Activity Tree - About Rivers Rivers High in the mountains, it is spring and the snow is melting. The dripping snow begins to trickle down the mountainside and gradually becomes a stream. As the stream works its way down, it becomes wider and deeper. Many rivers in our world start this way, including the second-longest river in the world, the Amazon River in South America. That is not the only way that rivers start.
Some rivers start in lakes and underground springs.
The place where a river begins is called its source. From its source, a river winds downstream and drains the water from the area around it. The area a river drains is called a river basin. Rainwater, streams and other rivers drain into larger rivers. The streams and rivers that flow into larger rivers are called tributaries.