A tributary
They join together; Many small streams becomes on big one and the big ones lead to the river
A stream or brook can get bigger and become a river.
In many cases rivers begin at a source that has snow fall. The run off from melting snow can be the beginning of a river. Small streams built upon the items mentioned above can combine with other small streams and thus become the beginning of a river.
With other streams or tributaries joining, a stream's flow of water increases until it can be considered a river. For example, the mighty Mississippi starts out as a trickle of water near the Canadian border. Many similar trickles begin to join it and the flow increases.
tributaries
Many rivers and small streams flow into the Ohio River. Some of the major ones are: Allegheny River Monongahela River Wabash River Tennessee River Cumberland River Muskingham River Source: Riverlorian.com
The Hudson River used the Mohawk River and other small streams to connect to the Hudson River at Albany.
There are no rivers in Denmark, only small streams
A river can form through ice melting from the mountains or through rainfall that collects in wetlands. Small streams that flow downhill join up and make larger streams which also combine to form rivers.
No less then 15 major river systems combine to make up the Colorado River plus hundreds of small streams and creeks.
the Mississippi headwaters is a kind of thing that is located in the Mississippi river. The Headwaters of a river are it's origins. The multiplicity of small streams that converge to form the main body of the river proper.
A small river or stream is not called a river basin. A river basin is a portion of land drained by a river and it's tributaries. It encompasses all of the land surface dissected and drained by streams and creeks that flow downhill into one another, and eventually into one river.