The model is presented to the user through a series of computer windows. The windows, in turn have sub-windows that include list boxes and drop-down lists that identify more specific information needed in the windows. List boxes are passive in the sense that they provide a series of options that are always visible. Drop-down lists are activated and become visible only when a selection is made in a list box.
As a convenience the complete logical structure of the MAGNET interface is laid out in an Appendix. The goal is to allow you to find any of the named buttons etc. in the windows without having to search through the GUI structure to find them. It would be helpful if you turn now to the Appendix and scan the contents so you know what you can find and where you can find it when you need it. We will shortly, via an example, learn how these GUI elements work individually and work together.
The MAGNET model is essentially two integrated models, one to solve the groundwater flow equations and one to solve the mass (contaminant) transport equations. To solve the mass transport model, you require a priori knowledge of the velocity of the groundwater.
To obtain the velocity of the groundwater, you need the hydraulic head distribution (water level elevations). Given the head distribution and knowing the porosity of the geological materials through which the water is flowing one can use Darcy’s law to obtain the velocity of the dissolved species (such as salt or organic contaminants). So, there are three separate steps 1) solve the groundwater flow equations for hydraulic head, 2) solve Darcy’s law for the dissolved species velocity and 3) introduce the fluid-flow velocity into the mass transport equation and then solve it for the concentration.
As noted, one objective of the GUI is to translate known model information from a visual format, such as a map, into a series of numbers that are readable by a computer. A second GUI responsibility is to translate the numbers generated by the computer model into a visual format understandable to the user. In addition, the GUI can visualize using buttons etc. computer commands such as printing, file saving, and file selection.