Lake Smith IA 04-EDM-981

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Lake Smith are assessed (monitored) as "partially 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 2010-2014 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 65, 66, and 71 respectively for Lake Smith. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Lake Smith in between the Eutrophic and the Hypereutrophic categories. These values suggest high levels of chlorophyll a and suspended algae in the water, poor water transparency, and very high levels of phosphorus in the water column. The data show one violation of the Class A1 criterion for pH in 15 samples.

 A TMDL for noxious aquatic plants at Lake Smith was prepared by IDNR and approved by EPA in 2005.   The basis of the impairment at this lake was high populations of cyanobacteria (=noxious aquatic plants).   Based on recent monitoring, a fish kill in the winter of 2000-01 and a subsequent lake renovation has significantly decreased the amount of cyanobacteria in this lake.   Recent ISU lake monitoring data strongly suggest that the impairment due to noxious aquatic plants (cyanobacteria) no longer exists.   Non-cyanobacteria algal populations, however, remain elevated at this lake and suggest "partial support" of the Class A1 uses.   Because algae populations are addressed in the TMDL this lake is placed in IR Category 4a (impaired; TMDL approved) for the 2014 cycle.

The level of inorganic suspended solids was relatively low at Lake Smith, and does not suggest water quality problems due to non-algal turbidity. The median level of inorganic suspended solids in Lake Smith (2.5 mg/L) was ranked 39th 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 Lake Smith. These data show that cyanobacteria comprised 44% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (7.2 mg/L) was ranked 21st 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 one violation of the criterion for pH in 15 samples(7%). 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 Lake Smith.

Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S.   EPA/IDNR fish contaminant (RAFT) monitoring at Lake Smith in 2013.    The composite samples of fillets from largemouth bass and channel catfish had low levels of contaminants.    Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.248 ppm.    Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: total PCBs: <0.6 ppm; and technical chlordane: <0.2 ppm.    The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses.     The fish contaminant data generated from the 2013 RAFT sampling conducted at this lake show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.