Assessment Summary
The Class A1 use is assessed (monitored) as “not supported” due to poor water transparency and nuisance algae blooms that violate Iowa’s narrative water quality standard protecting against aesthetically objectionable conditions as well as violations of the state’s pH criterion. The Class BLW use is assessed (monitored) as “not supported” due to violations of the state’s criterion for DO, pH and a single non-pollutant fish kill. All other designated uses are “not assessed.”
Note: A TMDL for algae and turbidity at Swan Lake was prepared by DNR and approved by EPA in 2004. Because algal growth, turbidity, and pH Section 303(d) impairments are identified for the 2018 assessment/listing cycle are addressed by the TMDL, these impairments will be placed in IR Category 4a. However, the dissolved oxygen impairment is not addressed by the TMDL, this impairment will be placed in Category 5a of the current Integrated Report (i.e., Section 303(d) list).
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 2014-2018
|
22140001
|
Swan Lake Max Depth
|
|
Class A1 -
Indicator Bacteria: No Data
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
|
|
22140001
|
6
|
15 / 5
|
9.48
|
8.79
|
8.9
|
5
|
33%
|
YES
|
Monitored
|
Not
|
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
|
|
22140001
|
6
|
Chlorophyll a TSI
|
15 / 5
|
36
|
85
|
63
|
NO
|
Monitored
|
Full
|
|
22140001
|
6
|
Secchi TSI
|
15 / 5
|
54
|
83
|
70
|
YES
|
Monitored
|
Not
|
|
22140001
|
6
|
Total Phosphorus TSI
|
15 / 5
|
68
|
102
|
87
|
NA
|
NA
|
NA
|
|
22140001
|
6
|
Inorganic suspended solids
|
15 / 5
|
0.4
|
8
|
2.5
|
NA
|
NA
|
NA
|
- Although the
index value for Chlorophyll a is below the impairment trigger of 65 for this
assessment cycle, Swan 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,
Swan Lake will 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
|
|
22140001
|
6
|
Ammonia
|
15 / 5
|
0.587
|
0.13
|
0.02
|
0 / 2
|
0% / 13%
|
NO
|
Monitored
|
Full
|
|
22140001
|
6
|
Dissolved oxygen
|
15 / 5
|
14.8
|
8.8
|
8.3
|
NA / 4
|
NA / 27%
|
YES
|
Monitored
|
Not
|
|
22140001
|
6
|
pH
|
15 / 5
|
9.48
|
8.79
|
8.9
|
5 / NA
|
33% / NA
|
YES
|
Monitored
|
Not
|
|
22140001
|
6
|
Temperature
|
15 / 5
|
25.9
|
22.1
|
23.6
|
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
|
|
22140001
|
6
|
11
|
129.169
|
95.8 %
|
12.796
|
43.4 %
|
NO
|
Evaluated
|
NA
|
Class BLW -
Fish Kill:
The Class BLW
uses are assessed (evaluated) as “partially supported” due to fish kills that
occurred in 2015. Because the cause of the fish kill was not identified, or the
fish kill was attributed to a non-pollutant cause (e.g., winterkill), the
assessment type is “evaluated.” Segments assessed using “evaluated” assessments
are placed in Category 3b and are added to the state list of waters in need of
further investigation. If no additional fish kills are reported in the segment
for a 10 year period, the Category will be changed from 3b to 3a (water not
assessed).
Details about
the 2011 fish kill can be found here: https://programs.iowadnr.gov/fishkill/Events/893
Class HH - No
Data
