Establish Prior Knowledge
Call on students to share what they know about the water cycle. For more information, you may want to direct them to the diagram of a water cycle at the U.S. Geological Survey site: http://ga.water.usgs.gov/edu/watercycle.html Call on volunteers to describe the movement of water through this cycle. Have them note that groundwater is water that filters down through the earth and is eventually discharged into lakes, streams and oceans. Tell students that the Snapshot they are about to see describes how land use in the past affects our water supply today.
Have students view the Snapshot and read the synopsis. Use the following questions to guide a class discussion:
- How do maps help scientists recreate how land use changed over time?
- How has the area around Muskegon River changed over the last 100 years?
- The Snapshot states that pollutants from 100 years ago are just now affecting the river’s water quality. Can scientists know for sure what pollutants entered the water 100 years ago? How do you think scientists are able to calculate this? (If students have trouble answering this question, remind them that scientists often use computer models to gather and analyze information.) Direct students to the model used for Muskegon River.http://ltm.agriculture.purdue.edu/default_back.htm
You can use the following question to wrap up your class discussion:
· Scientists have determined how past decisions affect the Muskegon watershed. How can this information and the model be used in the future?