Canals

November 27, 2012 11:48 am

Until 1914, ships traveling between New York City and San Francisco had to sail all the way around the tip of South America. That adds up to a distance of more than 13,000 miles (21,000 kilometers). The opening of the Panama Canal in 1914 changed all that. The canal cuts across Panama in Central America. It created a shortcut that saves ships nearly 8,000 miles (13,000 kilometers) and weeks of travel time!
WHAT IS A CANAL?
Canals are waterways dug across land. A canal looks like a giant ditch. The bottom is flat and the sides are usually sloped. Some canals are lined with concrete or stone. That helps prevent water from eroding(wearing away) the sides. It can also keep water from seeping out of the canal and into the ground.
TWO KINDS OF CANALS
There are two main kinds of canals. One kind is used for carrying water from one place to another. Farmers rely on irrigation canals to bring water to their crops. Many cities rely on canals for their water supply.
Another kind of canal, called a navigation canal, is used by boats. Navigation canals may connect different waterways, such as major or . They may also connect inland port cities to a sea, lake, or major river. Navigation canals allow ships to take short, direct routes, instead of long, inconvenient ones. In some cities, such as Amsterdam and Venice, a network of navigation canals are used like streets.
Some navigation canals are deep and wide. They are often called ship canals because they are big enough for large, ocean-going ships to sail through. Barge canals are much shallower. Barges are flat-bottomed boats that sit high in the water, so barge canals are often just a few feet deep.
A HILLY PROBLEM
For a long time, the main drawback with navigation canals was that they could only cross flat land. Unlike roads, navigation canals could not go uphill or downhill. The water would all run to the lowest point, leaving the rest of the canal dry.
CANAL LOCKS
The invention of canal locks in the late 1400s solved the hill problem. A lock is a section of a canal that can be closed off by water gates at both ends. The water level in a lock can be raised or lowered to match the level in a higher or lower section of the canal. In this way, a boat can travel uphill or downhill.
To travel uphill, a boat enters the lock and the gates are closed behind it. Then water from the upper section of the canal gently enters the lock so the water level rises. When the water level in the lock is the same as the upper section of the canal, the gates ahead are opened and the boat can leave. The same process in reverse lets a boat travel downhill.
AN OLD IDEA
People have dug canals for thousands of years. Nearly 3,500 years ago, the ancient Egyptians built a navigation canal that linked the Nile River with the Red Sea. Thousands of years earlier, in a region of the Middle East called Mesopotamia, people began to dig irrigation canals. The canals helped the Mesopotamians build productive farms and a rich civilization.
One of the world’s most impressive canals is the Grand Canal of China. The first part of the canal was completed by the AD 600s. Construction continued for the next 600 years. The canal, which links Beijing to Hangzhou, is still in use today. It extends for 1,200 miles (1,900 kilometers) and is the longest canal system ever built.
Building a canal is hard work. It was especially difficult long ago, before the age of modern machines. Even in Europe in the 1800s, canals were still dug by people using shovels. Can you imagine the amount of work needed to dig a canal that extended hundreds of miles?
PANAMA AND SUEZ CANALS
In many countries, canals form important inland waterway systems. But the world’s most important canals are the Panama and Suez canals.
The Panama Canal cuts across Central America and links the Atlantic and Pacific . The canal is 40 miles (64 kilometers) long and was completed in 1914. Today, the Panama Canal is one of the world’s busiest canals.
The Suez Canal runs across northeastern Egypt and connects the Mediterranean Sea with the Red Sea. The Suez canal is 121 miles (195 kilometers) long and first opened in 1869. It provides a shortcut for ships traveling between European ports and ports in the Americas, Asia, and Africa.
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