Assessment Comments
Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2006 through 2010 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2006 through 2008 by University Hygienic Laboratory (UHL), and (3) information from the IDNR Fisheries Bureau.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” due to high levels of algae that violate Iowa's narrative criteria protecting against aesthetically objectionable conditions. Violations of Iowa’s water quality criterion for pH also contribute to this impairment. The Class B(LW) (aquatic life) uses are assessed (monitored) as “partially supported” due to violations of Iowa’s water quality criterion for pH. Fish consumption uses remain “not assessed” due to a lack of fish contaminant monitoring at this lake. Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2006 through 2010 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2006 through 2008 by University Hygienic Laboratory (UHL), and (3) information from the IDNR Fisheries Bureau.
EXPLANATION: For the 2012 reporting cycle, the Class A1 (primary contact recreation) uses for Kent Park Lake are assessed (monitored) as “partially supported” due to high levels of algae and violations of the state’s water quality criteria for pH. Using the median values from the ISU and UHL lake surveys from 2006 through 2010 (approximately 22 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 62, 63, and 65 respectively for Kent Park Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Kent Park Lake in between the eutrophic and the hypereutrophic categories. These values suggest moderately high levels of chlorophyll a and suspended algae in the water, moderately poor water transparency, and high levels of phosphorus in the water column.
NOTE: The trophic state index value for chlorophyll a at Kent Park Lake is below the impairment trigger of 65. However, Kent Park Lake was assessed as "partially supporting" the Class A1 uses due to algae for the 2010 assessment/listing cycle. Based on IDNR's assessment methodology, two assessment/listing cycles with TSI values less than or equal to 63 are necessary to suggest de-listing of the algae impairment. Therefore, Kent Park Lake will remain assessed as "partially supported" for the 2012 Integrated Report.
The levels of inorganic suspended solids at this lake were moderately high and do not suggest that non-algal turbidity contributes to the impairment at this lake. The median level of inorganic suspended solids in Kent Park Lake (3.0 mg/L) was the 54th lowest median of the 134 lakes sampled by the ISU and UHL programs.
Data from the 2006-2010 ISU and UHL surveys suggest a moderate population of cyanobacteria exists at Kent Park Lake, which does not contribute to impairment at this lake. These data show that cyanobacteria comprised 67% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (20.5 mg/L) was the 69th lowest of the 134 lakes sampled.
The Class B(LW) (aquatic life) uses are assessed as “partially supported” based on information from IDNR’s Fisheries Bureau and results from the ISU and UHL lake surveys. The ISU and UHL lake surveys data from 2006-2010 show no violations of the Class B(LW) criteria for ammonia in 21 samples, or dissolved oxygen in 22 samples. The pH data show 1 violations of the Class A1,B(LW) criterion for pH in 22 samples (5%). Based on IDNR’s assessment methodology these violations are not significantly greater than 10% of the samples and therefore do not suggest impairment of the Class A1,B(LW) uses at Kent Park Lake. However, Kent Park Lake was assessed as "partially supporting" the Class A1,B(LW) uses for the 2010 assessment/listing cycle due to violations of the pH criteria. Based on IDNR's assessment methodology 2 consecutive assessment/listing cycles where there are not significantly greater than 10% of the samples violating the standard are necessary to suggest de-listing of the pH impairment. Therefore, Kent Park Lake will remain assessed as "partially supported" for the 2012 Integrated Report. These violations likely reflect primary productivity at Kent Park Lake and do not reflect the input of pollutants into this lake.
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this lake.
