Snyder Bend Lake IA 06-WEM-1734

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Snyder Bend Lake are assessed (monitored) as "not supported" due to poor water transparency and aesthetically objectionable conditions caused by algae blooms based on information from the ISU lake survey. Using the median values from these surveys from 2011-2014 (approximately 10 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 81, 67, and 75 respectively for Snyder Bend Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Snyder Bend Lake in between the Eutrophic and the Hypereutrophic categories. These values suggest high levels of chlorophyll a and suspended algae in the water, extremely poor water transparency, and extremely high levels of phosphorus in the water column. The data show no violations of the Class A1 criterion for pH in 10 samples.

The level of inorganic suspended solids was extremely high at Snyder Bend Lake, and does suggest that non-algal turbidity contributes to the impairment at this lake. The median level of inorganic suspended solids in Snyder Bend Lake (38 mg/L) was ranked 137th among the 138 lakes by the ISU lake survey.

Data from the 2011-2014 ISU lake survey suggest a moderate population of cyanobacteria exists at Snyder Bend Lake. These data show that cyanobacteria comprised 76% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (16.6 mg/L) was ranked 50th of the 138 lakes sampled.

The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” due to two fish kills in 2004 and 2005. Results of the ISU lake survey from 2011-2014, however, show there were no violations of the criterion for ammonia in 10 samples(0%), no violations of the criterion for dissolved oxygen in 10 samples(0%), and no violations of the criterion for pH in 10 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 Snyder Bend Lake.

The first of these kills occurred on or before June 9, 2004.   The kill was attributed to natural causes (“spawning stress”) related to below-normal water levels in the lake.   At the time of the kill, the lake level was estimated to be approximately 18 inches below normal.   The normal pumping of water into the lake from the Missouri River had been suspended for a two-week period due to high levels of turbidity and suspended solids in the river, thus adversely affecting the lake level.   An estimated 200 common carp and buffalo were killed; other fish species appeared to be healthy.   No estimate of the value of the fish killed was provided.   The pumping of water to the lake from the Missouri River was expected to raise the lake level and help prevent additional stress to the fish populations.  

The second of these kills occurred on or before July 18, 2005.   The kill was attributed to natural causes (high water temperature).   An estimated 65 fish were killed; all the fish were northern pike of from 3 to 15 pounds.   No estimate of the value of the fish killed was provided.   Because northern pike are susceptible to high water temperatures, and because other species were not affected, the kill was attributed to high water temperature (85F).   Although unrelated to the kill, the lake area received 0.7-inch of rainfall the evening prior to the kill.  

This is the same assessment as that developed for the 2008, 2010, 2012 and 2014 assessment/listing cycles.   The continuance of the IR Category 3b listing is based on IDNR's assessment methodology that states the following  the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired”.   If a cause of the kill was not identified during the IDNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated” and will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation.   Thus, this assessment segment will remain in Category 3b of Iowa’s Integrated Report.  

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

Note: Lake bathymetry was changed in 2011 when the lake was inundated by flood waters. The lake was additionally became infested with Asian carp during this event.