Little River Watershed Lake IA 05-GRA-1358

Results of IDNR beach monitoring from 2014 suggest that the Class A1 uses are "Partially Supported." Levels of indicator bacteria at Little River Recreation Area Beach were monitored once per week during the primary contact recreation seasons (May through September) of 2014 (12 samples), as part of the IDNR beach monitoring program.   According to IDNR’s assessment methodology two conditions need to be met for results of beach monitoring to indicate “full support” of the Class A1 (primary contact recreation) uses: (1) the geometric mean of the samples from each recreation season of the three-year assessment period are less than the state's geometric mean criterion of 126 E.  coli orgs/100 ml and (2) not more than 10% of the samples during any one recreation season exceeds the state's single-sample maximum value of 235 E.  coli orgs/100 ml. If a sampling season geometric mean exceeds the state criterion of 1000 orgs/100 ml during the three-year assessment period, the Class A1 uses should be assessed as “not supported.” Also, if a sampling season geometric mean exceeds the state criterion of 126 orgs/100 ml during the three-year assessment period and/or if significantly more than 10% of the samples in any one of the three recreation seasons exceed Iowa's single-sample maximum value of 235 E.  coli orgs/100 ml, the Class A1 uses should be assessed as “partially supported.” This assessment approach is based on U.S.   EPA guidelines (see pgs 3-33 to 3-35 of U.S.   EPA 1997b).

At Little River Recreation Area Beach, the geometric means from 2014 were all below the Iowa water quality standard of 126 E.  coli orgs/100 ml.   The geometric mean was 12 E.  coli orgs/100 ml in 2014.   The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E.  coli orgs/100 ml) was 0% in 2014.   None of these are significantly greater than 10% of the samples and therefore do not suggest impairment of the Class A1 uses.   According to IDNR's assessment methodology and U.S.  EPA guidelines, these results suggest "Fully Supported" of the Class A1 uses. However, in the 2014 assessment/listing cycle, the Class A1 uses were listed as "partially supported" due to geometric mean and single sample maximum exceedances.  According to IDNR's methodology, lakes must meet water quality standards for two consecutive assessment/listing cycles to suggest de-listing.  Therefore, the Class A1 uses will remain listed as "partially supported" for the 2016 cycle. 

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Little River Lake are assessed (monitored) as "partially supported" due to high levels of turbidity based on information from the ISU lake survey. Using the median values from these surveys from 2010-2014 (approximately 11 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 67, 50, and 71 respectively for Little River Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Little River Lake in between the Eutrophic and the Hypereutrophic categories. These values suggest low 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 11 samples.

Note: A TMDL for turbidity and total phosphorus at Little River Watershed Lake was prepared for and approved by EPA in March 2014.  Because the indicator bacteria impairment at Little River Watershed Lake was not addressed in this TMDL, it will remain listed in category 5a; impaired - TMDL needed.  

The level of inorganic suspended solids was moderately high at Little River Lake, and does suggest that non-algal turbidity may contribute to the impairment at this lake. The median level of inorganic suspended solids in Little River Lake (3.7 mg/L) was ranked 77th among the 138 lakes by the ISU lake survey.

Data from the 2010-2014 ISU lake survey suggest a moderate population of cyanobacteria exists at Little River Lake. These data show that cyanobacteria comprised 91% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (16.4 mg/L) was ranked 49th of the 138 lakes sampled.

The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported” based on information from IDNR’s Fisheries Bureau.   Information from the IDNR Fisheries Bureau indicates that Little River Lake water has greatly improved since renovation in 2011.  With the removal of common carp aquatic vegetation has rebounded and there is a defined weedline around the lake.  The fishing has been outstanding with quality bluegill, crappie, walleye, and some bass caught by anglers. Results of the ISU lake survey from 2010-2014 show there were no violations of the criterion for ammonia in 11 samples(0%), one violation of the criterion for dissolved oxygen in 11 samples(9%), and one violation of the criterion for pH in 11 samples(9%). 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 Little River Lake.

The Class C (drinking water) uses remain assessed (evaluated) as “partially supported” due to increasing turbidities in the lake following the failure of a silt dam at the upper end of the lake in 2007. The only parameter collected as part of the ISU lake surveys relevant to support of Class C (drinking water) uses is nitrate. While the results of the ISU surveys from 2010-2014 show that nitrate levels are relatively low at this lake (maximum value = 1.5 mg/l; median = 0.8 mg/l).

Results of Syngenta's "Iowa Voluntary Atrazine Monitoring Program" from 2004 through 2006, however, show low levels of atrazine in this lake and no impact to the Class C drinking water uses.   NOTE: Little River Lake was not monitored as part of the Syngenta Voluntary Atrazine monitoring program in 2007 or 2008.   The monitoring from 2004 through 2006 showed that the time-weighted mean levels of atrazine in the samples collected in calendar years 2004, 2005, and 2006 were well-below the MCL of 3.0 ug/l.   The mean and median atrazine level over this three-year period (N=78) were 1.2 ug/L and 1.1 ug/L, respectively.   The maximum value for this period was 2.7 ug/l.   None of the 65 moving annual averages for atrazine for the years 2004, 2005, and 2006 at Little River Lake exceeded the MCL (maximum average = 1.6 ug/l).   Based on DNR's Section 305(b) assessment methodology, if the average contaminant level in source water is less than the MCL, the Class C (drinking water) uses of the source water should be assessed as "fully supported." In addition, results of the ISU and UHL lake surveys from 2008-2012 show that nitrate levels are low at this lake (maximum: 1.25 mg/L, median: 0.8 mg/L) relative to the MCL (10 mg/L).  

Fish consumption uses are assessed (monitored) as “fully supported” based on fish contaminant monitoring in 2005, 2006, and 2008.   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 composite samples of fillets from channel catfish and white crappie in 2005 had generally low levels of contaminants.   Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.92 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.   Levels of primary contaminants in the composite sample of white crappie fillets were as follows: mercury: 0.12 ppm; total PCBs: <0.09 ppm; and technical chlordane: <0.03 ppm.   The level of mercury in the sample of channel catfish fillets, however, exceeds the IDNR/IDPH trigger level of 0.30 ppm for a one meal per week consumption advisory.   According to the IDNR/IDPH advisory protocol, two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.   Follow up sampling was conducted in 2006.   The level of mercury in channel catfish was 0.186 ppm.   The level of mercury in largemouth bass was 0.174 ppm.   Both of these levels were below the trigger level for a fish consumption advisory, therefore Little River Lake is assessed as “fully supporting” the fish consumption uses.   Follow up sampling was again conducted in 2008.   The level of technical chlordane (<0.15 ppm) in channel catfish was below the trigger level for a fish consumption advisory.   The level of total PCBs in the fillets of channel catfish was <0.45 ppm.   Due to interference when analyzing the sample, the detection limit for this sample was above the advisory trigger level (0.2 ppm).   Because the level of total PCBs is below the detection limit and past levels of PCBs in this lake were very low (<0.09 ppm) this result does not suggest cause for concern.   Also the likelihood of high levels of PCBs at this lake is low, therefore this lake will remain assessed as "fully supporting" the fish consumption uses.   Additional follow-up monitoring will be conducted in the future.