Pump Method: Using the river's own flow against it!
I've actually found a fairly good way to dam a river using pumps. Unsure how to best edit it to show up, so, going to describe it and let someone else do the honors. Materials: a fair amount of building materials, 5 mechanisms, a few logs, and enough mats to make a pump for each tile the river is wide.
##### Walls all around to keep from overflow
#XXX# Pumps that pump South to North
+XXX* Gear connected to lever
+77X* Waterwheel + gear (stable foundation as gear)
Be sure to construct floors underneath the pumps as well for them to count as stable foundations, as we will be using a lever on the gear next to them, would not want them to deconstruct.
--Jayseesee 10:30, 24 June 2010 (UTC)