Terrain

Does the terrain in guild wars affect spellcasting? For example would water spells be more powerful in water? or does the terrain have nothing to do with the spells effectivness?

Not that I know of yet anyway. But Height does, as in .. your more likely to get hit on the head if your opponent is above you. Thus your armor on your head better be good !

Nope - Terrain doesn't have any bearing on the effectiveness of your spells. However, it can influence certain other things aside from height/tactical advantages. There are a couple of terrain types which will slow a character down (Tar, Ice) and walking through lava? That's never a good idea.. just to cite some examples.

Although its not in the game i think its a great idea. You should post this on the suggestion forum. Elementalists damage/cast speeds being scalable to what elements are around them is quite a nice feature and i would imagine it would add a layer of tactics.