Locks are watertight chambers built on canals to help raise and lower ships in areas where the canal bed is not uniform. A ship’s motion through locks is similar to ascending and descending staircases.
Geographical disparity across the globe has been the greatest hindrance to trade and movement by sea. Given that the sea is the most popular avenue for bulk transport, even to this day, engineers are perpetually seeking solutions to reduce the costs associated with lengthy sea travels.
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Why are canals needed?
Canals are artificial waterways constructed mainly for transportation or irrigation purposes. The use of watercraft on irrigation canals is mostly prohibited. Similarly, water used in transportation canals is deemed hazardous for irrigation purposes.

(Photo Credit : envato)
What are canal locks?
Oceangoing container vessels are huge by any stretch of the imagination. When fully loaded, they displace water by several hundred feet, making them susceptible to any obstruction in the beds of shallow waters. To overcome this problem, watertight cabins were designed to elevate the surface of the water, and along with it, the ship. This would clear the hull of any obstruction in the canal bed and help them pass more easily.

(Photo Credit : Flickr)
Construction of a canal lock

Construction of a lock (Photo Credit : Kanguole/Wikimedia commons)
1. Watertight chambers
Canal beds and walls are lined with concrete to prevent the seepage of water into the ground. These chambers are supplied and emptied to raise and lower boats that enter the locks.
2. Flood gates
These simultaneously activated split doors enable a ship to enter the lock. They close against the direction of water flow, enabling the lock to remain watertight.
3. Sluices / Paddles
Sluices are channels of water that connect two locks. They supply water to and from the watertight chambers.
4. Lock gear
Lock gears are responsible for lock operation, such as the opening or closing of flood gates and water sluices that fill up or empty the lock. In locks that see heavy use, these are either automated or manned by a crew dedicated to this purpose.
Working of a canal lock
This brings us to our main question: “Can boats really climb staircases?” In order to clear the ever-changing canal bed, locks are arranged in succession so that the boat may ‘ascend’ into the canal and ‘descend’ out of it, much like a staircase. A vessel going through a canal encounters the following steps:
1. Entry
The vessel enters the first lock and the floodgates close behind it, forming a watertight system
2. Elevation
The boat is then moored to the canal walls while the sluices open, bringing in water from the lock in front. This inflow of water raises the ship, while bringing the water in equilibrium with the ‘donor’ lock. The floodgates between the two locks can now open and the ship can sail through to the next lock.
3. Descent
Descent is the exact opposite of elevation, wherein the lock with the ship empties into the ‘recipient’ lock. The water level decreases in the donor lock and becomes equal to that of the recipient lock, descending the ship along with it. The floodgates can now open and allow the ship to pass through to the next lock.
4. Exit
The entry and exit locks have water levels that are in equilibrium with the rest of the canal. This enables the ship to continue its journey in the rest of the canal with relatively uniform beds. Here is a video showing canal locks in operation.
Advantages and disadvantages of a canal lock
The inherent advantages of canal locks are that they make traversing through water bodies quite easy. They also eliminate the prohibitive expenses of maintaining a consistent depth for the entire stretch of a canal. However, there are also some disadvantages to canal locks. Water to canals, and consequently their locks, must be supplied from nearby waterbodies, such as rivers or oceans.

Areas near water bodies that supply canal locks can often get flooded (Photo Credit : twenty20)
Examples of canal locks
Canal locks are not only deployed on significant water bodies, but can also be found on small streams and rivers. However, some of the most prominent canal locks are found on transportation canals. Notable for their size and the amount of traffic handled daily, these locks are not only engineering marvels, but also epicenters of global commercial activity. Some of these famous canals are explained below:
1. Panama canal locks, Panama

Panama Canal locks (Photo Credit : GameOfLight/Wikimedia commons)
2. Grand canal locks, China

Hangzhou Section Locks of the Grand Canal of China (Photo Credit : Pixabay)
3. Caen hill locks, England

(Photo Credit : Neiljforsyth/Wikimedia commons)