Green Belt Lake IA 02-CED-548

Assessment Comments

Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2009-2012 by Iowa State University (ISU), and (2) information from the IDNR Fisheries Bureau. NOTE: Green Belt Lake was not sampled in 2008 because it was inaccessible due to flooding.

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 2009-2012 by Iowa State University (ISU), and (2) information from the IDNR Fisheries Bureau.   NOTE: Green Belt Lake was not sampled in 2008 because it was inaccessible due to flooding.

EXPLANATION:  For the 2014 reporting cycle, the Class A1 (primary contact recreation) uses for Green Belt Lake are assessed (monitored) as “fully supported.”  Results from the ISU lake survey suggest good water quality at Green Belt Lake.   Using the median values from these surveys from 2009-2012(approximately 12 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 54, 53, and 55 respectively for Green Belt Lake.   According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Green Belt Lake in the eutrophic category.   These values suggest low levels of chlorophyll a and suspended algae in the water, very good water transparency, and low levels of phosphorus in the water column.  

The levels of inorganic suspended solids at this lake were relatively low and do not suggest that non-algal turbidity causes an impairment at this lake.   The median level of inorganic suspended solids in Green Belt Lake (2.5 mg/L) and ranked 26th of the 134 lakes sampled by the ISU program.

Data from the 2009-2012 ISU survey suggests a relatively small population of cyanobacteria exists at Green Belt Lake.   These data show that cyanobacteria comprised 70% of the phytoplankton wet mass at this lake.   The median cyanobacteria wet mass (11.1 mg/L)and ranked 31st of the 134 lakes sampled.  

The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported.”  Results from the ISU lake survey from 2009-2012 show no violations of the Class B(LW) criteria for ammonia in 12 samples,no violations for pH in 12 samples, and dissolved oxygen in 12 samples.  Based on IDNR’s assessment methodology these data suggest "full support" of the Class B(LW) uses.

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