- Where do rivers begin and end?
- What is a river system?
- What are the parts of a river system?
What makes up a river system?
A river is a natural stream of flowing water. Over time, rivers carve large valleys into the ground. In the deepest part of the valley, a long and narrow riverbed meanders, which is the path that the river takes, flowing downwards from a higher ground towards a sea, lake, or another river.
A river starts as a small stream from a spring, or flows out of a lake or swamp. The beginning of the river is its source. The end of a river, or its mouth, is where the river either joins another larger river, or reaches a lake or sea.
Smaller tributaries flow into the long and water-rich river called the mainstem from both banks, which adds water and makes the mainstem wider and more water-rich. Near the mouth of a slow-flowing river, the mainstem branches into distributaries. The mainstem, together with its tributaries and distributaries, form a river system.
If you stand on a bridge and look downstream, the right bank will be on your right, and the left bank will be on your left. Depending on which side the tributaries flow into the mainstem, they are also called right-bank or left-bank tributaries.
- Mouth
- Source
- Tributary
- Right bank
- Riverbed
- River road
- Distributary
- Spring
- Lake
- Mainstem
Think!
- Use the map to find out how many right-bank and left-bank tributaries the Kasari river has.
- Come up with two ways to determine where the left bank and the right bank are when there is no bridge nearby.
How does a delta form?
Near the mouth of a very slow-flowing river, the sand and mud transferred there by the river sink to the bottom. This results in the formation of long and narrow islets that become an obstacle along the river. Water needs to find a new path for itself, so the stream bed branches off. The resulting distributaries flow into the lake or sea independently. A river mouth where the mainstem branches into several distributaries is called a river delta.
Important terms
- river – a natural stream of flowing water
- riverbed – the channel in which the river flows
- source – the place at which a river begins
- mouth – the place where a river empties into the sea or lake
- delta – a river mouth where the mainstem branches into several distributaries
- river system – the mainstem with its tributaries and distributaries
I now know that…
A river is a natural flowing freshwater body. The beginning of the river is called a source, and the end is called a mouth. A delta is a river mouth where the mainstem branches into several distributaries. Delta occurs only in slow-flowing rivers. The mainstem together with its tributaries and distributaries forms a river system.
