What makes this river so much fun to raft?
This raft trip is on the Gallatin River in Montana. The river is fast because its in the mountains traveling down a steep slope. There is a lot of water because it's early summer. The snow from up higher is melting. Did you ever go whitewater rafting? It's fun!
What Are Streams and Rivers?
A stream is a body of freshwater that flows downhill in a channel. The channel of a stream has a bottom, or bed, and sides called banks. Any size body of flowing water can be called a stream. Usually, though, a large stream is called a river .
Features of Streams and Rivers
All streams and rivers have several features in common ( Figure below ). The place where a stream or river starts is its source . The source might be a spring, where water flows out of the ground. Or the source might be water from melting snow on a mountain top, like the stream pictured below ( Figure below ). A single stream may have multiple sources.
A stream flows fast and steep where it originates in the mountains. This stream, in Glacier National Park in Montana, is coming from snow melt.
Water in a stream flows along the ground from higher to lower elevation. What force causes the water to keep flowing?
A stream or river probably ends when it flows into a body of water, such as a lake or an ocean. A stream ends at its mouth . As the water flows into the body of water, it slows down and drops the sediment it was carrying. The sediment may build up to form a delta.
Several other features of streams and rivers are also shown above ( Figure above ).
- Small streams often flow into bigger streams or rivers. The small streams are called tributaries . A river and all its tributaries make up a river system.
- At certain times of year, a stream or river may overflow its banks. The area of land that is flooded is called the floodplain . The floodplain may be very wide where the river flows over a nearly flat surface.
- A river flowing over a floodplain may wear away broad curves. These curves are called meanders . Pictured below is an example of this ( Figure below ).
A river meanders across an estuary in Florida.
River Basins and Divides
All of the land drained by a river system is called its basin, or watershed . One river system’s basin is separated from another river system’s basin by a divide . The divide is created by the highest points between the two river basins. Precipitation that falls within a river basin always flows toward that river. Precipitation that falls on the other side of the divide flows toward a different river. A continental divide separates rivers that flow into different oceans.
Pictured below are the major river basins in the U.S. ( Figure below ).
River basins in the U.S.
- continental divide : Divide that separates water that goes to different oceans.
- divide : Ridge that separates one water basin from another.
- floodplain : Region near a stream where water overflows during floods.
- headwaters : Location where a stream forms, often high in the mountains.
- meander : Bend in a stream channel.
- mouth : Where a stream enters a larger body of water such as a lake or an ocean.
- source : Where a stream begins; usually in mountains.
- stream : Body of moving water, contained within a bank (sides) and bed (bottom).
- tributary : Smaller of two streams that join together to make a larger stream.
- watershed : All of the land area that is drained by a river and its tributaries.
- A moving body of water of any size is a stream. A river is a large stream.
- A tributary begins at its headwaters on one side of a divide. Two tributaries come together at a confluence.
- A river ends at an estuary. If the river drops sediment, it may create a delta.
Use the resources below to answer the questions that follow.
- Streams and Rivers at http://www.youtube.com/watch?v=TxI9gTvNY0M (3:45)
- Where is water speed and weight the greatest?
- What is created by this fast moving water?
- Explain what is occurring where the water moves slowly.
- Minnesota River Sediment at http://www.youtube.com/watch?v=FvZcDTFXguY (2:59)
- What has destabilized the Minnesota River area?
- What speeds up the water as it moves down the river?
- What caused the ravines to form?
- Where does most of the sediment end up?
- List the sources of the sediment.
- Describe the features of a river from where it begins to where it ends.
- What happens to two drops of water that fall on opposite sides of a divide?
- Why does a tributary not cross over a divide?