Assessment Comments
Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 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 violations of Iowa’s water quality criterion for pH. 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 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), and (3) information from the IDNR Fisheries Bureau.
EXPLANATION: For the 2008 reporting cycle, the Class A1 (primary contact recreation) uses for Kent Park Lake are assessed (monitored) as “partially supported” due to violations of the state’s water quality criteria for pH. Additional results from the ISU and UHL lake surveys, however, suggest full support of the Class A uses at Kent Park Lake. Using the median values from the ISU and UHL lake surveys from 2002 through 2006 (approximately 23 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 62, 64, and 66 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.
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 (4.0 mg/L) was the 69th highest median of the 132 lakes sampled by the ISU and UHL programs.
Data from the 2002-2006 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 90% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (21.8 mg/L) was the 58th highest of the 132 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 2002-2006 show no violations of the Class B(LW) criteria for ammonia in 15 samples, or dissolved oxygen in 23 samples. The pH data, however, show 5 violations of the Class B(LW) criterion for pH in 23 samples (22%). Based on IDNR’s assessment methodology these violations are significantly greater than 10% of the samples and therefore the Class B(LW) uses are assessed as “partially supporting.” 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.
