hysep(1) U.S. Geological Survey (wrdapp) hysep(1) 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 7 Jul 1998 1 hysep(1) U.S. Geological Survey (wrdapp) hysep(1) 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 7 Jul 1998 2 hysep(1) U.S. Geological Survey (wrdapp) hysep(1) 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 7 Jul 1998 3