# CHARACTERISTIC_CURVES (Saturation functions)¶

This section specifies the saturation functions, both the capillary pressures and relative permeabilities. Multiple characteristic curves can be defined within an input desk. Analytical functions or tables can be used to define the saturation functions, described in their respective sections.

## Mixed approach¶

PFLOTRAN-OGS can define capillary and relative permeability functions by the means of tables and analytical expressions. The two approaches can be mixed, as long as the end points are consistent. The software will perform a check after reading the input, and where different values for the end points are found in the saturation functions, an error will be thrown.