Lake Ahquabi IA 04-LDM-1080
Warren County S14T75NR24W 4 mi SSW of Indianola.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 12/28/2021 10:12:02 AM
- Updated
- 1/27/2022 9:36:42 AM
| Cycle Added | Class | Cause | Data Source | Rationale |
|---|---|---|---|---|
| 2008 | Class A1 | Algal Growth: Chlorophyll a | Ambient monitoring: Iowa DNR-lakes | New data: WQ improvement (chemical / physical / bacterial) |
| 2012 | Class A1 | Bacteria: Indicator Bacteria- E. coli | Ambient monitoring: Iowa DNR-lakes | New data: WQ improvement (chemical / physical / bacterial) |
The Class A1 use was assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by non-algal turbidity. The Class BLW use was assessed (monitored) as “fully supported.” The Class C use was assessed (monitored) as “fully supported.” The Class HH (fish consumption) use was assessed as "fully supported" based on fish tissue sampling data.
Data Sources: Data
Source Data
Source ID Data
Type Data
Age Site
ID Site Name Site Description Iowa
DNR 6 WQ CY
2018-2020 21910001 Lake Ahquabi Beach (Lake Ahquabi
State Park) Iowa
DNR 6 WQ CY
2016-2020 22910002 Lake Ahquabi Iowa
DNR 6 FT See
Below 71 Lake Ahquabi S of Indianola
Class A1 - Indicator Bacteria: Site ID Data Source ID # Samples per Year (2018/ 2019/2020) 2018 Geometric Mean 2019 Geometric Mean 2020 Geometric Mean Violates Annual Geometric Mean? # 2018 SSM violations / SSM Violations needed for impairment # 2019 SSM violations / SSM Violations needed for impairment # 2020 SSM violations / SSM Violations needed for impairment Violates Annual SSM Significantly >10% Rule? Assessment Type Support Level 21910001 6 1/1/8 5 98 31 NO 0 / NA 0 / NA 2 / 3 NO Monitored Full 22910002 6 3/5/3 1 5 8 NO 0 / NA 0 / NA 0 / NA NO Evaluated Full Lake Ahquabi was assessed as "not supported" for the
2012 assessment/listing cycle based on Dissolved Oxygen. Based on DNR’s
assessment methodology 2 consecutive assessment/listing cycles without
significantly greater than 10% of the samples violating the single-sample
maximum criterion are necessary to propose delisting based on Dissolved Oxygen
violations. There were less than 10% of the samples exceeding the single-sample
maximum criterion for the 2020or current 2022assessment listing
cycle. Therefore, the impairment for Dissolved Oxygen is suggested for
delisting for the 2022 assessment/listing cycle. 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 22910002 6 30 / 5 7 10.03 8.36 1 6 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 22910002 6 Chlorophyll a TSI 29 / 5 15 71 62 NO Monitored Full 22910002 6 Secchi TSI 15 / 5 41 77 67 YES Monitored Not 22910002 6 Total Phosphorus TSI 29 / 5 53 80 64 NA NA NA 22910002 6 Fixed suspended solids 15 / 5 0.6 29 3 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 de-listing of an impairment. The chlorophyll a TSI value
for the 2008 assessment listing cycle was 66, 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 58), and because the TSI value for the
current listing cycle is also 62, based on DNR's methodology, these values
suggest "full support" of the Class A1 uses protecting against
aesthetically objectionable conditions and the impairment (5a) for chlorophyll
a is suggested for delisting 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 22910002 6 Ammonia 27 / 5 0.0003 0.23 0.06 NA 0 / 0 6 NO Monitored Full 22910002 6 Dissolved Oxygen 29 / 5 4.1 11.3 8.2 2 NA / NA 6 NO Monitored Full 22910002 6 pH 30 / 5 7 10.03 8.36 1 NA / NA 6 NO Monitored Full 22910002 6 Temperature 30 / 5 12.4 30.8 23.3 0 NA / NA 6 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 22910002 6 6 13.63 95.4% 9.11 85.8% NO Evaluated NA Class C - Conventional Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Mean Value Median Value # Violations Violates Significantly >10% Rule? Assessment Type Support Level 22910002 6 Chloride 14 / 1 7.5 11 9.3 9.6 0 NO Monitored Full 22910002 6 Inorganic nitrogen (nitrate and nitrite) 29 / 5 0.02 0.63 0.06 0.05 0 NO Monitored Full 22910002 6 pH 30 / 5 7 10.03 8.36 8.4 1 NO Monitored Full
Class HH - Fish
Tissue Sampling: Site ID Biopart Year Species # in sample / # of samples Avg Length (cm) (Avg) Hg (ppm) Chlordane (ppm) Sum PCBs (ppm) 71 tissue plug 2019 largemouth bass 10 34 0.218
Support Level Full