@Sheb:
You'll have to build pipes as close to the corners as possible for the water to reach them. Or build Walls around the rest of the map, so the water has to flow out over the corners.
Yes, the river will stop flowing when you turn it into massive obsidian via magma. One of the few points of DF that seem very logical
If you pour magma on the edge tiles at the source, the river will stop forever and can't be started again, because you can't dig out the edge tiles. If you leave those tiles alone, you can restart it later, when you need it.
Anyway for a solution: Windmills or a floating perpetuum mobile generator. The former is almost realistic and needs a lot of space, the latter sounds very dwarfy and may be considered cheating by some people.
Different kinds of armor can and should be stacked. Works very nicely and the difference in speed is unnoticeable with superdwarfenly agile and strong champions. I only give my soldiers less then three layers of armor (leather, chain, plate) when I don't have enough metal or want to challenge myself.
@Hortun: No, a stone is stone is stone currently. Doesn't matter if it's pitchblende or cinnabar, they're all the same and don't make people sick. You'll have to drown your elves the old fashioned way.
Though i do like exporting all the lovely lead toys and cups and other poisonous stuff to people I don't like, though poisonous minerals are not in the game yet. It's all about roleplaying