Model Setup

Acknowledgement: This description and the following lessons were originally written by Carmen Nale in 2004 as part of her Master's Project in Environmental Engineering.

The graphical interface system of the IGW model is shown in Figure 0.1. The button palette (located on the left hand-side of the models main menu) allows the user to add different types of features including wells, rivers, plumes, particles, etc.; create a zone with certain aquifer properties, control the models functions; solve the model; and edit graphical features. The step adjustment and time display interface (lower left-hand corner) allows the user to change the visual, plume, flow, and particle display time steps, t. The time processor selector (upper right hand corner) allows the user to visually monitor: the head, concentration, and probability at a monitoring well; zone mass and water balance; and polylines. The working area (center of the figure) is where the model is developed (Users Manual, 2002).

The curser-activated table (mid to lower right-hand side corner) allows the user to collect data from anywhere in the working area by placing the pointer on a given location. The working area attribute display shows the type of flow and elapsed time of the simulation. For further details readers can refer to the users manual available on the website at (http://www.egr.msu.edu/~lishug/research/igw). The reader is encouraged to go through the available tutorial example to become familiar with the model. Please note that the lessons and tutorials on this website were designed for IGW version 3.5.6 -- we recommend using this version of the software to ensure compatability between the step-by-step instructions and what you see on your computer screen.

Figure 0.1 shows the general format used in the model simulations on this website. Initially, a parent zone (green square that covers entire work area) is assigned basic characteristics for the site. Another zone is created to represent the contaminant source (the small red box) with specific properties such as concentration; type of source (i.e., instantaneous or continuous); partitioning coefficient, Kd, and other properties characterizing the contaminant. Darcy’s Law, the governing analytical groundwater velocity equation, is used to construct the velocity field by creating a head gradient using polylines (vertical blue/purple line on the left/right-hand side). For this example, the model was then allowed to run for a simulation time step of 1.8 years (displayed below the work area) to provide an example of a continuous source plume. The vertical red lines represent lines of constant head and the blue arrows represent the direction of groundwater flow. The simulation shows a uniform groundwater flow field that is created between the constant head boundaries. The contaminated plume that develops from a continuous source naturally flows perpendicular to the head contours and along the groundwater flow arrows. Notice that the concentration of the plume decreases moving away from the source (i.e., red to blue areas represent high to low contaminant concentration, respectively) due to dilution effects.

Continue on to Lesson 1: Groundwater Divide

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