Arrowhead Pond IA 06-WED-1702
Pottawattamie County S29T77NR41W 1.5 mi SE of Neola
- Cycle
- 2020
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 8/31/2020 3:45:27 PM
- Updated
- 10/15/2020 11:03:14 AM
The Class A1 uses of Arrowhead Pond are assessed (monitored) as "partially supported" due to poor water transparency and algae blooms. The Class BLW uses are assessed (evaluated) as “partially supported” due to sediment and turbidity concerns at this lake. All other designated uses are “not assessed.” Note: A TMDL for siltation at Arrowhead Pond was prepared by DNR and approved by EPA in 2001. Not all Section 303(d) impairments identified for the current assessment/listing cycle (algae) are addressed in the TMDL. Thus, this waterbody remains in IR Category 5a (impaired; TMDL required.)
Sources of
Data: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 WQ CY 2014-2018 22780002 Arrowhead Lake (Pottawatamie)
Class A1 -
Indicator Bacteria: No Data Class A1 - pH: Site ID Data Source ID # Samples / # Years Maximum Value Mean Value Median Value # Violations % Violations Significantly >10% Violations Assessment Type Support Level 22780002 6 14 / 5 8.5 8.1 8.1 0 0% 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 22780002 6 Chlorophyll a TSI 15 / 5 44 78 64 NO Monitored Full 22780002 6 Secchi TSI 15 / 5 45 73 65 YES Monitored Not 22780002 6 Total Phosphorus TSI 15 / 5 53 83 71 NA NA NA 22780002 6 Inorganic suspended solids 15 / 5 0.3 21 2 NA NA NA Although the index value for Chlorophyll a is below the impairment trigger of 65 for this assessment cycle, Arrowhead Lake was listed as partially supporting its Class A1 uses due to aesthetically objectionable conditions. Based on DNR's methodology, the median TSI value for Chlorophyll a must be 63 or less for two consecutive assessment/listing cycles before a lake can be removed from the state's Section 303(d) list (IR Category 5). Therefore, Arrowhead Lake will remain listed as "not supported" for the 2020 assessment/listing cycle. Class BLW -
Conventional Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Acute / Chronic Violations % Acute/ Chronic Violations Significantly >10% Violations Assessment Type Support Level 22780002 6 Ammonia 14 / 5 0.201 0.11 0.13 0 / 0 0% / 0% NO Monitored Full 22780002 6 Dissolved oxygen 15 / 5 13.46 9.22 9.4 NA / 2 NA / 13% NO Monitored Full 22780002 6 pH 14 / 5 8.5 8.1 8.1 0 / NA 0% / NA NO Monitored Full 22780002 6 Temperature 15 / 5 27.9 23.87 24 0 / 0 0% / 0% 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 Wet Mass = 75th
Percentile Assessment Type Support Level 22780002 6 10 58.069 98.6 % 3.547 36.6 % NO Evaluated NA Class BLW - Fish Kill: The Class BLW uses that were assessed (evaluated) as "partially supporting" due to a fish kill in 2005 has been removed based on the assessment methodology. The 3b impairment is switched to 3a "not assessed" based on the age of the non-pollutant caused fish kill.
Class HH - No Data