Classroom Ideas: Kindergarten-Fourth Grade
brought to you by nationalgeographic.com and Compaq

The Building of a Dam

OVERVIEW

A dam is a barrier built across a stream to prevent water from flowing freely. As water collects behind the dam, a reservoir is formed. A dam may be used to control the supply of water. In areas prone to periodic droughts, for example, the reservoir behind a dam can store water for future use. When there is an overabundance of water, on the other hand, a dam can help prevent downstream flooding.

Dams can be used to create hydroelectric power, to provide recreational areas, and to aid with water transportation.

In this lesson, students will create their own dams in order to compare the suitability of different materials and to gain a greater understanding of the hows and whys of dam construction.

Connections to the curriculum: geography, social studies, science

Connections to the National Geography Standards:

Standard 4: “The physical and human characteristics of places”
Standard 7: “The physical processes that shape the patterns of Earth’s surface”
Standard 14: “How human actions modify the physical environment”
Standard 15: “How physical systems affect human systems”

Time: Two to four hours

Materials Required:

• Illustrations of various dams, as in Geoguide Online
  
• Shallow rectangular trays made of metal or plastic (one or two for each group)
  
• Containers to hold and pour water
  
• Water
  
• Soil, sand, gravel, modeling clay, and other construction materials
  

  Purpose:

  Investigate how dams are constructed and why particular materials are used.

  Objectives:
  

  
  

  Students will:

  • Test various dam materials to compare their viability
    
  • Design their own dams using a combination of the materials they tested
    
  • Draw and label a cutaway diagram of their completed dams (third and fourth grades)

  SUGGESTED PROCEDURE
  

  Opening:
  
  

  1. Discuss a beaver dam with your class:

  • Why does a beaver build a dam?
  • What materials does a beaver use when building a dam?

  2. Tell students that humans, like beavers, build dams across rivers and streams to control the water supply.

  Development:
  

  Activity 1
  
  1. Prior to the construction of dams, have students predict what they think will happen with each of four construction materials: soil, sand, pebbles or gravel, and modeling clay.
  2. Divide students into groups of four.
  3. Ask each group to use narrow trays or to construct troughs in dense modeling clay to simulate stream channels. Elevate one end so that water can flow the length of the channels.
  4. Build a dam of soil across one of the channels.
  5. Fill the area on one side of the dam with water. Observe the dam and the water. Does the soil dam retain water? If so, for how long?
  6. Build a dam across a second channel using sand. Observe how the sand dam behaves.
  7. Follow the same procedure with pebbles or gravel and with clay. Observe the results.
  8. Discuss the four dam experiments. Which materials retained water the best?
  9. Talk with students about how these materials are actually used in dam construction—in combination with one another, as well as with concrete and steel.
  10. Look at pictures of a variety of dams—including the Kariba Dam from “Down the Zambezi” in the October 1997 issue of NATIONAL GEOGRAPHIC—and discuss differences in their design.

  Activity 2
  
  1. Have your students construct their own dams using some combination of the materials tested earlier.
  2. Ask them to test their new dams for water retention.

  Closing:

  1. Have each group share its finished dam and discuss construction choices.
  2. Have older students (third and fourth graders) draw a cutaway diagram of their dam and label each of its parts.

  Suggested Student Assessment:

  • Completion of dam
    
  • Diagram of dam (older students)
    
  • Explanation of dam
    

  Extending the lesson:

  • Visit a local dam.
    
  • Use a map to:

  1. Locate a local dam
  2. Locate the reservoir formed by the dam
  3. Locate the stream or river leading into the reservoir
  4. Locate the stream or river fed by water from the reservoir
  5. Assess the dam’s impact

  Melanie Campbell of West Indianola Elementary School in Topeka, Kansas, contributed classroom ideas for this Geoguide.

  ©1997 National Geographic Society. All rights reserved.