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A more effective (and common) method of plotting
concentration contours is to plot the contour lines at
logarithmic intervals (e.g 0.01, 0.1, 1.0, 10, 100, etc.).
[Options] button from the left-hand toolbar.
A Contour Options window for C(O) - JP-4 will
appear, as shown in the figure to the right:
Notice that the minimum concentration value is -100.
Obviously, a negative concentration value is not
possible in a natural environment. This negative
concentration value is a result of numerical dispersion
encountered during the solution of the contaminant
transport simulation.
Automatic contour levels (to remove
the automatic contour line)
Custom contour levels
Type the following custom contour levels in the text boxes provided:
10↵
100↵
500↵
1000↵
4000
Although this is not a strict logarithmic scale, it does provide a much better representation of
the concentration contours.
Next you will increase the drawing speed of the concentration contour lines by changing the
Contouring resolution/speed setting from Highest/Slowest to High/Slow.
Finally, you will turn the color shading option on to display a color map of the concentrations.
Color Shading tab.
The Color Shading options will appear, as shown in the
figure to the right:
Use Color shading
In the Cutoff Levels section,
Lower Level: 10
The Lower Level setting will ‘clip’ the color map at 10
mg/L (all concentration values below 10 mg/L will not
be shown on the color map). The Lower level setting of
10 mg/L is an action level. If the contamination will be
present in the lower aquifer at a value equal to or greater
than 10 mg/L, then some action must be performed to
remediate the situation.
The Ranges to color section lists the range of concentration values for the current Output
times. In the Ranges to Color section Type the following:
Min: 0.0
Max: 4000
Visual MODFLOW: Introduction and Tutorial
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