Lizard Lake IA 04-UDM-1281
Pocahontas County S22T91NR34W 4 mi SW of Gilmore City.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Improving
- Created
- 6/13/2019 1:59:16 PM
- Updated
- 6/13/2019 2:16:49 PM
The Class B(LW) aquatic life uses are assessed (monitored) as "not supported" due to high levels of total suspended solids that leads to an impairment of the narrative criteria protecting against aesthetically objectionable conditions. High levels of algae at this wetland also suggest impairment due to aesthetically objectionable conditions. The fish consumption uses remain "not assessed" due to the lack of water quality information upon which to base an assessment. Sources of data for this assessment include (1) results of water quality, aquatic vegetation, and fish monitoring conducted by the IDNR shallow lakes and wetlands monitoring program in 2014-2016 and information from the IDNR Wildlife Bureau and (2) results of the statewide survey of Iowa lakes conducted from 2014 through 2016 by Iowa State University (ISU).
Note: Lizard Lake was drawn down in 2012 and 2013 for restoration work, thus, monitoring was not completed while the lake was drained. Using the overall median values from the DNR shallow lakes and wetlands monitoring program from 2014 through 2016 (approximately 23 samples), the median growing season total suspended solids concentration was 5.5 mg/L; this median value is well below the UMRCC guideline and suggests (monitored) "full support" of the aquatic life uses.Lizard Lake was listed as "not supporting" its Class B(LW) uses due to violations of the UMRCC guidelinefor Turbidity: Suspended Solids in the 2016 assessment cycle. According to DNR's methodology, a lake must meet water quality standards for two consecutive cycles to suggest de-listing. Therefore, Lizard Lakewill remain listed for the 2018 cycle as "not supporting" its Class B(LW) uses due to Turbidity: Suspended Solids. In addition, the level of algae also suggests (monitored)"full support" of the aquatic life uses at Lizard Lake. The Carlson’s (1977) trophic state index value for chlorophyll a was 58. According to Carlson (1977), the index value for chlorophyll a places Lizard Lake in the eutrophic category. This value suggests relatively low levels of chlorophyll a and suspended algae in the water and (monitored) "full support" of the aquatic life uses.Based on DNR's methodology, the median TSI value for chlorophyll a must be 63 or less for two consecutive assessment/listing cycles before a lake can be removed from the state's Section 303(d) list (IR Category 5). Therefore, Lizard Lake will remain listed as "partially supported" for the 2018 assessment/listing cycle.
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.
NOTE:The TSI value for Secchi depth is not used to evaluate the attainment of aquatic life goals 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 B(LW) 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 B(LW) uses are impaired in these shallow systems.