You could either make a 3d object that looks like the water, and scroll a texture on it (maybe even have it animating), or you could use particle effects for the water. If you do a search for particles on the forum, you should find quite a lot of info - in particular, look for 'waterfall' effects.
Failing that, and if you're using DBPro, I had a try at a particle system myself for the Open MMORPG Project - link
here.
The code is well commented if you want to make your own effect - but maybe a bit too much code for just a small effect.
DBPro has it's own particle system, you can check the help files for more info.