Nationwide benthic macroinvertebrate assemblage multimetric indices: identifying inconsistencies and limitations in reporting stream impairment status, USA.

The objective of this study was to identify the current status of stream water-quality assessment and reporting methods for four states in the Ohio River basin (Indiana, Ohio, Tennessee, and Virginia), as required by the 305(b) section of the United States (US) Clean Water Act. Specifically, we clarified the discrepancies that exist among stream-impairment status classified by benthic macroinvertebrate multimetric indices (MMIs) and depicted using Geographic Information Systems shapefiles. In addition, we provided guidance in solving some of the comparability problems that arise when developing state-specific MMIs and depicting stream-impairment status using Geographic Information Systems technology. The MMI variation among states and differences in shapefile formats resulted in a nationwide dataset, which cannot be directly compared. Incorporating the changes suggested in this study allow for a uniform assessment and reporting method nationwide. Successful implementation of these changes would strengthen the US Environmental Protection Agency efforts to identify impaired streams and sources of those impairments without the limitations of state-by-state .developed assessment methods.