Nelson Park Lake IA 06-BOY-1506
Crawford County S2T82NR41W 4 mi. WNW of Dow City.
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 are “not assessed” due to a lack of information to base an assessment on. Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2010 through 2014 by Iowa State University (ISU), and (2) information from the IDNR Fisheries Bureau.
For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Nelson Lake are assessed (monitored) as "fully supported" based on information from the ISU lake survey. Using the median values from these surveys from 2010-2014 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 41, 46, and 52 respectively for Nelson Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Nelson Lake in between the Mesotrophic and the Eutrophic categories. These values suggest extremely low levels of chlorophyll a and suspended algae in the water, exceptional water transparency, and low levels of phosphorus in the water column. The data show no violations of the Class A1 criterion for pH in 15 samples. The level of inorganic suspended solids was low at Nelson Lake, and does not suggest water quality problems due to non-algal turbidity. The median level of inorganic suspended solids in Nelson Lake (2 mg/L) was ranked 10th among the 138 lakes by the ISU lake survey. Data from the 2010-2014 ISU lake survey suggest a small population of cyanobacteria exists at Nelson Lake. These data show that cyanobacteria comprised 22% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (0.9 mg/L) was ranked 1st of the 138 lakes sampled. The Class B(LW) (aquatic life) uses are assessed (monitored) as "fully supported." Results of the ISU lake survey from 2010-2014 show there were no violations of the criterion for ammonia in 15 samples(0%), one violation of the criterion for dissolved oxygen in 15 samples(7%), and no violations of the criterion for pH in 15 samples(0%). Based on IDNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest (fully supported/monitored) of the Class B(LW) uses of Nelson Lake. Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this lake.