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Opus GUI
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Opus Graphical User Interface
(Opus-GUI Beta version)

A win95-based graphical user interface for the Opus simulation model

Hamid J. Farahani and Roger E. Smith, USDA-ARS-NPA-WMU, Ft. Collins, CO


Platform:  PC



Opus (not an acronym) is a computer model for the transport of materials in soil and surface water. The model is a simulation tool for studying the potential pollution from various agricultural management practices.

The data input to Opus is organized into functional or topical groups. Data are normally read from two files; one contains meteorological information, and the other contains parameters describing the field and management. A third input file may be used to provide real measured data, to obviate certain hydrologic simulations (e.g., daily temperatures, runoff volume and peak, and erosion amounts).

The parameter file contains the data necessary to define the problem for simulation. Input data are grouped by general types into ten sections as listed in table 3 (User's Manual). The data input for Opus are identified in this interface using these sections. The Meteorological datafile contains statistical parameters and data describing the watershed's climate. Depending on the options chosen, the file may also contain (a) daily rainfall records for years to be simulated, (b) statistical parameters for generating daily rainfall, (c) monthly record statistics for generating daily temperature and/or radiation, or (d) breakpoint rainfall records for the period to be simulated. The actual (or Measured) datafile is optional. It contains any or all of the following daily data: measured runoff, peak flow, storm erosivity index (EI), total storm sediment delivery, recorded daily maximum and minimum temperatures, and daily solar radiation. If an actual data file is called for, Opus assumes that it contains at least daily maximum and minimum temperatures. The user may input daily values of these meteorologic and hydrologic variables to obviate simulation of particular processes. The section entitled "Actual Data File" in the User's Manual describes the Measured datafile in detail.

The purpose of the Opus GUI is to simplify and help the user to prepare the required parameter datafile needed to run the Opus simulation model. Using this interface, the user can create a new Opus datafile, read and edit an existing (complete and/or incomplete) datafile, or read and edit the Opus sample datafile from sites in Watkinsville, GA. Note that only the parameter datafile may be created using this version of the user interface. In designing this interface, care was taken to ensure consistency among screens. Efforts were directed towards interface simplicity, ease of use, and functionality. In addition to brief descriptive text material given directly on the screen, three levels of help are also available to further explain each parameter. The entire User's Manual for the Opus Win95 interface is available for both viewing and printing (not active in the Beta version). It is distributed with this package as a MSword document named "UserManual1.Doc" (not available with the Beta version).


System Requirements:


Windows 95 with a pentium processor 32 megs of memory and about 30 megs of free disk space. (Note: a few users has installed the interface on Windows NT operating system).


Documentation and Availability:


A Beta-version of the interface with example files is provided on our FTP site. Contact Roger E. Smith ( for permission and more information.