Prairie Lake IA 06-LSR-1647
Dickinson County S23T99NR36W 3.5 mi. SE of Spirit Lake.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Unknown
- Created
- 1/4/2022 9:31:18 AM
- Updated
- 2/17/2022 3:10:34 PM
The Class BLW use was assessed as "not supported" due to violations of the Class BLW criterion for pH. All other designated uses were “not assessed.”
Class A PH Not. Lake TSI TSI (Secchi) Not. Class B PH Not. Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2016-2018 22300021 Prairie
Lake
Class BLW - TSI's Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Median Value Median TSI Violation? Assessment Type Support Level 22300021 6 Chlorophyll a TSI 10 / 2 24 82 57 NO Evaluated Full 22300021 6 Total Phosphorus TSI 10 / 2 50 85 61 NA NA NA 22300021 6 Inorganic suspended solids 10 / 2 0 71.5 4.1 NA NA NA The TSI value for Secchi depth is not used to evaluate the attainment of aquatic life use in shallow lakes. Due to the depth of these shallow lakes, TSI values for Secchi depth can be misleading. In some instances, the Secchi disk remains visible at the bottom of the lake and the depth of the lake is recorded as the Secchi depth. In these instances, water clarity may be sufficient to support the Class BLW uses, but the index value is limited by the depth of the lake. Thus the combination of total suspended solids and chlorophyll a will be used to determine whether or not the Class BLW uses are impaired in these shallow systems. 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 22300021 6 Ammonia 5 / 1 0.025 0.324 0.13 NA 0 / 2 2 NO Evaluated Full 22300021 6 Dissolved Oxygen 10 / 2 3.36 12.86 8.94 1 NA / NA 3 NO Monitored Full 22300021 6 pH 10 / 2 7.58 12.08 9.61 5 NA / NA 3 YES Monitored Not 22300021 6 Temperature 10 / 2 14.8 26.2 21.7 0 NA / NA 3 NO Monitored Full Class BLW - Protection of Submerged Aquatic Vegetation: Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Median Value Median Value = SAV Assessment Type Support Level 22300021 6 Total suspended solids 10 / 2 1.4 186.5 8.9 NO Monitored Full Guidelines for wetland assessment from the Upper Mississippi
River Conservation Committee’s Water Quality Technical Section (2003) state
that an average total suspended solids concentration during the growing season
of less than 30 mg/L is necessary to provide sufficient water clarity to
support the growth of submersed aquatic vegetation in wetlands and shallow
lakes. High levels of total suspended solids impede the growth of submersed
aquatic vegetation (SAV). Submersed aquatic vegetation is critical to the
health of wetland and shallow lake ecosystems. The elimination of SAV can
degrade habitat quality such that undesirable aquatic species such as
cyanobacteria, common carp and fathead minnows dominate. As such, the
suppression of SAV constitutes a violation of Iowa’s narrative water quality
criteria protecting against undesirable or nuisance aquatic life.
Class HH: No Data