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View Maps

Following a successful model simulation, outputs are generated and Outputs branch in the Model Explorer tree for the active run.


oHeads and Drawdown









Heads and Drawdown

At the View Maps step, you can view contours and color shading of the flow and transport results.


By default, you will see color shading and contours of the calculated heads, in layer view. You can display heads along a row, and along a column, and in 3D, using the same tools as you used earlier.

If your model is transient, use the time controls above the Flex Viewer to change the output time; as you do this, all active viewers (layer, row, column, 3D), will refresh to show the heads for the new output time.



The display settings (color classes, contour line intervals, etc.) for the Layer, Cross-section, or 3D views can be adjusted in the Style settings. To load these settings, right click on Heads or Drawdown in the Outputs section of the Model Explorer, and select "Settings".  For more details about these settings, see the section on 3D Gridded Data Settings.


Cell-by-cell flows read from the MODFLOW .BGT file can be viewed in a stand-alone 3D Viewer.  Once displayed in the viewer, load the Style settings for Flux, and choose the desired display type (Cells is turned on by default). Under the Colors panel (shown below), you can select from various Flux attributes:



XFlux: lateral flux into the cell from the right and left face (adjacent columns)

YFlux: lateral flux into the cell from the front and rear face (adjacent rows)

ZFlux: vertical flux into the cell from cells in the upper and lower layer face (adjacent layers)

ModuleFlux: absolute value of the flux for that cell


Calculation Cell Flow–in/ Flow–out Based on Inter–Cell Flow Terms

Inter–cell flow terms are saved in the output budget file (.BGT) for three neighbors of a given cell(j,i,k):

RIGHT FACE (j+½,i,k)

FRONT FACE (j,1+½,k)

LOWER FACE (j,i,k+½)


 Indices for the six adjacent cell faces surrounding cell j,i,k.

The inter-cell flows for the remaining three faces are given by:

LEFT FACE(j-½,i,k) = RIGHT FACE([j-1]+½,i,k)

FRONT FACE(j,i+½,k) =  REAR FACE(j,[i-1]+½,k)

UPPER FACE(j,i,k+½) = LOWER FACE(j,i,[k-1]+½)


 Indices for the six adjacent cells surrounding cell j,i,k.
 Adapted from MODFLOW-2005 Users Manual, USGS Publication TM6-A16


InFlowRate (Flow In): total amount of flux into that cell. Calculated as follows:

InFlowRate =

 FLOW RIGHT FACE[i,j–1,k] * H(FLOW RIGHT FACE[i,j–1,k])

+ FLOW FRONT FACE[i–1, j, k] * H(FLOW FRONT FACE[i–1, j, k])

+ FLOW LOWER FACE[i,j,k–1] * H(FLOW LOWER FACE[i,j,k–1])


- FLOW FRONT FACE[i, j, k] * H(–FLOW FRONT FACE[i, j, k])



OutFlowRate (Flow Out): total amount of flux out of that cell. Calculated as follows:

OutFlowRate =


+ FLOW FRONT FACE[i, j, k] * H(FLOW FRONT FACE[i,j,k])


- FLOW RIGHT FACE[i,j–1,k] * H(–FLOW RIGHT FACE[i,j–1,k])

- FLOW FRONT FACE[i–1,j,k] * H(–FLOW FRONT FACE[i–1,j,k])

- FLOW LOWER FACE[i,j,k–1] * H(–FLOW LOWER FACE[i,j,k–1])


Where H(x) is a known Heaviside Step Function; for more details on this function, see:

BaseFlowRate = InFlowRate - OutFlowRate



At the View Maps step, you can view groundwater velocities in a variety of ways as described in the section on 3D Gridded Data Settings. By default, velocity vectors are shown as vectors.



Calculation of Velocities in Visual MODFLOW Flex

Model velocities are estimated in Visual MODFLOW Flex using a two-step process:

1.Estimate inter-cell velocities at each cell face in each component direction (X, Y, and Z)

2.Interpolate component velocities to the cell centroid


Inter-cell Darcy and Average Linear Velocity

Inter-cell Darcy velocities are calculated in Visual MODFLOW Flex using the following equations:


Inter-cell average linear velocities are estimated from the Darcy velocities:


where is the effective porosity of the current cell


Interpolate component velocities to the cell centroid

Component velocities are interpolated to the cell centroid by:



Water Table

This is the elevation where the calculated head value is equal to the Water table elevation (pressure head equals zero).  In 2D (Layer) and 3D views, the Water table is displayed as a surface object, and as such has style settings similar to Surfaces (for more details on these options, see Style Settings: Surfaces.   In 2D cross-sectional view (by row or column), the water table is drawn as a solid line.  On the toolbar above the view, you have an option to control how the line is calculated and displayed.


Smooth WTL (Water Table Line): the line is smoothed (interpolated) between each grid cell. Since the line is interpolated, this is an approximation.



Discrete WTL (Water Table Line): the line is drawn as piecewise constant, with a flat line drawn across each grid cell at the elevation corresponding to the water table. This option better reflects the actual output data and the MODFLOW grid cell geometry.



If your model is Transient, you can adjust the output time as explained above, and the Water table display will update to reflect the new values for that output time.


 The Water Table is currently only calculated for MODFLOW-2000, -2005, -NWT, -SURFACT, and SEAWAT model runs; it is not calculated for MODFLOW-LGR.




The water table data can also be exported to .CSV file for further post-processing. Right-click on Water Table from the Model Explorer and select "Export..."


The format of this file is as follows:

x (x-coordinate at center of cell)

y (y-coordinate at center of cell)

ztop (elevation of the top of layer 1; this can be used to calculate depth to water table)




wt_"time": water table value at the defined MODFLOW time step; for transient models, you will see additional columns for each saved MODFLOW time step.






If you ran MT3DMS, you will also see output nodes for Concentration (one for each species).  Only one 3D Gridded results can be shown in a 2D viewer at a given time, so in order to view Concentrations, you need to first turn off Heads or Drawdown from the model tree. (Note: the 3D viewer supports displaying multiple 3D Gridded results simultaneously; just create a new 3D viewer (Window / 3D Window from the main menu bar).



The settings allow you to clip the upper and/or lower levels - for example if we use the Lower Cutoff of 20:



This would result in the following rendering of the concentrations:




The option to use lower and upper cutoffs are available both for Colormap and ThreeSlices display options.



Adjusting Style Settings

The style settings of either the 2D or 3D views can be adjusted (note, each one must be defined independently)

First make the desired property group selected and visible in the Flex Viewer.

Next make the desired 2D viewer active

Then right-click on the desired property group in the tree as shown below and select `Settings`







The 2D Colors and Contour line settings can be adjusted. For more details, see Color and Contour settings



Export Heads, Drawdown, or Concentrations.

The calculated heads or drawdown can be exported to shapefile; see Export for more details.


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