Don Williams Lake IA 04-UDM-1249

Boone County S5T84NR27W 5 mi. N of Ogden.

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: 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
Trophic: Eutrophic
Trend: Stable
Created: 12/30/2021 9:26:47 AM
Updated: 1/28/2022 7:17:56 AM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Algal Growth: Chlorophyll a

Support Level

Not Supported

Impairment Code

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

Cause Magnitude

Slight

Status

Continuing

Source

Agriculture

Source Confidence

Moderate

Cycle Added

2020

Impairment Rationale

Narrative criteria violation: aesthetically objectionable conditions

Data Source

Ambient monitoring: Iowa DNR-lakes

Class BLW

Aquatic Life - Lakes and wetlands

Not Supported

Sedimentation/Siltation

Support Level

Not Supported

Impairment Code

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

Cause Magnitude

Moderate

Status

Continuing

Source

Agriculture

Source Confidence

Moderate

Cycle Added

2004

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Biological monitoring: Iowa DNR Fisheries

Class HH

Human Health -

Fully Supported

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by algae blooms. The Class BLW use was assessed (evaluated) as “not supported” due to siltation impacts, especially in the upper portions of the lake. The Class HH use was assessed (monitored) as "fully supported" based on fish tissue sampling data. Note: A TMDL for organic enrichment and siltation at Don Williams Lake was prepared by DNR and approved by EPA in 2005. Because all Section 303(d) impairments identified for the current assessment/listing cycle are addressed by the TMDL, this waterbody remains in IR Category 4a.

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	22080004	Don Williams Lake (maximum water depth)

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2018/ 2019/2020)

2018 Geometric Mean

2019 Geometric Mean

2020 Geometric Mean

Violates Annual Geometric Mean?

# 2018 SSM violations / SSM Violations needed for impairment

# 2019 SSM violations / SSM Violations needed for impairment

# 2020 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

22080004

3/3/3

0 / NA

1 / NA

Evaluated

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
22080004	6	15 / 5	7.4	8.5	8.1	0	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
22080004	6	Chlorophyll a TSI	15 / 5	26	80	57	NO	Monitored	Full
22080004	6	Secchi TSI	15 / 5	49	83	66	YES	Monitored	Not
22080004	6	Total Phosphorus TSI	15 / 5	33	96	64	NA	NA	NA
22080004	6	Inorganic suspended solids	15 / 5	0.3	26	3	NA	NA	NA

Although the index value for Chlorophyll a was below the impairment trigger of 65 for this assessment cycle, the Class A1 use of Don Williams Lake remains "not supported" 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, Don Williams Lake will remain listed as "not supported" 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
22080004	6	Ammonia	15 / 5	0.0003	0.244	0.07	NA	0 / 0	4	NO	Monitored	Full
22080004	6	Dissolved Oxygen	14 / 5	4.9	14.2	9.4	1	NA / NA	4	NO	Monitored	Full
22080004	6	pH	15 / 5	7.4	8.5	8.1	0	NA / NA	4	NO	Monitored	Full
22080004	6	Temperature	15 / 5	12.1	27.8	21.8	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
22080004	6	6	29.23	88.5%	0.11	0.6%	NO	Evaluated	NA

Class HH – Fish Tissue sampling:

Site ID

Date

Species Name

Biopart

# in sample

chlordane result

chlordane violation?

PCBs result

PCBs violation?

Hg result

Hg violation?

Assessment Type

Support Level

7/20/10

largemouth bass

fillet

0.0978

Evaluated

Full

7/23/10

channel catfish

fillet

<0.03

<0.09

0.0443

Evaluated

Full

Monitoring and Methods

Assessment Key Dates

5/16/2016

Non-fixed Monitoring Start Date

8/24/2020

Non-fixed Monitoring End Date

7/23/2010

Fish Tissue Monitoring

3/10/2005

TMDL Completed

Methods

120

Surveys of fish and game biologists/other professionals

222

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

260

Fish tissue analysis

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)

420

Indicator bacteria monitoring