Rodgers Park Lake IA 02-CED-526

Assessment Comments

Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2009-2012 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted in 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 “fully supported.”  The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported.”  Fish consumption uses remain “not assessed.”  Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 200-2012 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted in hrough 2008 by University Hygienic Laboratory (UHL), and (3) information from the IDNR Fisheries Bureau.

EXPLANATION: Results from the ISU and UHL lake surveys suggest that the Class A1 uses at Rodgers Park Lake are “fully supported.”  Using the median values from these surveys from 2008-2012 (approximately 15 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 54, 57, and 62 respectively for Rodgers Park Lake.   According to Carlson (1977) the Secchi depth and chlorophyll a values place Rodgers Park Lake in the eutrophic category, while the total phosphorus value places Rodgers Creek Lake in between the eutrophic and hypereutrophic categories.   These values suggest moderately high levels of chlorophyll a and suspended algae in the water, moderately poor water transparency, and moderately high levels of phosphorus in the water column.  

The level of inorganic suspended solids is moderately high at this lake and does not suggest an impairment due to high non-algal turbidity.   The median inorganic suspended solids concentration at Rodgers Park Lake was 2.8 mg/L, and ranked 55th of the 134 monitored lakes.

Data from the 2008-2012 ISU and UHL surveys suggest a relatively small population of cyanobacteria exists at Rodgers Park Lake, which does not contribute to impairment at this lake.   These data show that cyanobacteria comprised only 15% of the phytoplankton wet mass at this lake.   The median cyanobacteria wet mass (3.0 mg/L) and ranked 5th of the 134 lakes sampled.  

The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported” based on information from the IDNR Fisheries Bureau, and results from the ISU and UHL lake surveys.   The ISU and UHL lake surveys suggest relatively good chemical water quality at Rodgers Park Lake.   Data from these surveys show that during 2008-2012 show there were no violations of the Class B(LW) criterion for ammonia in 15 samples,  or pH in 17 samples.  There was one violation of the Class B(LW) criterion for dissolved oxygen in 15 samples (7%).  This violation is not significantly greater than 10% of samples violation the dissolved oxygen criterion, and therefore, constitutes "full support" of the Class B(LW) uses.  

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring at this lake.