Modeling a Stream

Modeling a Stream

Did you ever wonder why a stream or river has so many twists and turns? Why don’t rivers run as straight as a ditch? Summer time is a great time to explore how moving water finds a route across the ground. All you need is a bucket or a hose and the outdoors. Here is what to do.

Get permission from an adult to play with water outside. It might be good to tell them that you want to learn about how streams and rivers flow.

Ask to have the hose turned on to just a trickle of water. You don’t want the water running at full force. If there is no hose you can use, fill a bucket with water and pour some water on the ground. Watch the path the water takes. Does it go in a straight line? If it makes a turn, what do you notice about where it turns? If the water was turned on more or if you dumped the water from the bucket faster, do you think it would still take the same route? Try it.

Rivers and streams sometimes cut a path through the soil and rock they are flowing on. This is called erosion. Erosion can be very slow, taking a long time if the surface is hard or can be very fast if the surface is not hard. Pieces of soil or rock are picked up by the water and carried along. Sometimes these pieces are dropped at another spot downstream. Can you find any places where this is happening in your model river? If you do, can you figure out why the model stream is dropping some soil at that spot?

Scientists who study the geology of rivers and streams have a modeling tool called a stream table. It is a box or tray filled with soil or dirt. It lets them run water into the box at one end and out of the box at the other so the water runs across the soil like a little river. This is what you are doing outdoors. Scientists can raise one end of the stream table to make the model river run down a steeper hill. They can change the kind of soil in the box to see how this impacts the model river. Can you think of ways you can change how your model river flows? What about a board with soil on it so you can raise one end to make a steep path for your model river? What about running the hose stream across different surfaces like bare dirt, sand, grass, a sidewalk, a driveway? 

Write a sentence or two or make a drawing that tells what you have learned about running water.

  • How does the amount or speed of the water affect the route it takes?
  • How does the material the water is flowing on affect the route it takes?
  • How does the slope affect the route the water takes?

See if an adult family member can take you to visit a river or stream to check your ideas against a bigger flow of water. Did your model stream studies help you understand a real river or stream?

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