Assessment Comments
Assessment remains based on information from the IDNR Wildlife Bureau and on watershed modeling by the IDNR Water Quality Bureau.
Basis for Assessment
SUMMARY: The Class B(LW) aquatic life uses remain assessed (evaluated) as "fully supported” based on information from the IDNR Wildlife Bureau. The fish consumption uses remain "not assessed" due to the lack of water quality information upon which to base an assessment. This waterbody remains in IR Category 2a.
EXPLANATION: The Class B(LW) aquatic life uses remain assessed as "fully supporting." The upgrade in support of the aquatic life uses from "partially supporting" (see assessments for the 1998 and 2000 reports above) to "fully supported" is based on the following information from the Iowa DNR Water Quality Bureau that was used for the 2004 Section 305(b) assessment. Watershed modeling on this wetland indicates that sediment delivery to the wetland is estimated at 1.6 tons/2" rainfall event from the entire watershed. This is a very low sediment delivery rate and would be difficult to reduce further. Based on this information, the previous identification of "siltation" as impairing the aquatic life uses of this wetland was probably in error. Thus, the level of support of the aquatic life uses is upgraded from "partially supported" to "fully supporting." The assessment category for this wetland is "evaluated." In terms of Section 305(b) reporting, "monitored assessments" are based primarily on recent, site-specific ambient monitoring data and thus have relatively high confidence. "Evaluated assessments" are those based on data older than five years or other than site-specific ambient monitoring data (e.g., desktop models or questionnaire surveys of fish and game biologists [=best professional judgement]) and thus have relatively lower confidence.
Limited water quality sampling was conducted at this wetland in 2008 by IDNR. One sample was collected in September of 2008. Carlson’s (1977) trophic state indices for chlorophyll a from this one sample was 80, which puts Elm Lake in the hypereutrophic category. These results suggest extremely high levels of suspended algae in the water column. These data are not sufficient to make an assessment of water quality at this wetland. Additional monitoring is necessary to evaluate the Class B(LW) uses at Barringer Slough.
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring. In general, Iowa wetlands are not managed for recreational fisheries; thus, fish contaminant monitoring is not typically conducted at these waterbodies.
