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Essential Question

  • To what extent can people predict the consequences from human alterations to the physical environment?

Background

Dams are constructed for water supply, flood protection or hydroelectric power generation. The environmental impacts of large dams on river systems are well documented. One such controversial large dam project in the world is the Three Gorges Dam on the Yangtze River, China. When completed, this will be the largest man-made structure in the world. However, such a large structure inevitably has considerable impacts on the local inhabitants and the environment.

Yangtze River in China

The above satellite image shows a 60-kilometer stretch of the Yangtze River in China. The construction site of the Three Gorges Dam, slated to be the world’s largest, sits on the left-hand side of the image along the big bend in the river.

The Three Gorges refers to towering limestone cliffs of the Qutang, Wu, and Xiling gorges, which stretch for about 200 km from Fengjie (Sichun province) to Yichang (Hubei province) along the middle reaches of the Yangtze. Along with the Yellow River in the north, the Yangtze is of fundamental importance to the culture and psyche of the Chinese, as well as the economic well-being of the country. At 6,300 kilometers long, the Yangtze (meaning Long River) ranks as the third largest in the world and the largest in China. The river drains from the Tibetan Plateau in the east, flows through China's largest and heavily polluted city, Chongqing, and enters the sea in the west near Shanghai. The catchment of the Yangtze represents 25% of entire crop land, 350 million people (33% of China's population), 40% of grain, 70% of rice, 40% of agricultural and industrial output in China.

Instructional Strategies

Strategy 1

Gathering Information: Think–Pair-Share

Post the essential question for this lesson. Have students conduct a Think – Pair – Share in which they first think about a response to the question (and possibly write a response for themselves), then discuss the question and possible responses with another student, and then share results of the discussion with the class.

Check for Understanding = Formative Assessment

  • Handout the A-B-C Graffiti worksheet to students. Give the partners from the Think-Pair-share a few minutes to brainstorm a list of human modifications to the environment, with one modification for each letter of the alphabet. For example, next to the “D” students might write “dams.” For the “P,” students might suggest pollution.
  • Evaluate the potential consequences of each modification listed. Place a plus (+) or minus (-) symbol next to each. Explain your reasoning.

Some modifications, like pollution, would be near-unanimously negative. Others, like dams, would be more ambiguous in their effects, with obvious benefits and obvious costs. Use this ambiguity to begin Strategy 2.

Scoring Guide

Strategy 2

Extending and Refining: Inquiry Chart

Dams have been identified as a significant modification to the environment. Have students examine http://www.nationalgeographic.com/geoguide/dams/ for a discussion on why and how dams are constructed along a river.

Have students complete an Inquiry Chart using the website to answer this question:

What are the consequences of human modifications to the physical environment?

Post several questions for students to explore, found at the top of each individual column. The rows are for recording, in summary form, the information you think you already know and the key ideas pulled from several different sources of information. The final row gives you a chance to pull together the ideas into a general summary or write new questions to which you still need answers. It's at this time you'll also try to resolve competing ideas found in the separate sources or, even better, develop new questions to explore based on any conflicting or incomplete information.

TOPIC:
DAMS: Human modifications
to the physical environment
Why and how are
dams constructed?
What are the costs and benefits of dam construction on people and the environment?
How effective are dams in achieving their objectives without harming the
environment?

What do I already know?

What did I learn from researching?

Summarize the information.
What questions do I have?

Check for Understanding = Formative Assessment

  • Remember what you discussed with a partner and then shared with the class about the essential question.
  • What new information did this site provide?
  • How helpful was this information in helping you answer the essential question?
Scoring Guide

Strategy 3

Extending and Refining: Making Predictions

Prior information helps bring meaning to new information. Have students review what they already know about building dams from the completed Inquiry Chart. "Constructing meaning" occurs as students gather new information and link it to what they already know. This thinking process is needed for students to engage in problem solving or in analyzing issues.

Give students an index card and ask students to Predict the impact dams have had on the environment and people historically. Post these index cards/predictions. As the students continue in the unit, periodically come back to them and have students see if their original ideas still hold up.

Check for Understanding = Formative Assessment

  • Imagine that you are an environmental specialist who has been asked to make recommendations about the building of a dam in your own area. What issues might a community need to consider before, during, and after the dam is constructed?

Scoring Guide

Strategy 4

Application: Reciprocal Teaching

One way to examine the impact of dams is to conduct a case study. Students will examine the environmental impact of the Three Gorges Dam construction in China.

The goal of a reciprocal teaching strategy is to summarize, question, clarify, and predict while reading content material. For instance, after reading a passage quietly, one student is asked to summarize. Then other students may add to the discussion with the teacher providing guidance and input. As discussion takes place students are expected to begin questioning, predicting, and clarifying when a student leader calls for it.

Divide students into groups of four and assign each student one of the four categories (summarize, question, clarify, and predict). As they read each online resource, the students will participate in their role & then have a group discussion. After the discussion the students switch roles & then begin the process again with the next page or chapter.

Thinking out loud is an important part of this reading strategy because it allows students to receive immediate feedback from the teacher and other students. It is important for students to understand the expectations of summarizing, questioning, clarifying, and predicting. Teachers should post a list of prompts addressing each of the four. Questions or prompts may include:

  • One word I didn't understand was…(Clarifying)
  • One question someone may ask after reading this passage is… (Questioning)
  • What do I think will happen in the next chapter? (Predicting)
  • The main idea of this article is… (Summarizing)

Online resources for the Three Gorges Dam construction in China: Students can view maps, pictures, and read about the region where the Three Gorges Dam is being built in order to collect geographic information and draw inferences.

Check for Understanding = Formative Assessment

  • How might you evaluate the scale of the project (i.e. size, cost, impact)?
  • What are the potential effects on China’s economy and environment?

Scoring Guide