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
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
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,
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.
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
wdm(1) - Watershed Data Management system