[GRASSLIST:4625] Modeling water flux in canals...

[Andrea Aime]

I need to model a network of canals (irrigation draing, ditches, or 
whatever is
the correct english term...) with a simulation software that can answer 
the following
questions:
- what happens if a pullutant in introduced in the network, where does 
it go,
   in which quantity, what kind of underground drainage I can expect, ...
- what happens if a lot of water is coming in (let's say the network is
   connected with a river), where is it going
- what happens if the topology of the network is modified, (maybe
   because a dam has been closed)
I know the question is quite vague, but what the heck, I'm only a software
engineer ;-)
Best regards and many thanks to anyone who will try to give an answer
Andrea Aime

PS: I'm interested in any kind of software, commercial or open source
(of course I prefer the latter).