Lab 6: Drying of the American West

The lab activity described here was created by Betsy Youngman of Phoenix Country Day School and LuAnn Dahlman and Sarah Hill of TERC for the EarthLabs project.

Summary and Learning Objectives

When populations live in areas where natural resources are scarce, conserving the resources becomes critical for survival. The case study presented in this lesson introduces students to a real drought that has been developing in the Colorado River basin for many years. The Colorado River is the major source of water for people in the driest part of the United States. More than 30 million people in 7 states depend on this river as the primary source of their water.

In this lesson, students discover how changes in climate over the Colorado watershed are reducing the amount of fresh water available in the river. They also see how the population of the region that uses this water has grown, resulting in increasing demands on a dwindling resource.

After completing this investigation, students will be able to:

  • Visualize the geographic location and scale of the Colorado River Basin.
  • Use tabular data to generate and interpret graphs of water consumption in the states supplied by the Colorado.

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Context for Use

In this activity, students learn about the impending issue of water scarcity in the Colorado River Basin. Because of its "real world" rather than theoretic nature, the activity can be used as an introductory case study to stimulate student interest in drought, or as a culminating activity in which students can apply what they've learned about drought to the current situation in the Colorado River Watershed.

Time Required

  • Parts A and B: 1 hour; could be assigned as homework
  • Part C: Graphing - 30 minutes (if students are familiar with Excel)

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Activity Overview and Teaching Materials

In Part A, students read an article and a view a short video that describe the situation at Lake Mead, a reservoir on the Colorado River system. Students view an online base map of the basin and gain a general sense of the region.

Part B has students read the article Climate Change is Shrinking the Colorado River that addresses how climate has changed across the Colorado River Basin. The article is based on the study by the same authors, The twenty‐first century Colorado River hot drought and implications for the future. Students view a short video about how snow impacts a watershed. They also explore the root causes of the changing reservoir levels in Lake Mead by reading about the source of the river's water and how short-term climate variations such as ENSO affect river volume. Students consider a graph of the river's reconstructed natural flow to discover that less water is entering the river system over time.

In Part C, students graph water consumption data from the Bureau of Reclamation - data after 2006 can be found in the Bureau's Water Accounting Reports. This activity requires the use of a spreadsheet program, such as Excel.

Printable Materials

You may want to provide a hard copy of the Activity Sheet on which students can record their answers (

, ). Suggested Answers: ,   Educators are encouraged to customize the questions and add new ones to meet specific learning goals in your location.

Teaching Notes and Tips

Parts A and B require students to read several articles and study graphs. Depending on student experience this can be assigned as a homework assignment, allowing more time in class for the more interactive Part C.

Part C includes instructions for viewing tabular data from the BLM and graphing it using a spreadsheet program such as Excel. To avoid connectivity or bandwidth issues, you may want to download the spreadsheet file and make it available on student computers in the days preceding the lesson.


You can assess student understanding of topics addressed in this Investigation by grading their responses to the Stop and Think questions. Additional assessments include having students present their thoughts and impressions from the reading assignments to their classmates.

State and National Science Teaching Standards

Additional Resources

Background Information

US Dept of Interior - Drought in the Colorado River Basin

NASA Earth Observatory - 25 Years of Drought in Las Vegas

Scripps Oceanography - Welcome to the New Normal April 2008

Content Extension

  • The non-fiction book, Cadillac Desert by Marc Reisner, delves deeply into the historical and political issues of water in the American West. The Wikipedia entry for Cadillac Desert provides an overview.
  • University of Arizona's Institute for the Study of Planet Earth's Climate Assessment for the Southwest (CLIMAS) program offers further information and links to current research on the climate of the Southwestern United states.