


wdm(1)           U.S. Geological Survey (wrdapp)           wdm(1)


NAME
       wdm - Watershed Data Management files

ABSTRACT
       The WDM file is a direct-access, binary file used to store
       hydrologic, hydraulic, meteorologic, water-quality, and
       physiographic data.  There is a well-supported programmers' library
       of source code that can be used to implement the WDM file as a data
       base for a wide range of applications.  The WDM file is organized
       into data sets.  Each data set contains a specific type of data,
       such as streamflow at a specific site or air temperature at a
       weather station.  Each data set also contains attributes that
       describe the data, such as a station identification number, the time
       increments at which the data were collected (time step), latitude,
       or longitude.  The WDM file can contain up to 32,000 data sets.
       Each data set may be described by either a few attributes or by
       hundreds of attributes.

       The WDM file's disk space is allocated as needed in 40,960-byte
       increments (20 2,048-byte records).  Data can be added, deleted, and
       modified without restructuring the data in the file.  Space
       previously used by deleted data sets will be reused as new data sets
       are added.  Thus, the WDM file requires no special maintenance
       processing.

       Before data are added to a WDM file, a unique data-set number is
       assigned for the data and values are specified for required
       attributes that describe how the data are stored.  Once data have
       been added, the required attributes can no longer be modified.
       Hundreds of optional attributes exist for further characterization
       of the data that can be added to a data set at any time.

       Time-series data are most commonly stored in WDM files.  Time-series
       data can have time steps from 1 second to 1 year and can be
       "grouped" in periods of 1 hour to 1 century.  Data are grouped for
       more rapid access.  Data may be tagged with a "quality" flag to
       indicate that, for example, the data are estimated instead of
       observed.

       Time-series data can be stored in an uncompressed or compressed
       format.  The uncompressed format stores a value for every time step.
       The compressed format stores one value for multiple time steps when
       adjacent values are identical or when they differ by an amount less
       than a preset tolerance.  The number of identical or nearly
       identical time steps is stored with that value.

       Another type of data set stored in WDM files is a table data set.
       This type of data set contains a table of data having application-
       defined columns and rows.  The program PEAKFQ, which performs flood-
       frequency analysis, and the bridge scour data management system,
       BSDMS, uses table data sets to store peak flow data and bridge scour
       data, respectively.  Columns of the tables in PEAKFQ's data sets are
       designated for annual flow, gage height, and associated
       qualification codes.  Each row in the tables contains the data



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wdm(1)           U.S. Geological Survey (wrdapp)           wdm(1)


       values for each year stored for a given station.

       Space-time, dlg (vector), and message (text) data can be stored in
       WDM files although software for storage and manipulation of these
       types of data have not been fully developed.

METHOD
       A WDM file is a binary, direct-access file used to store hydrologic,
       hydraulic, meteorologic, water-quality, and physiographic data.  The
       WDM file is organized into data sets.  Each data set contains a
       specific type of data, such as streamflow at a specific site or air
       temperature at a weather station.  Each data set contains attributes
       that describe the data, such as station identification number, time
       step of data, latitude, and longitude.  A WDM file may contain a
       single data set or as many as 200,000 data sets.  A data set may be
       described by a few attributes or by hundreds of attributes.  Data
       can be added, deleted, and modified without restructuring the data
       in the file.  Space from deleted data sets is reused.

HISTORY
       The original design and implementation of the WDM file was a
       cooperative effort with the USGS and the Soil Conservation Service
       in 1983.  Additional types of data sets have been implemented by the
       USGS and the Environmental Protection Agency (EPA).  ANNIE, IOWDM,
       and HSPF were the original programs that used the WDM file in 1984.
       Since then, over a dozen programs developed by the USGS and EPA have
       been developed or modified to use the WDM file.  USGS maintains and
       distributes the official version of the WDM library.

DATA REQUIREMENTS
       Data may be input to a WDM file by hand but can be converted (more
       effectively) to WDM format by the IOWDM program.  IOWDM can convert
       data to WDM format from the following formats:  Carter 80-character
       format, HSPF output, PLTGEN output, and WATSTORE daily, unit, basin,
       peak, and n-day data.

OUTPUT OPTIONS
       Data stored within a WDM file may be output or "exported" to a text
       file for import to another WDM file.  This is most useful for
       transferring data between different computer platforms when an
       application that uses WDM files is implemented on both systems.

SYSTEM REQUIREMENTS
       UNIX-based computers (supported:  Data General AViiON and Sun
       SPARCstation).

       DOS-based computers having a math coprocessor and 4 mb of memory
       (supported: IBM-compatible computers with a 386 or greater
       processor).

       WDM is written in Fortran and C.  Generally, it is easily installed
       on other platforms.





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wdm(1)           U.S. Geological Survey (wrdapp)           wdm(1)


APPLICATIONS
       The WDM file was initially created for use by the program ANNIE for
       storage, manipulation, graphical display, and statistical analysis
       of watershed data.  With the implementation of other programs
       capable of accessing data stored in WDM files, each WDM file serves
       as a common data base from which data are shared among multiple
       applications and across different computer platforms.  Examples of
       programs using WDM files include the HSPF and SWSTAT, which performs
       the statistical analyses previously found in ANNIE.  Other examples
       of programs that use WDM files are listed under SEE ALSO.

DOCUMENTATION
       Lumb, A.M., Carsel, R.F., and Kittle, J.L., Jr., 1988, Data
          management for water-quality modeling development and use:
          Proceedings of the International Conference on Interactive
          Information and Processing Systems for Meteorology, Oceanography,
          and Hydrology.

REFERENCES
       Flynn, K.M., Hummel, P.R., Lumb, A.M., and Kittle, J.L., Jr., 1995,
          User's manual for ANNIE, version 2, a computer program for
          interactive hydrologic data management:  U.S. Geological Survey
          Water-Resources Investigations Report 95-4085, 211 p.

CONTACTS
       Operation and Distribution:
          U.S. Geological Survey
          Hydrologic Analysis Software Support Team
          Kate Flynn
          437 National Center
          Reston, VA 20192

          h2osoft@usgs.gov

       Official versions of U.S. Geological Survey water-resources analysis
       software are available for electronic retrieval via the World Wide
       Web (WWW) at:

                  http://h2o.usgs.gov/software/

       and via anonymous File Transfer Protocol (FTP) from:

                  h2o.usgs.gov (path: /pub/software).

       WDM is part of the lib library.  The WWW page and anonymous FTP
       directory from which the LIB software can be retrieved are,
       respectively:

                  http://h2o.usgs.gov/software/lib.html
                                --and--
                  /pub/software/general/lib

SEE ALSO
       annie(1) - Program to list, table, plot data in a WDM file



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wdm(1)           U.S. Geological Survey (wrdapp)           wdm(1)


       branch(1) - One-dimensional Branch-network flow model
       conrout - Hourly or daily streamflow routing by
                    convolution of unit responses
       daflow(1) - Streamflow routing in upland channels or channel
                   networks
       dr3m(1) - Distributed Routing Rainfall-Runoff Model
                 --version II
       hspexp(1) - Expert system for calibration of HSPF
       hspf(1) - Hydrological Simulation Program--Fortran
       iowdm(1) - Program to store time-series data in a WDM file
       peakfq(1) - Flood-frequency analysis based on Bulletin 17B
       prms(1) - Precipitation-Runoff Modeling System
       swstat(1) - Surface-water statistics












































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