West Swan Lake IA 04-UDM-1754

Emmet County S31T99NR32W 3 mi. SE of Gruver.

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.
Trend: Stable
Created: 9/9/2020 1:43:11 PM
Updated: 10/13/2020 3:11:15 PM

Use Support

Class BLW

Aquatic Life - Lakes and wetlands

Not Supported

Algal Growth: Chlorophyll a

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Agriculture

Source Confidence

Moderate

Cycle Added

2012

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Ambient monitoring: Iowa DNR-shallow lakes & wetlands

TMDL Priority

Tier IV

Turbidity: Suspended Solids

Support Level

Not Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

Moderate

Status

Continuing

Source

Agriculture

Source Confidence

Moderate

Cycle Added

2012

Impairment Rationale

Adverse impacts on plant/animal communities

Data Source

Ambient monitoring: Iowa DNR-shallow lakes & wetlands

TMDL Priority

Tier IV

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 BLW use is assessed as "not supported" due to high levels of total suspended solids that leads to an impairment of the narrative criteria protecting against undesirable or nuisance aquatic life. High levels of algae at this wetland also suggest impairment due to aesthetically objectionable conditions. All other designated uses are “not assessed”. This assessment is the same as that developed for previous assessment/listing cycles.

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 2012-2013	29320002	West Swan Lake (center)-Emmet-2

Class BLW - TSI's

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Median Value	Median TSI Violation	Assessment Type	Support Level
29320002	6	Chlorophyll a TSI	9 / 2	64	78	74	Yes	Monitored	Not

The TSI value for Secchi depth is not used to evaluate the attainment of aquatic life goals in shallow lakes. Due to the depth of these shallow lakes, TSI values for Secchi depth can be misleading. In some instances, the Secchi disk remains visible at the bottom of the lake and the depth of the lake is recorded as the Secchi depth. In these instances, water clarity may be sufficient to support the Class BLW uses, but the index value is limited by the depth of the lake. Thus the combination of total suspended solids and chlorophyll a will be used to determine whether or not the Class BLW uses are impaired in these shallow systems.

Class BLW - Protection of Submerged Aquatic Vegetation:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Median Value	Median Value >= SAV	Assessment Type	Support Level
29320002	6	Total suspended solids	9 / 2	7	98	42	Yes	Monitored	Not

Guidelines for wetland assessment from the Upper Mississippi River Conservation Committee’s Water Quality Technical Section (2003) state that an average total suspended solids concentration during the growing season of less than 30 mg/L is necessary to provide sufficient water clarity to support the growth of submersed aquatic vegetation in wetlands and shallow lakes. High levels of total suspended solids impede the growth of submersed aquatic vegetation (SAV). Submersed aquatic vegetation is critical to the health of wetland and shallow lake ecosystems. The elimination of SAV can degrade habitat quality such that undesirable aquatic species such as cyanobacteria, common carp and fathead minnows dominate. As such, the suppression of SAV constitutes a violation of Iowa’s narrative water quality criteria protecting against undesirable or nuisance aquatic life.

Class HH - No Data

Additional information:

Additional monitoring of fish and aquatic vegetation populations at West Swan Lake by DNR staff also suggests that the high levels of total suspended solids and algae have adverse effects on fish populations and limit the production of rooted aquatic vegetation in this wetland. These results further indicate that the aquatic life uses of this wetland should be assessed as "not supported."

Monitoring and Methods

Assessment Key Dates

5/15/2012

Fixed Monitoring Start Date

9/16/2013

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)