Elm Lake IA 02-IOW-657
Wright County S21T92NR24W 1 mi. S of Cornelia.
- Cycle
- 2026
- Current Phase
- Public Comment
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Hypereutrophic
- Trend
- Stable
- Created
- 10/27/2025 3:11:36 PM
- Updated
- 1/12/2026 11:07:07 AM
The Class BLW use was assessed as "not supported" due to high levels of total suspended solids that lead to an impairment of the narrative criteria protecting against undesirable or nuisance aquatic life. High levels of algae at this shallow lake also suggested 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 2020-2024 22990006 Elm
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 22990006 6 Chlorophyll a TSI 14 / 4 68 87 78 YES MONITORED NOT 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 - Binomial 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 22990006 6 Dissolved Oxygen 14 / 4 5.18 13.24 8.18 0 NA / NA 4 NO MONITORED FULL 22990006 6 pH 8 / 3 7.62 8.46 8.19 0 NA / NA 3 NO MONITORED FULL 22990006 6 Temperature 14 / 4 9.48 28.62 20.01 0 NA / NA 4 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 22990006 6 Total suspended solids 14 / 4 38 600 78 YES MONITORED NOT Class BLW - Toxic Parameters: Site ID Data Source ID Parameter Name # Samples / # Years Maximum Value Mean Value Median Value # Acute / Chronic Violations >1 Acute / Chronic Violation Assessment Type Support Level 22990006 6 Ammonia 5 / 2 0.05 0.03 0.02 0 / 0 NO EVALUATED FULL
Class BLW: Elm Lake has been on the list for shallow lakes management for some time. An effective downstream fish barrier in needed before management strategies can start. The fishery is in poor quality, dominated by Common Carp and Bullheads. These results
further indicated that the aquatic life use of this wetland should be assessed
as "not supported." Class HH - No Data