How though? I'm a noob when it comes to do with the physics and/or Traps in this game.
Here's some tips for simple gravity driven water supply :-
#1 - you need a refilling water source like a river, aquifer or underground lake (one touching the edge of the map)
Important part to master :-
#2 - dig a short tunnel for water up to, but not actually touching the water source. build a floodgate (mason's workshop) blocking the tunnel. Link this to a lever (reqs 3 mechanisms from mechs workshop, b-T-l to build, then use q menu on lever), somewhere AWAY from the waters path. After linking, have the lever pulled twice to open and close the floodgate to test it.
#3 - channel from above the bit of ground between the river and the floodgate. You now have a 'tap' which can turn the water on or off. Give a couple more 'lever pull' orders to open and close the floodgate.
#4 place more floodgate as needed. hatches, both types of bridge, doors etc also block water ad can be controlled by levers. Read the wiki and experiment with these.
With this set-up you can send water anywhere on the same or lower-z-level with no pumps or advanced mechanics needed. Water allows underground farms to be built on any stone, not just soil, btw.
You can try without the floodgates/levers but then you have no way of shutting the water off once it's flowing.
what I don't get is how do I place water or channel it without drowning my dorfs ETC
Simple, do the digging when it's dry, finish up, release water!
EDIT : I just had to add, a Real-Life plumber turns off the water mains before opening the pipes. Do this in DF too !!