The next variation is to add additional layers.
Select Model|MODFLOW Layer Groups... Click the Add layer group button 
. Change the name of the aquifer to "Second Aquifer" Switch to the Discretization tab and change the Vertical discretization of Second Aquifer to 3 and click the OK button. Select Data|Edit Data Sets... Select the Second_Aquifer_Bottom data set and change its formula to "Aquifer_Bottom - 20." In the top view of the model, locate the red selection cube in the upper left corner. Click beneath the red square to move down one layer. Draw a polygon that completely surrounds the grid. Use it to assign Low_Kx_Zone a value of True. Notice that the formulas for the higher and lower Z coordinate set the top and bottom of the object to include the entire layer group consisting of 3 layers. Color the grid with Kx and check that the hydraulic conductivity is what you expect it to be. Draw another polygon that covers just part of the grid and set High_Kx_Zone to True. Check the value inside this object. Because the Low_Kx_Zone and High_Kx_Zone are both true inside this object, the value inside it should be 200 instead of 150.
