U.S. GEOLOGICAL SURVEY
                WATER-RESOURCES INVESTIGATIONS REPORT 93-4076

                         HYDRO-CLIMATIC DATA NETWORK
                                    (HCDN)
                        STREAMFLOW DATA SET, 1874-1988

                   [This is the \DOCFILES\NON-DOS.DOC file]

                                THE HCDN FILES

         There are two types of data on the HCDN CD-ROM: supporting data
      and the streamflow data.

                             THE SUPPORTING DATA

         The supporting data gives information about the stations at
      which the streamflow data was collected and their environment and
      setting.  Four files which contain supporting data and are the
      most useful for searching for desired stations are:

         STATIONS.DAT is the master index to the streamflow records and
            gives the number, name, location, hydrologic unit code, and
            other information about each station.
         BASINS.DAT gives eleven items of physical information about the
            drainage basin such as stream length, percent of forest
            cover, and precipitation for each station.
         WYEARS.DAT gives the temporal extent (period of record) of the
            streamflow data for each station.
         COMMENTS.DAT gives comments about the suitability, environment,
            and situation of many of the stations.

      Each of these files is in the \HCDN directory.  Further
      information describing the contents of these files may be found in
      the 1ST_READ,ME file in that directory.  Detailed information on
      the format or layout of each of these files may be found in the
      STATIONS.FMT, BASINS.FMT, WYEARS.FMT, and COMMENTS.FMT files,
      respectively, in the FORMATS sub-directory of the HCDN directory.

         The common element (key) among these files is the eight digit
      USGS station number.  It is the first eight characters of each
      line (record) of these four files.  Each file is ordered (sorted)
      on this common field.

         Once you have examined these files and determined which
      stations you wish to use, note the first two digits of the
      Hydrologic Unit Code (HUC) associated with each of the desired
      stations in the STATIONS.DAT file.  This tells which REGIONrr sub-
      directories (described below) the streamflow data is in.

                             THE STREAMFLOW DATA

         The streamflow data is available in the HCDN directory in two
      forms - ASCII and binary.  The ASCII (text) form is for the user
      who may want to use a word processor or data-base package to
      extract and manipulate the data and feed it to another program
      such as a statistics package or spread-sheet.  Data in the ASCII
      form can be read and processed on any computer that can handle a
      CD-ROM in the ISO 9660 format.  The binary form is specifically
      for the user who intends to write a program (Fortran, C, Pascal,
      etc.) to read the files since reading binary data is 6 to 15 times
      faster than reading ASCII data.

      Sub-directories in the HCDN directory:

         FORMATS directory contains the detailed formats and
            descriptions of the files of streamflow and supporting data.
            This sub-directory contains the .FMT files.
         ASCII directory contains the streamflow data in ASCII form in
            three sub-directories according to the time span of the
            data.
            DAILYA directory contains the daily values in ASCII form in
               21 sub-directories.
            MONTHLYA directory contains the monthly mean values in ASCII
               form in 21 sub-directories.
            ANNUALA directory contains the annual mean values in ASCII
               form in 21 sub-directories.
         BINARY directory contains the streamflow data in binary form in
            three sub-directories according to the time span of the
            data.
            DAILYB directory contains the daily values in binary form in
               21 sub-directories.
            MONTHLYB directory contains the monthly mean values in
               binary form in 21 sub-directories.
            ANNUALB directory contains the annual mean values in binary
               form in 21 sub-directories.

      Structure within the ASCII and binary data sub-directories:

         Within each of the ASCII and binary directories, there are 21
      sub-directories holding the files containing the data.  Each of
      these directories has the name REGIONrr.  The data for a
      particular station is located in the directory REGIONrr where rr
      is the first two digits of the hydrologic unit code (HUC) for the
      station.  This is the Water Resources Council region in which the
      station is located.  (See HUCS.TXT in the HCDN directory for a
      detailed explanation.)

                                RECORD FORMATS

         The ASCII and binary data formats are designed to carry all of
      the data in the most concise manner possible and be of fixed
      length.  The records do not exceed 128 characters in the ASCII
      form.  All of the data is organized by water year.  A water year
      starts on October 1st and ends on the following September 30th.  A
      water years is called by the year it ends in.  For example, water
      year 1988 - the last water year considered for inclusion in the
      HCDN - runs from October 1, 1987 through september 30, 1988.

                       ASCII AND BINARY DATA FILE NAMES

         For the ASCII and binary forms of the data, there is one file
      for each station for each form of data and each time interval of
      data.  The name of each file is ssssssss.ttt where

           ssssssss is the eight digit USGS station name and
           ttt is AAM for ASCII Annual Mean values
                           (under sub-directory ANNUALA),
                  ADV for ASCII Daily Values
                           (under sub-directory DAILYA),
                  AMM for ASCII Monthly Mean values
                           (under sub-directory MONTHLYA),
                  BAM for Binary Annual Mean values
                           (under sub-directory ANNUALB),
                  BDV for Binary Daily Values
                           (under sub-directory DAILYB), and
                  BMM for Binary Monthly Mean values
                           (under sub-directory MONTHLYB).

      Within each file there is one record for each year except for the
      ASCII form of the daily values where there is one record for each
      day of the month (31 records to a water year).  See the
      appropriate .FMT file in the FORMATS sub-directory of the HCDN
      directory.