Combination of GRASS with hydrogeolgical/solute transport modelling

Hi netters,
I am a new GRASS user and I would like to ask if GRASS can be combined with
modelling software as MODFLOW, ASM (aquifer simulation model) and with finite
difference modelling techniques.
My GRASS knowledge is very poor but I suspect that GRASS can not describe time
variant conditions such as in solute transport. That's why I would like to
know if anybody uses GRASS with data already manipulated by such modelling code
s or techniques. If you have in mind any relevant publications please mention
them.
I hope you have undertood my problem
Thanks in advance
Giorgos

Giorgos Zacharioudakis
School of Earth Sciences
University of Birmingham
Edgbaston
Birmingham B15 2TT
E-mail ers4gxz2@sun1.bham.ac.uk