Assessment Summary
The Class A1 uses are assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by nuisance algae blooms that cause poor water transparency. The Class BLW uses are assessed (evaluated) as "partially supported" due to concern over fish kills, the introduction of gizzard shad and silver carp at this lake, and due to cyanobacteria blooms. All other designated uses are “not assessed”.
Note:A TMDL for organic enrichment and noxious aquatic plants (cyanobacteria) at Indian Lake was prepared by DNR and approved by EPA in 2005. Because all Section 303(d) impairments identified for the assessment/listing cycle (algal growth, pH, and cyanobacteria) are addressed by the TMDL, this waterbody is placed in IR Category 4a (impaired; TMDL approved).
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
|
22890001
|
Indian Lake (maximum water 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
|
|
22890001
|
6
|
15 / 5
|
9.2
|
8.4
|
8.4
|
1
|
7%
|
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
|
|
22890001
|
6
|
Chlorophyll a TSI
|
15 / 5
|
46
|
83
|
60
|
NO
|
Monitored
|
Full
|
|
22890001
|
6
|
Secchi TSI
|
15 / 5
|
52
|
83
|
73
|
YES
|
Monitored
|
Not
|
|
22890001
|
6
|
Total Phosphorus TSI
|
15 / 5
|
59
|
86
|
78
|
NA
|
NA
|
NA
|
|
22890001
|
6
|
Inorganic suspended solids
|
15 / 5
|
0.3
|
13
|
5.3
|
NA
|
NA
|
NA
|
- Although the index value for Chlorophyll a is below the impairment trigger of 65 for this assessment cycle, Indian 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, Indian 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
|
|
22890001
|
6
|
Ammonia
|
15 / 5
|
0.674
|
0.09
|
0.01
|
0 / 0
|
0% / 0%
|
NO
|
Monitored
|
Full
|
|
22890001
|
6
|
Dissolved oxygen
|
15 / 5
|
21.38
|
10.46
|
9
|
NA / 1
|
NA / 7%
|
NO
|
Monitored
|
Full
|
|
22890001
|
6
|
pH
|
15 / 5
|
9.2
|
8.4
|
8.4
|
1 / NA
|
7% / NA
|
NO
|
Monitored
|
Full
|
|
22890001
|
6
|
Temperature
|
15 / 5
|
30
|
26
|
26
|
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
|
|
22890001
|
6
|
11
|
113.994
|
98.5 %
|
33.717
|
82.9 %
|
YES
|
Evaluated
|
3b
|
Class BLW - Additional information:
The Class BLW uses are assessed (evaluated) as “partially supported” due to exotic invasive species based on information from DNR’s Fisheries Bureau and results from the ISU lake survey. Information from the DNR Fisheries Bureau shows that due to the crest elevation of the lake it is susceptible to flooding during extreme flooding events. This occurred in 1993, 2008, and 2010. As a result, common carp, bighead, and silver carp are present in this lake. Fish kills also remain a concern at this lake. These potential impairments are not appropriate for Iowa’s Section 303(d) list of impaired waters (Integrated Report Category 5) but are appropriate for IR Category 3b of Iowa’s Integrated Report and Iowa’s list of waters in need of further investigation.
Class HH - No Data
Note: Gizzard shad were removed in 2014 through a low concentration of rotenone.
