they get big long pipes and walk to the sea so they can join the pipes and make a water sucking tunnel.
watershed
watershed
A river
A catchment.
Land drained by a river is a watershed. This is an area of land that feeds all the water running under it and draining off of it into a body of water.
river
I believe you might be referring to a "watershed".
watershed
jjj
polder
Drained lands are lands which used to be swamps, but which had a lot of water removed in order to make them into more usual dry land that can be used for farming, housing etc.
The everglades have not been drained.