SWSTAT - Surface-Water Statistics
VERSION/DATE: Version 4.1 - 02/25/2002
OPERATING SYSTEM: DOS
DISTRIBUTOR: USGS
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.
SYSTEM REQUIREMENTS
To install and run SWSTAT, the following are necessary:
- Pentium-class PC
- Windows 9x/Me, Windows NT 4.0, or Windows 2000
- up to 4.9 megabytes of free disk space
- 4.1 megabytes of free memory
DOCUMENTATION (see ANNIE)
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