Assessment Comments
Assessment is based on results of IDNR/UHL biological (biocriteria) monitoring in 2001: Fish IBI= 22(poor), BM-IBI= 62(good).
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed (monitored) as "partially supported" based on results of IDNR/UHL biological (biocriteria) sampling in 2001.
EXPLANATION: This assessment is based on the results of IDNR/UHL biological (biocriteria) monitoring conducted in 2001. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biocriteria sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (F-IBI) and a benthic macroinvertebrate index (BM-IBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2001 Fish IBI score was 22 (poor) and the BM-IBI score was 62 (good). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the F-IBI and BM-IBI scores with biological assessment criteria established specifically for the 2002 Section 305(b) report. The biological assessment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2001. This is the same assessment as that developed for the 2002 reporting cycle.
The previous (2002) assessment of the aquatic life uses ("partially supported") was based, in part, on the occurrence of a fish kill in 1998 (see assessment developed for the 2000 reporting cycle). According to IDNR's assessment methodology, the absence of a fish kill in the three-year period following a fish kill suggest that impacts from the kill have dissipated. Thus, due to the lack of a subsequent kill in this stream reach, the occurrence of the 1998 fish kill is not considered in development of the current (2004) assessment.
