A river is a stream of water that flows through a channel in the surface of the ground. The river bed is where it flows and the earth on each side is called a river bank. A river begins on high ground or in hills or mountains and flows down from the high ground to the lower ground, because of gravity. A river begins as a small stream, and gets bigger the farther it flows.
The water in a river is called fresh water. It comes from rain or snow and it can usually be drunk safely, unless it has been polluted. The water in a sea cannot be drunk safely because it is salt water. Both people and animals often live near rivers. They need water to survive and, for humans, rivers were once the only means of fast transport.
The beginning of a river
The start of a river is called the source or head water. The part of the river that is near the source is called a ‘young’ river. A young river is often in a V-shaped river bed, and flows quickly downhill over stones and around big rocks. Young rivers often have lots of small waterfalls and rapids.
- The source of a river may be a spring, where water flows from underground.
- The source of a river may be a lake.
- A river may begin in mountains where there is snow. The melting snow runs together to form a small stream that runs down the mountain.
The middle part of a river
The middle part of a river is called a mature river. A mature river makes a riverbed that is U-shaped. It might be very deep and run fast. It sweeps over small rocks and boulders, and makes big turns around hills and mountains. It is much wider than a young river, but not as wide as an old river.
The last part of a river
A river usually ends by flowing into an ocean, a lake or a bigger river. The place where the river flows out into a bigger body of water is called the ‘mouth‘ of the river.
As a river flows towards its mouth, the countryside around the river often changes from hilly to flat. As it flows over the flat land the river becomes wider and slower. A wide slow river is called an ‘old river’. An old river often floods across the land after there is lots of rain at the headwaters.
Look at the picture below to see how a river winds by eroding the land around it. Water erodes, or wears away, the bank. Maybe the placement of a large rock causes water to rush past more quickly in one spot. More is then eroded away in that spot, eventually really changing the direction of the river so that it bends. This can happen again and again, causing a river to bend and wind. Find where the river will eventually connect. It will then become a lake there.
Some rivers flow underground through caves. Underground rivers form in places where there are lots of cracks in the rocks above, so that in rainy weather, the water runs downs and collects in small underground streams. Sometimes the underground water trickles or gushes out of the ground to form a small spring of water.
Edited from source