1984, a Biological Stream Characterization (BSC) Work Group convened
to develop a multi-tiered classification of streams based primarily
on fish communities.
The use of letter
grades "A" through "E" for evaluated reaches established
a means of communicating levels of biotic integrity to diverse stakeholders.
In 1992, the Illinois Natural History Survey (INHS) published a list
of biologically significant streams (BSS) for the purpose of conserving
biodiversity across the state. The BSS process expanded on BSC "A"
rated streams by adding additional information on endangered and threatened
species and mussel diversity. Despite the lack of regular updates, both
BSC and BSS processes generated products that are used extensively by
diverse stakeholders. As Illinois
resource managers move forward with implementing the Wildlife Action
Plan, current stream ratings generated with diverse aquatic biological
information and a process by which ratings can be updated were needed.
The IL Department of Natural Resources - Office of Resource Conservation,
in partnership with INHS, initiated a project to combine, update, and
enhance the two previous approaches for rating
streams. This new process incorporates
biological data from 1997 through 2007.
most significant differences among the past rating systems and the
new system are:
reaches are now rated for diversity, integrity, and biological significance
depending on available data.
present rating system includes information on taxonomic groups that
were not included previously and limits ratings to stream sizes
where existing biotic indices work (e.g., wadeable streams that are mostly third to seventh order).
other than fish can be used to generate the highest rating for a
are applied to valley segments rather than a set distance upstream
or downstream of a sample site, which results in ratings at a finer
spatial scale than before.
designation is based on information from at least two different
Stream Rating Report
STREAM RATING DATA Please Note: These data are in ESRI "File Geo-Database" format. You must use ArcGIS 9.2, service pack 5 or higher or ArcGIS 9.3 to view this file geodatabase. Make sure that you refer to the field aliases for the reference names used in the metadata, etc.
CONTACT: Ann Marie
IDNR - Watershed Protection Section
One Natural Resources Way
Springfield, IL 62707