Program is called ILWIS, and it's open sourced.. (http://52north.org/communities/ilwis)
I haven't used it since school, which is uh.. years past.. but i really can't see it getting any worse.. last time i used it it was VERY similar to the ArcGIS Hydronomy tools, in a few cases a bit better (since at that time it was focused on hydronomy)... but now it looks like it might have even more open sourced DEM gold... i'm going to have to check it out!
Originally Posted by loogie
Much appreciated! I was just looking into hydrological modeling with GRASS plug-ins. Havign other options is great. Thanks a lot for you comments!
A general note: This project is undergoing a major re-design, using the release of the GMTED2010 elevation model. :D