Argus ONE Review

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 Last updated on Mon 20 Jul 1998 at 01:09 PM

I previously worked for Argus and developed the MODFLOW/MT3D PIE for them. I do not currently work for Argus.


General

Argus ONE is my favorite preprocessor for MODFLOW. One of its great strengths is that it separates the specification of boundary conditions and aquifer properties from the grid. This allows you to radically alter the grid without having to reenter any data. For example, if you had an existing model with 40 rows and columns at an angle of 10 degrees and you wanted to change it to 50 rows and columns at an angle of 35 degrees, you could do it in just a few seconds. This is not true of either Visual MODFLOW or Processing MODFLOW for Windows.

Although this review focuses on Argus ONE as a preprocessor for MODFLOW, Argus ONE can also act as a preprocessor for SUTRA, MOC3D, NAPL, PTC, HST3D.

Operating System

The current version of the MODFLOW/MT3D PIE will only run on Windows 95 or Windows NT. Argus ONE itself is also available for the Macintosh and Unix operating systems. I rarely encounter any problems using Argus ONE.

Preprocessing

Argus ONE is also extremely flexible in the way you enter data. You can enter numerical values for any spatial data or you can develop an "expression" that will calculate the data from other previously entered data. The use of expressions is a key innovation in Argus ONE. This capability can be put to all sorts of uses. One simple use would be to perform unit conversions but there are lots of other potential uses. Expressions can be applied to spatially variable data. For example, you can specify spatially variable top and bottom elevations of an aquifer and use an expression to calculate the thickness of the unit. (In fact, the MODFLOW PIE already uses an expression that does exactly that.) Expression can include logical operators such as "if-then-else" statements which is one of the reasons why expressions are so powerful. There are also a large number of built-in mathematical functions (log, sin, etc.) that can be included in expressions. Users can add new functions through the use of plug-in extensions - another key innovation in Argus ONE.

Plug-in extensions (PIE's) are dynamic-link libraries that provide added capability to Argus ONE. Anyone with the requisite programming skills can write such a PIE. I have written them using C++ and Object Pascal (Delphi). I understand that at least one has been written in Fortran. It would be nice to be able to write PIEs using pure Java but I don't think that is possible, at present, because Java lacks a pointer variable type. (You probably could use Java for the visual interface of a model and use another language such as C++ to act as an intermediary between the interface and and Argus ONE.)

Some of the things PIE's can be used to do include the following:

I have found it possible to implement almost any functionality I wanted using PIE's. There is one thing I would like to do with PIE's that I have not been able to do. Any data entered in Argus ONE can have a unit displayed with it. The user can change the units manually but I don't see any way to change the units with a PIE. This would have been convenient in some cases but it is not a substantial weakness.

The usual way that data is entered in Argus ONE is through "Contours" Contours can be points, polygons (closed contours), or a series of line segments (open contours). Argus ONE has a built-in interpolator for interpolating among point values. (Interpolation can also be applied to open and closed contours). However, you don't have to interpolate if you don't want to. You can define zones with closed contours and the value assigned to any point will be the value of the contour that encloses it. You can also have Argus ONE assign the value of the nearest contour to a point regardless of whether or not the contour encloses the point. There are several free PIEs that provide additional methods for interpolating values besides those built into Argus ONE.

It is possible to interpolate between the end points of an open contour to assign intermediate values to cells but this has not been implemented in the MODFLOW/MT3D PIE.

The MODFLOW/MT3D PIE allows you to have non-simulated units for aquitards if you so choose. Thus you can have both fully 3D and quasi 3D models.

Both steady state and transient models are supported. In transient models, you can either enter new values for transient data for each stress period or enter a single set of values for the first stress period and reuse them for subsequent stress periods.

In addition to the "standard" packages that were part of the first version of MODFLOW, the MODFLOW/MT3D PIE supports the PCG2 and DE4 solvers and the BCF5 package. The executable that comes with the MODFLOW/MT3D PIE has all the packages the USGS distributes with MODFLOW plus a variable anisotropy package developed by Kladias and Ruskauff.

One potential weakness in Argus ONE is that it does not allow you specify the properties of cell faces but only of the cell interiors. If the Horizontal-Flow Barrier Package were implemented in Argus ONE, this would be a problem because it would make it difficult to visualize exactly where in the grid horizontal flow barriers occur.

On-line help is provided through a series of linked web pages that are installed on the users machine.

The MODFLOW/MT3D PIE places no limits on the size of the model other than those imposed by MODFLOW itself.

Modflow Execution

When you have finished entering data for MODFLOW, you can instruct Argus ONE to export the MODFLOW input files and run MODFLOW. The export process is a bit slow because Argus ONE must perform a lot a calculations during the export process. This is the inevitable result of the flexibility Argus ONE provides for specifying aquifer properties. For example, instead of just exporting a number for the transmissivity of a cell as do some other MODFLOW preprocessors, Argus ONE calculates the transmissivity from the top and bottom elevations of the cell and it's hydraulic conductivity. The added work slows down the export process. This is particularly true if you use the built-in interpolator. Some of the free interpolation PIE's appear to be much faster than the built-in interpolator and may be desirable for that reason in some circumstances.

During the export process, there is some limited checking of the validity of the data that has been entered.

Postprocessing

When you are finished running MODFLOW you can display the results in a variety of formats including contour maps and 3D surfaces. I feel that the postprocessing is one of the weak points of Argus ONE. For example, the contour lines on contour maps are not labeled so it can be difficult to determine what a particular contour line represents.

The PIE can not generate hydrographs of selected points.

Bugs

One bug has been reported to me since I completed the current version of the MODFLOW/MT3D PIE in March 1998. It could cause Argus ONE to crash during the export process. That was fixed on July 22, 1998 and the fixed version had not been placed on the Argus ftp site.

Suggested improvements

There are some features of the MODFLOW interface that I would like to see improved. (I've been hired by the USGS to work on their interfaces so I may get a chance to address some of these points.)

Summary

Pros:

Argus ONE is an extremely powerful and flexible preprocessor for MODFLOW. In my opinion, it is the best preprocessor currently on the market. (I haven't tried every preprocessor however.) It can also be used to run other programs such as SUTRA using free PIE's developed by the USGS. In addition to MODFLOW, PIE's have been developed for SUTRA, MOC3D, NAPL, PTC, and HST3D. Some of these are from the USGS and others are commercial products.

Cons:

The current PIE's for MODFLOW do not support as many packages or related programs as do some other preprocessors. The postprocessing is not as good as provided by some other programs.

User Comments

Availability

Argus ONE can be purchased from The MODFLOW/MT3D PIE can be downloaded from the Argus web site. It is based on the public-domain MODFLOW PIE developed by the USGS

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