Lake Pahoja IA 06-BSR-1532
Lyon County S23T99NR48W 5 mi SSW of Larchwood.
- Cycle
- 2026
- Current Phase
- Public Comment
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 10/27/2025 3:10:21 PM
- Updated
- 1/8/2026 1:03:15 PM
The Class A1 use was assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by elevated levels of algae and due to violations of the state water quality criteria for indicator bacteria. The level of inorganic suspended solids was relatively low and does not suggest water quality problems due to non-algal turbidity. An additional impairment exists due to violations of the Class A1 criteria for pH. The Class BLW use was assessed (monitored) as "not supported" due to violations of the Class BLW criteria for pH. Additionally, The Class BLW use was assessed (evaluated) as “WINOFI” due to cyanobacteria blooms. All other designated uses are “not assessed.” NOTE: A TMDL for impairments at Lake Pahoja due to algae and pH was prepared by Iowa DNR and approved by the U.S. EPA in 2018. Because not all of the impairments are covered by the TMDL for the current assessment cycle (indicator bacteria) the waterbody is placed in IR Category 5a (impaired and TMDL required.)
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2021-2024 22600001 Lake
Pahoja
Class A1 - Indicator Bacteria: No Data. See 2018 assessment for
indicator bacteria impairment. 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 22600001 6 12 / 4 8.05 9.44 8.77 4 4 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 22600001 6 Chlorophyll a TSI 12 / 4 40 83 68 YES MONITORED NOT 22600001 6 Secchi TSI 12 / 4 44 85 70 YES MONITORED NOT 22600001 6 Total Phosphorus TSI 12 / 4 72 93 81 NA NA NA 22600001 6 Fixed suspended solids 12 / 4 1.7 19 3.5 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 22600001 6 Dissolved Oxygen 12 / 4 4.6 10.2 7.7 1 NA / NA 4 NO MONITORED FULL 22600001 6 pH 12 / 4 8.05 9.44 8.77 4 NA / NA 4 YES MONITORED NOT 22600001 6 Temperature 12 / 4 16.9 25.8 22.8 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 22600001 6 4 71.83288822 100.00% 20.63288771 91.79% YES EVALUATED 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 22600001 6 Ammonia 12 / 4 0.433 0.11 0.05 0 / 1 NO MONITORED FULL
Class HH - No Data