Lock #11 on the Mississippi

In the foreground is a picture of the Lock (and Dam) #11 on the Mississippi. As a boat (or barge) approaches the lock, they contact the gatekeeper.

If the boat is coming from 'down stream' (the south),

• the gatekeeper will open up the gate,
• wait for the boat to come in,
• close the gate, and then
• open chutes to allow water into the lock.
• The water level rises, and up goes the boat.
• When the level is equal to that above the dam, the upper gate is opened and the boat sails through.

The reverse happens if the boat is coming the other way (from the North/up river) - the upper gate is opened, the boat sails in, the gate is closed, the water drains out of the lock, the boat lowers, and the lower gate opens so it can sail through.

That's all, I hope you enjoyed looking at these pictures about Dubuque, and hope you get to visit some day!