Lake Darling IA 03-SKU-924
Washington County S21T74NR9W 3 mi W of Brighton.
- Assessment Cycle
- 2020
- Release Status
- Final
- Data Collection Period
- Overall IR Category
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Hypereutrophic
- Trend
- Unknown
- Created
- 7/30/2020 10:01:19 AM
- Updated
- 10/14/2020 10:27:34 AM
The Class A1 uses are assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by algae blooms, by poor water clarity due mainly to non-algal turbidity, and by violations of the state's criteria for indicator bacteria. Violations of the Class A1,B(LW) criterion for pH also contribute to the impairment of Class A1 uses at this lake. The Class BLW uses are assessed (monitored) as “partially supported” due to violations of the state’s pH criterion and impacts of nutrients and sediment at this lake. The Class C uses are "not assessed" due to a lack of enough information upon which to base an assessment. All other designated uses are “not assessed”. Note: A TMDL for siltation and nutrients at Lake Darling was prepared by IDNR and approved by EPA in 2003. Because, however, the Section 303(d) impairment due to indicator bacteria (aka, pathogens) was not addressed in the TMDL, this waterbody is placed in IR Category 5a (impaired; TMDL required) for the current assessment/listing cycle.
Sources of
Data: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 WQ CY 2016-2018 21920001 Lake Darling Beach (Lake Darling State Park)
Iowa DNR 6 WQ CY 2014-2018 22920004 Lake Darling Max Depth
Class A1 -
Indicator Bacteria: Site ID Data Source ID # Samples / # Years 2016 Geometric Mean 2017 Geometric Mean 2018 Geometric Mean Annual Geometric Mean Violation # Violations % Violations Significantly >10% Violations Assessment Type Support Level 21920001 6 20 / 3 221.48 20 302.21 Yes 8 40% YES Monitored Partial 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 22920004 6 14 / 5 9.4 8.4 8.4 4 29% 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 22920004 6 Chlorophyll a TSI 14 / 5 44 75 66 YES Monitored Not 22920004 6 Secchi TSI 14 / 5 50 77 66 YES Monitored Not 22920004 6 Total Phosphorus TSI 14 / 5 63 90 75 NA NA NA 22920004 6 Inorganic suspended solids 14 / 5 0.3 13 3.6 NA NA NA 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 22920004 6 Ammonia 14 / 5 0.624 0.09 0.03 0 / 1 0% / 7% NO Monitored Full 22920004 6 Dissolved oxygen 14 / 5 16.8 9.2 9.5 NA / 2 NA / 14% NO Monitored Full 22920004 6 pH 14 / 5 9.4 8.4 8.4 4 / NA 29% / NA YES Monitored Not 22920004 6 Temperature 14 / 5 29.4 24.7 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 22920004 6 10 563.134 100 % 20.937 85.6 % NO Evaluated NA Class C -
Conventional Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Violations % Violations Significantly >10% Violations Assessment Type Support Level 22920004 6 Inorganic nitrogen (nitrate and nitrite) 14 / 5 4.4 0.87 0.2 0 0% NO Monitored Full Class HH - No Data Note: Lake Darling was drawn down in 2009 as part of a restoration project at this lake. It remained drawn down in 2010.