U.S. Geological Survey swstat(1) NAME swstat - Surface-water statistics ABSTRACT SWSTAT contains a number of options for statistically analyzing time-series data. The time-series data are read from a Watershed Data Management (WDM) file. The computed statistics and (or) time series can be written back to the WDM file or to a text file. The statistics options include: Basic Computes minimum, maximum, mean, and standard deviation of a time series (any time step). Compare Uses flow-duration analysis and class intervals to compute absolute error, root mean square error, and bias by class interval for two time series. The standard error of estimate is computed. The flow-durations curves can be plotted. Data may be any time step. Duration Performs traditional flow-duration analysis by counting occurrences of all time-series values within flow intervals. The duration curve can be plotted. Data are analyzed at a daily time step. Frequency Analyzes time series using log-Pearson Type III distribution, without the extra features of Bulletin 17B found in the PEAKFQ program. The distribution is fitted by method of moments. Based on the USGS A193 WATSTORE program. Data are read from time-series data sets and analyzed at an annual time step. Hydrograph Computes duration hydrograph tables and curves. Based on the USGS K956 WATSTORE program. The duration hydrograph curves may be plotted. Data are analyzed at a daily time step. Although originally developed for streamflow data, any time series may be analyzed. N-day Computes annual n-day high and (or) low flows from a daily time series. A default set of 1-, 2-, 3-, 7-, 10-, 30-, 60-, 90-, 183-, and 365-day periods can be selected, or up to 10 durations may be specified. Analysis may be over a calendar year, water year, or a season. Based on the USGS A969 WATSTORE program. Trend Tests annual time series for trends. Computes Kendall's tau, the associated p-level and the slope of the trend line. The p-level is the Last change: 25 February 2002 1 U.S. Geological Survey swstat(1) attained (two-sided) significance level of the test. The data may be read from a time-series data set or from a table data set. METHOD Standard textbook procedures are used. The log-Pearson Type III and Pearson Type III distributions are fit using the method of moments. The Kendall Tau procedure is used for trend analysis. Class intervals used for flow-duration and comparison analysis are created as uniform log units or are user defined. HISTORY Some of the options in the program were originally implemented as programs in the WATSTORE system. These procedures were included under the statistics option in the 1990 version of the ANNIE program. In 1993, the software was ported to the UNIX platform, the user interface was enhanced, and the statistics options were removed from the ANNIE program and placed into the SWSTAT program. Version 4.1 2002/02/25 - Corrections in the N-day computations and in the specification for minimum and maximum values for plots with probability axis. Corrected problems in Frequency option where data set did not contain season attributes or a recognized value for TSTYPE. In the Frequency option, added the 3-year recurrence to the printed table and added attributes L07050, L07100, and L04003 for optional WDM output. In Frequency option, corrected problem where negative Parameter Values were sometimes reported for low flows. Miscellaneous spelling corrections. Version 4.0 2000/12/01 - All WDM data sets now contain the date the data set was created and the date the data set was last modified. Attributes SEADBG and SEADND introduced with version 3.2 of SWSTAT are in conflict with the creation and modification attributes. If you have N-day data sets created with Version 3.2 of SWSTAT, you will need to run the WDMRX program to resolve this conflict. WDMRX is included in the bin directory of the SWSTAT distribution. The N-day option was modified to rank high flow values in descending order. Version 3.2 1998/03/09 - Updated to incorporate corrections and changes made in the swstat program and in the lib library; there are four noteworthy changes. (1) The compare option had been reporting incorrect values for the total mean absolute error (percent) and root mean square error (percent); this is fixed. (2) In some instances, the common time period that was determined by the software may actually have been shorter than the Last change: 25 February 2002 2 U.S. Geological Survey swstat(1) actual common time period; this has been corrected. (3) The n-day option now includes the option to compute duration for one or more months. (4) The n-day option now includes the option to compute seasonal durations that begin or (and) end on days other than the first and last, respectively, of