Water is constantly rising from the oceans up into the air to form clouds of water vapour. Clouds are carried by the winds across the land. When the clouds meets mountains, they are forced to rise which makes the water inside them turn into drops and come falling down as rain. Some of this water runs down the sides of the mountains, and some sinks into the ground and runs along in small streams under the ground. Eventually it will bubble up again as a “spring.” This is the beginning of a river.
A small little stream flows from the spring and other little streams will join it and form a bigger stream. As it flows on, it is joined by more and more little streams until gradually it becomes a wide and deep river. Finally, it finds it way back to the ocean.
The source of a river is called its headwaters. The water flows quickly around and between the great rocks in it’s way, and the tumbling and bubbling of the water fills it with oxygen. There is usually very little plant life where the water is moving quickly – just rocks and stones and maybe some moss.
All the while this little spring is bubbling up and running down the mountainside, it is taking bits of the mountain with it. The fast moving water wears away at the rock taking tiny pieces of rock and minerals, or silt, with it.
Sometimes a river will flow over a ledge of rock, making a great noise and splash. This is called a waterfall or cataract. Perhaps you have been to visit Niagara Falls? The power in this rushing, moving water is often used to create electricity by building dams so that the river is forced to turn great turbines.
Further down the river, the land is lower and the water spreads out and becomes calmer, muddier, slower and deeper. Sometimes it becomes a lake. Slower moving water can not carry as much silt, and so the silt that is carried so quickly down the earlier part of the river is left behind here making the bottom muddier. This allows more plant life to grow such as pondweed, reeds and rushes. It also is home to more kinds of wildlife such as fish, worms, watersnakes, frogs and herons.
As the land becomes flatter, the river may become more winding. When the water is running so quickly down the hillside, it is not easily turned aside, but when the water is running slowly it can more easily change direction.
Where the river finally runs into the ocean, the land is marshy and the water is part salt and part fresh. This is a very important place for sea creatures. Many lay their eggs here and the young grow up in the shallows where there is plenty of food. It is also a nesting ground for many kinds of birds.
Unfortunately rivers can be damaged by dumping harmful chemicals such as bleach from papermills, building dams which prevent fish from swimming upstream to lay their eggs, and from gas-powered boats and ships. And it is important to keep the streams near you free from trash and pollution.
PROJECT: Do you know the major rivers in Canada? See if you can find the following on a map: Mackenzie, Yukon, Saint Lawrence, Nelson, Slave, Columbia, Saskatchewan, Peace, Churchill, Fraser, Athabasca, Assiniboine, Red.
Do you have a river near you? Find out where it begins and where it flows out to the ocean. Find some examples of animal and plant life that depend on it.
BOOKS: Tales of a Great White Fish by Maggie de Vries, Greystone Books, c2006.