How A Canal Lock Works

The Welland Canal locks allow large ships over 200 yards in length that may weigh approximately 30,000 tons to travel between Lake Ontario and Lake Erie in spite of the 326.5 ft. difference in elevation. The Welland Canal locks lift and lower these ships with the help of gravity and large quantities of water. The force of gravity is used to fill or drain a lock moving about 20 million gallons of water in about 11 minutes. It is this movement of water that actually lifts or lowers a ship in a lock. The force of gravity is so strong that it draws this water a distance of 27 miles from lake Erie to Lake Ontario filling and draining the 8 locks in between.

The above illustration shows a ship in the reach section (the area before or after a lock) of the canal preparing to enter a canal lock. The open gate is black in color. This gate is at the lower water level end of the lock and therefore is labeled the downbound gate.
On the other end of the lock is the upbound gate which is at a higher water level. The upbound gate is closed, holding back the water that the force of gravity is attracting downstream.

In the following illustration, the ship is in the lock and both gates are closed making a somewhat water tight concrete lock chamber. At this point in time, the ship is secured in the lock chamber by ropes tied to concrete bollards located along the sides of the lock so that the ship remains stable during the lifting or lowering process. Once the ship is secured, water from the higher source of elevation or reach fills the lock chamber by way of a filling valve shown in the bottom right corner of the picture. When the water level in the lock reaches the same water level as that on the outside of the lock, the ship is untied from the bollards and the gate is opened to allow the ship to leave the lock. Before the ship leaves the lock it signals its departure with a loud blast from the ship's whistle.

You now have an idea of what a lock is and how it works. Lets put your knowledge to work. You will be asked to pilot a ship through a canal lock but before you do, review the concepts discussed. The following list of the major operational components of the Welland Canal can be used to help you with your task.

A large concrete post situated alongside of a lock chamber used to tie ships to, in order to keep them secure during the filling and draining of the lock chamber.
The moveable end part of a lock that holds water in and back when closed. When open the gate is also the point at which the ship enters and exits the lock. A lock chamber ususally has two gates.
A water tight chamber that consists of concrete walls, gates and valves that enable a ship to be raised or lowered from one level to another by the use of gravity and water.
The area before and after a lock that ships use to dock and wait their turn for passage through a lock. Also the area where a lock chamber draws or empties its water from or to, when lifting and lowereing ships.
A device that allows water to flow from or into a lock chamber when the gates are closed. A lock must have a filling and an emptying valve in order to work.

Now that you know how a lock works, try piloting a ship in and out of a lock using the simulator.

Click here to start using the simulator.