Classroom Ideas: Ninth-Twelfth Grade
brought to you by nationalgeographic.com and Compaq

The Purpose of Dams: A Local Watershed Study

OVERVIEW

Dams have many uses, and an individual dam may serve different purposes over time. This lesson will have students analyze the purposes of dams in a local watershed (A watershed is the land drained by a particular river and its tributaries.)

Connections to the curriculum: geography, language arts, science, social studies

Connections to the National Geography Standards:

Standard 1: “How to use maps and other geographic representations, tools, and technologies to acquire, process, and report information from a spatial perspective”
Standard 14: “How human actions modify the physical environment”
Standard 16 “The changes that occur in the meaning, use, distribution, and importance of resources”

Time: Two hours

Materials Required:

• Copies of maps that show a watershed in your area
• Blank overhead transparency and projector or chalk board
• White paper

Purpose:

• Locate dams found in the local watershed
• Analyze the purposes of the dams

Objectives:

Students will:

• Locate the dams in a local watershed
  
• Analyze the various purposes that the dams serve
  
• Rank the purposes in order of importance

SUGGESTED PROCEDURE

Opening:

1. Suggest to your students that the varied human needs served by dams are many and may change over time.
2. Ask students to compile a list of motives for building a dam. These purposes may include flood control and river regulation, irrigation, power production, and recreation. Record the list on an overhead transparency or the board.
3. Tell students that they will try to determine the purposes served by dams in a local watershed.

1. Divide the students into groups of three or four.
2. Distribute the watershed maps and a piece of paper to each group.
3. Have students list the dams found in the watershed, beginning with the largest stream or river running through it, then examining all its tributaries on the map.
4. Ask your students to use clues on the map to determine why people built the dams they find on their maps. If it appears that the dams serve multiple purposes (as many do), ask your students to list all the potential reasons for having the dams.
5. Ask students their opinions about what prompted people to build each dam. They should look at the course of the river and its valley, the locations of cities, nearby land use, and the topography of the land. One student in each group should take notes.
6. Ask students to share their conclusions with the other groups. Did all reach the same conclusions? Why or why not?

Closing:

1. Have each group explain how the purposes for a dam may change over time. Discussion may focus on these geographic questions:

• How has the level of flood control been affected by the dam?
  
• How has the river‘s course been regulated by the dam?
  
• How have people taken advantage of the water in the reservoir?
  
• How has power production affected the surrounding region?
  
• Have the dams produced any negative consequences as well as benefits?

2. Have each student create a hand-drawn map showing dams on a watershed—actual or imagined.
3. Have students compare the benefits and consequences of dams near their homes to those of the Kariba Dam covered in the October 1997 NATIONAL GEOGRAPHIC article “Down the Zambezi.”

Suggested Student Assessment:

• Completed location maps of the dams on a local watershed
  
• Written comparison of one dam on the watershed to the Kariba Dam
  
• Journal entry about the use of inferences from maps to make judgments
  

Extending the Lesson:

• Students can complete a research project about a real dam near their homes, including a diagram and a history of the dam.
  
• Students can interview people who live or work near the dam to record their views about the benefits and costs of the dam.

Stan Masters of Blissfield High School in Blissfield, Michigan, contributed classroom ideas for this Geoguide.