Lake Pahoja IA 06-BSR-1532
Lyon County S23T99NR48W 5 mi SSW of Larchwood.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 1/4/2022 7:20:42 AM
- Updated
- 1/20/2022 8:47:56 AM
The Class A1 use was assessed (monitored) as “not supported” due to violations of the state water quality criteria for indicator bacteria. The Class BLW use was assessed (evaluated) as "WINOFI" base on a naturally caused fish kill. The Class HH (fish consumption) use was assessed (evaluated) as “fully supported” based on fish tissue sampling data. 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 2014-2016 21600001 Lake
Pahoja Recreation Area Beach Iowa DNR 6 WQ CY 2016-2019 22600001 Lake
Pahoja Iowa DNR 6 FT See Below 134 Lake
Pahoja Near
Larchwood
Class A1 - Indicator Bacteria: Historical 2018 Assessment
Site ID Data Source ID # Samples / # Years 2014 Geometric Mean 2015 Geometric Mean 2016 Geometric Mean Annual Geometric Mean Violation # Violations % Violations Significantly >10% Violations Assessment Type Support Level 21600001 6 36 / 3 186 48 36 No 10 28% Yes Monitored Not 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 7.7 9 8.3 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 22600001 6 Chlorophyll a TSI 12 / 4 36 74 50 NO Monitored Full 22600001 6 Secchi TSI 12 / 4 39 88 56 NO Monitored Full 22600001 6 Total Phosphorus TSI 12 / 4 33 94 72 NA NA NA 22600001 6 Inorganic suspended solids 12 / 4 0.3 42 1.3 NA NA NA 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 22600001 6 Ammonia 12 / 4 0.003 0.128 0.06 NA 0 / 0 4 NO Monitored Full 22600001 6 Dissolved Oxygen 12 / 4 6.1 11.8 8.9 0 NA / NA 4 NO Monitored Full 22600001 6 pH 12 / 4 7.7 9 8.3 0 NA / NA 4 NO Monitored Full 22600001 6 Temperature 12 / 4 14.8 27.3 21.7 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 6 4.98 87.7% 1.06 17.3% NO Evaluated NA Class BLW - Fish Kill: The Class BLW use was assessed (evaluated) as “WINOFI” due to
fish kills that occurred in 2012. Because the cause of the fish
kill was not identified, or the fish kill was attributed to a non-pollutant
cause (e.g., winterkill), the assessment type is “evaluated.” Segments assessed
using “evaluated” assessments are placed in Category 3b and are added to the
state list of waters in need of further investigation. If no additional fish
kills are reported in the segment for a 10 year period, the Category will be
changed from 3b to 3a (water not assessed). Details about the 2012 fish kill can be found
here:https://programs.iowadnr.gov/fishkill/Events/858 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) 134 tissue plug 2012 largemouth bass 5 39.2 0.203
Support Level Full