The idea for this lesson plan was inspired by Michael Arquin of Santa Catalina School in Monterey, California, who received a teacher grant from the National Geographic Education Foundation in support of a year-long project called Life on the Other Side of the Monterey Bay: An Integrated Study of the Carmel River Watershed.

This lesson introduces students to river ecology and addresses the societal and environmental impacts associated with dams and their construction. By understanding dams and their effects on the environment, students will propose the construction or abolition of a dam in their hometown or other geographic area. They will think objectively and critically about real issues affecting the future of rivers.

Geography, biology, ecology, social science

Standard 4: "The physical and human characteristics of places"
Standard 8: "The characteristics and spatial distribution of ecosystems on Earth's surface"
Standard 14: "How human actions modify the physical environment"

Two to three hours

• Computer with Internet access
• Colored pencils, crayons, or markers
• Blank Xpeditions outline maps for each pair of students [Note: Students' choice of watershed will determine which map(s) they need.]

Students will

• learn the basics of river ecology;
• research how dams affect the environment, particularly the food chain; and
• study a specific watershed in the United States being affected by human intervention and make recommendations about how to address any resulting environmental problems.

Rivers have long been sources of transportation, food, and water. Even ancient civilizations like those in Mesopotamia and Egypt established irrigation systems to promote agriculture and access potable water. Today, the world's rivers contain a vast network of levees, dams, and locks to control water and harness its potential.

Ask students to name the rivers that exist in their area. Do they know how these rivers are being used? Are they being protected in some way?

Before the lesson, quickly poll your students if they think all rivers flow from the north to the south. If there were any hands raised, teach them that stream flow is entirely dependent upon the gradient of the streambed. Thus, streams move from high to low. Have them explore National Geographic's Geography Action! Rivers 2001 site, especially the interactive piece about river systems ("Click here to explore a river system.").

Explain to students that one way to determine how healthy a river system is is to study the macroinvertebrates in it. Macroinvertebrates are animals that have no backbone and are visible without magnification. They are an important part of the riparian food chain: they eat leaves and algae, and are in turn eaten by fish.

Many factors determine what kinds of macroinvertebrates are present in the stream. Species that provide an indication of an environmental risk are called bioindicator species. Have students click on the three links about macroinvertebrates' sensitivity to pollution. Which link describes species that are bioindicator species? What would finding gilled snails in a river system tell you that finding midge flies would not?

Ask students to form small groups and explore U.S. species that have been affected by dams and other human impacts on river systems. The following Web sites will help them begin their research:

National Geographic: Wild World—Southeastern U.S. Rivers and Streams
National Geographic: Virtual World—Columbia River
National Geographic: Eye in the Sky—Floods and Dams
American Rivers: Most Endangered Rivers of 2002
Columbia River Basin: Dams and Salmon

Ask students to think about the following questions:

• What kinds of human activities are causing damage to river systems?
• What are some of the indications that a river system is being damaged?
• What is being done to combat the negative effects of the human activities?

Bring students back together as a class and discuss what they have learned about the impact of dams and other human structures on rivers and watershed areas. Why do students think they are built in the first place? Do people just not care, or are many of them older projects that were built before the extent of damage being caused was fully understood?

Ask students to work in pairs and select a watershed area within the United States that is being threatened by some form of human intervention. They may want to use the Environmental Protection Agency's Surf Your Watershed site. Students may find more about the individual watersheds they choose at the following Web sites:

American Rivers
River Network
USGS: Science in Your Watershed

Have each pair print out a blank outline map corresponding to the watershed it has chosen using the Xpeditions atlas and ask them to outline and shade in the watershed on the map.

On the map or on a separate sheet of paper, have students draw the reasons the area is threatened as well as the consequences of the threats. Write paragraphs alongside the pictures naming construction projects, endangered species, etc., and explaining in detail the problems. Finally, ask them to explore and explain what is being done about the current situation.

• Time, location, and lab equipment permitting, have your students explore a local stream and identify the macroinvertebrates using the key provided. Once identified, ask students if finding these particular species tells them anything about the quality of the water in this stream.
  
  When back in class, ask your students what might happen if the macroinvertebrates were disturbed or even eliminated from the stream.
  
  
• Other stream monitoring experiments can be found in the Save Our Streams Volunteer Trainer's Handbook.

American Rivers
Conservation Fund Sustainable Programs
National Geographic: Eye in the SkyFloods and Dams
National Geographic: Virtual WorldColumbia River
National Geographic: Wild WorldSoutheastern U.S. Rivers and Streams