West Swan Lake IA 04-UDM-1754
Emmet County S31T99NR32W 3 mi. SE of Gruver.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Stable
- Created
- 1/5/2022 7:15:40 AM
- Updated
- 2/17/2022 2:53:43 PM
The Class BLW use was assessed as "not supported" 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.”
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site
Name Site
Description Iowa DNR 6 WQ CY 2017-2020 29320002 West
Swan Lake (center)-Emmet-2
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 29320002 6 Chlorophyll a TSI 19 / 4 47 83 66 YES Monitored Not 29320002 6 Total Phosphorus TSI 19 / 4 65 86 74 NA NA NA 29320002 6 Inorganic suspended solids 10 / 2 6 31 12 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 29320002 6 Ammonia 14 / 3 0.01 0.47 0.07 NA 0 / 0 4 NO Monitored Full 29320002 6 Dissolved Oxygen 20 / 4 4.05 13.86 9.32 2 NA / NA 5 NO Monitored Full 29320002 6 pH 20 / 4 7.28 10.48 8.56 2 NA / NA 5 NO Monitored Full 29320002 6 Temperature 20 / 4 12.8 29.5 22.2 0 NA / NA 5 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 29320002 6 Total suspended solids 19 / 4 12 62 35 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 Additional
information:
Additional monitoring of
fish and aquatic vegetation populations at West Swan Lake by DNR staff also
suggests that the high levels of total suspended solids and algae have adverse
effects on fish populations and limit the production of rooted aquatic
vegetation in this wetland. These results further indicate that the aquatic
life uses of this wetland should be assessed as "not supported."