North Branch Volga River IA 01-VOL-330

Assessment Comments

Assessment based on the results of IDNR/UHL biological (biocriteria) sampling in 2001: FIBI = 68 (good), BMIBI = 84 (excellent). Non-riffle site FIBI BIC = 44, and natural substrate BMIBI BIC = 70.

Basis for Assessment

SUMMARY:  The Class B(LR) aquatic life uses are assessed (monitored) as "fully supported"  based on results of IDNR/UHL biological (biocriteria) sampling in 2001.   This is the same assessment as that developed for the 2004 reporting cycle.

EXPLANATION:  This assessment was based on data collected in 2001 as part of the DNR/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 (FIBI) and a benthic macroinvertebrate index (BMIBI).   The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum).   The 2001 FIBI score was 68 (good) and the BMIBI score was 84 (excellent).   The aquatic life use support was assessed as fully supported (=FS),  based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established for previous Section 305(b) reports.  The biological impairment criteria were determined from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2004.   The non-riffle site FIBI BIC for this ecoregion is 44 and the natural substrate BMIBI BIC for this ecoregion is 70.