Formulas are used to help define the distribution of values in data sets. One simple example of a formula would be just the name of another data set. For example, a valid formula for the Ky data set (which defines the hydraulic conductivity in the Y direction) would be “Kx.” (Kx is the data set that defines the hydraulic conductivity in the X direction.) Setting the formula for Ky to “Kx” would mean that the value of Ky in a given element would be equal to the value of Kx within that element.

Another simple example of a formula would be to set the formula for the Kz data set (Kz defines the hydraulic conductivity in the Z direction) to “Kx/10.” This formula would mean that in a given element, the value of Kz would be equal to the value of Kx in that element divided by 10.

Each data set has a "default formula" that is used to assign a value to each cell, node, or element when such values are not defined in some other way.

These examples only hint at the power of formulas. In addition to simple arithmetic operations, it is possible to use mathematical functions such as “sin” and “ln.” Geographic Information System (GIS) functions, logic functions, and functions related to the grid and objects are also available in formulas.

See "Formulas," "Functions," and "Formula Editor dialog box" for more information about formulas.