Rush Lake IA 06-LSR-1773
Osceola County S36T100NR40W 1 mi NE of Ocheyedan.
- Cycle
- 2026
- Current Phase
- Public Comment
- Overall IR
- 3 - Insufficient data exist to determine whether any designated uses are met.
- Trophic
- Hypereutrophic
- Trend
- Unknown
- Created
- 1/12/2026 12:46:55 PM
- Updated
- 1/12/2026 12:48:59 PM
The Class BLW use remains 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 shallow lake also suggest (evaluated) impairment "WINOFI" due to aesthetically objectionable conditions. All other designated uses remain “not assessed.”
Data Sources: Data Source Data Source ID Data Type Data Age Site ID Site Name Site Description Iowa DNR 6 WQ CY 2021-2021 14000360 Rush Lake Class BLW – Shallow Lake TSI: Site ID Data Source ID Parameter Name # Samples / # Years Minimum Value Maximum Value Median Value Median TSI Violation? Assessment Type Support Level 14000360 6 Chlorophyll a TSI 5 / 1 73 80 76 YES Evaluated WINOFI The TSI value for Secchi depth is not used to evaluate the attainment of the 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 use, but the index value is limited by the depth of the lake. Thus, the combination of total suspended solids and chlorophyll a was used to determine whether or not the Class BLW use was impaired in these shallow systems. 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 14000360 6 Total suspended solids 5 / 1 29 140 65 YES Evaluated WINOFI Guidelines for wetland assessment from the Upper Mississippi River Conservation Committee’s Water Quality Technical Section (2003) state that a median 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 (SAV) in wetlands and shallow lakes. High levels of total suspended solids impede the growth of SAV. SAV 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