Stream ratings are an important tool in identifying which streams are the most biologically diverse and have a high degree of integrity

SPRINGFIELD, IL – The Illinois Department of Natural Resources (IDNR) announces the release of biological stream ratings that combine, update, and enhance the two previous approaches for rating Illinois streams.  Stream ratings are an important tool in identifying which streams are the most biologically diverse and have a high degree of integrity.  These ratings are regularly used by the IDNR and watershed and environmental groups that focus on stream protection and enhancement.

The new ratings for diversity, integrity, and significance replace the Biological Stream Characterization (BSC) and Biologically Significant Streams (BSS) that were developed in 1984 and 1992 respectively.

“Both BSC and BSS processes generated products that are used extensively by diverse stakeholders,” said IDNR Acting Director Sam Flood.  “The new stream ratings will provide the Illinois Department of Natural Resources with a mechanism for identifying high-quality examples of all stream communities and will guide management and restoration activities throughout the state.”

The new ratings use fish, macroinvertebrates, crayfish, mussels, and threatened and endangered species information to generate an overall score of biological diversity and integrity in streams.  The purpose behind the new ratings was not only to update outdated information, but to establish baseline conditions against which change promoted by the Wildlife Action Plan could be measured and understood.  Since the Wildlife Action Plan broadly addresses all types of wildlife including fish, mussels, amphibians, and reptiles, these new ratings will help resource managers to determine if aquatic organisms are responding to management activities promoted by the plan.

The information contributing to integrity and diversity ratings is then used to identify a sub-set of stream reaches as “biologically significant”.  The revised ratings are limited mostly to wadeable streams and incorporate biological information from 1997 – 2007.    

“We believe that including additional groups of organisms into both integrity and diversity measures in ratings provides a more robust assessment of stream biological condition, thereby improving our confidence in stream ratings,” said Mike Conlin Director of IDNR – Office of Resource Conservation. 

More information about how the ratings were developed and what biological information was used can be found at:  http://www.dnr.state.il.us/orc/BioStrmRatings/