Lake Miami IA 04-LDM-1016

Monroe County S20T73NR17W 5 mi. SE of Lovilia.

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 2014 - 2016
Stream/River Water Quality Data	CY 2014 - 2016
Lake Water Quality Data	CY 2012 - 2016
Biological Sampling Data	CY 2012 - 2016*
Fish Kill Data	CY 2012 - 2016
Fish Tissue Sampling Data	CY 2012 - 2016
Continuous Dissolved Oxygen Sampling Data	CY 2012 - 2016
*Biological sites sampled in both 2011 and 2015 were also assessed.

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Cycle: 2018
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Hypereutrophic
Trend: Stable
Created: 4/8/2019 2:58:46 PM
Updated: 4/8/2019 3:02:51 PM

Use Support

Class A1

Recreation - Primary contact

Not Supported

Turbidity

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

2002

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: Siltation/Turbidity

Support Level

Partially Supported

Impairment Code

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

Cause Magnitude

Moderate

Status

Continuing

Source

Agriculture

Source Confidence

Moderate

Cycle Added

2002

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Biological monitoring: Iowa DNR Fisheries

Class HH

Human Health -

Partially Supported

Fish Consumption Advisory: Mercury

Support Level

Partially Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

High

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

Moderate

Cycle Added

2012

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

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” (IR 4a) due to poor water clarity caused by non-algal turbidity. The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” (IR 4a) due to excessive algal production, reduced water transparency related to the presence of common carp populations, and sedimentation problems in the lake. Fish consumption uses are assessed (monitored) as “partially supported” (IR 5a) based on results of fish tissue monitoring in 2009 and 2010. Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2012 through 2016 by Iowa State University (ISU), (2) information from the IDNR Fisheries Bureau, and (3) results of U.S. EPA/IDNR fish tissue (RAFT) monitoring in 2009 and 2010.

Assessment Explanation

For the 2018 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Lake Miami are assessed (monitored) as "not supported" due to poor water transparency based on information from the ISU lake survey. Using the median values from these surveys from 2012-2016 (approximately 13 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 73, 60, and 70 respectively for Lake Miami. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Lake Miami in between the Eutrophic and the Hypereutrophic categories. These values suggest moderately high levels of chlorophyll a and suspended algae in the water, very poor water transparency, and very high levels of phosphorus in the water column. The data show one violation of the Class A1 criterion for pH in 13 samples (8%).

Note:A TMDL for siltation and nutrients at Lake Miami was prepared by DNR and approved by EPA in 2001; thus, this lake was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. Because the Section 303(d) impairment for mercury in fish tissue was not addressed by the TMDL, this waterbody will be moved to IR Category 5a (impaired; TMDL needed) for the 2016 assessment/listing cycle.

The level of inorganic suspended solids was high at Lake Miami, and does suggest that non-algal turbidity contributes to the impairment at this lake. The median level of inorganic suspended solids in Lake Miami (8.8 mg/L) was ranked 117th among the 138 lakes by the ISU lake survey.

Data from the 2012-2016 ISU lake survey suggest a moderate population of cyanobacteria exists at Lake Miami. These data show that cyanobacteria comprised 60% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (10.6 mg/L) was ranked 49th of the 138 lakes sampled.

The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” due to reduced water transparency related to the presence of common carp populations and sedimentation problems in the lake. Information from the DNR Fisheries Bureau suggests that turbidity remains an issue at this lake. Results of the ISU lake survey from 2012-2016 show there were no violations of the criterion for ammonia in 13 samples(0%), one violation of the criterion for dissolved oxygen in 13 samples(8%), and one violation of the criterion for pH in 13 samples(8%). Based on DNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest (fully supported/monitored) of the Class B(LW) uses of Lake Miami.

Fish consumption uses are assessed (monitored) as “partially supported” based on results of U.S.EPA/DNR fish contaminant (RAFT) monitoring at Lake Miami in 2009 and 2010. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of support of fish consumption uses in Iowa’s rivers and lakes. The fish contaminant data generated from the 2009 RAFT sampling conducted at Lake Miami showed that levels of mercury were sufficiently high for concern and thus justified follow-up monitoring. Results from the 2009 sampling show that the level of mercury in the sample of largemouth bass fillets (0.353 ppm) exceeded the 1 meal/week trigger level (0.30 ppm) as defined in Iowa’s revised (2007) fish consumption advisory protocol. According to DNR’s assessment methodology, the single occurrence of contaminant above an advisory trigger level neither warrants issuance of an advisory nor indicates impairment of the fish consumption uses: two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.Follow-up sampling conducted in 2010 showed that levels of mercury in largemouth bass (0.394 ppm) again exceeded the 1 meal/week trigger level (0.30 ppm).Thus a one meal per week fish consumption advisory was issued for Lake Miami and the fish consumption uses are assessed as “partially supported.”Levels of primary contaminants in channel catfish were all below the advisory trigger levels: mercury: 0.109 ppm; total PCBs: 0.09 ppm; technical chlordane: <0.03 ppm.

Monitoring and Methods

Assessment Key Dates

5/21/2012

Fixed Monitoring Start Date

8/21/2016

Fixed Monitoring End Date

10/26/2009

Fish Tissue Monitoring

7/27/2010

Fish Tissue Monitoring

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)

260

Fish tissue analysis

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)