Pickerel Lake IA 04-RAC-1180
Buena Vista County S1T93NR35W 4 mi NE of Marathon.
- Cycle
- 2024
- Release Status
- Final
- Overall IR
- 2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 11/14/2023 3:20:36 PM
- Updated
- 1/3/2024 1:31:10 PM
| Cycle Added | Class | Cause | Data Source | Rationale |
|---|---|---|---|---|
| 2020 | Class BLW | Organic Enrichment: Low Dissolved Oxygen | Ambient monitoring: Iowa DNR-shallow lakes & wetlands | New data: WQ improvement (chemical / physical / bacterial) |
The Class A1 use was assessed (monitored) as "fully supported." The Class BLW use was assessed (monitored) as "fully supported." 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 22110004 Pickerel
Lake
Class A1 - pH: Site ID Data Source ID # Samples / # Years Minimum Value Maximum Value Mean Value # Violations Violations needed for impairment Violates Significantly >10% Rule? Assessment Type Support Level 22110004 6 10 / 2 7.8 9.4 8.3 1 3 NO Mon Full 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 22110004 6 Chlorophyll a TSI 12 / 3 44 79 62 NO Evaluated Full 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 22110004 6 Dissolved Oxygen 12 / 3 5.92 16.86 10.11 0 NA / NA 4 NO Mon Full 22110004 6 pH 10 / 2 7.8 9.4 8.3 1 NA / NA 3 NO Mon Full 22110004 6 Temperature 12 / 3 14.5 26.5 21.7 0 NA / NA 4 NO Mon Full Pickerel Lake was assessed as "not supported" for the 2020 assessment/listing cycle based on Dissolved Oxygen. Based on DNR’s assessment methodology the current assessment/listing cycles must have fewer violations of the criterion based on the minimum required by on the 10% Rule to propose delisting. There were less than 10% of the samples exceeding the single-sample maximum criterion for the current assessment listing cycle. Therefore, the impairment for Dissolved Oxygen is suggested for delisting for the 2024 assessment/listing cycle. 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 22110004 6 Total suspended solids 12 / 3 4 52 13 NO Mon Full 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 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 22110004 6 Ammonia 5 / 1 0.09 0.04 0.02 0 / 0 NO Evaluated Full
Class HH - No Data