	NO	Evaluated	NA

Class C - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
14000143	6	Chloride	13 / 1	10	5	3.5	0	0%	NO	Monitored	Full
22930001	6	Chloride	13 / 1	10	5	3.6	0	0%	NO	Monitored	Full
14000143	6	Inorganic nitrogen (nitrate and nitrite)	13 / 1	1.3	0.55	0.53	0	0%	NO	Monitored	Full
22930001	6	Inorganic nitrogen (nitrate and nitrite)	28 / 5	3.7	0.7	0.3	0	0%	NO	Monitored	Full

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

4/23/2014

Fixed Monitoring Start Date

8/16/2018

Fixed Monitoring End Date

1/28/2002

TMDL Completed

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)

420

Indicator bacteria monitoring