Minecraft wiki entry for Water_gate, associated text: There are a few things you can do with a water gate. One of the most useful ways to use a water gate is to harvest crops by channeling the flow of water over your mature crop and it will automatically pick your crops for you. By channeling the water, you can also designate a pickup area for the already harvested crops. Water gates could also be useful for mob traps, water elevators, and safe passages up and down a cliff side.