Assessment Comments
Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, and (4) results of the IDNR-county voluntary beach monitoring program in 2004.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “fully supported.” The Class B(LW) aquatic life uses are assessed (evaluated) as “partially supported” due to the impacts of siltation. Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring at this lake. Sources of data for this assessment include: (1) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, and (4) results of the IDNR-county voluntary beach monitoring program in 2004.
Note: A TMDL for siltation at Yellow Smoke Lake was prepared by IDNR and approved by EPA in 2002; thus, this waterbody was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. Because all Section 303(d) impairments identified for the 2008 assessment/listing cycle (siltation) are addressed by the TMDL, this waterbody remains in IR Category 4a (TMDL approved) for the 2008 assessment/listing cycle.
EXPLANATION: Results of IDNR county beach monitoring from 2004 suggest that the Class A1 uses are assessed (evaluated) as “fully supported.” Levels of indicator bacteria Yellow Smoke Lake Beach were monitored approximately once per week during the primary contact recreation season (May through August) of 2004 (13 samples) as part of the IDNR county 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) all thirty-day geometric means for 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 5-sample, 30-day geometric mean exceeds the state criterion of 126 orgs/100 ml during the three-year assessment period, the Class A1 uses should be assessed as “not supported.” Also, 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 Yellow Smoke Lake Beach, the geometric means of all 5 thirty-day periods during the summer recreation season of 2004 were below the Iowa water quality standard of 126 E. coli orgs/100 ml. Also, no samples exceeded Iowa’s single-sample maximum criterion (235 E. coli orgs/100 ml) in 2004. According to IDNR’s assessment methodology and U.S. EPA guidelines, these results suggest full support of the Class A1 (primary contact recreation) uses.
Results from the ISU and UHL lake surveys suggest that the Class A1 (primary contact recreation) uses at Yellow Smoke Lake are “fully supported.” Using the median values from these surveys from 2002 through 2006 (approximately 25 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 43, 50, and 57 respectively for Yellow Smoke Lake. According to Carlson (1977) the Secchi depth and chlorophyll a values place Yellow Smoke Lake in the mesotrophic category, while the total phosphorus value places Yellow Smoke Lake in the eutrophic category. These values suggest low levels of chlorophyll a and suspended algae in the water, exceptional water transparency, and relatively low levels of phosphorus in the water column.
The level of inorganic suspended solids is low at Yellow Smoke Lake and suggests that non-algal turbidity does not cause water quality problems. The median inorganic suspended solids concentration at Yellow Smoke Lake was 1.8 mg/L, which was the 13th lowest of the 132 monitored lakes.
Data from the 2002-2006 ISU and UHL surveys suggest a very small population of cyanobacteria exists at Yellow Smoke Lake, which does not cause water quality problems at the lake. These data show that cyanobacteria comprised only 30% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (1.8 mg/L) was the 9th lowest of the 132 lakes sampled.
The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported.” Information from the IDNR Fisheries Bureau suggests that the Class B(LW) aquatic life uses should remain assessed as "partially supported" due to siltation impacts in the lake. According to IDNR's December 13, 2001 TMDL for Yellow Smoke Lake, the primary water quality impact at this lake is accumulated sediment and its interference with reproduction and growth of fish and other aquatic life; this impact occurs primarily in the eastern portion of the lake. The lake has steep sides and a hard clay bottom; these conditions present less than optimal conditions for spawning of species such important fish species as bluegill and largemouth bass. Prior to sedimentation impacts, however, the east arm of the lake was shallow and was ideal as spawning habitat for these and other fish species. That area is now covered with several feet of fine silt that make successful spawning almost impossible. Although this is a very small portion of the lake overall (under 10% of the total surface area of the lake), it is a key habitat (50%-70% of available spawning habitat). The deposition of sediment in the east arm has severely limited the fishery in the entire lake.
Data from the ISU and UHL lake surveys, however, show good chemical water quality at Yellow Smoke Lake. Results from these surveys show that during 2002-2006 there were no violations of the Class B(LW) criterion for ammonia in 19 samples, dissolved oxygen in 25 samples, and pH in 25 samples. These results suggest “full support” of the Class B(LW) uses at Yellow Smoke Lake.
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this lake.
