METHODS.DAT contains definitions of
the laboratory analytical methods codes corresponding to
the values of stream water quality. These codes are reported
beginning in 1985, and are stored in the water-quality data files as
described in WQ.FMT.
information is given for 209 laboratory methods used to
analyze 76 of the 121 water-quality constituents (other
analytical methods not listed in this file may have been
used to analyze some of these constituents; information on
these methods was unavailable at the time of CD-ROM production).
The remaining 46 constituents include 17 laboratory-analyzed
parameters for which codes were unavailable at the time
of production of the CD-ROM, 27 field parameters, and 2
computed parameters. The 17 constituents include 1
trace element, 4 radiochemicals, and 12 biological
constituents (these predated the use of method codes).
Although method codes are reported in the water-quality
data base for the 27 field and 2 computed parameters,
these codes are not officially supported by the USGS.
See the METHODS.FMT file for details of
the file layout.