DefinitionA Study Reach is a length of stream selected for sampling purposes; it is the principal sampling unit for collecting (and analyzing) physical, chemical, and biological data. Typically the reach is selected to be representative of the stream's condition and the length sampled is usually proportional to the channel dimensions (i.e. channel width); however, for a particular sampling program the reach length may have a minimum or maximum value (domain range) or be a fixed length within a certain range of values | 
