Rice Lake IA 02-WIN-832

Results of water quality monitoring conducted at Rice Lake indicate that the aquatic life uses should be assessed (Monitored) as "fully supported."

Guidelines for wetland assessment from the Upper Mississippi River Conservation Committee’s Water Quality Technical Section (2003) state that an average total suspended solids concentration during the growing season of less than 30 mg/L is necessary to provide sufficient water clarity to support the growth of submersed aquatic vegetation in wetlands and shallow lakes.High levels of total suspended solids impede the growth of submersed aquatic vegetation (SAV).Submersed aquatic vegetation is critical to the health of wetland and shallow lake ecosystems.The elimination of SAV can degrade habitat quality such that undesirable aquatic species such as cyanobacteria, common carp and fathead minnows dominate.As such, the suppression of SAV constitutes a violation of Iowa’s narrative water quality criteria protecting against undesirable or nuisance aquatic life.

Using the overall median values from the DNR shallow lakes and wetlands monitoring program from 2015 through 2016 (approximately 10 samples), the median growing season total suspended solids concentration was 9.25 mg/L; this median value is well below the UMRCC guideline and suggests (monitored) "full support" of the aquatic life uses.RiceLake was listed as "not supporting" its Class B(LW) uses due to violations of the UMRCC guideline for Turbidity: Suspended Solids in the 2016 assessment cycle. According to DNR's methodology, a lake must meet water quality standards for two consecutive cycles to suggest de-listing. Therefore,RiceLake will remain listed for the 2018 cycle as "not supporting" its Class B(LW) uses due to Turbidity: Suspended Solids.

In addition, the level of algae also suggests "no support" of the aquatic life uses at Rice Lake. The Carlson’s (1977) trophic state index value for chlorophyll a was 63. According to Carlson (1977), the index value for chlorophyll a places Rice Lake in the hypereutrophic category. This value suggests relatively low levels of chlorophyll a and suspended algae in the water and (monitored) "full support" of the aquatic life uses. Based on DNR's methodology, the median TSI value for chlorophyll a 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 5). Therefore, RiceLakewill remain listed as "partially supported" for the 2018 assessment/listing cycle.

NOTE:The TSI value for Secchi depth is not used to evaluate the attainment of aquatic life goals in shallow lakes.Due to the depth of these shallow lakes, TSI values for Secchi depth can be misleading.In some instances the Secchi disk remains visible at the bottom of the lake and the depth of the lake is recorded as the Secchi depth.In these instance, water clarity may be sufficient to support the Class B(LW) uses, but the index value is limited by the depth of the lake.Thus the combination of total suspended solids and chlorophyll a will be used to determine whether or not the Class B(LW) uses are impaired in these shallow systems.

Fish consumption uses remain "not assessed."In general, Iowa wetlands are not managed for recreational fisheries; thus, fish contaminant monitoring is not typically conducted at these waterbodies.