Up Previous Next Print This example reproduces the model in the MODFLOW-2005 documentation (Harbaugh, 2005) except that parameters are not used.

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This example reproduces the model in the MODFLOW-2005 documentation (Harbaugh, 2005) except that parameters are not used.

The model is a quasi-3-D model with three simulated layers and two nonsimulated confining beds. The model has 15 rows and columns. The cells are square with sides that are 5000 feet long.

Start ModelMuse and select Create new MODFLOW model and click the Next button. Enter the grid data shown in the illustration below and click Finish.

Simple Model

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Model Configuration (Harbaugh, 2005)

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The model is a quasi-3-D model in which some layers are not simulated. To specify the layers that are not simulated, select Model|MODFLOW Layer Groups. If the names of the layers are too long to be fully displayed, it may be helpful to widen the area in which the layer names are displayed by clicking down just to the right of the list of layers and drag to make the list wider. Select the upper confining bed and change it from Confined to nonsimulated. Do the same for the lower confining bed. The middle and bottom aquifers are confined but the upper aquifer is unconfined so change it from Confined to Convertible. Click OK to close the dialog box.

Finally, change the length units of the model from meters to feet by selecting Model|MODFLOW Options..., changing to the Options tab and changing the length units. If desired, it is also possible to specify the information on the Description tab.

The only aquifer properties that need to be specified are the horizontal and vertical hydraulic conductivities as shown in the table below. The horizontal hydraulic conductivity only needs to be simulated for the simulated layers. The vertical hydraulic conductivity needs to specified in both the simulated and nonsimulated layers.

To illustrate different methods of assigning properties, objects will be used to assign Kx whereas a formula will be used to assign Kz. First confirm that the selected layer is the top layer. One way to do that is to move the cursor over the red Selection cubeon the top view of the model. The selected layer will be displayed on the Status bar. Next select Object|Create|Rectangle and click twice on the top view of the model to create a rectangle that completely encloses the grid. The Object Properties dialog box will appear. Change the name of the object to "Upper_Aquifer_Kx". Examine the formulas for the Higher Z coordinate and Lower Z coordinate and verify that they are "Model_Top" and "Upper_Aquifer_Bottom". Select the Data Sets tab, expand "Required|Hydrology" and check the check box next to "Kx". Change the formula for the Kx data set to "0.001" and click the OK button. Next change the selected layer to layer 3 (the middle aquifer). One way to do that is to click twice beneath the red square on the Selection cube on the top view of the model to move the selected layer down. You will need to click twice to move the selected layer down two layers from layer 1 to layer 3. Create another rectangle object that completely surround the grid. In the Object Properties dialog box, change the name of the object to "Middle_Aquifer_Kx". Examine the formulas for the Higher Z coordinate and Lower Z coordinate and verify that they are "Upper_Confining_Bed_Bottom" and

Initial grid specification for the Simple Model.

Simple Model: Aquifer Properties

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Layer Kx Kz

Upper Aquifer 0.001 1

Upper Confining Bed 1e-6

Middle Aquifer 0.0001 1

Lower Confining Bed 5e-7

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"Middle_Aquifer_Bottom". These formulas mean that the top of the object is at the top of layer 3 and the bottom of the object is at the bottom of layer 3. On the Data Sets tab, check the check box for the Kx data set and leave the formula for the Kx data set to "0.0001" and click the OK button. Repeat this process again to assign Kx a value of 0.0002 in layer 5. (Be sure to change the selected layer to the bottom layer before creating the object used to specify Kx for the bottom layer.)

To define different values of Kz for each layer, select Data|Edit Data Sets... Expand

"Required|Hydrology" and select Kz. The default formula for the Kz data set is "Kx / 10". Click the Edit formula button to display the Formula Editor. Expand "Functions|Logical" and double click on CaseR.The formula will change to "CaseR(Index, Real_Result1, Real_Result2, ...)". In the formula, double-click on "Index" to select it. In the list of formulas, close "Logical" and expand "Grid". Then double click on "Layer". The formula should now be "CaseR(Layer, Real_Result1, Real_Result2, ...)". Type in the values of Kz for each layer so that the formula becomes "CaseR(Layer, 1, 1e-6, 1, 5e-7, 1)". This formula will assign a different value to Kz for each layer. Kz in layers 1, 3, and 5 will be assigned a value of 1; Kz in layer 2 will be assigned a value of 1e-6; and Kz in layer 4 will be assigned a value of 5e-7. Click OK to close the Formula Editor. Then click OK again to close the Data Sets dialog box.

The model has a single, steady-state stress period with a length of 86400 seconds. To specify it, select Model|MODFLOW Time... In the dialog box, set the Starting time to 0, the Ending time to 86400 and the Max first time step length to 86400. Together, the length of the stress period, the maximum length of the first time step, and the time step multiplier control the number of time steps in the stress period. Click OK to close the dialog box.

If you would prefer to set the number of time steps rather than the length of the first time step, click the cell in the table for the length of the first time step. Then click the "F()" button that appears in that cell to display the Time Step Length Calculator.

Four boundary condition packages are used in this model, the CHD, DRN, RCH, and WEL packages. To activate them, select Model|MODFLOW Packages and Programs. Then expand Boundary conditions and each of the items beneath it. Locate the check boxes for each of the packages and check them. Then click OK to close the dialog box.

