  We report an imbibition experiment in 2D random porous media in which height
- height correlation function grows with a nonuniversal exponent. We find the
exponent to depend on evaporation. A cellular automaton model for imbibition
based on first principles is presented. A numerical study of the model gives
results which are consistent with the experiment. The interface is shown to
exhibit self-organised criticality (SOC).
