2020 assessment for Lake Wapello

Lake Wapello IA 04-LDM-1035

Davis County S34T70NR15 7 mi. W of Drakesville.

2020
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.

Open Segment Map
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Overall IR

5 - Water is impaired or threatened and a TMDL is needed.

Trophic

Eutrophic

Trend

Stable

Created

8/12/2020 11:30:29 AM by

Updated

10/14/2020 11:32:51 AM by

Use Support

Class A1

Recreation - Primary contact

Partially Supported

Bacteria: Indicator Bacteria- E. coli

Support Level

Partially Supported

Impairment Code

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

Cause Magnitude

Slight

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2012

Impairment Rationale

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

Data Source

Beach monitoring: Iowa DNR WQMA

TMDL Priority

Tier II

Class BLW

Aquatic Life - Lakes and wetlands

Fully Supported

Class C

Drinking Water -

Not Assessed

Class HH

Human Health -

Partially Supported

Fish Consumption Advisory: Mercury

Support Level

Partially Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

303(d) Listing Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

N/A

Cycle Added

2014

Impairment Rationale

Fish consumption advisory in effect: no more than 1 meal/week

Data Source

Fish contaminant monitoring: Iowa DNR

TMDL Priority

Tier IV

General Use

General Use water -

Not Assessed

303(d) Delistings for this Cycle

Cycle Added	Class	Cause	Data Source	Rationale
2016	Class A1	Turbidity: Secchi Disk Transparency	Ambient monitoring: Iowa DNR-lakes	New data: WQ improvement (chemical / physical / bacterial)

Documentation

Assessment Summary

The Class A1 use is assessed (monitored) as “partially supported” due to violations of the state's indicator bacteria criteria. The Class BLW use is assessed (monitored) as “fully supported”. The Class C use is "not assessed" due to a lack of enough information upon which to base an assessment. Class HH use is assessed as “partially supported" due to high levels of mercury in predator fish.

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 2016-2018	21260001	Lake Wapello Beach (Lake Wapello State Park)
Iowa DNR	6	WQ	CY 2014-2018	22260001	Lake Wapello
Iowa DNR		FT	See Below	312	Lake Wapello

Class A1 - Indicator Bacteria:

Site ID	Data Source ID	# Samples / # Years	2016 Geometric Mean	2017 Geometric Mean	2018 Geometric Mean	Annual Geometric Mean Violation	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
21260001	6	44 / 3	79.42	36.58	15.84	No	6	14%	NO	Monitored	Full

According to DNR's methodology, a lake must meet water quality standards for two consecutive cycles to suggest de-listing. Therefore, Lake Wapello will remain listed for the 2020 cycle as "partially supported" its Class A1 uses due to indicator bacteria.

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
22260001	6	15 / 5	9	8.4	8.3	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
22260001	6	Chlorophyll a TSI	15 / 5	15	68	62	NO	Monitored	Full
22260001	6	Secchi TSI	15 / 5	40	67	59	NO	Monitored	Full
22260001	6	Total Phosphorus TSI	15 / 5	46	66	55	NA	NA	NA
22260001	6	Inorganic suspended solids	15 / 5	0.3	8.8	2	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 Secchi depth TSI value for the 2016 assessment listing cycle was 65, 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 2018 assessment/listing cycle was less than the trigger of 65 (2018 listing for Secchi depth a was 62), and because the TSI value for the current listing cycle is also 59, based on DNR's methodology, these values suggest "full support" of the Class A1 uses protecting against aesthetically objectionable conditions and the impairment (5a) for Secchi depth is suggested for delisting 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
22260001	6	Ammonia	15 / 5	0.058	0.01	0.01	0 / 0	0% / 0%	NO	Monitored	Full
22260001	6	Dissolved oxygen	15 / 5	13	9.17	8.7	NA / 0	NA / 0%	NO	Monitored	Full
22260001	6	pH	15 / 5	9	8.4	8.3	0 / NA	0% / NA	NO	Monitored	Full
22260001	6	Temperature	15 / 5	28	24.2	25.1	0 / 0	0% / 0%	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 Wet Mass = 75th Percentile	Assessment Type	Support Level
22260001	6	11	78.101	99.2 %	16.872	86 %	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
22260001	6	Inorganic nitrogen (nitrate and nitrite)	15 / 5	0.035	0.027	0.03	0	0%	NO	Monitored	Full

The Class C uses are not assessed due to the lack of data sufficient for developing a valid assessment of support of the Class C uses.

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

312

8/1/13

channel catfish

fillet

<0.2

<0.6

0.13

Evaluated

Full

312

8/1/13

largemouth bass

plug

1.212

Yes

Evaluated

Partial

Monitoring and Methods

Assessment Key Dates

5/28/2014

Fixed Monitoring Start Date

8/27/2018

Fixed Monitoring End Date

8/1/2013

Fish Tissue Monitoring

8/18/2014

Fish Tissue Monitoring

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