Lizard Lake IA 04-UDM-1281
Pocahontas County S22T91NR34W 4 mi SW of Gilmore City.
- Cycle
- 2016
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trend
- Improving
- Created
- 8/3/2016 9:53:17 AM
- Updated
- 8/3/2016 9:53:17 AM
The Class B(LW) aquatic life uses are assessed (evaluated) 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 2012-2014 and information from the IDNR Wildlife Bureau and (2) results of the statewide survey of Iowa lakes conducted from 2012 through 2014 by Iowa State University (ISU).
Results of water quality monitoring conducted at Lizard Lake indicate that the aquatic life uses should be assessed (evaluated) as "not supported" due to high levels of total suspended solids and algae at this lake. This assessment of "not supported" remains from previous assessments because only 7 samples were collected between 2012-2014. Based on IDNR's assessment methodology, 9 samples within the most recent three year period are necessary to accurately characterize water quality for the purposes of identifying impaired waters. Using the overall median values from the IDNR shallow lakes and wetlands monitoring program from 2012 through 2014 (approximately 7 samples), the median growing season total suspended solids concentration was 5 mg/L; this median value is well below the UMRCC guideline and suggests (evaluated) "full support" of the aquatic life uses, however this assessment remains "not supported" due to a lack of enough data during the sampling period. In addition, the level of algae also suggests (evaluated) "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 (evaluated) "full support" of the aquatic life uses, however this assessment remains "not supported" due to a lack of enough data during the sampling period.
Note: Lizard Lake was drawn down in 2012 and 2013 for restoration work, thus, monitoring was not completed while the lake was drained.
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 instance, 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.