Personally I like creating huge farms with the help of a river. I create a 4 spaces wide corridor between the river and the farm (about 4 shift spaces high and 2 shift spaces wide) make 9 floodgates (4 for the endrance of the river, 4 for the endrance for the farm and 1 for entrance to the well I set nearby).
It works pretty well for me. Except for that one time I forgot I'm flooding a farm and I ended up with a farm with 5/7 tall water... Good thing I already had quite a complex mining complex that soaked up the water when I flooded it xP
Here is how that looks most of the time
River:
Farm:
As for the answer by Krall I personally don't like using screw pumps for something as important (to be done quickly after you start a game) because it can take a lot of time for them to start working (I mean constructing them, manning and making sure everything is correct)
I personally only use them to flood entrenchments around my fortress.