East Twin Lake IA 02-IOW-777
Hancock County S29T94NR24W 3 mi. E of Kanawha.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 3 - Insufficient data exist to determine whether any designated uses are met.
- Trend
- Unknown
- Created
- 12/22/2021 8:14:36 AM
- Updated
- 2/17/2022 2:38:15 PM
The Class BLW use was assessed (evaluated) as "WINOFI" due to high levels of total suspended solids that leads to an impairment of the narrative criteria protecting against undesirable or nuisance aquatic life. High levels of algae at this wetland also suggest impairment due to aesthetically objectionable conditions. All other designated uses were “not assessed.” This assessment was the same as that developed for the previous assessment/listing cycles (not impaired).
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2019-2020 14000289 East
Twin 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 14000289 6 Chlorophyll a TSI 9 / 2 50 83 74 YES Evaluated WINOFI 14000289 6 Total Phosphorus TSI 9 / 2 73 101 86 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 B(LW) 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
B(LW) 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 14000289 6 Ammonia 8 / 2 0.025 3.6 0.5 NA 0 / 0 3 NO Evaluated Full 14000289 6 Dissolved Oxygen 9 / 2 4.26 15.35 9.71 2 NA / NA 3 NO Evaluated Full 14000289 6 pH 9 / 2 7.27 9.41 8.16 1 NA / NA 3 NO Evaluated Full 14000289 6 Temperature 9 / 2 11.5 24.9 18.7 0 NA / NA 3 NO Evaluated 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 14000289 6 Total suspended solids 9 / 2 13 160 90 Yes Evaluated WINOFI 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 - Fish Tissue sampling: No Data - In general, Iowa wetlands are not managed for recreational
fisheries; thus, fish contaminant monitoring is not typically conducted at
these waterbodies.