3.   Aquatic Life Standards  

a. Aquatic Life Use Designations

Ohio EPA has four different aquatic life use designations that are assigned based on the fish, bugs, and vegetation of a sampling area as compared to other typical streams found in the same region.  For example, Big Darby Creek has the fish, bugs, and habitat to perform at the highest level of water quality, an Exceptional Warmwater Habitat (EWH), whereas portions of Flat Branch have undergone significant modification and therefore only perform at the Modified Warmwater Habitat (MWH) level.  Map 19 displays the various proposed aquatic life use designations on the Darby Streams. 

LRW (Limited Resource Water) – Very small streams that typically totally dry up during the year (i.e., no pools remain) that have a very limited biological potential (Think Lizard Run in Pickaway County )

MWH (Modified Warmwater Habitat) - Streams in an essentially permanent altered or maintained state (Think County Maintained Ditches and Flat Branch)  

WWH (Warmwater Habitat) - Stream capable of supporting diverse and healthy organisms (Think Robinson Run or Buck Run)

EWH (Exceptional Warmwater Habitat) – Streams that display an unusually diverse array of natural habitat and unique or rare organisms (Think Big and Little Darby Creek)

The designations listed above are based on natural stream conditions in Ohio which include meandering channel with numerous rifles, runs, pools, islands, gravel bars, and backwater areas.  The combination of theses features creates a habitat that supports diverse and healthy fish, bugs, and vegetation.  The above designations are determined based on a combination of the aquatic life (biological) data and stream habitat.

Stream Habitat (QHEI) + Biological (ICI + IBI + MIwb) = Aquatic Life Use Designations. 

The other variables in the equation will be defined in the following sections.

In addition to the four aquatic life use designations above.  Ohio EPA has proposed a Coldwater Habitat (CWH) on four streams in the watershed.  During sampling a significant number of coldwater bugs and fish were found at sites along these streams.  There is large groundwater input into these streams from the Cable Moraine complex in Logan and Champaign Counties that is responsible for the coldwater.  Figure 88 below explains the stream segments designated as both warmwater and coldwater habitats. 

Ohio EPA in June of 2004, published their proposed aquatic life use designations for the Darby Watershed.  Map 19 illustrates the proposed aquatic life use designations for sampled streams in the Darby Watershed. 

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Last updated: November 18, 2008.