Lessons learned from the calibration of the generalized BCG model for Pennsylvania wadeable streams

Pennsylvania and EPA Region 3 have been working to calibrate the generalized BCG model for high gradient freestone streams and larger cool/warm water streams. We examined which aspects of the general BCG model were fairly straightforward to apply (e.g. attributing taxa, assigning sites to BCG tiers, and developing relationships between BCG tiers and the PADEP multi-metric index), which aspects were more challenging (e.g. certain limitations of the PA field and laboratory bioassessment methods and the relationship of the BCG model results to existing aquatic life uses) or not attempted (e.g. we lacked any data to explore functional attributes). We encountered some difficulty using only the BCG tier assignments, the taxa lists and Pennsylvania’s genus-level multi-metric index to discriminate between the very best sites, which are designated as Exceptional Value and High Quality in Pennsylvania’s water quality standards. The BCG attributes which address wider connectivity and watershed scale condition proved useful in these cases. These lessons should be useful to other states and regions as we continue our work to integrate the results of the calibrated BCG models into state water quality standards.