Tuesday, June 5, 2007
411

Application of the Mississippi Benthic Index of Stream Quality as a Water Quality Assessment Tool

Valerie E. Alley, Natalie Guedon, and Brad Segrest. Field Services Division, Mississippi Department of Environmental Quality, 1542 Old Whitfield Rd, Pearl, MS 39208

The Mississippi Benthic Index of Stream Quality (MBISQ), a regionally calibrated benthic index of biotic integrity, was developed by partnership of MDEQ with Tetra Tech, Inc in 2001 from 434 wadable (perennial, 1st-4th order streams) in the state excluding the Yazoo Delta.  This index defined 5 bioregions for the state, and established 25 percentile of the least disturbed condition for each bioregion as threshold of impairment of the state of Mississippi’s wadeable streams. This threshold is now applied to samples taken in subsequent years (2001-2004) for assessment purposes. 2005-2006 samples are in process, and will be assessed using the index for the next water quality assessment.  For 2007, a recalibration of the original MBISQ is scheduled; some 100 least disturbed sites are being revisited.  To date, we have made assessments on approximately 650 wadable stream segments, representing approximately 7500 stream miles (25% of total perennial miles).  Just over half of the assessed stream miles are considered impaired.  The individual metrics are then examined in the stressor identification process for TMDL development purposes. Future plans include use of this index as an assessment tool along with a probabilistic sampling design, with an assessment goal of 100% of wadable streams.

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