NAME
hysep - Hydrograph separation program
ABSTRACT
HYSEP performs hydrograph separation, estimating the ground-water,
or base flow, component of streamflow. The program provides an
automated and consistent method for estimating base flow. Any of
the three hydrograph-separation techniques of Pettyjohn and Henning
(1979) can be used: fixed interval, sliding interval, or local
minimum.
METHOD
See Pettyjohn and Henning (1979).
HISTORY
Version 2.2 1997/06/10 - Includes implementation of a seasonal-
distribution table and bar graph of base flow and surface runoff.
Problems with the fixed-interval separation method were
corrected: (1) the accuracy of computed base flow was improved
for the first year in the period to be analyzed by including the
final days of the immediately previous year in the analysis, when
available (using data from adjacent years in this way was
previously done with all years except the first year in the
period to be analyzed); and (2) fixed-interval separation is now
correctly performed for the final days of the final year in the
period to be analyzed when that year coincides with the end of
the available input data. Previously, if the number of days in
the final year was not evenly divisible by the interval length,
fixed-interval separation was not correctly handled for the final
days in the year, with the result of those days being treated as
missing values.
Version 2.1 1996/03/01 - General release.
The original version was written by Ronald Sloto in 1982. That
version was enhanced to read input from Watershed Data Management
(WDM) files (see below) in addition to files in the conventional
format from the U.S. Geological Survey Water Data Storage and
Retrieval System (WATSTORE) and Automated Data Processing System
(ADAPS) data bases. A character-based user interface was also added
to the program. See HASS-CUI for details on the interface.
Some additional changes were made to Sloto's original program:
- Base-flow separation is performed using a period of data beginning
and ending in any month specified by the user, i.e., input is no
longer restricted to complete water or calendar years. The user
can also specify summary output to be in water, calendar, or any
other user-defined years. Output in both calendar year and water
year in a single run was dropped, however. The program must be
run twice in order to get both calendar and water year output for
the same input data.
- Periods of missing streamflow data of any length, falling anywhere
within the period of record specified by the user, are handled by
the program. Formerly, only complete missing years within the
period of record could be handled gracefully.
- Accuracy of base-flow separation was improved at the year
boundaries, i.e., base-flow values computed for the days at the
beginning and end of each 12-month period within a period of
record are more exact and consistent by using, when available,
data from adjacent years.
DATA REQUIREMENTS
Daily mean stream discharge in daily values card-image format or as
stored in WDM files is used as input to HYSEP. WDM files are
binary, direct-access files that allow for efficient storage and
fast retrieval of data. Stream discharge in the daily values card-
image format also can be reformatted to a WDM file using the program
IOWDM.
OUTPUT OPTIONS
Tables of statistical output are produced by HYSEP, namely
frequency, flow-duration, and seasonal-distribution tables as well
as monthly and annual summaries of the hydrograph separation. A
program option allows for storage of the estimated daily base flow
and (or) surface runoff on the user's WDM file, making the base-flow
data available for further processing, such as the performance of
flow-duration analysis using the program SWSTAT. The estimated
daily base flow and (or) surface runoff can also be output in card-
image format.
HYSEP can direct graphical output to any of the devices allowed in
your system's implementation of the Graphical Kernel System (GKS).
Alternate output devices are specified in a local file called
"TERM.DAT". See HASS-CUI and your system's GKS documentation for
details.
SYSTEM REQUIREMENTS
HYSEP is written in Fortran 77 with the following extension: use of
include files. The ANN, WAIDE, GRAPH, STATS, AIDE, WDM, ADWDM, and
UTIL libraries from LIB are required to recompile. For more
information, see System Requirements in LIB.
DOCUMENTATION
Sloto, R.A., and Crouse, M.Y., 1996, HYSEP: A computer program for
streamflow hydrograph separation and analysis: U.S. Geological
Survey Water-Resources Investigations Report 96-4040, 46 p.
REFERENCES
Pettyjohn, W.A., and Henning, Roger, 1979, Preliminary estimate of
ground-water recharge rates, related streamflow and water quality
in Ohio: Ohio State University Water Resources Center Project
Completion Report Number 552, 323 p.
Sloto, R.A., 1988, A computer method for estimating ground-water
contribution to streamflow using hydrograph-separation
techniques: National Computer Technology Meeting, Phoenix, Ariz.
TRAINING
There is no regularly scheduled class for HYSEP. Base-flow
separation techniques are included in Ground-water/Surface-water
Relationships (ID2015TC), offered annually at the USGS National
Training Center.
CONTACTS
Operation and Distribution:
U.S. Geological Survey
Hydrologic Analysis Software Support Program
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://water.usgs.gov/software/
and via anonymous File Transfer Protocol (FTP) from:
water.usgs.gov (path: /pub/software).
The WWW page and anonymous FTP directory from which the HYSEP
software can be retrieved are, respectively:
http://water.usgs.gov/software/hysep.html
--and--
/pub/software/surface_water/hysep
SEE ALSO
hass-cui - Character-based user interface
iowdm(1) - Program to store time-series data in a WDM file
swstat(1) - Surface-water statistics
wdm(1) - Watershed Data Management system