Green Belt Lake IA 02-CED-548

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 2007 by University Hygienic Laboratory (UHL), and (3) 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 2006 through 2010 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2006 through 2007 by University Hygienic Laboratory (UHL), and (3) 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 2012 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 and UHL ambient monitoring program suggest good water quality at Green Belt Lake.   Using the median values from these surveys from 2006 through 2010 (approximately 20 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 52, 50, and 52 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 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 (2.0 mg/L) was the 15th lowest median of the 134 lakes sampled by the ISU and UHL programs.

Data from the 2006-2010 ISU and UHL surveys suggest a relatively small population of cyanobacteria exists at Green Belt Lake.   These data show that cyanobacteria comprised 93% of the phytoplankton wet mass at this lake.   The median cyanobacteria wet mass (10.5 mg/L) was the 27th lowest of the 134 lakes sampled.  

The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported.”  Results from the ISU and UHL lake surveys from 2006-2010 show no violations of the Class B(LW) criteria for ammonia in 20 samples, or dissolved oxygen in 20 samples.   The pH data show 2 violations of the Class B(LW) criterion for pH in 20 samples (10%).   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 B(LW) uses at Green Belt Lake.

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