Diamond Lake IA 06-LSR-1672
Dickinson County S15T100NR37W 2.5 mi N of Montgomery.
- Cycle
- 2022
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Stable
- Created
- 1/4/2022 1:19:36 PM
- Updated
- 1/27/2022 12:37:11 PM
The Class BLW use was assessed as "not supported" due to frequent violations of the Class BLW criteria for pH. 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 2016-2020 29300002 Diamond
Lake (center)-Dickinson-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 29300002 6 Chlorophyll a TSI 15 / 4 24 69 50 NO Monitored Full 29300002 6 Total Phosphorus TSI 15 / 4 46 90 53 NA NA NA 29300002 6 Inorganic suspended solids 10 / 2 0 17 0.5 NA NA NA 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 is used to determine whether or not the Class BLW
use is 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 29300002 6 Ammonia 14 / 4 0.01 2.36 0.25 NA 0 / 1 4 NO Monitored Full 29300002 6 Dissolved Oxygen 14 / 4 2.3 16.5 9.8 1 NA / NA 4 NO Monitored Full 29300002 6 pH 14 / 4 7.38 12.75 9.28 6 NA / NA 4 YES Monitored Not 29300002 6 Temperature 14 / 4 13.2 29.7 22.7 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 29300002 6 Total suspended solids 15 / 4 0.5 23 3 NO Monitored Full 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 (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
Additional Notes: The water
level at Diamond Lake was lowered in 2007 for a restoration project that
renovated fish populations and increased rooted aquatic vegetation at this
lake. The goals of this project were to improve wildlife habitat and water
quality at this shallow lake.