the months. Version 3.1 1996/09/25 - Corrections made in the Hydrograph option. February 29, leap day, was not being correctly handled during leap years--the value for February 29 was used for February 28. The program now skips February 29. The number of data values tagged as missing is now being correctly computed. Version 3.0 1996/03/26 - New release of program. Includes addition of the duration hydrograph (DURHYD) program as the Hydrograph option in SWSTAT. Corrections were made in the n-day option so that the correct year was reported for seasons shorter than a year. Version 2.1 1994/06/28 - Corrections made in the n-day option. The seasons the user entered were not being used for the high- and (or) low-flow computations. The program was always using the full climate year for low flows and the water year for high flows. Both low and high flows were always being calculated. The program now recognizes the seasons requested by the user and also that the user may not want both high and low flows. The user may now enter different durations for the low and the high flows. DATA REQUIREMENTS Input comes from WDM files. OUTPUT OPTIONS Statistical output can be placed in a text output file or stored on the user's WDM file in addition to being viewed on the screen. The graphs produced in the flow-duration and frequency analyses meet USGS publication standards and can be viewed on the screen. Additional plot output options depend on the devices supported by the GKS library used and may include PostScript, Computer Graphics Metafile (CGM), Hewlett-Packard Graphics Language (HP-GL), and assorted printers and plotters. See the installation instructions (README.TXT) for details of output devices available with precompiled distributions of the program. SYSTEM REQUIREMENTS SWSTAT is written in Fortran 77 with the following extension: use of include files. The ANN, WAIDE, AWSTAT, GRAPH, STATS, AIDE, WDM, ADWDM, and UTIL libraries from LIBANNE are required to recompile. For more information, Last change: 25 February 2002 3 U.S. Geological Survey swstat(1) see System Requirements in LIBANNE. APPLICATIONS There have been hundreds of applications throughout the United States and published as State or regional high- or low-flow frequency reports. DOCUMENTATION Lumb, A.M., Kittle, J.L., Jr., and Flynn, K.M., 1990, Users manual for ANNIE, a computer program for interactive hydrologic analyses and data management: U.S. Geological Survey Water-Resources Investigations Report 89-4080, 236 p. (Documents the 1990 version included in the ANNIE program.) RELATED DOCUMENTATION 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. REFERENCES Arihood, L.D., and Glatfelter, D.R., 1991, Method for estimating low-flow characteristics of ungaged streams in Indiana: U.S. Geological Survey Water-Supply Paper 2372. Bingham, R.H., 1985, Low flows and flow duration of Tennessee streams through 1981: U.S. Geological Survey Water-Resources Investigations Report 84-4347. Bingham, R.H., 1986, Regionalization of low-flow characteristics of Tennessee streams: U.S. Geological Survey Water-Resources Investigations Report 85-4191. Giese, G.L., and Mason, R.R., 1990, Low-flow frequency characteristics of streams in North Carolina: U.S. Geological Survey Open-File Report 90-399. Hayes, D.C., 1991, Low-flow characteristics of streams in Virginia: U.S. Geological Survey Water-Supply Paper 2374. Ludwig, A.H., 1992, Flow duration and low-flow characteristics of selected Arkansas streams: U.S. Geological Survey Water-Resources Investigations Report 92-4026, 77 p. Ruhl, K.J., and Martin, G.R., 1991, Low-flow characteristics of Kentucky streams: U.S. Geological Survey Water- Resources Investigations Report 91-4097, 51 p. Last change: 25 February 2002 4 U.S. Geological Survey swstat(1) Telis, P.A., 1991, Low-flow and flow-duration characteristics of Mississippi streams: U.S. Geological Survey Water-Resources Investigations Report 90-4087, 214 p. TRAINING Statistical Approach to Surface-Water Hydrologic Analysis (SW2011TC), 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 SWSTAT software can be retrieved are, respectively: http://water.usgs.gov/software/swstat.html --and-- /pub/software/surface_water/swstat See http://water.usgs.gov/software/ordering_documentation.html for information on ordering printed copies of USGS publications. SEE ALSO annie(1) - Program to list, table, plot data in a WDM file glsnet(1) - Regional hydrologic regression and network analysis using generalized least squares hass-cui(1) - Character-based user interface iowdm(1) - Program to store time-series data in a WDM file Last change: 25 February 2002 5 U.S. Geological Survey swstat(1) wdm(1) - Watershed Data Management system Last change: 25 February 2002 6