Assessment Comments
Assessment is based on results of IDNR/UHL biological (biocriteria) monitoring in1996: Fish IBI=40 (fair).
Basis for Assessment
[NOTE: For the 2002 report, the previous waterbody segment for Little Rock River (IA 06-BSR-0060-0), which extended 46 miles from its mouth in Lyon County to the Iowa/Minnesota state line, was split into three subsegments: (1) from mouth to Otter Creek near George (IA 06-BSR-0060-1), (2) (this one) Otter Creek to Argo Slough near Little Rock (IA 06-BSR-0060-2), and (3) Argo Slough to the Iowa Minnesota state line (IA 06-BSR-0060-3). See assessment information found in this subsegment (IA 06-BSR-0060_2) for previous Section 305(b) assessments for the entire 46-mile reach.]
SUMMARY: The Class B(LR) aquatic life uses remain assessed (evaluated) as "fully supported / threatened" (minor impacts) based on results of IDNR/UHL biological monitoring for fish and aquatic macroinvertebrates conducted in 1996 as part of the IDNR/UHL biocriteria project. Due to the age of this data (i.e., greater than five years), the assessment category is changed from "monitored" (higher confidence assessment) to "evaluated” (lower confidence assessment).
EXPLANATION: Continue to use the assessment developed for the 2000 and 2002 reports that was based on results of the 1996 IDNR/UHL biocriteria assessment (see the assessment developed for the 2000 reporting cycle for more information).
As stated in the assessment developed for the 2000 reporting cycle, only the Fish-IBI was calculated for this assessment. The F-IBI score was 40 (fair). The aquatic life use support was assessed as fully supported / threatened (=FST), based on a comparison of the F-IBI score with biological assessment criteria established specifically for the 2000 Section 305(b) report. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-1998. The assessment type is considered "evalauted" (lower-confidence assessment) because (1) these data are now considered too old (greater than five years) to accurately characterize current water quality conditions and (2) only one of the two biological indicator communities (fish) typically sampled as part of biocriteria monitoring was sampled.
