Working in Grid Mode Page: 8

Working in Grid Mode

Open Graphic Groundwater (see Running the Program). A start-up screen is displayed describing the shareware agreement. Point and click on the blue grid in the upper left corner of the start-up screen to enter Grid mode. Notice the bar at the top of the screen that says 'Graphic Groundwater: Grid Mode'. We will refer to this as the title bar. Just underneath the title bar is the main menu or menu bar. The menu bar contains six menus. Just under the menu bar is a toolbar containing six buttons. At the bottom of the screen is a status bar with four panels. These panels will display important information as you develop your grid. The portion of the screen between the toolbar and the status bar is called the Model window.

Graphic Groundwater displays a graphic representation of your model. Therefore, your first step is to calibrate the Model window to scale it to the real world. You then create the grid system, which can have uniform or variable grid spacing. The example problem has a uniform grid with seven rows and seven columns, each 100 feet wide. Therefore, the model domain is 700 feet by 700 feet. We need to set the scale so that a model of this size will just fit in the Model window.

Point and click on the Grid menu, then point and click on the Set Scale command. The Set Scale window will appear. Point and click on one of the option buttons to select the length unit for the scale (in this case, feet). Now point and click on the Length text box. Note that the number in the box is highlighted, with a flashing I-beam after it. Highlighted text will be replaced with any action of the keyboard. In other words, Graphic Groundwater is waiting for you to enter a number. Type the number 750.

Move the mouse pointer near the upper left corner of the Model window. Note that the mouse icon changes, indicating it is ready to draw a scale line. Press and hold the left mouse button, then move the pointer to the bottom of the Model window. Notice that a line appears that grows as you move the mouse. The process of moving the pointer across the screen while pressing and holding the mouse button is called dragging. When this action is required, we may request that you drag the mouse or pointer. Our objective is to draw a line on the screen with a length equal to the value we entered in the Set Scale window just a moment ago. This will ensure that our model grid will be fully visible on the screen without any adjustments in magnification. Since our model has dimensions of 700 feet by 700 feet, scaling the Model window so that it can include objects of 750 feet on a side will accomplish this objective, but we could have selected any dimension just over 700 feet. You can reposition the Set Scale window by dragging it by its upper right corner if the window is in the way.

When you are satisfied with the length of the line, point and click on the Set Scale button in the Set Scale window. By doing this you inform Graphic Groundwater of the scale of your model. The first panel of the status bar will describe the scale, but if you wish you can repeat the above process and reset the scale. Select the Finished button to close the Set Scale window.

Point and click on the Grid menu. The Uniform Grid and Variable Grid commands are listed, along with the Set Scale, Offset Grid and Move Grid commands. Point and click on the Uniform Grid command. The Uniform Grid window will appear for setting the number and spacing of columns and rows. The default values are 10 rows and columns with a spacing of 50 units.

Select the text boxes in sequence and enter 7 for both the number of columns and the number of rows. Enter 100 for the row and column spacing. You may move from one text box to another by using the mouse and clicking on the appropriate box, or by pressing the Tab key. After you have entered the correct values, click on the Create Grid button. A grid will appear in the Model window of the specified dimensions. You can start the process over again if you make a mistake. Once you are satisfied, click on the Finished button.

As you work with your grid system, you may need to adjust its position or size on the screen. Point and click on the View menu and note the commands Enlarge, Reduce, and Original Scale. Point and click on each of these commands to see the effect. Likewise, you can enlarge, reduce, or reposition the image by selecting one of the left three buttons in the toolbar just above the Model window. Click on the button with a magnifying glass with a positive sign in the center. Note that the mouse pointer over the Model window looks like the icon in the button you selected. Point and click anywhere in the grid. The image will enlarge and the grid will be repositioned. The center of the screen is now the coordinate of the grid that you clicked. The View menu commands and the toolbar buttons are described in Chapter 3. You can always return to the original screen scale by selecting the Original Scale command.

Point and click on the Model menu, then the Go to Model Mode command. A warning will appear. If you are satisfied with your grid, press the Enter key or click on the Yes button. If not satisfied, point and click on the No button and fix the grid. If you press the Enter key at the prompt, Graphic Groundwater will create a series of files, and in a few moments display the Layer Qualities window for setting the default values for the first layer of the model. The example model has only one layer. Enter the initial head, hydraulic conductivity, bottom elevation, and the primary storage coefficient into the appropriate text boxes using values listed in Table 2.1. Point and click on the check box to the right of the text boxes. A check mark next to the value indicates homogeneous conditions, i.e. values are the same in all grid cells. No check mark indicates heterogeneous conditions. Click on the Unconfined Conditions option button. When you are satisfied with all of the values, click on the Finished button. Graphic Groundwater will enter Model mode.