Watershed Modeling

The following activity demonstrates how watersheds drain into streams, rivers and eventually, lakes, and how pollutants are carried from watersheds to bodies of water. The activity also demonstrates the relationship between small and large watersheds.

Student Objectives
1. The student will recognize that bodies of water are the end product of drainage from watersheds.
2. The student will predict where the water and pollutants will flow.
3. The student will observe the watershed in action and record observations.
4. The student will see the end results of polluting within a watershed and how it impacts bodies of water.

Materials (for each group)
1. One container at least 22 cm wide, 33 cm long, and 6 cm deep. A metal baking pan will work fine.
2. Two sheets of newspaper.
3. One sheet of thin plastic at least 20 cm larger in all dimensions than the container.
4. One spray bottle.
5. One book.
6. Baby powder. (Or some very fine soil will also work.)
7. Blue food coloring.

1. Divide students into groups of three or four. Each group will need a container, two sheets of newspaper, one sheet of plastic, one book, some baby powder (or soil) and one spray bottle filled with water and a few drops of blue food coloring.
2. Crumple each sheet of newspaper separately and place them next to each other at one end of the container. Try to vary the shape of the two. Place the sheet of plastic over the crumpled newspaper, causing it to form hills over the high places, and streams and rivers in the low places. Put a book under the end of the container with the newspaper, which will allow water to flow down the streams and rivers and collect in the lake at the front of the container. The sides of the plastic sheet should be placed down into the container.
3. The plastic sheet represents the ground surface covering the watershed. Looking at the watershed model, try to guess where the main rivers will flow. Now, it's time to put the model to the test. Spray several pumps of water from the spray bottle on the model. Notice that each stream has its own watershed (the area that drains into it) and that the entire model is a larger watershed because all the water eventually flows into the pool at the bottom of the container. Count the number of small watersheds.
4. The model now represents a clean watershed. Letís add some pollutants. Sprinkle a little baby powder over the model. The baby powder represents a variety of pollutants, including oil, road salt, animal manure, excess fertilizers, pesticides, tiny particles of soil and other harmful materials. Rapidly spray nine pumps of water over the upper portion of the watershed. Observe the way in which the pollutants are carried by the water and the end condition of the lake. Repeat if necessary.

1. Describe the relationship between small and large watersheds.
2. What are some possible solutions to keep bodies of water clean?
3. Who pollutes watersheds?
4. Think about the watershed(s) in which you live. What possible pollutants exist there?

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Last Updated: 01/24/00
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