Little River Watershed Lake IA 05-GRA-1358
Decatur County S19T69NR25W approx 2 mi NW of Leon.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 5 - Water is impaired or threatened and a TMDL is needed.
- Trophic
- Eutrophic
- Trend
- Stable
- Created
- 10/16/2018 9:21:11 AM
- Updated
- 6/6/2019 2:04:25 PM
The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to poor water clarity caused by non-algal turbidity and violations to the state's water quality criteria for indicator bacteria. The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” due to high turbidity that is adversely affecting the lake's fish populations. The Class C (drinking water) uses are assessed (evaluated) as "partially supported" due to increased levels of turbidity. Fish consumption are assessed as (evaluated) "partially supporting" due to potential of a fish consumption advisory. Sources of data for this assessment include (1) results of IDNR/UHL beach monitoring from 2014 through 2016, (2) results of the statewide survey of Iowa lakes conducted from 2012 through 2016 by Iowa State University (ISU), (3) information from the IDNR Fisheries Bureau, (4) results of Syngenta’s voluntary atrazine monitoring program (VMP) from 2004-2006, and (5) results of U.S. EPA/IDNR fish contaminant monitoring in 2008 and 2016.
Results of DNR beach monitoring from 2014 through 2016 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), 2015 (14 samples) and 2016 (14 samples), as part of the DNR beach monitoring program. According to DNR’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, 2015 and 2016 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, 52 E. coli orgs/100 ml in 2015 and 7 E. coli orgs/100 ml in 2016. The percentage of samples exceeding Iowa's single-sample maximum criterion (235 E. coli orgs/100 ml) was 0% in 2014, 21% in 2015 and 0% in 2016. None of these are significantly greater than 10% of the samples and therefore do not suggest impairment of the Class A1 uses. According to DNR's assessment methodology and U.S. EPA guidelines, these results suggest "Fully Supported" of the Class A1 uses. However, in the 2016assessment/listing cycle, the Class A1 uses were listed as "partially supported" due to geometric mean and single sample maximum exceedances. According to DNR'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 2018cycle. For the 2018 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 2013-2016 (approximately 12 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 61, 52, and 68 respectively for Little River Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Little River Lake in the Eutrophic category. These values suggest low levels of chlorophyll a and suspended algae in the water, moderately poor water transparency, and high levels of phosphorus in the water column. The data show 2 violations of the Class A1 criterion for pH in 12 samples (17%).Although the index value for Secchi is below the impairment trigger of 65 for this assessment cycle, Little River Lake was listed as partially supporting its Class A1 uses due to aesthetically objectionable conditions. Based on DNR's methodology, the median TSI value for Secchi must be 63 or less for two consecutive assessment/listing cycles before a lake can be removed from the state's Section 303(d) list (IR Category 4a). Therefore, Little River Lake will remain listed as "not supported" for the 2018 assessment/listing cycle. 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 2013-2016 show that nitrate levels are extremely low at this lake (maximum value = 1.5 mg/l; median = 0.1 mg/l), these data are not sufficient for developing a valid assessment of support of the Class C uses.
Data from the 2013-2016 ISU lake survey suggest a moderate population of cyanobacteria exists at Little River Lake. These data show that cyanobacteria comprised 86% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (14.8 mg/L) was ranked 62nd of the 138 lakes sampled.
The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported” based on information from DNR’s Fisheries Bureau. Information from the DNR Fisheries Bureau indicates that Little River Lake water has greatly improved since the renovation in 2011. With the removal of common carp aquatic vegetation has rebounded and there is a defined weed line 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 2013-2016 show there were no violations of the criterion for ammonia in 12 samples(0%), 2 violations of the criterion for dissolved oxygen in 12 samples(17%), and 2 violations of the criterion for pH in 12 samples(17%). Based on DNR'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.
Fish consumption uses were assessed (evaluated) as “partially supported”based on fish contaminant monitoring in 2008 and 2016. 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. Sampling was 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.The composite samples of fillets from channel catfish and white crappie in2016 had generally low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.0909 ppm; total PCBs: <0.06 ppm; and technical chlordane: <0.02 ppm. Levels of primary contaminants in the composite sample of largemouth bass for mercury was 0.453 ppm. The level of mercury in the sample of largemouthbass, however, exceeds the DNR/IDPH trigger level of 0.30 ppm for a one meal per week consumption advisory. According to the DNR/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.