Read the following passage to students:
"San Francisco is facing a severe water shortage in the early 20th century. The only nearby sources of water are the Pacific Ocean and the nearby smaller rivers. The salt water of the ocean cannot be filtered using available technology, and the rivers cannot adequately supply the growing population for much longer. A larger river to the east could be dammed, but the dam would have to be built inside a national park originally set aside as a nature preserve."
"As president, you are ultimately responsible for making the decision whether or not to allow this dam to be built. Give the potential consequences of building and of not building the dam. What decision would you ultimately make, and why? Explain how this decision makes you a resource conservationist or nature preservationist in your environmental philosophy."
Have students work in small groups to decide whether or not to construct the dam. Have them list specific justifications for their decision. Allow each group to share their decision and the reasons they recorded.
End the lesson by showing a present-day picture of the Hetch Hetchy dam, as well as a map of Yosemite showing the size of the reservoir created by it.