Why Was the Rideau Canal Built? How Locks Lift Boats

A water road from Ottawa to Kingston

You can paddle a canoe from Ottawa all the way to Kingston on Lake Ontario. Parks Canada says this route, the Rideau Canal, is 202 kilometres long. It joins the Ottawa River, the Rideau River, a chain of small lakes and the Cataraqui River.

A canal is a waterway that people build or change so boats can travel through it. Why build one through forests and swamps nearly 200 years ago? The answer is a chain of causes and effects.^[1]

Why build it? A chain of causes

Parks Canada explains the chain like this. After the American Revolution, Britain saw the United States as a threat to its colonies in Canada. The most important route to the Great Lakes was the St. Lawrence River. But much of the river's southern shore belonged to the United States, so boats carrying soldiers and supplies along it could be attacked.

In 1812, Britain and the United States went to war. The war lasted two years. It showed that the St. Lawrence route was a weak spot. The Canadian Encyclopedia puts it this way: the war proved how vulnerable the St. Lawrence lifeline was to attack from the south.

So Britain wanted a second, safer route from Montréal to the Great Lakes, away from the border. Parks Canada's heritage listing describes the canal as a military supply route between Montréal and Lake Ontario, built as an alternative to the St. Lawrence. UNESCO says it was built primarily for strategic military purposes.^[1]

Colonel By and the builders

Lieutenant-Colonel John By of the Royal Engineers was put in charge. He arrived in 1826. His headquarters grew into a settlement called Bytown, named after him. Today we call it Ottawa, Canada's capital. Parks Canada says By pushed for larger locks than first planned, at least 134 feet long and 33 feet wide, so that new steamboats could fit.

The Canadian Encyclopedia says the work was done almost entirely by hand. Workers drilled holes in rock with hand chisels and filled them with gunpowder to blast it apart. Parks Canada says that each year as many as 5,000 to 6,000 workers gathered at more than two dozen worksites. Most labourers were Irish and French Canadian, working with skilled craftsmen such as Scottish stonemasons.

The work was dangerous. Many workers caught malaria, which the men called swamp fever, in the swamps along the route. Parks Canada says workers endured injury and disease and that hundreds died. The Canadian Encyclopedia says the exact number who died is not known. Both sources describe disease as one of the greatest dangers.

Parks Canada also notes that Indigenous peoples helped the construction by harvesting and supplying goods and food to the British military and to workers.^[4]

Dams make lakes, locks make steps

Boats cannot travel up rapids and waterfalls. The Canadian Encyclopedia says Colonel By built dams to create calm, deep lakes above them that boats could use. This kind of canal is called a slackwater canal, because the water behind each dam is slow, or slack. When the canal opened, it had 47 masonry locks and 52 dams.

But a dam leaves the water above it much higher than the water below. That is where a lock comes in. A lock is like a staircase made of water. Going from Ottawa up to Upper Rideau Lake, boats climb 83.2 metres through 31 locks, one step at a time.^[4]

How a lock lifts a boat, step by step

Parks Canada describes how a boat goes up, or locks up, through one lock. Step 1: the water inside the lock chamber is at the same level as the lower channel, so staff open the lower gates and the boat moves in. Step 2: staff close the lower gates and their valves, so the chamber is watertight.

Step 3: staff slowly open the valves at the upper end. Water from the higher level flows into the chamber through tunnels, pulled down by gravity, and the boat floats up with it. Step 4: when the water in the chamber reaches the upper level, staff crank open the upper gates. Step 5: the boat leaves at the higher level.

To go down, the steps run the other way. The chamber starts full, the boat enters through the upper gates, the gates close, and staff open valves in the lower gates so water drains out. When the water matches the lower level, the lower gates open and the boat floats out.

Parks Canada says the gates are opened and closed with cranks called crabs, and that the system runs on water, gravity, levers and gears, and human muscle power. UNESCO says most of the lock gates are still worked by hand-powered winches.^[2]

Lands and peoples along the canal

Long before the canal, these lakes and rivers were important travelling and trading routes for Indigenous peoples. Parks Canada's management plan says archaeological information shows that Algonquin peoples have lived in the Ottawa Valley for many generations.

The plan says the canal passed mainly through lands traditionally used by the Algonquin, Mohawk and Mississauga peoples, and that this military project had an impact on their relationship to the land. Today, Parks Canada says it engages with the Algonquins of Ontario, the Mississauga of Alderville and the Mohawks of Akwesasne and Tyendinaga in planning for the canal.^[6]

After 1832 and today

The canal opened in the summer of 1832. Parks Canada says it cost £800,000. Parliament criticized the spending and held an inquiry, which found no mismanagement. By died in 1836.

The canal became a busy trade route. Then, by 1849, locks were built around the rapids on the St. Lawrence, and shippers switched to that route. Commercial traffic on the Rideau fell, and from the 1880s on, recreation and tourism took over. Parks Canada says the canal is open to boats from May to October.

In winter, the National Capital Commission turns part of the canal in Ottawa into the Rideau Canal Skateway. It first opened in the 1970–1971 season and now winds over 7.8 kilometres.

The Rideau Canal was named a national historic site in 1925 and was added to UNESCO's World Heritage List in 2007. UNESCO calls it the best-preserved example of a slackwater canal in North America, and says it has worked as a waterway without interruption since it was built.^[1]