Assessment Summary
The Class A1 use was assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by poor water transparency. The Class BLW use was assessed (evaluated) as "WINOFI" due to concern over fish kills, the introduction of gizzard shad and silver carp at this lake. All other designated uses were “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
Data Sources:
|
Data Source
|
Data Source ID
|
Data Type
|
Data Age
|
Site ID
|
Site
Name
|
Site
Description
|
|
Iowa DNR
|
6
|
WQ
|
CY 2016-2019
|
22890001
|
Indian
Lake (maximum water depth)
|
|
Class A1 - Indicator Bacteria: No Data
Class A1 - pH
|
Site ID
|
Data Source ID
|
# Samples / # Years
|
Minimum Value
|
Maximum Value
|
Mean Value
|
# Violations
|
Violations needed for impairment
|
Violates Significantly >10% Rule?
|
Assessment Type
|
Support Level
|
|
22890001
|
6
|
12 / 4
|
7.7
|
9
|
8.2
|
0
|
4
|
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
|
12 / 4
|
46
|
83
|
59
|
NO
|
Monitored
|
Full
|
|
22890001
|
6
|
Secchi TSI
|
12 / 4
|
56
|
83
|
73
|
YES
|
Monitored
|
Not
|
|
22890001
|
6
|
Total Phosphorus TSI
|
12 / 4
|
59
|
84
|
73
|
NA
|
NA
|
NA
|
|
22890001
|
6
|
Inorganic suspended solids
|
12 / 4
|
0.3
|
13
|
4.2
|
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 removal of an impairment. The chlorophyll a
TSI value for the 2004 assessment listing cycle was 71, 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 2020 assessment/listing cycle was less than the trigger of 65
(2020 listing for chlorophyll a was 60), 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 (4a) for chlorophyll
a is suggested for removal for the 2022 assessment/listing cycle.
Class BLW - Conventional Parameters:
|
Site ID
|
Data Source ID
|
Parameter Name
|
# Samples / # Years
|
Minimum Value
|
Maximum Value
|
Mean Value
|
# Violations
|
# Acute / Chronic Violations
|
Violations needed for impairment
|
Violates Significantly >10% Rule?
|
Assessment Type
|
Support Level
|
|
22890001
|
6
|
Ammonia
|
12 / 4
|
0.0003
|
0.674
|
0.1
|
NA
|
0 / 0
|
4
|
NO
|
Monitored
|
Full
|
|
22890001
|
6
|
Dissolved Oxygen
|
12 / 4
|
3.6
|
16.6
|
8.4
|
1
|
NA / NA
|
4
|
NO
|
Monitored
|
Full
|
|
22890001
|
6
|
pH
|
12 / 4
|
7.7
|
9
|
8.2
|
0
|
NA / NA
|
4
|
NO
|
Monitored
|
Full
|
|
22890001
|
6
|
Temperature
|
12 / 4
|
19.1
|
30.5
|
26.2
|
0
|
NA / NA
|
4
|
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 Concentration = 75th Percentile
|
Assessment Type
|
Support Level
|
|
22890001
|
6
|
6
|
64.44
|
98.5%
|
7.35
|
54.8%
|
NO
|
Evaluated
|
NA
|
Class BLW - Additional information:The Class BLW use was assessed (evaluated) as “WINOFI” 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
