Assessment Comments
Assessment based on results of IDNR/UHL biological (biocriteria) monitoring in 1999.
Basis for Assessment
SUMMARY: The Class B(LR) aquatic life uses are assessed as "partially supported" based on results of IDNR/UHL biological (biocriteria) sampling in 1999. This assessment is the same as that developed for the 2002 reporting cycle.
EXPLANATION: This assessment was based on data collected in 1999 as part of the IDNR/UHL stream biocriteria project. 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 1999 Fish IBI score was 27 (fair) and the BM-IBI score was 45 (fair). 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. Previous assessments of this segment were based on the occurrence of fish kills in 1998 (see assessment for the 2000 report). Because more than three years have elapsed since these kills, any kill-related impacts have likely dissipated.
