RMA: Interpolation

This variation illustrates one way to use interpolation to assign values in a multiplier array.

Select Model|MODFLOW Packages and Programs... and check the Use Multiplier checkbox next to Low_K. Click the OK button to close the dialog box. Select Data|Edit Data Sets... Create a new data set and name it "UpperMult." You will use this to be the multiplier for the upper layer. Set its Orientation to 2-D Top, its Interpolation to Nearest Point, and its Default formula to 1. Create another new data set and name it LowerMult. You will use this to be the multiplier for the lower group of layers. Set its Orientation to 2-D Top, its Interpolation to Fitted Surface. and its Default formula to 1. Now select the Low_K_Multiplier data set and change its formula to "CaseR(Layer, UpperMult, LowerMult, LowerMult, LowerMult)" (In the Formula Editor, CaseR is classified under "Functions|Logical" and Layer is classified under "Functions|Grid.") This formula is what ensures that UpperMult is used as the multiplier in layer 1 and LowerMult is used as the multiplier in layers 2 through 4. Now create some point objects at various random positions. Use them to set values of either UpperMult or LowerMult. However for each point, uncheck Set values of intersected cells and check Set values of cells by interpolation. Keep the grid colored with the Kx data set as this is done and observe how Kx changes as new points are added. (You will have to add at least three points that affect the LowerMult data set by interpolation before the interpolation method is used.) Finally draw a polygon that surrounds part of the grid. Have it set the value of the LowerMult data set but set its formula to UpperMult. Observe how this affects the distribution of Kx in layers 2, 3 and 4. Try coloring the grid with the Low_K_Multiplier data set.