Cold Springs Lake IA 05-NSH-1420

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Cold Springs 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 60, 64, and 62 respectively for Cold Springs Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Cold Springs Lake in the Eutrophic category. These values suggest moderately high levels of chlorophyll a and suspended algae in the water, moderately poor water transparency, and moderately high levels of phosphorus in the water column. The data show 2 violations of the Class A1 criterion for pH in 15 samples.

The level of inorganic suspended solids was relatively low at Cold Springs Lake, and does not suggest water quality problems due to non-algal turbidity. The median level of inorganic suspended solids in Cold Springs Lake (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 Cold Springs Lake. These data show that cyanobacteria comprised 76% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (10.8 mg/L) was ranked 31st 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%), no violations of the criterion for dissolved oxygen in 15 samples(0%), and 2 violations of the criterion for pH in 15 samples(13%). 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 Cold Springs Lake.

Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S.   EPA/IDNR fish contaminant (RAFT) monitoring at Cold Springs Lake in 2012 and 2014.    The composite samples of fillets from largemouth bass and channel catfish had moderate levels of contaminants.    Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.3125 ppm.  This composite value is above the 1 meal/week advisory threshold.  The levels of mercury generated from this monitoring data are sufficiently high for concern and to justify follow-up monitoring.  According to IDNR's assessment methodology, the single occurrance of a contaminant above the advisory trigger level neither warrants issuance of an advisory not indicated impairment of the fish consumption uses: two consecutive sampoings that show contaminant levels above the trigger level are needed to justify impairment.  Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.0507 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 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 2012 and 2014 RAFT sampling conducted at this Cold Springs Lake show that the levels of contaminants do not yet warrant an advisory.  

Note: According to Iowa DNR Fisheries Biologists, the clear water and shallow lake basin of Cold Springs Lakes has been ideal for growing aquatic plants. In 2014, a dye treatment was used to suppress aquatic plant growth. It worked very well reducing plant and algae growth down to an acceptable level. The dye treatment was repeated in 2015 with poor results. In 2016 the dye was applied at a higher rate in hopes to repeat 2014 results and it is working.  Curly leaf pond weed an invasive plant showed up in Cold Springs a few years ago.  Curly leaf pondweed has been on the increase ever since.  In other lakes curly leaf emerges early, crowds out native plants, and dies off in late June promoting algae blooms.