Lower Gar Lake IA 06-LSR-1646
Dickinson County S32T99NR36W 2 mi. NE of Milford.
- Cycle
- 2026
- Current Phase
- Public Comment
- Overall IR
- 2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
- Trophic
- Eutrophic
- Trend
- Improving
- Trend Comment
- Chlorophyll a TSI values are continuing to improve.
- Created
- 10/27/2025 3:10:26 PM
- Updated
- 11/24/2025 9:20:27 AM
The Class A1 use was assessed (monitored) as “fully supported.” The Class BLW use was assessed (evaluated) as “WINOFI” due to due to an invasive species introduction (Zebra Mussels) and based on the results of a fish kill investigation. All other designated uses were “not assessed.” Note: A TMDL for turbidity at Lower Gar Lake was prepared by DNR and approved by EPA in 2002.
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2020-2024 22300012 Lower
Gar Lake
Class A - 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 22300012 6 12 / 4 8.07 8.64 8.44 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 22300012 6 Chlorophyll a TSI 15 / 5 30 74 60 NO MONITORED FULL 22300012 6 Secchi TSI 15 / 5 51 79 63 NO MONITORED FULL 22300012 6 Total Phosphorus TSI 15 / 5 55 75 66 NA NA NA 22300012 6 Fixed suspended solids 15 / 5 0.7 24 6 NA NA NA Class BLW - Binomial 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 22300012 6 Dissolved Oxygen 13 / 5 6.9 10.7 8.6 0 NA / NA 4 NO MONITORED FULL 22300012 6 pH 12 / 4 8.07 8.64 8.44 0 NA / NA 4 NO MONITORED FULL 22300012 6 Temperature 13 / 5 19.5 27.8 24.1 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 22300012 6 2 15.34656129 41.35% 7.679870831 21.53% NO EVALUATED NA Class BLW - Toxic Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Acute / Chronic Violations >1 Acute / Chronic Violation Assessment Type Support Level 22300012 6 Ammonia 12 / 4 0.07 0.04 0.04 0 / 0 NO MONITORED FULL Class BLW - Fish Kill Assessment: The Class BLW aquatic life
use assessment based on the 2020 fish kill placed this segment in Category 3b.
This assessment was “evaluated” because: (1) the cause of the fish kill was not
identified or (2) the fish kill was attributed to a non-pollutant cause (e.g.,
winterkill). Segments assessed using “evaluated” assessments are placed in
Category 3b and are added to the state list of Waters In Need Of Further
Investigation (WINOFI). If no additional fish kills are reported in this
segment for a 5-year period (2025), the Category will be changed from 3b to 3a
(not assessed). Details about the 2020 fish kill can be found here:https://programs.iowadnr.gov/fishkill/Events/995 Class BLW additional information: This lake was infested with
Zebra mussels in 2012 and the population exploded in 2015. This invasive
species will likely cause water quality to degrade in the future. This potential
impairment is not appropriate for Iowa’s Section 303(d) list of impaired waters
(Integrated Report Category 5) but is 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