There is a specified head boundary with a head of 0.0 in the first column of the model. It is present in both the upper and middle aquifers but not the lower boundary. (It also is not present in the confining bed because the confining bed is not simulated.) Select Object|Create|Polyline and then create a polyline on the top view of the model through column 1 for the full length of the model (row 1 to row 15). It doesn't matter if the object goes past the end of the model or doesn't go completely through the the first or last cell. Change the formula for the Higher Z coordinate and Lower Z coordinate to "Model_Top" and "Middle_Aquifer_Bottom" respectively. These will cause the object to extend vertically from the top of layer 1 to the bottom of layer 3. Go to the Model Features tab and check the check box for the CHD package. Enter a Starting time of 0, and Ending time of 86400, and a

Starting head and an Ending head of 0. If the starting and ending heads were different, the specified head at the end of each time step between the starting time and the ending time would be determined by linear interpolation between the starting head at the starting time and the ending head at the ending time. Click OK to close the Object Properties dialog box.

To check that the specified heads were assigned correctly, select Data|Color Grid... and set the Data set or boundary condition to "CHD Starting Head". (It is found under "Boundary Conditions, Observations, and Other Features|MODFLOW CHD". Click the Apply button. Then change the selected layer and verify that the specified heads are assigned only in layers 1 and 3. (They are not assigned to layer 2 because layer 2 is not simulated.)

The model has a uniform recharge rate of 3e-8 ft/s. On the top view of the model, create a Rectangle object that completely surrounds the grid. In the Object Properties dialog box, switch to the

MODFLOW Features tab and check the check box for the RCHpackage. Enter a Starting timeof 0,

Simple Model: Time

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Simple Model: Specified Head Boundary

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an Ending time of 86400 and a Recharge rateof 3E-8. Click OKto close the dialog box.

The next step is to specify the wells. There are 12 wells on layer 1, 2 more on layer 3 and 1 more on layer 5. Make sure the selected layer is layer 1. Select Object|Create|Point and click on column 8 row 9 in the top view of the model to create the first well. (The column and row of the cell beneath the cursor are displayed on the status bar.) In the Object Properties dialog box, go to the MODFLOW Features tab and check the check box for the WEL package. Change the Pumping rate

interpretation from Calculated to Direct. Enter a Starting time of 0, an Ending time of 86400 and a Pumping rate of -5. (Negative rates mean that water is being pumped out of the aquifer.) Click OK to close the dialog box. To check that the well pumping rate has been assigned correctly, color the grid with the well pumping rate.

It would be possible to specify the rest of the wells on layer 1 in the same way but because all these wells are identical, there is an easier way. Select Object|Edit|Add Point Sections . Then click on each of the cells that should be a well in the top layer. When you are done, your model should look similar to the figure below. All twelve of these wells are defined by a single object composed of 12 separate points.

Now make layer 3 the selected layer. Select Object|Create|Point and click on in column 6, row 4 to make another well. It will have the same times and pumping rate as the others. Select Edit|Copy

to copy the object to the clipboard. Select Object|Select Objects and drag the well object on column 6, row 4 to column 12, row 6. Select Edit|Paste to paste the object on the clipboard back into column 6, row 4.

Finally make layer 5 the selected layer. Select Object|Create|Point and click on in column 11, row 5 to make another well. It will have the same times and pumping rate as the others. Change the selected layer and on each layer check that the wells are in the right places. There should be 12 wells on layer 1, 2 wells on layer 3 and 1 well on layer 5.

The drains could be created in much the same way as the wells. However, this is time consuming. Instead open the file Drains.txt (in the data\SimpleModel folder) in a text editor, select all the text in the file and copy it to the clipboard. Then go back to ModelMuse and select Edit|Paste. The objects in Drains.txt define the drains required for the model.

This model uses the SIP solver. To use it select Model|MODFLOW Packages and Programs. Expand the Solvers and check the radio button for the SIP package. Change MXITER to 50, IPCALC to 0, and WSEED to 0.001. Then click OK to close the dialog box.

Simple Model: Wells

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Wells in layer 1.

Simple Model: Drains

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Select File|Save , select a name for your ModelMuse file, and save it.

To verify that MODFLOW is installed, select Model|Program Locations. If it isn't, the edit box where it should be specified will be colored red. If it isn't installed, you can click on the the URL above the edit box to open a web browser and navigate to the MODFLOW-2005 page. You can then

download and install it. If it is installed but not at the location specified in the dialog box, click the button next to the edit box, navigate to where it is installed and select it.

To run the model, select File|Export|MODFLOW Input Files . Select the name of the name file to export and the model will be exported. The rest of the files for the model will have the same name as the name file except that the file extension will be changed. By default, the file name will be the same as the ModelMuse file name with the extension changed to ".nam".

ModelMonitor will display the percent discrepancy in the model as the model runs. The model should finish almost immediately. Close ModelMonitor. Then close the listing file and the command line (DOS) window.

To see the heads calculated by MODFLOW, select File|Import|Model Results... In the Open file dialog box, the file containing the heads will already be selected. Click Open to select it. In the Select Model Results to Import dialog box, click OK. The grid will be colored with the heads for the single stress period. If desired, you can turn off coloring the grid with the model results and instead view contour lines of the results. You specify the contours in the Contour Data dialog box. In the Contour Data dialog box, the data set for the heads will be named "Head_P1_S1". You will find it under "Data Sets|Optional|Model Results|3D Data."

Simple Model: Save the Model

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Simple Model: Running the Model

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Figure

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References

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