A Study Reach is a length of stream selected for sampling purposes. 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.
- Site and Reach Name are required.
- Delineation Date is highly recommended.
- BioData Study Reaches are project and station-specific, so the full reach name is a combination of 1) SiteNumber, 2) ReachName, and 3) Project (e.g. SiteNumber-ReachName-Project). For example, '43185411440912–visitor center-SilverTNC' is a reach near NWIS station 43185411440912 used byt the SilverTNC project that they called "visitor center"
- The design of the BioData Study Reach incorporates ideas from NAWQA, NRSA, and other ecological studies. You may delineate a study reach in several ways, including:
- Narrative description
- In relation to a Reference Location
- Upstream and downstream boundaries (Latitude/Longitude or Description)
Conventions for recording reach boundaries
Curvilinear distance (along thalweg) from the reference location to the upstream and downstream reach boundaries, follows this convention:
If either boundary is upstream from the reference location, its value is negative; otherwise, value is positive. When this convention is followed, the "Curvilinear distance to downstream boundary" MINUS "Curvilinear distance to upstream boundary" = "Curvilinear Reach length"
An illustration of this convention. The stars represent reference locations, in three examples, A, B, C.