(1:24,000) is provided; record the local coverage scale of the highest
resolution available.
- 21. Mean annual precipitation: Use National Weather Service information to record mean
annual precipitation for the basin. Methods for calculating mean annual
precipitation can vary among sites. Therefore, record how mean annual
precipitation was calculated for the basin.
A stream segment is defined as that part of a stream bounded by tributary junctions (fig. 1) or
discontinuities, such as major waterfalls, landform features, significant
changes in gradient, or point-source discharges (Frissell and others,
1986). Teti (1984) demonstrated that water chemistry patterns vary where
tributaries converge. In addition, Burns and others (1984) suggested that
stream segments represented discrete units based on changes in benthic
invertebrate communities below tributary junctions. Thus, a segment
should be a distinct stream unit that is relatively homogeneous with
respect to physical, chemical, and biological properties.
A segment characterization is conducted at fixed and synoptic sites using 7.5' maps
or recent aerial photographs. A form for conducting segment
characterizations of streams is presented in figure 3. The instructions
for completing a segment characterization form are detailed below, with
the numbers corresponding to the items as presented in figure 3.
- 1. Study unit: Use the code (table 1) designated for
each study unit.
- 2. Date: Record the date
as month, day, year.
- 3. Station name: List
the USGS station name, if available, or create a station name for the
site.
- 4. Station identification number:
List the USGS station identification number for the site.
- 5. Investigators: Self-explanatory.
- 6. Reference location: Briefly describe reference
location, and record its latitude and longitude. The reference location
should be a permanent structure such as a USGS gage or a bridge. When a
permanent structure is not present, a semipermanent marker (such as an
iron pipe) is installed at a site. The reference location serves as a
classification variable, providing a geographic marker linking habitat
data collected at the segment level with data collected at other levels of
the spatial hierarchy. Record the latitude and longitude of the
reference location.
- 7. State: Record the U.S. Postal Service two-letter designation for the state.
- 8. County: Record the full name of the county (or parish).
- 9. Township: Record the township designation, if available.
- 10. Range: Record the appropriate range designation, if available.
- 11. Section: Provide the appropriate two- or three-digit
number of the section, if available.
- 12.Quad: Record the name and year of the appropriate 7.5' map that
includes the reference location.
- 13. Segment code: The U.S. Environmental Protection Agency's River Reach data base
(RF3) is a GIS national hydrographic data base of surface-water features
that contains code numbers for each stream segment. Record the segment
code number that corresponds to the study segment.