Pleasant Lake IA 06-LSR-1649
Dickinson County S7T99NR35W 5 mi. SE of Orleans.
The Class BLW use was assessed (monitored) as "not supported" due to high levels of algae and turbidity at this wetland that suggest impairment due to adverse impacts on plant/animal communities. Additionally, the Class BLW use was assessed (monitored) as "not supported" due to violations of the class BLW criteria for pH. All other designated uses were “not assessed.”
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2018-2020 22300020 Pleasant
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 22300020 6 Chlorophyll a TSI 10 / 2 44 74 66 YES Evaluated Not 22300020 6 Total Phosphorus TSI 10 / 2 61 77 76 NA NA NA 22300020 6 Inorganic suspended solids 5 / 1 3 76 6 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 22300020 6 Ammonia 4 / 1 0.02 0.16 0.06 NA 0 / 0 2 NO Evaluated Full 22300020 6 Dissolved Oxygen 10 / 2 8.1 14.2 10.5 0 NA / NA 3 NO Monitored Full 22300020 6 pH 10 / 2 8.21 11.96 9.29 5 NA / NA 3 YES Monitored Not 22300020 6 Temperature 10 / 2 13.56 26.83 22.1 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 22300020 6 Total suspended solids 10 / 2 4 76 40 Yes Monitored Not 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