Belva Deer Lake IA 03-NSK-6241

Assessment Comments

Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted in 2006 and 2007 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2008 by University Hygienic Laboratory (UHL), (3) results of the IDNR-county voluntary beach monitoring program in 2006 and 2007, and (4) information from the IDNR Fisheries Bureau.

Basis for Assessment

SUMMARY: NOTE: Belva Deer Lake is not designated for Class A1 uses in the Iowa Surface Water Classification.   The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported.”  Fish consumption uses are “not assessed.”  Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted in 2006 and 2007 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2008 by University Hygienic Laboratory (UHL), (3) results of the IDNR-county voluntary beach monitoring program in 2006 and 2007, and (4) information from the IDNR Fisheries Bureau.

EXPLANATION: Results of IDNR county beach monitoring from 2006 through 2007 suggest that levels of indicator bacteria are low at Belva Deer Lake.   Levels of indicator bacteria at Belva Deer Lake beach were monitored approximately once per week during the primary contact recreation seasons (May through August) of 2006 (16 samples) and 2007 (14 samples) as part of the IDNR county beach monitoring program.   Because only two years of data were collected at this lake, these data are considered not sufficient to accurately characterize current water quality conditions, therefore the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).   According to IDNR’s assessment methodology, all thirty-day geometric means for the three-year assessment period must be less than the state’s geometric mean criterion of 126 E.  coli orgs/100 ml for results of beach monitoring to indicate “full support” of the Class A1 (primary contact recreation) uses.   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”.   This assessment approach is based on U.S.  EPA guidelines (see pgs 3-33 to 3-35 of U.S.  EPA 1997b).    

At Lake Belva Deer beach, the geometric means of all 22 thirty-day periods during the summer recreation seasons of 2006 and 2007 were below the Iowa water quality standard of 126 E.  coli orgs/100 ml.   These results suggest generally low levels of indicator bacteria at this lake.   Also, there were no violations of the single-sample maximum criteria of 235 orgs/100 ml in 2006 or 2007.   Thus, results from Lake Belva Deer beach do not suggest an impairment.  

Results from the ISU and UHL lake surveys also show good water quality at Belva Deer Lake.  Using the median values from these surveys from 2005 and 2008 (approximately 19 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 45, 50, and 57 respectively for Belva Deer Lake.   According to Carlson (1977) the Secchi depth and chlorophyll a values place Belva Deer Lake in the mesotrophic category, while the value for total phosphorus places Lake Belva Deer 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 was extremely low at this lake and does not suggest impairment due to high non-algal turbidity.   The median inorganic suspended solids concentration at Belva Deer Lake was 1.0 mg/L, which was the 4th lowest of the 132 monitored lakes.

Data from the 2005-2008 ISU and UHL surveys suggest a very small population of cyanobacteria exists at Belva Deer Lake.   These data show that cyanobacteria comprised 75% of the phytoplankton wet mass at this lake.   The median cyanobacteria wet mass (6.0 mg/L) was the 31st lowest of the 132 lakes sampled.  

The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported” based on information from the IDNR Fisheries Bureau, and results from the ISU and UHL lake surveys.   Information from the IDNR Fisheries Bureau suggests that water clarity is very good at Belva Deer Lake.   The ISU and UHL lake survey results show good chemical water quality at Belva Deer Lake.   During 2005 through 2008 there were no violations of the Class B(LW) criterion for ammonia (19 samples), dissolved oxygen (19 samples), or pH (19 samples).   Based on IDNR’s assessment methodology these results suggest full support of the Class B(LW) uses of Belva Deer Lake.  

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this lake.