Silver Lake IA 04-UDM-1229
Palo Alto County S20T95NR34W 2 mi W of Ayrshire.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Hypereutrophic
- Trend
- Stable
- Created
- 12/29/2021 11:30:58 AM
- Updated
- 2/17/2022 10:20:02 AM
The Class A1 use was assessed (monitored) as “not supported” due to poor water transparency caused by inorganic suspended solids, algae blooms that violate Iowa’s narrative water quality standard protecting against aesthetically objectionable conditions and due to frequent violations of the state criterion for pH. The Class BLW use was assessed (monitored) as "not supported" due to violations of the Class B(LW) criterion for pH. All other designated uses were “not assessed.” Note: A TMDL for algae and turbidity at Silver Lake was prepared by DNR and approved by EPA in 2005. Thus, these impairments are moved from IR Category 5a (impaired; TMDL required) to Category 4a (impaired; TMDL approved). Because not all the impairments identified for this lake are covered by this TMDL (pH), this lake remains in IR Category 5a.
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2016-2020 22740003 Silver
Lake (Palo Alto County)
Class A1 - 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 22740003 6 12 / 4 8.1 9.3 8.7 3 4 NO Monitored Full According to DNR's methodology, a lake must meet water
quality standards for two consecutive cycles to suggest
de-listing. Therefore, Silver Lake will remain listed for the 2022
cycle as "not supported" its Class A1 use due to pH. 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 22740003 6 Chlorophyll a TSI 14 / 5 26 83 69 YES Monitored Not 22740003 6 Secchi TSI 14 / 5 59 89 77 YES Monitored Not 22740003 6 Total Phosphorus TSI 14 / 5 64 92 81 NA NA NA 22740003 6 Inorganic suspended solids 14 / 5 0.6 128 16.8 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 22740003 6 Ammonia 12 / 4 0.0003 0.1804 0.05 NA 0 / 0 4 NO Monitored Full 22740003 6 Dissolved Oxygen 13 / 5 6.5 15.5 9.6 0 NA / NA 4 NO Monitored Full 22740003 6 pH 12 / 4 8.1 9.3 8.7 3 NA / NA 4 NO Monitored Full 22740003 6 Temperature 13 / 5 16.2 27.3 22.7 0 NA / NA 4 NO Monitored Full According to DNR's methodology, a lake must meet water
quality standards for two consecutive cycles to suggest
de-listing. Therefore, Silver Lake will remain listed for the 2022
cycle as "not supported" its Class BLW use due to pH. 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 22740003 6 5 71.81 91.9% 7.79 67.5% NO Evaluated NA
Class HH: No Data